Sintef Blowout

SINTEF REPORT TITLE

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Blowout and Well Release Characteristics and Frequencies, 2006

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AUTHOR(S)

Enterprise No.: NO 948 007 029 MVA

Per Holand, ExproSoft CLIENT(S)

Multiclient REPORT NO.

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CLIENTS REF.

STF50 F06112

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Espen Fyhn Nilsen, Statoil

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504016

77/0

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CHECKED BY (NAME, SIGN.)

\\Phantom\es201016\ \\Phantom\es201016\BLOWOUT\TEKST BLOWOUT\TEKST 2006\Annual 2006\Annual report 2006 final.doc

Per Holand

Lars Bodsberg

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DATE

APPROVED BY (NAME, POSITION, SIGN.)

2006-10-05

Lars Bodsberg

ABSTRACT

This report is based on the 2006 Version of the SINTEF Offshore Blowout Database. The report gives an overview of offshore blowout and well release characteristics and frequencies. Blowout data from the US Gulf of Mexico Outer Continental Shelf, the Norwegian waters, and the UK waters from the period 1980-01-01 until 2005-01-01 have been focused on.

KEYWORDS

ENGLISH

NORWEGIAN

GROUP 1

Marine Technology

Marin Teknikk

GROUP 2

Offshore

Offshore

SELECTED BY AUTHOR

Risk

Risiko

Blowout

Utblåsnin

Frequencies

Frekvenser

Blowout and Well Release Characterist ics and Frequencies, 2006 version

Page: 3

PREFACE This report is based on the SINTEF Offshore Blowout Database, version 2006. The intention o f the report is to give an overview of blowout/well release characteri stics and frequencies, and not to analyse and evaluate the different blowout types. The format of the report is similar to the report that was issued last year. Appendix 1 to the Users Manual (and also the Help file) for the SINTEF Offshore Blowout Database list criteria used us ed for the database fiel fields ds in general. The Users Manual/help Manual/ help file has has been updated to reflect some recent changes in the database categorizing.

Some key updates from 2005 version Exploration wells Exploration wells have now been separated in Appraisal wells and Wildcat wells in the exposure data after 1980 for the areas US GoM OCS, UK waters, and Norwegian waters. The exploration blowouts and well releases have also been re-categorised to reflect this change.

To differ between the Wildcats and Appraisal wells the following were assumed; - For Norwegian waters the NPD classification has been used as it is. - For the UK waters all wells classified as Exploration wells are regarded as Wildcats, while the wells classified as Appraisal wells are of regarded as Appraisals. - For the US GoM OCS a different approach has been used. All exploration wells drilled in certain areas are numbered from 1 and further, where well number 1 is the first well drilled. For the US GoM OCS all exploration wells numbered as 1 have been regarded as Wildcats, while all the other wells are regarded as Appraisal wells. This may be inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to no. of Appraisal wells for the US GoM OCS. Exposure data The general exposure data has been updated also to include the 2004 exposure data. Exploration Wildcat wells vs. exploration Appraisal wells have been given some more focus. The water depth related exposure data has also been updated. This year also data from the UK waters has also been included. Deleted Blowouts No blowouts have been deleted from fro m the database this year. New Blowouts Six new blowouts/well releases have been added to the database (ID547 – ID552). They were observed for the following countries and years: US GoM OCS, three incidents, they were from 1994, 2003 and 2005 • Australia, one incident from 1991 • • US GoM NOT OCS, one incident from 1998 • Azerbaijan, one incident from 2005

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Blowout and Well Release Characteristics and Frequencies, 2006 version

Edited Blowouts Twenty-four blowouts/well releases have been significantly edited. Table 0.1 shows where and when these blowouts/ell releases occurred. Table 0.1 Edited blowouts and well releases Incident Id Number 207 350 431 532 503 192 197 217 237 265 269 324 386 369 390 425 420 460 463 476 502 518 544 545

Country Norway Norway Norway UK US/GoM not OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS US/GoM OCS

Year of occurrence 1981 1985 1996 2001 1999 1980 1980 1981 1983 1984 1985 1989 1991 1993 1993 1996 1997 2000 2000 2001 2001 2002 2005 2005


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LIST OF CONTENTS PREFACE..............................................................................................................................................................3 1. ABOUT THE DATABASE ...................................................... ........................................................... .............7

1.1 PARTICIPANTS ...............................................................................................................................................7 1.2 DATABASE STRUCTURE .................................................................................................................................7 1.3 IMPORTANT DEFINITIONS ..............................................................................................................................9 1.4 CATEGORY AND SUB-CATEGORY .................................................................................................................10 1.5 PHASE OF OPERATION ..................................................................................................................................11 1.6 NORTH SEA STANDARDS .............................................................................................................................11 2. OVERVIEW OF BLOWOUTS/WELL RELEASES INCLUDED IN THE DATABASE........................13

2.1 I NTRODUCTION ............................................................................................................................................13 2.2 DATA QUALITY ...........................................................................................................................................13 2.3 OVERVIEW OF COUNTRIES R EPRESENTED IN THE DATABASE .......................................................................14 2.4 DURING WHAT OPERATIONAL PHASES DO BLOWOUTS /WELL R ELEASES OCCUR ? .......................................16 2.5 NO. OF BLOWOUTS /WELL RELEASES PER YEAR ...........................................................................................17 3. BLOWOUTS VS. WELL RELEASES..........................................................................................................19 4. OVERALL BLOWOUT/WELL RELEASE EXPERIENCE.................... .................................................. 21

4.1 BLOWOUT /WELL R ELEASE VS . FLOW MEDIUM ............................................................................................21 4.2 BLOWOUT /WELL R ELEASE VS . FLOW-RATES ...............................................................................................22 4.3 SEVERITY ....................................................................................................................................................22 4.4 IGNITION OF BLOWOUTS /WELL R ELEASES ...................................................................................................22 4.5 BLOWOUT /WELL R ELEASE DURATION .........................................................................................................24 4.6 BLOWOUT /WELL R ELEASE FLOW-PATHS AND R ELEASE POINTS ..................................................................25 4.7 BLOWOUT /WELL R ELEASE CAUSES .............................................................................................................29 4.8 OPERATIONS AND ACTIVITIES WHEN BLOWOUT /WELL R ELEASE OCCURS ...................................................33 4.9 EXPLORATION WILDCATS VS . EXPLORATION APPRAISAL WELLS .................................................................36 4.10 BLOWOUTS FROM AUSTRALIA, CANADA EAST COAST, THE NETHERLANDS , AND US/CALIFORNIA OCS...37 5. “NORMAL” DRILLING AND PRODUCTION EXPOSURE DATA....................................................... 39

5.1 DRILLING EXPOSURE DATA .........................................................................................................................39 5.1.1 US GoM OCS .....................................................................................................................................39 5.1.2 United Kingdom .................................................................................................................................41 5.1.3 Norway ..................................................... ........................................................... ...............................41 5.1.4 The Netherlands .................................................................................................................................44 5.1.5 Canadian East Coast..........................................................................................................................45 5.1.6 US Pacific OCS ............................................................ ........................................................... ...........46 5.1.7 Australia ................................................... ........................................................... ...............................47 5.1.8 Denmark ................................................... ........................................................... ...............................47 5.1.9 Compiled Drilling Exposure Data......................................................................................................48 5.2 PRODUCTION EXPOSURE DATA ...................................................................................................................50 5.2.1 US GoM OCS .....................................................................................................................................50 5.2.2 United Kingdom .................................................................................................................................50 5.2.3 Norway ..................................................... ........................................................... ...............................51 5.2.4 US Pacific OCS ............................................................ ........................................................... ...........52 5.2.5 Compiled Production Exposure Data.................................................................................................53 6. VARIOUS EXPOSURE DATA ......................................................... ........................................................... .55

6.1 WELL DEPTH R ELATED EXPOSURE DATA ....................................................................................................55 6.1.1 US GoM OCS Wells............................................................................................................................55 6.1.2 Norwegian Wells ................................................................................................................................57 6.2 WATER DEPTH R ELATED DRILLING EXPOSURE DATA .................................................................................58 6.3 SHUT-IN WELLHEAD PRESSURE R ELATED EXPOSURE DATA ........................................................................62 6.3.1 US GoM OCS Drilling Wells..............................................................................................................62

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6.3.2 Norwegian Drilling Wells.................................................................................................................. 64 6.3.3 US GoM OCS Wells in Production.................................................................................................... 65 6.4 PRODUCTION R ATES AND GAS OIL R ATIO DATA, US GOM OCS................................................................ 66 6.4.1 Production Rates ............................................................................................................................... 66 6.4.2 Gas Oil Ratio ....................................................... ............................................................ .................. 68 6.5 WORKOVER FREQUENCY EXPOSURE DATA ......................................................... ....................................... 69 6.6 WIRELINE FREQUENCY EXPOSURE DATA................................................... ................................................. 70 6.7 COILED TUBING AND S NUBBING EXPOSURE DATA......................................................... ............................. 71 7. OVERALL BLOWOUT/WELL RELEASE FREQUENCIES ......................................................... ......... 73 REFERENCES..................................................................... ........................................................... ................... 77


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1. About the Database

1.1 Participants The SINTEF Offshore Blowout Database was initiated in 1984. By the end of 2005 the following companies were sponsoring the database: -

Norsk Hydro a.s. Statoil Total E&P Norge Shell Research Limited BP Norge Safetec A/S Scandpower Risk Management AS DnV Chevron Energy Technology Company Lilleaker Consulting a.s Eni Norge AS ConocoPhillips Norge

1.2 Database Structure The blowout database resides in a Microsoft Access 2000 data file named blowout.mdb. The main programming tool used is Microsoft Visual Basic 6.0. The Seagate Crystal Reports version 8.5 is used for making all the reports from the program. The SINTEF Offshore Blowout Database includes blowout/well release descriptions, drilling and production exposure data for certain areas in the world. Blowout/ well release descriptions The database contains 51 different fields describing each blowout/well release. The various fields are grouped in six different groups. They are:

1. 2. 3. 4. 5. 6.

Category and location Well description Present operation Blowout causes Blowout Characteristics Other

Category and location Includes information related to the incident category (blowout vs. well leak), offshore installation such as location, operator, installation name and type, and water depth.

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Well description Includes well and casing depths, last casing size, mud weight, botto m hole- and shut in pressure, GOR, formation age and rock type. Present operation Includes the phase (exploration drilling, development drilling, workover etc.), the operation presently carried out (for example casing running) and the present activity (for example cementing) Blowout causes Include external cause (stating if an external cause contributed to the incident), loss of the primary barrier, loss of the secondary barrier (describing how primary and secondary barrier were lost) and human error. It should be noted that the field regarding human error in general holds low quality information. Human errors are frequently masked. A field named North Sea standards highlights if the development of the blowout could have been avoided if North Sea type equipment had been used (for instance in other parts of the world a blind shear ram is not required in surface BOP stacks) Blowout characteristics Twelve fields are included comprising flow-path, flow medium, flow-rate (low quali ty), release point, ignition type, time to ignition, lost production (low quality), duration, fatalities, consequence class, material loss and pollution Other In the Other screen five fields is included, they are: control method, remarks (includes a description of the incident, data quality (includes an evaluation of the source data quality), last revision date and references. Exposure data The various areas represented with exposure data area shown in Table 1.1. Table 1.1 Overview of exposure data included in the database Country US GoM OCS Norway United Kingdom The Netherlands Canada East Coast Australia US Pacific Denmark

Drilling exposure data Yes Yes Yes Yes Yes Yes Yes Yes

Production exposure data Yes Yes Yes No No No Yes No

Search possibilities and reporting facilities Almost any type of search may be performed to select sp ecific blowout /well release event types. Search criteria may be established by selecting predefined codes, specific numeric values, specific free text, or any combinations of these. The predefined codes are spelled out to ease understanding.


Page: 9

The database program counts and presents the events satis fying the search criteria. The selected data may be viewed, printed or copied to separate files for further analyses, for example by database or spreadsheet programs. The exposure data and the blowout data are not linked. Blowout frequencies can therefore not directly be established.

1.3 Important Definitions The following main definitions have been utilised when categorising the blowouts/well releases in categories and sub-categories. Blowout definition NPD came up with a blowout definition in their proposal for the new regulations. (“Aktivitetsforskriften, eksternt høringsutkast av 3.7.2000, høringsfrist 3.11.2000”).

Med utblåsing som nevnt i denne paragrafen første ledd, menes formasjonsfluid som strømmer ut av brønnen eller mellom formasjonslagene etter at alle definert e tekniske brønnbarrierer eller operasjon av disse har sviktet. Translated to English the definition will be: A blowout is an incident where formation fluid flows out of the well or between formation layers after all the predefined technical well barriers or the activation of the same have failed . The definition does however not seem to have become a part of the final new NPD regulation, but remains the database blowout definition. Well release definition: The reported incident is a well release if oil or gas flowed from the well from some point were flow was not intended and the flow was stopped by use of the barrier system that was available on the well at the time the incident started. Shallow gas definition: Any gas zone penetrated before the BOP has been installed. Any zone penetrated after the BOP is installed is not shallow gas (typical Norwegian definition of shallow gas).

All shallow gas incidents in the database have at the extent possible been categorised acco rding to the typical Norwegian definition of shallow gas. This definition is not relevant for all US GoM incidents because: 







US GoM OCS reservoirs vary highly in depth. Some reservoirs were as shallow as 200 meters. For some incidents they had sat a full BOP stack, but had now intention to use it because it would likely cause a blowout outside the casing and a possible crater. For some incidents they had drilled very deep without running an extra casing string and the BOP. And for some incident they had used a combination of a BOP and a diverter.

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Further, for many of the incidents the description of the incident in the sources is insufficient, and some assumptions have to be made. A general comment is that it is not easy to categorise all the incidents in shallow and deep incidents because of the above.

1.4 Category and Sub-category The categories and subcategories utilised when classifying the incidents in the SINTEF Offshore Blowout Database are shown in Table 1.2. Table 1.2 Main

Blowout and well release

Main categories and subcategories for the incidents in the SINTEF Offshore Blowout database Category Blowout (surface flow)

Blowout (underground flow)

Sub category 1. Totally uncontrolled flow, from a deep zone 2. Totally uncontrolled flow, from a shallow zone 3. Shallow gas “controlled” subsea release only 4. Underground flow only 5. Underground flow mainly, limited surface flow

Well release

6. 7.

Diverted well release Unknown

8.

Limited surface flow before the secondary barrier was activated Tubing blown out of well, then the secondary barrier is activated

Shallow gas controlled flow (diverted) Unknown

Comments/Example Totally uncontrolled incidents with surface/subsea flow. Typical the diverter system fails Typical incident is that riserless drilli ng is performed when the well starts to flow. The rig is pulled away The limited surface flow will be i ncidents were a minor flow has appeared, but typical the BOP has been activated to shut the surface flow Typical incident will be that flow is through the drillpipe and the shear ram is activated Typical incident occurring during completion or workover. Shear ram is used to close the well after the tubing has been blown out of the well. All incidents were the diverter system functioned as intended. Unknown may be selected for both the category and the subcategory

The list of sub-categories, shown in Table 1.2, may be extended if found appropriate. One option will be to split the sub category for Well release further down to highlight incidents with an ignition potential.


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1.5 Phase of operation Each of the blowout/well releases in the database is categorised in the phase of operation they occurred. Table 1.3 shows the pre-set codes used for phase of operation. Table 1.3

Phase of operation

Description COMPLETION DEV.DRLG EXPL.DRLG PRODUCTION UNKNOWN DRLG UNKNOWN WIRELINE WORKOVER

Remarks Activities associated to well completion activities Development drilling Exploration drilling, includes wildcats and appraisal wells Production, injection, closed in wells When it is not known whether it is DEV.DRLG or EXPL.DRLG Unknown Wireline operations in connection with a production/injection well, not wireline operations carried out as a part of well drilling, well completion or well workover Workover activities, not including wireline operations. Snubbing and coiled tubing operations

1.6 North Sea Standards The intention with the field North Sea Standards is to identify blowout/well release incidents that likely would have been prevented in North Sea operations because the procedures or equipment utilised when the incident occurred are different from North Sea equipment or procedures. Table 1.4 presents the coding used for this field. Table 1.4

North Sea standards Description

Yes No, no shear ram No, BOP not North Sea standard No, two barrier principle not f ollowed Sometimes not relevant, BOP removed to install casing seal Unknown Not evaluated

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Page: 13

2. Overview of Blowouts/Well releases Included in the Database

2.1 Introduction The SINTEF Offshore Blowout Database does per January 2006 include information about 524 offshore blowouts/well releases that have occurred world-wide since 1955. The number of blowouts/well releases related to the different periods is presented in Table 2.1 Table 2.1

Number of blowouts/well releases related to the different periods Period

No. of blowouts/well releases

1950-ties 1960-ties 1970-ties 1980-ties 1990-ties 2000 - 2006

9 54 114 176 112 65

Total

530

Blowouts/well releases that have occurred in the period 1980-01-01 - 2005-01-01 in US GoM OCS, UK, and Norway are focused on. Blowouts/well releases that have occurred after 2005-0101 are not included in this report at all. Blowouts/well releases from before 1980 and the rest of the world are only briefly included. The database structure and coding are presented in "SINTEF Offshore Blowout Database, Version 4.0”, User's Manual, September 2006” and the help file for the database program.

2.2 Data Quality SINTEF's intention is to collect data from all occurring blowouts. However, it is a fact that many blowouts/well releases occurring in this period have never been recorded in the database. This because, public sources, which are the main source of information for blowouts/well releases occurring outside US GoM OCS, and UK, and Norway, do frequently not describe blowouts/well releases with small consequences. Therefore, several blowouts/well releases are believed to be missing from the database. It is SINTEF's belief that from 1980-01-01 most blowouts occurring in the US Gulf of Mexico (GoM) Outer Continental Shelf (OCS), the UK, and Norway have been included in the database. The quality of data related to blowouts occurring after 1970-01-01 is significantly better than the data from before 1970. However, for many blowouts the quality still is low because proper descriptions of the incidents are lacking. Blowout information is frequently hidden from the public.

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For each of the blowout/well release records in the databas e the quality of the source material is given. Table 2.2 shows an overview of the data quality for the blowouts/well releases that have occurred in the period 1980-01-01 – 2005-01-01. Table 2.2

Quality of blowout/well release data source material

Quality of blowout/well release data source material Very good Good Fair Low Very low Total

All blowouts except US GoM OCS, UK, and Norwegian blowouts in the period 1980-01-01 – 2005-01-01

Only US GoM OCS, UK, and Norwegian blowouts in the period 1980-01-01 – 2005-01-01

7 9 19 32 72 139

55 44 51 39 20 209

2.3 Overview of Countries Represented in the Database In Table 2.3 shows an overview of the number of blowouts and well releases for the countries represented in the database.


Table 2.3

Page: 15

Overview of countries represented in the database

COUNTRY ANGOLA AUSTRALIA AZERBAIJAN BRAZIL BRUNEI BURMA CABINDA CANADA EAST CANADA NORTH CHINA CONGO DENMARK DUBAI EGYPT EQUATORIAL GUINEA ETHIOPIA GABON GERMANY INDIA INDONESIA IRAN ITALY LIBYA MALAYSIA MEXICO NETHERLANDS NIGERIA NORWAY PAPUA NEW GUINEA PERU PHILLIPPINES QATAR SAUDI ARABIA SOUTH KOREA SPAIN TAIWAN THAILAND TRINIDAD UK UNKNOWN US US/ALASKA State US/CALIFORNIA OCS US/CALIFORNIA state US/GOM NOT OCS US/GOM OCS USSR VENEZUELA VIETNAM YUGOSLAV Total

50ties

60ties

70ties 2

80ties 1 1

2 1

1 1 1 1 2

90ties 1

1Jan 00 31 Dec 04 1 3

3 1 1 2 2 1 2

later than 1 Jan 05

1 1 1

1

1

1 3

2 1

1 1 1

1 1

4 4 1 1 2

3

3 3

1

3 11 7 1 2 6 1 2 13 1

5 2 1 1

4

2

1

1 10

2

2 1 2 1

3

1 1

1

4

4 1

1 8

2 2 1 11

2 4

1

1 3

9 52

5 32

1 1 1 1 2 6

5 30

1 3

17 58 2

2 7 77 6 3

4

1 1

9

1 54

114

176

112

60

5

Total 1 5 4 4 4 1 2 2 3 3 3 1 3 5 1 1 1 1 8 21 13 3 1 3 11 1 9 28 2 2 1 2 5 1 1 2 2 8 28 1 2 5 5 2 45 259 8 4 1 1 530

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2.4 During what Operational Phases do Blowouts/Well Releases Occur? In Table 2.4 and Table 2.5 no. of blowouts/well releases have been related to the operational phases. Table 2.4

No. of blowouts/well releases experienced during different operational phases (including all blowouts/well releases until 2005-01-01)

PERIOD

Dev. drlg 43 24.3% 87 25.0% 130 24.8%

Before 1980 1980 to 2005-01-01 Total

Table 2.5

UK, and Norwegian waters US GoM OCS

* **

Unk. drlg 1 0.6% 7 2.0% 8 1.5%

Completion 12 6.8% 21 6.0% 33 6.3%

Workover 18 10.2% 52 14.9% 70 13.3%

Produ- Wireline Unction known 20 3 5 11.3% 1.7% 2.8% 36 8 14 10.3% 2.3% 4.0% 56 11 19 10.7% 2.1% 3.6%

Total 177 348 525

Area specific overview of no. of blowouts/well releases experienced during different operational phases (including all blowouts/well releases 01-01-1980 - 2005-01-01)

AREA

Rest of the world Total

Expl. drlg 75 42.4% 123 35.3% 198 37.7%

Dev. drlg

Expl. Unk. Comp- WorkProduction WireUndrlg ** drlg letion over External No ext. line known cause* cause* 7 25 2 3 6 1 1 3 4.2%

Total

Total excl. ext. cause* 48 47

14.6%

52.1%

6.3%

12.5%

2.1%

2.1%

6.3%

50

46

12

31

6

9

5

2

100.0%

161

31.1%

28.6%

7.5%

19.3%

3.7%

5.6%

3.1%

1.2%

100.0%

30

52

5

6

15

10

9

12

139

21.6%

37.4%

3.6%

4.3%

10.8%

7.2%

6.5%

8.6%

100.0%

87

123

7

21

52

17

19

8

14

25.0%

35.3%

2.0%

6.0%

14.9%

4.9%

5.5%

2.3%

4.0%

348

155 129 331

100.0%

External causes are typical; storm, military activity, ship collision, fire and earthquake. One of the Expl. drilling blowouts in the "rest of the world” was caused by volcanic activities

When reading Table 2.5, it is important to note that the most thorough data is from the US GoM OCS, UK, and Norway. In the US GoM OCS they have experienced a relatively high no. of blowouts/well releases during development drilling compared to exploration drilling. This is explained by the fact that in US GoM OCS they are drilling relatively more development wells than exploration wells, compared to UK and Norway. Further, the relatively high no. of well workover blowouts/well releases in US GoM OCS area does indicate that the number of workovers in that area is high. It should, further, be noted that external loads caused approximately 50% of the production blowouts. External causes are discussed in Section 4.7, on page 29.


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2.5 No. of Blowouts/Well releases per Year In Table 2.6 shows a year-to-year overview of no. of blowouts/ well releases for US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01. Table 2.6 Year

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

*

Year to year overview of no. of blowouts/well releases for US GoM OCS, UK, and Norway in the period 1980-01-01 – 2005-01-01

Dev. Drlg 2 2 5 7 1 2 1 1 1 4 3 4 2 2

1 3 3 3 3 3 2 1 1 57

Appraisal 1 1 2 2

Expl. Drlg WildUncat known 2 2 3 6 6

2 5 2 1 1 2 1

3 2 2 3 1 1 1 2 4

1 2

3 1 1

1 24

2 45

UnComp- WorkProduction Wire- UnTotal known letion over External No ext. line known drilling cause* cause* 1 2 1 9 5 2 11 4 1 11 1 1 14 1 8 2 12 1 2 1 1 2 1 8 1 1 6 3 2 1 17 3 1 11 1 1 10 1 1 3 8 5 1 1 4 1 2 4 2 1 6 2 2 11 1 1 2 1 9 2 5 1 1 1 11 1 1 4 1 11 1 1 1 6 1 1 1 5 2 5 2 2 15 37 10 7 8 2 209

External causes are typical; storm, military activity, ship collision, fire and earthquake.

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3. Blowouts vs. Well Releases As explained in Section 1.4 on page 10 the incidents in the database has been categorised in blowouts and well releases. When excluding the blowouts with external causes the database includes 202 blowouts/well releases for the US GoM OCS, Norway and UK in the period January 1980 until January 2005. Table 3.1 shows an overview of the no. of blowouts/well releases within the main phases of operation, categories and sub categories. Table 3.1

Incident category

Overview of the no. of incidents within the main phases of operation, categories and sub categories for US GoM OCS, Norway and UK blowouts/well releases in the period Jan. 1980 until Jan. 2005 Sub category Shallow gas "controlled" subsea release only

Totally uncontrolled flow, from a deep zone Blowout (surface flow)

Totally uncontrolled flow, from a shallow zone

Total Underground flow mainly, Blowout limited surface flow (undergro Underground flow only und flow) Total Diverted Shallow gas controlled flow well (diverted) release Total Limited surface flow before the secondary barrier was activated Well Other release String blown out of well, then the secondary barrier is activated Total Unknown Unknown Total Total all

According to North Dev. Expl. Unk. Compl- Work- Prod- WireUnTotal Sea standard? (See drlg drlg drlg etion over uction line known Table 1.4 page11) Yes 6 1 7 Total 6 1 7 No, no acoustic backup 1 1 BOP control system No, no shear ram 1 3 5 7 16 No, two barrier 1 1 2 principle not followed Sometimes not relevant, BOP removed 2 1 1 4 to install casing seal Unknown 1 2 3 1 7 Yes 4 15 3 9 6 3 40 Total 8 22 9 20 6 4 1 70 No, BOP not North Sea 1 1 standard Sometimes not relevant, BOP removed 1 1 to install casing seal Yes 21 16 1 38 Total 22 17 1 40 30 45 1 9 20 7 4 1 117 Yes

1

2

Yes

3 4

5 7

Yes

16

9

25

16

9

25

Yes

5

8

Yes

1

1

Yes

1 7

Yes 57

9 1 1 71

3 1 1

1

5

10

2

1 1

4

10 13

35 2

1

7

9

1

6

17

2

4

2

15

37

10

8

2

46 1 1 202

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4. Overall Blowout/Well Release Experience

4.1 Blowout/Well Release vs. Flow Medium Table 4.1 shows an overview of the blowout/well release flow medium for the different incidents. Only US GoM OCS, UK, and Norwegian incidents in the period 1980-01-01 - 2005-01-01 are included. Table 4.1 Incident category

Blowout (surface flow)


Diverted well release Unknown

Well release

Total * **

Blowout/well release flow medium for US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01 Flow medium Condensate, Gas (deep) Condensate, Gas (deep), water Gas (deep) Gas (deep), Mud, Water Gas (deep), Water Oil Oil, Gas (deep) Oil, Gas (deep), H2S Oil, Gas (deep), Mud Oil, Gas (deep), Water Shallow water Shallow gas Shallow gas H2S Shallow gas, Water Shallow, unknown fluid Unknown Water Total Condensate, Gas (deep) Gas (deep) Oil, Gas (deep) Shallow gas Unknown Water Total Shallow gas Shallow gas, Mud Shallow gas, Water Total Gas (deep) Total Condensate, Gas (deep) Condensate, Gas (deep), water Gas (deep) Gas (deep), Methanol Gas (deep), Mud Gas (gas lift gas) Gas (trapped gas) Mud Oil Oil, Gas (deep) Oil, Gas (deep), Mud Oil, Water Shallow gas Shallow gas, Mud Unknown Total

Dev. Drlg

Expl. Drlg

Unk. Drlg

Comp- Work- ProdWireletion over uction* line 4 1 1 8 10 2

2 2

15 1 1

2

1 1 1

1 1 18 1 1 1 1 30 2

1

4

3

Unknown

1 2

1 17 3 3 1 1 45 1 4 1

1 1

1

9

20

7

1

1

4

1

1

1 1 1 4 14 1 1 16

1

7 7 1 1 9 1 1

1

1

1 1 1 2 1

2

3

2

1

1

8 1 1

1

1 1 1 1 2

1

1 1

1 2 1 1 1 1 3 1 7 9 1 6 17 2 4 57 71 2 15 37 10 8 2 Blowouts caused by external loads are excluded (storm, military activity, ship collision, fire and earthquake). Stems from a blowout outside the casing from a shallow zone during production

Total 7 1 37 1 1 1 13 1 1 2 1 36 4 5 1 3 2 117 1 6 2 1 2 1 13 21 2 2 25 1 1 1 1 6 1 3 1 1 5 1 11 3 1 3 1 7 46 202

Page: 22


4.2 Blowout/Well Release vs. Flow-rates The blowout/well release flow-rates from the actual incidents described in the database are poorly documented. For some blowouts flow-rate figures exis t, but for most blowouts they do not exist. The database has, however, three fields that describe the flow-rates during well tests for the actual well or close by wells. These fields are Gas volume, Oil volume and Water volume. Flow-rates are important figures in risk and environment analyses. To establish a realistic distribution of flow-rates to expect for specific fields, field specific productivity data should be compared to blowout/well release experience with respect to remaining restrictions in the wells during the blowout/well release situations. For several blowouts/well releases there are significant flow restrictions that will reduce the flow.

4.3 Severity The blowout/well release database contains a specific field describing blowout/well release severity. The quality of the information in this field is relatively low. These data are therefore not presented in this report. However, it should be noted that most of the blowouts/well releases do cause relatively small damages.

4.4 Ignition of Blowouts/Well Releases In Table 4.2 and Table 4.3 experienced data related to ignition of blowouts/well releases are presented. Only incidents from the period 1980-01-01 - 2005-01-01 have been included. It has been chosen to separate US GoM OCS, UK, and Norwegian blowouts/well releases from the rest of the world. Blowouts caused by external loads (storm, fire etc. are not included) Please note that it should not be differed between ignition probability for an oil blowout/well release and a gas blowout, because for oil blowouts the volume of gas blowing is very high compared to the volume of oil blowing.


Table 4.2

Page: 23

Experienced ignition for US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads (storm, fire etc.) are not included

PHASE

Deep or shallow

No ignition

Immediate ignition (<5 mins)

5 mins – 1 hour

Delayed ignition 1 hour – 6 hrs – 6 hrs 24 hrs

>24 hrs

Total

Blowout (surface flow) Dev.drlg Expl.drlg Unknown drlg Completion Workover Production Wireline Unknown

Deep Shallow Deep Shallow Shallow

Total

5 16 16 22 1 6 15 7 4 1 93 79.5%

2 2 2

1 2

1 4

1

1 2 1

9 7.7%

3 2.6%

1

1 1

2

2 1.7%

7 6.0%

3 2.6%

8 22 22 23 1 9 20 7 4 1 117 100.0%

Blowout (underground flow) Dev.drlg Expl.drlg Production Unknown

Deep Shallow Deep

3 1 7 1 1 13 100.0%

Deep Shallow Deep Shallow Deep

5 1 7 2 1 6 16 2 4 44 95.7%

Total

3 1 7 1 1 13 100.0%

Well release Dev.drlg Expl.drlg Unknown drlg Completion Workover Production Wireline Total

5 2 7 2 1 6 17 2 4 46 100.0%

1

1

2 4.3%

Diverted well release Dev.drlg Expl.drlg

Shallow Shallow

Total

16 8 24 96.0%

1 1 4.0%

16 9 25 100.0%

4 2.0%

1 1 100.0% 202 100.0%

Unknown Expl.drlg

Deep

Total

All blowouts/well releases

1 1 100.0% 175 86.6%

11 5.4%

2 1.0%

7 3.5%

3 1.5%

Page: 24

Table 4.3


Experienced ignition for rest of the world (US GoM OCS, UK, and Norway are not included) blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads are not included.

PHASE

Development drilling Exploration drilling Unknown drlg Completion Workover Production Unknown Total

No ignition 15 35 2 1 8 5 6 72 56.3%

Ignited blowouts Immediate ignDelayed ition (<5mins) ignition 11 4 8 5 1 2 4 1 4 3 1 3 3 32 18 25.0% 14.1%

Total Unknown

3

3 6 4.7%

30 51 5 6 15 9 12 128 100.0%

If comparing Table 4.2 and Table 4.3, far more ignited blowouts/well releases in the material for the "rest of the world". The main reason is probably that from "rest of the world" blowouts with small consequences are more seldom reported.

4.5 Blowout/Well Release Duration In Table 4.4 the experienced blowout/well release duration is presented. Only US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01 have been included. Blowouts caused by external loads (storm, fire etc.) are not included. It should be noted that bridged or depleted are listed as primary cause for regaining well control for 30 out of the 45 exploration drilling Blowout (surface flow), and 13 of the 30 development drilling Blowout (surface flow). For the diverted well releases (both exploration and development drilling) bridged or depleted are listed as primary cause for regaining well control for 13 out of the 25 well releases.


Table 4.4

Page: 25

Blowout/well release duration for US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads (storm, fire etc.) are not included

Shallow 10min < T Q 40min < T Q 2 hrs < T 12 hrs < T 2 days < T T Q10 mins or deep 40min 2 hrs Q 12 hrs Q 2 days Q 5 days Blowout (surface flow) Deep 1 2 1 1 Dev.drlg Shallow 3 2 4 4 Deep 1 2 6 4 Expl.drlg Shallow 1 2 4 2 7 Unknown drlg Shallow Completion 1 3 1 Workover 1 4 8 2 Production 4 1 Wireline 1 2 1 Unknown 1 2 7 17 29 20 Total 0.9% 1.7% 6.0% 14.5% 24.8% 17.1% Phase

Blowout (underground flow) Deep Dev.drlg Shallow Expl.drlg Deep Production Unknown

1 1

Total Diverted well release Dev.drlg Shallow Expl.drlg Shallow

2 2 8.0%

Total

3 1 4 16.0%

4 1 5 20.0%

1

1 7.7%

1 7.7%

1 7.7%

3 4 7 28.0%

1 2 3 12.0%

1 1 2 8.0%

T>5 days

Unknown

1 4 4 4

2 5 5 3 1

4 4 1

22 18.8% 1 1 4 1 7 53.8%

1 1 1 19 16.2% 1 1 1 3 23.1% 2 2 8.0%

Total 8 22 22 23 1 9 20 7 4 1 117 100.0% 3 1 7 1 1 13 100.0% 16 9 25 100.0%

Well release Dev.drlg Expl.drlg Unknown drlg Completion Workover Production Wireline

Deep Shallow Deep Shallow Deep

3 1 1

2 12 26.1%

5 2 7 2 1 6 17 2 4 46 100.0%

1 1 100.0% 30 37 14.9% 18.3%

1 1 100.0% 202 100.0%

1 1

1 5 9

1

1

1 1 4

2 2

2 25 54.3%

Total Unknown Expl.drlg

2 1 5

2 4.3%

1 2.2%

3 6.5%

2 4.3%

1 2.2%

Deep

Total Total all blowouts/well releases

28 13.9%

8 4.0%

13 6.4%

28 13.9%

35 17.3%

23 11.4%

4.6 Blowout/Well Release Flow-paths and Release Points In Table 4.5 – Table 4.7 the experienced release point vs. the final blowout/well release flow paths for the various phases of operation are presented. Only US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 – 2005-01-01 have been included. Blowouts caused by external loads (storm, fire etc.) are not included.

Page: 26

Table 4.5 Incident main type

Development drilling shallow gas incidents


Release point vs. final flow-path for drilling shallow gas blowouts and well releases Final flow-path Release point

Through drill string

Blowout (surface flow) Diverted, BOP valve outlet Diverted, subsea - outside casing Diverter syst.leak Diverter syst.leak - line eroded Diverter syst.leak - line parted Diverter syst.leak - main divert Drillfloor - through rotary From wellhead Subsea - outside casing Subsea wellhead Blowout (surface flow) total Blowout (underground flow) From wellhead Blowout (underground flow) total

Exploration drilling shallow gas incidents

UnderOutside ground casing flow

Unknown

1 1

1 1

2 1 2

1 7 3

7

1 10

4

1 1 1

14 14

1 22

16 16

1 1 13

1

1 1 2 41

1 1

2 3 1 1 1 1 4 1 8 1 23

4

1

1 1 1 4 1 8 14

2

5

9 9

1

1 1 24

1

1 1 1 47

1 1 2 1 2 1 3 7 3 1 22

2 2

2 3 1

1

Total

1 1

1

Diverted well release Diverted Diverted well release total Well release Subsea wellhead Well release total Expl.drlg total Blowout (surface flow) Unknown drilling Subsea wellhead shallow gas Blowout (surface flow) total incidents Unknown drlg total Total all shallow gas incidents

Through outer annulus

1

Diverted well release Diverted Diverted well release total Well release Drillfloor - through rotary From wellhead Well release total Dev.drlg total Blowout (surface flow) Diverter syst.leak Diverter syst.leak - line eroded Diverter syst.leak - line parted Drillfloor - through rotary Drillfloor - top of drill string From wellhead Subsea - outside casing Subsea crater Subsea wellhead Unknown Blowout (surface flow) total

Through annulus

9 9 1 1 3

16

5

9

1

1

2 2 34

2

1 1 1 76

Most shallow gas blowouts/well releases have their final flow-path through the well bore annulus. The flow is either diverted without any problems, the diverter system fails, or the flow is released through the subsea wellhead.


Table 4.6

Page: 27

Release point vs. final flow-path for “deep” drilling blowouts and well releases

Incident Through Through Through UnderFinal flow-path Through Outside Unmain drill test outer ground Release point annulus casing known type string string annulus blowout Blowout (surface flow) Drillfloor - choke manifold 1 Drillfloor - through rotary 1 From wellhead 2 2 Subsea - outside casing 1 Unknown 1 5 2 1 Develop- Blowout (surface flow) total Blowout (underground flow) ment drilling No surface flow 3 deep 3 Blowout (underground flow) total Well release Drillfloor - through rotary 1 2 Subsea - outside casing 1 Unknown 1 Well release total 1 2 1 1 1 7 2 2 3 1 Total

Exploration drilling deep

Blowout (surface flow) Bop valve outlet Diverter syst.leak - line parted Drillfloor - through rotary Drillfloor - top of drill string From wellhead Shaker room Subsea - outside casing Subsea BOP Subsea BOP (choke line flexible) Subsea crater Subsea wellhead Blowout (surface flow) total Blowout (underground flow) No surface flow Subsea - outside casing Unknown Blowout (underground flow) total Well release Diverted Drillfloor - through rotary Drillfloor - top of drill string Drillfloor - tubing valve Well release total

1 1 2 1 2 1

1

3 5

1 1 1 1

10

7 5 1 1

5

1 1

1 3

2

4

Unknown Unknown Unknown total Total Well release Unknown Drillfloor - through rotary Drilling Well release total deep Total

3

TOTAL ALL DEEP

3

1

14

4

8

5

1 1 2

1 1 1

2

22

3 3 3 1 1 5 16

5 1 1 7 1 3 2 1 7

2 1 1

1 1 4 1 1 8

1 1 3 2 5 1 5 1 1 1 1 22

1

1 4

Total

1 1 37 1 1 1

6

10

8

3

54

Through annulus is the most common final flow-path for both exploration and development drilling “deep” blowouts/well releases. Forty percent of the deep drilling blowouts/well releases was flowing through the annulus. Ten incidents came outside the casing, causing subsea releases. One of them also ignited when the gas reached the surface. In general subsea releases are more frequent for exploration well blowouts than for development well blowouts. This was also observed for the shallow gas blowouts. Ten incidents only caused underground flow. Probably more of these incidents occur than reported in the database.

Page: 28


Table 4.7

Phase

Release point vs. final flow-path for completion, workover, production and wireline blowouts and well releases Final flow-path

Release point

Blowout (surface flow) Drillfloor - drill pipe valve Drillfloor - through rotary Drillfloor - top of drill string/tubing From x-mas tree (choke body) Mud room CompBlowout (surface flow) total letion Well release Drillfloor - through rotary Drillfloor - top of tubing Shaker room Well release total COMPLETION TOTAL Blowout (surface flow) BOP valve outlet Drillfloor - through rotary Drillfloor - top of drill string Drillfloor - top of tubing Drillfloor - tubing valve From wellhead From x-mas tree Mud room Subsea - outside casing WorkUnknown over Blowout (surface flow) total Well release BOP valve outlet Drillfloor - through rotary Drillfloor - top of drill string Drillfloor - top of tubing From above x-mas tree From x-mas tree Well release total WORKOVER TOTAL Blowout (surface flow) From wellhead From x-mas tree Subsea - outside casing Subsea crater Subsea x-mas tree ProdBlowout (surface flow) total uction Blowout (underground flow) No surface flow Blowout (underground flow) total Well release From x-mas tree Well release total PRODUCTION TOTAL Blowout (surface flow) Drillfloor - wireline stuffing box/BOP From above x-mas tree From x-mas tree Blowout (surface flow) total WireWell release line From above x-mas tree From x-mas tree Unknown Well release total WIRELINE TOTAL Blowout (surface flow) From wellhead Blowout (surface flow) total Unknown Blowout (underground flow) No surface flow Blowout (underground flow) total UNKNOWN TOTAL Total

Through Through Through Through Through Outside Undercoiled drill tubing annulus outer casing ground tubing string annulus blowout 1

1 1 5 1 1 9

1 3

4

2 1 1 4

1 3

3 2 1 6 15

2 1 1 5

2 6

3 4 4 2

1

4 2 4 3 1 2 1 1 1 1 20

1

1 9 1 2 2 2 17 37

4 1

2 1 1 1

1

1 1 1

1

5

3

5

1 1 2 1 1 6 9 1 1

1 9

1

1 8

1 1 11 20

1

1

1

3 1 1 1 1 7

1 1 1 3

2 2 5

1

1

1

1

2

2

1 1

1 1

1

2 2 10

1 2 1 3 2 1 1 4 7

1

10

27

25

Total

1

1 2 1 4

1

2 1 1 4 8

1 1

1 1

1 4

3

1 1 1 2

1 1 2 72


Page: 29

Most blowouts during completion result in flow through the tubing or the drill string/work string. It is important to note that for several of these blowouts the BOP stack did not include a blindshear ram (Table 3.1 on page 19). With a blind-shear ram these blowouts could have been stopped at an earlier stage, and they would in many cases not have been categorised as a blowout. It is not mandatory to use blind-shear rams in US OCS surface BOPs. The normal flow-paths for workover blowouts/well releases are either through the drill string/tubing or through the annulus. It is important to note that for several of these blowouts the BOP stack did not include a blind-shear ram (Table 3.1 on page 19). Further, the drill string/tubing blowouts are mostly released from the top of the drill string/tubing hanging in the rotary table slips. Annulus blowouts do mostly come through the rotary. Wireline blowouts typically flow through the tubing and the release point is above the X-mas tree. Eight of the ten production blowouts came to the air in the wellhead/X-mas tree area. The last two came outside casing at the sea bottom, one of them caused a crater.

4.7 Blowout/Well Release Causes Normally to experience a blowout, at least one primary and one secondary barrier have to fail. For drilling, workover and completion blowouts the primary barriers are usually the hydrostatic pressure from the mud column and the secondary barrier is the mechanical barriers, either subsea or on the installation. For production wells the primary and secondary barriers are mechanical barriers. It should be noted that when drilling in shallow zones there is normally only one blowout barrier. The installations do, however, have means for forcing the gas away from the installation. In this report those means are treated as a secondary barrier. The blowout database does contain fields for describing the blowout/well release causes, i.e. why were the primary and secondary barrier lost? Further, the database contains one field that describes whether the blowout/well release was "caused" by an external load. Out of the 209 blowouts/well releases from US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01, seven were "caused" by an external load (Table 2.6, page 17). It is, however, important to note that an external load normally only ruins the topside barrier. To ex perience a blowout, the downhole barrier also has to fail. So an external load will not be the single blowout cause. Typically the external load ruins the wellhead/X-mas tree barriers of an active well, and the downhole barrier fails to activate or is leaking.

Page: 30


Table 4.8 shows an overview of blowouts caused by external loads. Table 4.8

Overview of blowouts caused by external loads for US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01

Water OperPhase depth (m) ation 6 Closed Prodin gas uction well

Activity Well closed in

External cause Ship collision

143

12

10

13

10

15

Prod- Producuction ing oil

Fire/Gas lifting explosion

Prod- Producuction ing gas

Regular Ship production collision


Regular Storm production







Primary barrier C5.SCSSV/storm choke failure (Not enough surge to close valve) C5.SCSSV/storm choke failure & C4.Tubing to annulus communication, equipment or nipple failure (5 to 6 wells failed) C5.SCSSV/storm choke failure (not installed?)

Secondary barrier

Flowmedium

A8.X-mas tree failed (leakage between tubing head flanges and master valve)

Oil, Gas (deep)

A8.X-mas tree failed (all trees failed due to topside fire)

Oil, Gas (deep)

A8.X-mas tree failed (due to collision)

Oil, Gas (deep)

C5.SCSSV/storm choke failure A8.X-mas tree failed (Assumed, may also have been (damaged by storm) a tubing annulus communication) C5.SCSSV/storm choke failure A8.X-mas tree failed (Assumed, may also have been (damaged by storm) a tubing annulus communication) C5.SCSSV/storm choke failure A8.X-mas tree failed (Assumed, may also have been (damaged by storm) a tubing annulus communication) B4.Wellhead failed C5.SCSSV/storm choke failure (hurricane damage)

Oil

Oil

Oil Oil

Table 4.9 and Table 4.10 show the different causes for loosing the primary and secondary barriers, as reported in the database.


Table 4.9 Category

Blowout (surface flow)


Diverted well release

Well release

Unknown Total

Page: 31

Primary barrier failure causes listed in the database for the US GoM OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005

PRIMARY BARRIER FAILURE Too low mud weight Annular losses While cement setting Trapped gas Too Swabbing low Gas cut mud hyd. Improper fill up head Disconnected riser Unexpected high well pressure Reservoir depth uncertainty Cement preflush weight too low Unknown why Poor cement Formation breakdown Stripper bop failure Snubbing equipment failure X-mas tree failure Tubing to annulus tubing leakage communication equipm./nipple SCSSV/storm choke failure Well test string barrier failure Wireline stuffing box failure Wireline lubricator failure Packer plug failure Tubing plug failure Unknown Total no. of primary barrier failures Incidents with two prim. barrier failures No. of blowouts (surface flow) Too low mud weight Too Annular losses low While cement setting hyd. head Unexpected high well pressure Unknown why Tubing leakage Unknown No. of blowouts (underground flow) Too low mud weight Too Annular losses low While cement setting hyd. Swabbing Head Unexpected high well pressure Unknown why Total no. of primary barrier failures Incidents with two prim. barrier failures No. of diverted well releases Too low mud weight Annular losses Too Drilling into neighbour well low Trapped gas hyd. Swabbing Head Gas cut mud Unexpected high well pressure Unknown why Poor cement Coil tubing failure Snubbing equipment failure X-mas tree failure Tubing burst SCSSV/storm choke failure Well test string barrier failure Wireline lubricator failure Packer plug failure Other Unknown Total no. Of primary barrier failures Incidents with two prim. barrier failures No. of well releases Unknown No. of unknown incidents

Dev.drlg Expl.drlg Unk. drlg Comp- Work- Prod- Wire- Unk- Total Deep Shal.Deep Shal. Deep Shal. letion over uction line nown 2 3 3 2 3 13 1 1 2 1 1 6 3 9 4 2 1 19 1 1 6 2 3 2 4 17 2 2 4 1 1 2 1 1 2 1 3 5 1 10 1 1 2 1 1 1 3 2 4 1 1 12 1 1 1 1 4 1 1 2 1 1 4 4 1 1 1 1 2 1 1 2 1 4 5 1 1 1 1 2 2 1 1 1 1 2 1 1 2 8 23 23 23 1 9 20 7 4 1 119 1 1 2 8 22 22 23 1 9 20 7 4 1 117 1 1 2 1 1 1 1 1 1 2 1 2 3 1 1 2 1 3 3 1 7 1 1 13 1 2 3 4 1 5 3 1 4 9 9 1 4 5 1 1 18 9 27 2 2 16 9 25 1 1 2 1 1 1 1 1 5 6 1 1 1 3 2 8 1 1 3 1 1 5 1 1 1 3 1 1 2 1 1 2 2 1 1 1 1 2 1 2 5 1 1 2 1 1 1 1 2 1 3 1 1 2 5 2 7 2 1 6 19 2 4 48 2 5 2 7 2 1 6 17 2 4 46 1 1 1 1 16 41 37 34 1 1 15 37 10 8 2 202

Page: 32


Table 4.10 Secondary barrier failure causes listed in the database for the US GoM OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005. Category

SECONDARY BARRIER FAILURE

String safety valve failed String safety valve not available Failed to stab kelly valve SCCSV/storm choke failed X-mas tree failed Failed to close BOP Diverted - no problem Failed to operate diverter Diverter failed after closure Drilling without riser Disconnected riser Annulus valve failed Not sufficient frictional backpressure BOP failed after closure Blowout (sur- BOP/diverter not in place Wellhead failed face Casing head failed flow) Tubing to annulus communication Poor cement Casing valve failure Wellhead seal failed Inner casing failed Fracture at csg shoe Casing leakage Formation breakdown Not relevant Not relevant - only one barrier present Unknown Total no. of secondary barrier failures Incidents with two sec. barrier failures Blowout (surface flow) total Failed to close BOP Diverted - no problem Fracture at csg shoe Blowout Casing leakage (under- Formation breakdown ground Unknown flow) Total no. of secondary barrier failures Incidents with two sec. barrier failures Blowout (underground flow) total Divert- Diverted - no problem ed well Diverted well release total release String safety valve failed String safety valve not available Failed to stab kelly valve Wireline bop/lubricator not installed SCCSV/storm choke failed X-mas tree failed Coiled tubing stuffing box failed Failed to close BOP Diverted - no problem Well Drilling without riser release Not sufficient frictional backpressure BOP failed after closure Wellhead failed Wellhead seal failed Outer casing failed Fracture at csg shoe Not relevant Other Unknown Well release total UnUnknown known Unknown total Total no. of incidents

Dev.drlg Expl.drlg Unk. drlg Compl- Work- Prod- Wire- Unk- Total nown Deep Shal. Deep Shal. Deep Shal. etion over uction line 1 1 2 4 1 1 2 4 1 3 3 7 1 1 1 4 2 7 1 1 1 2 6 11 1 1 3 3 7 1 8 16 1 5 6 1 1 1 1 1 1 2 1 5 1 9 3 4 3 1 1 12 1 1 1 1 2 1 1 3 3 6 1 1 1 1 2 1 1 2 4 6 1 4 1 1 2 9 1 1 2 1 1 1 2 1 2 6 1 1 1 3 8 24 25 25 1 10 20 7 4 1 125 2 3 2 1 8 8 22 22 23 1 9 20 7 4 1 117 1 1 1 1 1 1 1 3 2 1 3 1 1 2 1 3 1 5 3 2 8 1 1 15 1 1 2 3 1 7 1 1 13 16 9 25 16

9

25

1

1 1 1

2

1

2

1 1

1

2

1 1 1 1

1 1

1

1 1

1

1

6 1

1 1

1 1

1 1

1

1 5

2

16

41

1 7 1 1 37

2

1

34

1

1

2

1 6

17

2

1 1 4

15

37

10

8

2

2 1 3 1 2 3 1 7 1 1 9 1 1 2 1 1 4 1 4 46 1 1 202


Page: 33

4.8 Operations and Activities when Blowout/Well Release Occurs In Table 4.11 to Table 4.16 an overview of the operations and activities in progress when the blowouts/well releases occurred is presented for the various operational phases. The data is from the US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Table 4.11 Operations and activities in progress when the shallow gas blowouts/well releases occurred Operation Activity BLOWOUT (SURFACE FLOW) Actual drilling Well suspended Tripping out Out of hole Coring Milling (and reaming) Cementing casing Wait on cement Install BOP Nipple down BOP Changing equipment Wait on weather Unknown Total no. of activities No. of blowouts listed with two activities No. of blowouts (surface flow) BLOWOUT (UNDERGROUND FLOW) Wait on cement No. of blowouts (underground flow) DIVERTED WELL RELEASE Actual drilling Tipping out Circulating Casing running Cementing casing Wait on cement Unknown No. of diverted well releases WELL RELEASE Actual drilling Tripping out Leak off test Unknown No. of well releases TOTAL ALL SHALLOW INCIDENTS

Casing running

Drilling activity Dev.

Expl.

Unk. drlg

2

10

1

Other/unknown operations

Dev. Expl.

Dev.

Expl.

1 6

2 1 1

Total Dev.

Expl.

Unk. drlg

2 1 6

10

1

1 1 9

1 2

1 9 1

1

1

1

1

1 9

2 17

1

9

17

1

11 1 10

3

1 1 3

1 3

3

3

3

1 1 2 8 1

1 2 23 1 22

5 1

2 8 1 2

1

5

23

1

1 2

1

16

5 1

7 9 1 2 1 3 2 25

2 9

1 1

1 1

1 1 24

1

1 1 17

4

3

1 6

1 2 41

13 1 8 1 1 1 2 11 1 1 1 1 5 47 1 46 1 1

3

1

1 21

1

1

3 1 6

3 23

1 1

2

11

2 1 1 1 1 2 1

Total

2 34

1

1 1 1 1 4 76

Page: 34


Table 4.12 Operations and activities in progress when the “deep” drilling blowouts/well releases occurred Drilling activity

Operation Activity

Dev.

Blowout (surface flow) Actual drilling Tripping out Out of hole Casing running Cementing casing Wait on cement Install bop Nipple down BOP Actual well test Unknown Pull wireline Total no. of activities No. of blowouts listed with two activities No. of blowouts (surface flow) Blowout (underground flow) Actual drilling Unknown No. of blowouts (underground flow) Well release Actual drilling Tripping out Gravel pack Circulating Pulling casing Pull/drill out well plugs Actual well test Maintenance surface equipment Unknown Total no. of activities No. of blowouts listed with two activities No. of well releases Unknown UNKNOWN No. of unknown incidents TOTAL ALL DEEP INCIDENTS

1

Casing running

Expl.

Dev.

Other/unknown operations Unk. Dev. Expl. Drlg

Expl.

10 3 1

Total Dev. 1

3 1

1 1 4

3 1

2

1

2

1

8

1

15

4

2

15

4

3

3 1 4

3

1 2

1 1 1 8

1

2

8 2 6

3 3 3

3

4

Total

10 3 1 1 1 4

24 2 22

11 3 1 1 1 7 1 2 1 3 1 32 2 30

3 4 7

6 4 10

2

4 1 1 1 1 1

1

5

1 1 1 1 1 1 1 1 7

1

5

7

16

1 1 37

1 1

1

1

1 4

2

1

4

2

1

1 6 1 5

3

1 1 10

9

Unk. Drlg

2 1

1

Expl.

21

4

6

1

1 1

4 1 1 1 1 2 2 1 1 14 1 13

1

1 1 54

1

Table 4.13 Operations and activities in progress when the completion blowouts/well releases occurred Activity

Operation

Blowout (surface flow) Tripping out Circulating Killing Perforating Gravel pack Other, bleed off pressure above SCSSV Unknown No. of blowouts(surface flow) Well release Tripping out Tripping in Flow check Perforating Gravel pack Maintenance well equipment Total no. of activities No. of well releases listed with two activi ties No. of well releases Total no. of incidents

Running well Well testing Coiled Other/ Circulating Perforating equipment incl.prepare tubing unknown 2 1 1 1 2 1 3

2

1 3

1

1

1 1

1 1 1 1 1 4

2 1 1 1

2

1

1 1

2

1 2

1 1

1 5

Total 2 1 1 1 2 1 1 9 2 1 1 1 1 1 7 1 6 15


Page: 35

Table 4.14 Operations and activities in progress when the workover blowouts/well releases occurred Pulling well equipment

Operation Activity BLOWOUT (SURFACE FLOW) Tripping out Tripping in Out of hole Circulating Pulling casing Cement squeeze Set well plug Pull tubing Perforating Gravel pack Cleaning well Coiled tubing operations Snubbing in Unknown Total no. of activities No. of blowouts listed with two activities No. of blowouts (surface flow) WELL RELEASE Circulating Install BOP Pull/drill out well plugs Nipple down x-mas tree Snubbing out Pull tubing Acidizing Run coiled tubing Coiled tubing operations Changing equipment No. of well releases Total no. of incidents

Running Well Installing Abanwell testing Circu- Snubb- Coiled Perforequipdon Total equipincl. lating ing tubing ating ment well ment prepare

2 1 1 1 1

1 1 1

1

1 1 1 1

5

1

2

1

2

1 1 3

5

1

2

1

2

3

1 1 2 4 1 3

1 1

2

1

2

1 1 1 1 2 6

1 1 1 1

7 12

1 2 4

1

1

2

2 5

2 5

1 2

3 5

2 1 1 2 1 1 1 2 1 1 2 1 4 1 21 1 20 1 1 1 1 2 7 1 1 1 1 17 37

Table 4.15 Operations and activities in progress when the production blowouts/well releases occurred Operation Activity BLOWOUT Regular production Failure diagnosing No. of blowouts

Producing Producing oil condensate 1

Producing gas 3

1

3

BLOWOUT (UNDERGROUND FLOW) Failure diagnosing No. of blowouts (underground flow)

Unknown

1 2 2

1

1 1

WELL RELEASE Regular Production No. of well releases TOTAL NO. OF INCIDENTS

Closed in gas/condensate well

2

5 2 7 1 1

2 2 1

Total

2 2 3

3

1

10

Page: 36


Table 4.16 Operations and activities in progress when the wireline blowouts/well releases occurred Operation Activity BLOWOUT (SURFACE FLOW) Run wireline Pull wireline Logging No. of blowouts WELL RELEASE

Rigging up wireline equipment

Changing Equipment Run wireline Unknown No. of well releases Total no. of incidents

Running wireline operations 2 1 1 4

2 1 1 4

2 1 3 7

1 2 1 4 8

1

1 1

Total

The blowout listed with “Unknown” as Phase was a Blowout (underground flow) with no information related to operation and activity.

4.9 Exploration Wildcats vs. Exploration Appraisal Wells The exploration wells for the US GoM OC, UK waters and Norwegian waters have now been categorized in exploration wildcats and exploration appraisal wells. Table 4.17 Table 4.17 Exploration wildcats and Exploration appraisal wells in the database for the US GoM OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005 Main category

Shallow or deep Deep

Blowout (surface flow) Shallow Blowout (surface flow) total Blowout (under-ground flow) Blowout (underground flow) total

Deep

Diverted well release

Shallow

Exploration well type Appraisal Wildcat Appraisal Wildcat Unknown Wildcat Appraisal Wildcat

Diverted well release total Deep Well release Shallow Well release total Unknown Unknown total Total all exploration incidents

Deep

Appraisal Wildcat Unknown Appraisal Wildcat Appraisal

No of incidents 9 13 8 14 1 45 7 7 2 7 9 3 3 1 1 1 9 1 1 71


Page: 37

4.10 Blowouts from Australia, Canada East Coast, The Netherlands, and US/California OCS Exposure data from from Australia, Canada East Coast, The Netherlands and US/California OCS has been included in this report (Section 5). The associated blowouts and well releases are, however, not included in the previous chapters of the report. Table 4.18 and Table 4.19 list key data for the observed blowouts in these areas in the period 1980-01-01 - 2005-01-01. Table 4.18 Key data for blowouts observed blowouts/well releases for the Canadian East Coast, Dutch waters, and Australian waters Id_no Country Phase Category

405 Netherlands Production Blowout (surface flow) Totally uncontrolled flow, from a deep zone 15-May-83 Gas (deep)

259 266 268 548 Canada East Coast Canada East Coast Australia Australia Expl.drlg Expl.drlg Production Expl.drlg Blowout (surface Blowout Blowout (surface Blowout flow) (underground flow) flow) (underground flow) Totally uncontrolled Underground flow Totally uncontrolled Underground flow Sub category flow, from a deep only flow, from a deep only zone zone 22-Feb-84 20-Sep-84 17-Dec-84 07/02/1991 Date Condensate, Gas Gas (deep) Oil, Gas (deep) Gas (deep) Flow medium (deep) NO NO NO NO NO Ignition type 10 10 270 10 Unknown Duration days A8.Too low hyd. C4.Tubing to A15.Too low hyd. Loss of primary C3.Tubing to annulus C14.Casing plug communication failure (HP zone head - unexpected annulus comhead - unknown why barrier tubing leakage isolating bridge plug high well pressure munication broke at 5200 equipm./nip-ple meters) failure (assumed) D2.Casing leakage B1.Failed to close D2.Casing leakage D2.Casing leakage D3.Formation Loss of BOP (First annular, (assumed) breakdown secondary obstruction in barrier BOP,then S/R,- to little power to cut, then acoustic close failed) P2.Producing gas D4.Well testing D1.Drilling activity P1.Producing oil Unknown Operation (preparing to test shallow zone) P1.Regular B1.Circulating A7.Fishing P1.Regular Unknown Activity production production Fair Very good Fair Very low Low Data quality

Page: 38


Table 4.19 Key data for blowouts observed blowouts/well releases for the US California OCS Id_no Country Phase Category Sub category

449 US/California OCS Workover Well release Limited surface flow before the secondary barrier was activated 7-Mar-98 Gas (deep), Water NO Unknown

475 US/California OCS Workover Well release Limited surface flow before the secondary barrier was activated 19-Nov-00 Oil, Water NO Unknown

482 US/California OCS Dev.drlg Well release Shallow gas controlled flow (diverted)

539 US/California OCS Workover Blowout (surface flow) Totally uncontrolled flow, from a deep zone

24-Mar-01 18/11/2004 Mud Gas (deep) NO NO 0.0104 0.1042 (2.5 hrs) (15 mins) Loss of primary A15.Too low hyd. head C13.Tubing plug failure A10.Too low hyd. head A10.Too low hyd. head - unknown why - annular losses - annular losses. (Stop barrier pumping for 30 minutes for removal of lock down pin) Not relevant B10.Diverted - no B4.Wellhead failed Loss of secondary Not relevant problem (removed lock down barrier pin) W1.Pulling well W1.Pulling well D1.Drilling activity W3.Installing Operation equipment equipment equipment A2.Tripping out D6.Pull/drill out well Unknown G4.Maintenance Activity plugs surface equipment Fair Low Good Very good Data quality Date Flow medium Ignition type Duration days


Page: 39

5. “Normal” Drilling and Production Exposure Data The exposure date in this section of the report includes yearly well drilling and no. of wells in production for some specific areas. The offshore drilling wells are from Norway, UK, US GoM OCS, East Coast of Canada and the Netherlands. The production data stems from Norway, UK, and US GoM OCS. The format of the exposure data varies for the different areas.

5.1 Drilling Exposure Data 5.1.1 US GoM OCS The drilling exposure data for the US GoM OCS stems from a computerised list of all wells drilled (/1/). A version from August 2006 was used for this report. The file include s information on borehole activities such as drilling activity, counts on the number of boreholes completed, and number of shut-in's. Additional information includes the lease number, well name, and spud date, the well class, surface area/block number, well depths, and statistics on well status summary. Per August 2006 the data-file includes information from more than 46000 wells drilled all time in the US GoM OCS. The number of wells drilled in the US GoM OCS area is presented in Table 5.1.

Page: 40

Table 5.1


Number of drilled wells in US GoM OCS area

Exploration wells Development wells Wildcat* Appraisal* Total Spud All wells Side All wells Side All wells Side All wells SideCompleted Completed year inc. tracked inc. tracked inc. tracked inc. tracked wells** wells** sidetracks wells sidetracks wells sidetracks wells sidetracks wells 1980 129 4 232 19 361 23 104 807 79 529 1981 147 8 190 13 337 21 99 870 98 571 1982 190 20 202 21 392 41 112 838 83 560 1983 177 13 204 26 381 39 112 762 116 511 1984 327 33 229 26 556 59 161 755 131 511 1985 295 28 216 39 511 67 147 662 120 439 1986 149 16 106 16 255 32 77 433 93 286 1987 196 23 200 28 396 51 116 448 84 301 1988 302 34 230 45 532 79 154 452 101 302 1989 220 31 235 38 455 69 132 511 101 348 1990 276 34 214 32 490 66 141 566 180 377 1991 164 21 166 19 330 40 98 430 127 285 1992 106 14 109 14 215 28 57 329 103 223 1993 175 20 170 39 345 59 98 570 202 385 1994 217 26 200 34 417 60 120 589 221 379 1995 187 31 189 50 376 81 110 675 293 431 1996 249 38 190 49 439 87 127 697 308 463 1997 272 52 249 70 521 122 153 837 430 565 1998 268 81 228 100 496 181 149 641 381 446 1999 200 55 170 70 370 125 121 662 367 462 2000 223 53 217 52 440 105 146 937 602 659 2001 229 56 182 56 411 112 123 852 544 531 2002 173 43 135 35 308 78 112 633 358 337 2003 200 62 154 57 354 119 114 539 306 309 2004 198 55 164 66 362 121 132 553 300 322 Total 5269 851 4781 1014 10050 1865 3013 16048 5728 10530 * To differ between Wildcats and Appraisal wells the following has been assumed; All exploration wells drilled in certain areas are numbered from 1 and further, where well number 1 is the first well dri lled. For US GoM OCS all exploration wells numbered as 1 have been regarded as Wil dcats, while all the other wells are regarded as Appraisal wells. This may be inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to no. of Appraisal wells for the US GoM OCS ** In the 2000 version and earlier versions of this report the number of completed wells as listed in the source file was used directly for this column. Closer investigation showed that when a production well is abandoned it would be re-categorized to abandoned. This will lead to an underestimation of number of completed wells. To adjust the figure to a more correct number 30 % of all exploration wells and 70% of all development wells are assumed to be completed each year for the whole period 1980 – 1999. These figures stems from the average in the period 1992 – 1997.

As seen from Table 5.1 many of the US GoM wells are side-tracked. The wells in the Gulf of Mexico are primarily side-tracked for deflecting the direction of the borehole to encounter an alternate target horizon or potential productive interval at a selected aerial l ocation. Deviation of a well bore to bypass junk in the hole is not classified as a side-track. Quite a number of wells in the Gulf of Mexico are completed in producing intervals at subsea depths between 1000 feet and 10 000 feet. In areas where the geology and formation pressures have previously been established, such development wells are routinely drilled in from 1 to 10 days, due to the unconsolidated nature of the formations at depths above 10 000 feet. It should further, be noted that the drilling period for many of the US GoM wells is of very short duration. If looking at all the wells (1980 – 2002); Approximately 25 % of the development wells were drilled in less than 10 days. Approximately 19 % of the exploration wells were drilled in less than 10 days. • •

Blowout and Well Release Characteristics Characteristics and Frequencies, Frequencies, 2006 version

Page: 41

5.1.2 United Kingdom The drilling exposure data for UK is based on "The Energy Report, Volume 2, Oil and Gas Resources of the United Kingdom", Department of Trade and Industry 1994 – 2001, and Department of Trade and industry web page (http://www.og.dti.gov.uk/information (http://www.og.dti.gov.uk/information)) for for the the past years. The number of wells drilled in the UK area is presented i n Table 5.2. 5.2. Table 5.2 Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Number of drilled wells in UK offshore sector

Exploration wells Wild cat Appraisal All wells inc. Sidetrack- All wells inc. Sidetracksidetracks ed wells sidetracks ed wells 32 22 48 26 68 43 77 51 106 76 93 64 73 40 69 63 93 3 84 14 94 2 89 14 159 7 65 11 107 1 79 19 74 2 57 16 51 1 59 12 62 3 37 10 60 7 38 12 72 3 40 7 61 2 35 12 47 4 33 17 16 2 20 3 26 3 33 11 24 2 36 18 16 2 28 10 26 2 19 9 29 3 34 12 1583 49 1171 207

Development wells Total 54 74 111 128 182 157 113 132 177 183 224 186 131 110 99 98 112 96 80 36 59 60 44 45 63 2754

All wells inc. Sidetracksidetracks ed wells 122 137 118 95 108 133 85 124 167 6 155 12 124 16 144 19 167 27 162 28 202 48 244 42 261 68 257 78 276 89 230 90 216 81 282 106 249 122 204 79 166 68 4428 979

5.1.3 Norway The drilling exposure data for Norway is based on the NPD Borehole list as published on the Internet (http://www.npd.no). NPD has from 2001 changed the well naming. This is also reflected in their borehole lists published on the Internet. The tables presenting presen ting number of drilled wells in earlier versions of this report have have been based on the number of wellbores. A wellbore is now categorized as; •

•

•

Initial well bore Re-entry Sidetrack

Page: 42

Blowout and Well Release Characteristics Characterist ics and Frequencies, 2006 version

Earlier another category named technical sidetrack also sidetrack also was included. This category is not used anymore. The practical effect is that the th e number of wells drilled has been reduced. reduced. NPD wellbore categorizing is described (http://ww http://www.npd.no/regelverk/r2002/B_og_b_betegnelser_og w.npd.no/regelverk/r2002/B_og_b_betegnelser_og_klass _klassifise ifisering_e ring_e.htm .htm ) The number and type of development wells are presented in Table 5.3. Table 5.4 presents the exploration wells drilled in the Norwegian area alongside the total number of development wells and the type of well bore. Table 5.5 shows the number of Norwegian wells drilled within each main NCS area Table 5.3

Norwegian development wells drilled

Spud year

Oil

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

20 8 12 14 16 16 25 37 25 38 44 35 48 55 68 70 58 84 72 87 89 111 123 105 111 96 1451

Gas

Production Gas/- Other/Oil/conden ungas sate known

6 5 6 1 10 11 4 13 4 3 4 2 7 7 6 11 20 19 10 8 15 13 9 7 4 203

1 2 3 3 1

2

1 4

2 6 8

1 3 2 2 2 1 22

Tota Totall 26 13 18 15 26 36 41 38 42 47 39 50 62 76 78 72 107 92 97 98 131 138 116 122 108 1688

Water Water

1 3 6 7 10 7 9 12 16 19 12 15 15 15 25 25 19 9 5 14 17 14 15 15 12 10 287

Injection Other/Water/Gas Gas unTotal gas known 2 2 2 3 2 5 3 9 1 8 2 12 2 9 1 10 1 13 3 19 2 21 1 13 1 16 3 18 4 29 3 1 23 6 1 16 10 1 1 17 8 1 23 3 6 26 10 1 25 4 2 2 23 6 2 2 25 2 6 5 25 4 14 82 19 16 404

Observation

1 8 11 13 14 20 26 19 25 29 39 26 18 16 265

All wells 28 16 23 24 34 48 50 48 55 66 60 64 86 105 120 109 143 135 139 149 185 200 167 165 138 2357

Blowout and Well Release Characteristics Characteristics and Frequencies, Frequencies, 2006 version

Table 5.4 Drilled year

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Page: 43

Number of drilled wells and type type of well bore in Norwegian offshore sector

Exploration wells Development Appraisal Wildcat Total Initial Multi- SideTotal lateral track developInitial Re- Side- Total Initial Re- Side- Total explorentry track entry track ation ment 10 1 11 26 5 31 42 27 1 28 15 1 16 24 3 27 43 16 16 13 1 1 15 35 2 37 52 21 2 23 8 2 10 32 32 32 42 21 3 24 13 2 15 33 4 1 38 53 31 3 34 20 1 21 30 2 32 53 47 1 48 10 2 1 13 24 5 1 30 43 35 15 50 11 3 1 15 24 3 27 42 36 12 48 8 2 3 13 18 18 31 46 9 55 5 4 2 11 21 3 24 35 47 19 66 8 4 2 14 26 6 32 46 43 17 60 11 7 2 20 33 3 1 37 57 52 12 64 10 5 15 27 2 1 30 45 65 21 86 7 4 11 19 4 1 24 35 75 30 105 2 3 1 6 17 3 1 21 27 78 1 41 120 10 1 4 15 22 3 25 40 73 36 109 7 1 2 10 21 1 22 32 91 52 143 8 1 4 13 33 4 5 42 55 81 1 53 135 6 3 2 11 15 3 18 29 90 3 46 139 6 1 1 8 12 1 3 16 24 95 54 149 4 2 6 18 3 21 27 107 6 72 185 5 2 4 11 24 3 1 28 39 93 18 89 200 2 2 3 7 11 1 3 15 22 73 18 76 167 6 2 2 10 12 2 2 16 26 59 32 74 165 4 4 8 10 10 18 60 28 50 138 209 50 46 305 567 63 23 653 958 1462 107 788 2357

Page: 44


Table 5.5 Norwegian drilled wells separated on main NCS area Spud year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Exploration wells Development wells Barents North Norwegian Barents North Norwegian Total Sea Sea Sea Sea Sea Sea 2 3 4 6 10 8 4 5 4 5 3 3 3 2 1

4 4

71

39 38 43 29 36 29 22 23 21 27 33 46 37 25 22 31 24 36 22 13 12 21 17 20 12 678

1 2 5 7 7 16 17 14 6 3 10 8 5 8 5 8 8 19 7 11 11 14 5 6 6 209

42 43 52 42 53 53 43 42 31 35 46 57 45 35 27 40 32 55 29 24 27 39 22 26 18 958

1 1

28 16 23 24 34 48 50 48 55 66 60 64 84 94 107 104 131 118 113 117 154 167 149 145 115 2114

2 11 13 5 12 17 26 32 31 33 18 20 22 242

Total 28 16 23 24 34 48 50 48 55 66 60 64 86 105 120 109 143 135 139 149 185 200 167 165 138 2357

Total all wells 70 59 75 66 87 101 93 90 86 101 106 121 131 140 147 149 175 190 168 173 212 239 189 191 156 3315

5.1.4 The Netherlands The drilling exposure data for The Netherlands is bas ed on information from the Dutch Ministry of Economic Affairs. The information is available on Internet: (http://www.nitg.tno.nl). The number of wells drilled in the Dutch Continental Shelf is presented in Table 5.6.


Table 5.6 YEAR 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Page: 45

Number of drilled wells on the Dutch Continental Shelf Exploration wells Exploration Appraisal Total 26 5 31 15 17 32 35 10 45 31 12 43 26 7 33 36 7 43 25 5 30 22 5 27 21 5 26 23 5 28 29 6 35 43 2 45 19 1 20 13 1 14 10 2 12 5 3 8 24 5 29 21 10 31 17 3 20 12 2 14 6 6 12 15 4 19 16 3 19 7 4 11 11 2 13 508 132 640

Development wells 7 5 20 15 24 35 15 13 21 17 14 18 15 17 10 16 6 13 13 6 9 12 13 13 6 353

Total all wells 38 37 65 58 57 78 45 40 47 45 49 63 35 31 22 24 35 44 33 20 21 31 32 24 19 993

5.1.5 Canadian East Coast Table 5.7 shows the number of wells drilled on the Canadian East Coast. Before 1980 approximately 225 wells were drilled. (http://www.gsca.nrcan.gc.ca/BASIN/DEMO/basin-f.cgi). There has in addition been drilled approximately 160 well in the Northern areas all time. No detailed data has, however, been made available from this area. Some drilling activity is also carried out on the West Coast of Canada.

Page: 46


Table 5.7 Year

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Number of drilled wells on the Canadian East Coast

Exploration Development Explora- DeliTotal DevelGas Water Cutting Service Total develtory neation exploration opment injector injector injector & relief opment 12 6 18 13 5 18 19 2 21 20 5 25 25 5 30 1 1 23 15 38 1 1 13 5 18 4 6 10 9 5 14 2 2 1 1 4 4 4 1 5 7 7 11 11 1 1 6 6 1 1 3 3 2 2 3 3 4 4 6 6 1 1 2 20 5 3 28 6 4 10 26 6 4 1 37 9 5 14 33 1 4 38 9 5 14 13 2 5 20 7 5 12 21 2 10 33 7 2 9 20 1 7 28 2 1 3 18 4 10 32 194 77 271 191 21 43 2 2 259

Total

18 18 21 25 31 39 18 10 14 2 1 9 7 11 7 4 5 10 30 47 52 34 45 37 35 530

5.1.6 US Pacific OCS Table 5.8 shows the number of wells drilled on the in the US Pacific OCS area. The data stems from MMS pacific division. Table 5.8 Number of drilled wells in the US Pacific OCS area Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Expl. wells spudded 10 14 27 38 19 6 5 4 3 4

130

Dev. wells spudded 40 50 58 44 45 39 34 39 29 15 17 8 5 21 25 19 31 29 19 11 13 16 21 18 20 666

Total 50 64 85 82 64 45 39 43 32 19 17 8 5 21 25 19 31 29 19 11 13 16 21 18 20 796


Page: 47

5.1.7 Australia Table 5.9 shows the number of wells drilled on the in Australian waters. The data stems from Geoscience Australia. Geoscience Australia is the national agency for geoscience research and geospatial information. Table 5.9 Number of drilled wells in Australian waters Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Exploration Wildcat Appraisal Original Side Original Side Total Total hole track hole track 15 3 18 2 2 13 13 5 5 42 5 47 4 4 41 3 44 4 4 29 3 32 12 12 23 23 18 18 20 20 7 7 9 1 10 6 6 27 5 32 9 1 10 32 10 42 10 4 14 46 8 54 19 6 25 34 5 39 6 4 10 28 3 31 13 2 15 36 1 37 14 3 17 28 6 34 20 1 21 32 2 34 23 2 25 34 9 43 15 15 39 1 40 19 2 21 61 5 66 10 1 11 45 5 50 9 9 60 10 70 4 4 48 3 51 10 10 31 4 35 16 3 19 44 5 49 16 16 36 36 14 4 18 853 97 950 285 33 318

Development Total 20 18 51 48 44 41 27 16 42 56 79 49 46 54 55 59 58 61 77 59 74 61 54 65 54 1268

Original hole 6 16 12 29 42 18 19 21 13 26 18 17 14 18 28 32 34 81 41 35 22 24 26 32 41 665

Side track

Total 1

1

1 6 5 1 3 6 8 4 14 8 3 3 7 8 12 7 98

7 16 12 29 43 18 19 21 13 27 24 22 15 21 34 40 38 95 49 38 25 31 34 44 48 763

Total all wells 27 34 63 77 87 59 46 37 55 83 103 71 61 75 89 99 96 156 126 97 99 92 88 109 102 2031

5.1.8 Denmark Table 5.10 shows the number of wells drilled on the offshore Denmark. The data stems from The Danish Energy Authority.

Page: 48


Table 5.10 Number of drilled wells offshore Denmark

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Exploration and appraisal 1 4 5 14 8 14 7 8 3 4 2 6 11 2 2 1 4 8 6 9 12 15 9 8 10

Total

173

Year

Development

Sum

7 9 18 13 15 18 3 3 13 9 15 14 15 30 15 16 13 15 23 17 17 29 27 24 23

8 13 23 27 23 32 10 11 16 13 17 20 26 32 17 17 17 23 29 26 29 44 36 32 33

401

574

5.1.9 Compiled Drilling Exposure Data Table 5.11 below is based on Table 5.1 to Table 5.4, and shows compiled offshore drilled wells in Norway, UK and US GoM OCS. Table 5.12 is based on Table 5.6 to Table 5.10 and shows compiled offshore drilled wells in the Netherlands, Canada East Coast, Australia, US Pacific OCS, and Denmark.


Page: 49

Table 5.11 An overview of offshore drilled wells in Norway, UK, and US GoM OCS Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Expl. US Dev. US Expl. UK Dev. UK GoM OCS GoM OCS 361 807 54 122 337 870 74 137 392 838 111 118 381 762 128 95 556 755 182 108 511 662 157 133 255 433 113 85 396 448 132 124 532 452 177 167 455 511 183 155 490 566 224 124 330 430 186 144 215 329 131 167 345 570 110 162 417 589 99 202 376 675 98 244 439 697 112 261 521 837 96 257 496 641 80 276 370 662 36 230 440 937 59 216 411 852 60 282 308 633 44 249 354 539 45 204 362 553 63 166 10050 16048 2754 4428

Expl. Norway 42 43 52 42 53 53 43 42 31 35 46 57 45 35 27 40 32 55 29 24 27 39 22 26 18 958

Dev. Expl. Total Dev. Total Norway 28 457 957 16 454 1023 23 555 979 24 551 881 34 791 897 48 721 843 50 411 568 48 570 620 55 740 674 66 673 732 60 760 750 64 573 638 86 391 582 105 490 837 120 543 911 109 514 1028 143 583 1101 135 672 1229 139 605 1056 149 430 1041 185 526 1338 200 510 1334 167 374 1049 165 425 908 138 443 857 2357 13762 22833

Table 5.12 An overview of offshore drilled wells in Canada East Coast, the Netherlands, Australia, US Pacific OCS, and Denmark Year

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Expl. Dev. Expl. Dev. Dutch Dutch Canada Canada E. Coast E. Coast 31 7 18 32 5 18 45 20 21 43 15 25 33 24 30 1 43 35 38 1 30 15 18 27 13 10 26 21 14 28 17 2 35 14 1 45 18 4 5 20 15 7 14 17 11 12 10 1 6 8 16 1 3 29 6 2 3 31 13 4 6 20 13 2 28 14 6 10 37 12 9 14 38 19 12 14 20 19 13 12 33 11 13 9 28 13 6 3 32 640 353 271 259

Expl. Dev. Expl. US Dev. US Expl. Dev. Expl. Aust- Aust- Pacific Pacific DenDentotal ralia ralia OCS OCS mark mark 20 7 10 40 1 7 80 18 16 14 50 4 9 86 51 12 27 58 5 18 149 48 29 38 44 14 13 168 44 43 19 45 8 15 134 41 18 6 39 14 18 142 27 19 5 34 7 3 87 16 21 4 39 8 3 65 42 13 3 29 3 13 88 56 27 4 15 4 9 94 79 24 17 2 15 117 49 22 8 6 14 104 46 15 5 11 15 77 54 21 21 2 30 70 55 34 25 2 15 70 59 40 19 1 16 69 58 38 31 4 13 93 61 95 29 8 15 104 77 49 19 6 23 105 59 38 11 9 17 92 74 25 13 12 17 112 61 31 16 15 29 109 54 34 21 9 27 94 65 44 18 8 24 93 54 48 20 10 23 80 1268 763 130 666 173 401 2482

Dev. total 61 80 108 101 128 111 71 76 76 68 70 67 57 100 90 94 91 158 132 109 102 108 128 127 129 2442

Page: 50


5.2 Production Exposure Data 5.2.1 US GoM OCS The production exposure data for US GoM OCS is shown in Table 5.13. The data is based on MMS Ogor A files from 1986 – 2006 (/1/). These files list the well individual activity for each month. It was selected to use the data from December each year. All the production wells listed with production in December are counted as active wells. Table 5.13 Producers in the US GoM OCS area. Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Oil production Gas Total Water injection Gas injection production production (active or inactive) (active or inactive) Flowing Gas lift Total NA NA 3165 3023 6188 107 NA NA 3260 3106 6366 121 NA NA 3412 3223 6635 143 NA NA 3539 3243 6782 187 NA NA 3688 3355 7043 219 2695 1101 3796 3229 7025 327 100 2523 1206 3729 3239 6968 327 88 2461 1284 3745 3311 7056 320 105 2382 1361 3743 3364 7107 327 100 2230 1270 3500 3429 6929 311 91 2283 1246 3529 3682 7211 320 89 2206 1339 3545 3580 7125 323 80 2195 1311 3506 3346 6852 325 80 2216 1326 3542 3458 7000 315 72 2228 1286 3514 3483 6997 307 72 2189 1258 3447 3430 6877 305 70 2016 1424 3440 3444 6884 294 61 2002 1434 3436 3467 6903 270 52 1936 1364 3300 3315 6615 261 51 1712 1538 3250 3282 6532 248 50 1723 1590 3313 3308 6621 246 45 1523 1716 3239 3217 6456 225 34 1327 1782 3109 2993 6102 207 27 1160 1926 3086 3043 6129 205 30 1060 1539 2599 2804 5403 199 35 85432 82374 167806 6439 1332

5.2.2 United Kingdom The production/injection exposure data for UK is shown in Table 5.14. The figures are valid for the number of wells that have been in service for the listed year. The data from before 1991 is based on well data systematically collected in the SINTEF study "Reliability of Well Completion Equipment" SINTEF report STF 75 F92019, "Develop ment of the Oil and Gas resources of the United Kingdom" 1980, 1992 and 1993 edition, North Sea Field Development Guide, 4th edition, OPL and coarse assumptions where well data are missing. The data is therefore not exactly correct. The data from 1991 to 1999 is based on statistics from Health & Safety Executive (HSE). HSE has now stopped reporting this information on an individual well basis. They now report the production data for each field. Deal Data Registry for UK Offshore Oil & Gas (http://www.ukdeal.co.uk/) reports individual well information, but the quality of information is variable, and the data cannot be used. The department of Energy was contact in October 2004, but is no longer collected by the


Page: 51

Department and has not in fact been collected since 1999. All they could suggest was that the oil companies that operate the field or well could be appro ached and requested for data. This will be a too time-consuming task. The exposure data for 2000 - 2003 has therefore been estimated. Table 5.14 Producers and injectors in the UK waters Year

Production wells Injection wells Total wells Oil Gas/con Total Gas Water Total 1980 291 249 540 10 92 102 642 1981 318 252 570 11 104 115 685 1982 349 256 605 13 116 129 734 1983 399 258 657 17 140 157 814 1984 448 266 714 22 170 192 906 1985 456 298 754 21 194 215 969 1986 525 322 847 27 206 233 1080 1987 558 355 913 29 218 247 1160 1988 550 390 940 35 217 252 1192 1989 575 419 994 35 227 262 1256 1990 599 474 1073 37 249 286 1359 1991 844 344 1188 68 350 418 1606 1992 918 502 1420 68 363 431 1851 1993 968 549 1517 66 369 435 1952 1994 1041 598 1639 62 399 461 2100 1995 1131 703 1834 60 413 473 2307 1996 1215 695 1910 69 428 497 2407 1997 1252 725 1977 68 434 502 2479 1998 1160 713 1873 58 369 427 2300 1999 1118 678 1796 37 345 382 2178 2000* 1027 726 1753 37 345 382 2135 2001* 953 714 1667 37 345 382 2049 2002* 943 696 1639 37 345 382 2021 2003* 867 685 1552 37 345 382 1934 2004* 777 640 1417 37 345 382 1799 Total 19282 12507 31789 998 7128 8126 39915 * Data are no longer available from HSE. The number of wells in production has been assumed to be relative to the UK annual oil and gas production. Injection wells remain unchanged.

5.2.3 Norway Table 5.15 shows the production/injection exposure data for the Norwegian waters. The figures

are valid for the number of wells in service per December 31 the listed year. The data is from the NPD Annual reports 1980 – 1999, and for the year 1999 and later the data stems from the NPD Borehole list as published on the Internet (http://www.npd.no).

Page: 52


Table 5.15 Production/injection exposure data for the Norwegian waters Year Oil 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Cond

84 89 114 113 128 145 160 176 201 235 258 285 324 371 385 434 494 519 535 746 787 813 820 849

29 34 35 32 31 29 38 41 43 38 33 31 29 31 32 35 33 31 25 25 25 21 32 30

848

32

Producers Gas Other/unknown 47 48 47 53 61 61 64 60 65 48 31 33 30 32 34 24 53 62 64 83 85 95 101 97

97

7

Total 160 171 196 198 220 235 262 277 309 321 322 349 383 434 451 493 580 612 624 854 897 929 953 976

984

Injection/- Suspended/observation closed in/plugged 8 23 11 26 13 24 17 37 23 42 32 60 41 71 41 102 59 110 74 151 88 191 109 207 116 247 136 280 163 357 180 409 189 459 194 544 211 649 259 549 259 701 266 833 257 1030 261 1111

264

1244

Total

191 208 233 252 285 327 374 420 478 546 601 665 746 850 971 1082 1228 1350 1484 1662 1857 2028 2240 2348

2492

Total 9913 795 1475 7 12190 3271 9457 24918 Note! NPD stopped listing the number of wells in production in the annual reports in 1999. From 1999 the no. of oil producers seems high, and the no. of closed in/suspended wells seems low, compared to the earlier years.

5.2.4 US Pacific OCS The production exposure data for US Pacific OCS is shown in Table 5.16. The data is based on MMS Ogor A files (/1/). These files list the well individual activity for each month. It was selected to use the data from December each year. All the production wells listed with production in December are counted as active wells.


Page: 53

Table 5.16 Producers in the US Pacific OCS area. Year 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Oil production Flowing Gas lift Total 262 79 341 280 81 361 284 83 367 293 79 372 305 72 377 321 65 386 340 49 389 337 54 391 322 79 401 300 104 404 287 118 405 289 107 396 285 100 385 264 100 364 264 103 367 255 105 360 257 120 377 256 122 378 251 121 372 5452 1741 7193

Gas production 20 20 16 13 19 20 19 20 17 17 13 17 19 18 16 17 16 15 15 327

Total Water injection Gas injection production (active or inactive) (active or inactive) 361 79 6 381 84 6 383 88 4 385 83 4 396 83 4 406 84 5 408 84 4 411 88 4 418 93 4 421 94 6 418 84 7 413 87 9 404 93 13 382 93 14 383 83 15 377 74 11 393 97 11 393 98 12 387 100 14 7520 1669 153

5.2.5 Compiled Production Exposure Data Table 5.17 is based on Table 5.13, Table 5.14 and Table 5.15, and shows overall production data for the Norway, UK and US GoM OCS. The figures are valid for number of wells in s ervice per December the listed year. Note that it has been selected not to included data from the US Pacific OCS. Table 5.17 Overall production data f or the US GoM OCS, UK, and Norway based on Table 5.13, Table 5.14 and Table 5.15. Year

US GoM OCS United Kingdom Production wells InjectProduction wells Injection ion Oil Gas/Total Oil Gas/- Total wells wells cond cond 1980 3165 3023 6188 107 291 249 540 102 1981 3260 3106 6366 121 318 252 570 115 1982 3412 3223 6635 143 349 256 605 129 1983 3539 3243 6782 187 399 258 657 157 1984 3688 3355 7043 219 448 266 714 192 1985 3796 3229 7025 427 456 298 754 215 1986 3729 3239 6968 415 525 322 847 233 1987 3745 3311 7056 425 558 355 913 247 1988 3743 3364 7107 427 550 390 940 252 1989 3500 3429 6929 402 575 419 994 262 1990 3529 3682 7211 409 599 474 1073 286 1991 3545 3580 7125 403 844 344 1188 418 1992 3506 3346 6852 405 918 502 1420 431 1993 3542 3458 7000 387 968 549 1517 435 1994 3514 3483 6997 379 1041 598 1639 461 1995 3447 3430 6877 375 1131 703 1834 473 1996 3440 3444 6884 355 1215 695 1910 497 1997 3436 3467 6903 322 1252 725 1977 502 1998 3300 3315 6615 312 1160 713 1873 427 1999 3250 3282 6532 298 1118 678 1796 382 2000 3313 3308 6621 291 1027 726 1753 382 2001 3239 3217 6456 259 953 714 1667 382 2002 3109 2993 6102 234 943 696 1639 382 2003 3086 3043 6129 235 867 685 1552 382 2004 2599 2804 5403 234 777 640 1417 382 Total 85432 82374 167806 7771 19282 12507 31789 8126

Norway Total Production wells InjeProduction wells Injection Oil Gas/- Total ction Oil Gas/- Total wells wells cond cond 84 76 160 8 3540 3348 6888 217 89 82 171 11 3667 3440 7107 247 114 82 196 13 3875 3561 7436 285 113 85 198 17 4051 3586 7637 361 128 92 220 23 4264 3713 7977 434 145 90 235 32 4397 3617 8014 674 160 102 262 41 4414 3663 8077 689 176 101 277 41 4479 3767 8246 713 201 108 309 59 4494 3862 8356 738 235 86 321 74 4310 3934 8244 738 258 64 322 88 4386 4220 8606 783 285 64 349 109 4674 3988 8662 930 324 59 383 116 4748 3907 8655 952 371 63 434 136 4881 4070 8951 958 385 66 451 163 4940 4147 9087 1003 434 59 493 180 5012 4192 9204 1028 494 86 580 189 5149 4225 9374 1041 519 93 612 194 5207 4285 9492 1018 535 89 624 211 4995 4117 9112 950 746 108 854 259 5114 4068 9182 939 787 110 897 259 5127 4144 9271 932 813 116 929 266 5005 4047 9052 907 820 133 953 257 4872 3822 8694 873 849 127 976 261 4802 3855 8657 878 848 136 984 264 4224 3580 7804 880 9913 1634 11547 3271 114627 96515 211142 19168

Page: 54



Page: 55

6. Various Exposure Data This section includes various exposure data. It should be noted that this exposure data does not include information from the complete period 1980 – 1999. Limitations related to the exposure data are explained where the data is presented. The exposure data presented in this section covers the following: 1. Well Depth Related Exposure Data US GoM OCS Wells Norwegian Wells 2. Water depth related drilling exposure data US GoM OCS Wells UK Wells Norwegian Wells 3. Shut-in Wellhead Pressure Related exposure data US GoM OCS Drilling Wells Norwegian Drilling Wells US Wells in Production 4. Gas Oil Ratio Related Exposure Data 5. Workover Frequency Exposure Data 6. Wireline Frequency Exposure Data 7. Coiled Tubing and Snubbing Exposure Data • •

• • •

• • •

Data from the US Mineral Management Service (MMS) and NPD has formed the main input to this section.

6.1 Well Depth Related Exposure Data 6.1.1 US GoM OCS Wells The information in this sub-section stems from the MMS Borehole file (/1/).The drilling vertical depths for the exploration and development wells in the US GoM OCS are presented in Figure 6.1 and Figure 6.2. Approximately 0.8 % of the exploration wells and 1.3% of the development wells were not listed with a True Vertical Depth (TVD). These wells are not included in Figure 6.1 and Figure 6.2.

Page: 56


Exploration wells, US GoM OCS (1980 - 2004) 10000 9000 8000 7000 ) r 6000 e t e m 5000 ( D V 4000 T

3000 2000 1000 0 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Percentage distribution

Figure 6.1

All exploration wells drilled in 1980 – 2004 listed with true vertical depth

Development wells, US GoM OCS (1980 - 2004) 12000

10000

8000 ) r e t e m ( D V T

6000

4000

2000

0 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


Figure 6.2 All development wells drilled in 1980 – 2004 listed with true vertical depth

100%


Page: 57

6.1.2 Norwegian Wells For Norwegian wells True Vertical Depth (TVD) of wells is not available for neither exploration nor development wells drilled before 1995. Measured Depths (MD) is, however, available. For most exploration wells the MD is a good approximation for the TVD. For development wells the MD will not be a good approximation. Figure 6.3 shows the true vertical depth for production wells drilled in the period 1995 – mid 1998. Figure 6.4 shows the measured depth for development wells drilled in the period 1980 – 2004. Figure 6.5 shows the measured depth for exploration wells drilled in the period 1980 2004. The data shown in Figure 6.3 stems from the NPD Daily Drilling Report system, Figure 6.4 and Figure 6.5 stems from the NPD well files as published on the Internet.

True vertical depth, production wells, (mainly drilled in 95 - mid 98) 5000 4500 4000 3500 ) B 3000 K R m2500 ( D V 2000 T

1500 1000 500 0 0%

10%

20%

30%

40%

50%

60%

70%

Percentage distribution (total 478 wells)

Figure 6.3

True Vertical Depth, Norwegian production wells

80%

90%

100%

Page: 58


Development wells, Norwegian waters (1980 - 2004) 12000 10000 ) m ( 8000 h t p e d 6000 d e r u s 4000 a e M

2000 0 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

90%

100%


Figure 6.4 Measured depth for development wells 1980 – 2004

Exploration wells, Norwegian waters (1980 - 2004) 9000 8000 7000 h t 6000 p e d 5000 d e r u 4000 s a e 3000 M

2000 1000 0 0%

10%

20%

30%

40%

50%

60%

70%

80%

Percentage distribution Figure 6.5 Measured depth, Norwegian exploration wells 1980 – 2004.

6.2 Water Depth Related Drilling Exposure Data The past years some deepwater blowouts have occurred. This section presents the water depth related drilling exposure data. Table 6.1 and Table 6.2 present the water depth specific no. of exploration and development wells drilled in the US GoM OCS.


Table 6.1 Spud year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Table 6.2 Spud year

Page: 59

Exploration wells drilled in the US GoM OCS vs. water depth (/1/) <50 206 190 264 248 318 249 124 212 288 238 261 168 99 180 225 179 207 229 228 148 215 165 148 176 173 5138

50 – 100 121 101 87 79 126 111 54 92 99 100 107 90 87 91 105 97 107 117 120 97 90 58 48 62 45 2291

Number of wells drilled within water depth range (m) 100 – 200 – 400 – 6001000 – 15002000200 400 600 1000 1500 2000 2500 17 25 18 28 36 56 32 45 57 46 49 24 13 37 25 31 28 39 23 18 18 26 8 17 18 734

10 9 8 16 29 44 17 16 27 16 15 19 8 10 13 17 20 27 16 7 9 18 7 9 19 406

2 8 5 7 23 23 15 10 23 19 13 4 2 11 5 14 9 20 30 14 12 7 12 8 8 304

>2500

1

13 22 13 11 23 23 31 15 2 6 27 21 29 24 33 27 35 39 23 19 22 459

4 4 10 2 10 6

1 1

4 4 4 8 6 2 9 8 25 51 35 25 34 55 25 29 27 353

Unknown

2 1 2 1 1 2 2 5 5 8 26 9 24 17 21 21 147

2 2 1 1

2 4 1 7 16 16 17 6 17 92

2 8 8 3 3 3 8 6 7 7 5 2 1 2 3 3 7 12 27

99

Total 361 337 392 381 556 511 255 396 532 455 490 330 215 345 417 376 439 521 496 370 440 411 308 354 362 10050

Development wells drilled in the US GoM OCS vs. water depth (/1/) <50

50 – 100

Number of wells drilled within water depth range (m) 100 – 200 – 400 – 6001000 – 15002000200 400 600 1000 1500 2000 2500

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

363 480 451 447 434 302 173 247 206 237 254 181 172 293 294 327 338 408 322 300 446 418 303 306 329

327 274 293 226 234 255 169 117 142 153 165 132 82 187 198 221 220 278 181 219 300 225 146 91 105

60 73 62 56 54 53 50 41 53 57 97 87 28 41 37 55 70 61 62 43 49 69 21 33 33

37 29 19 21 19 33 32 34 29 44 24 11 34 35 28 25 33 23 34 29 41 35 34 20 15

3 14 14 19 7 1 4 5 15 7 26 11 11 8 17 9 8 8

2 5 19 24 11 27 21 23 24 18 15

4 16 24 60 36 76 48 13

1 1 5 9 23 11 12 16

2 1 1 2 6 9 1 19

Total

8031

4940

1345

718

189

206

278

81

41

>2500

2 1 1 2 2 1 3 8 1 1 1

Unknown 20 14 13 12 14 17 8 5 6 4 6 9 4 9 24 26 10 10 2 3 1

807 870 838 762 755 662 433 448 452 511 566 430 329 570 589 675 697 837 641 662 937 852 633 539 553

217

16048

2 2

Total

Table 6.3 and Table 6.4 present the water depth specific no. of exploration and development wells drilled in Norwegian waters.

Page: 60


Table 6.3 Exploration wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/) Number of wells drilled within water depth range ( m)* Spud year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

< 50 2 23 34 47 43 29 43 58 58 60 49 29 31 39 32 29 22 15 9 9 9 10 12 11 703

50 – 100 15 30 44 42 73 45 40 39 46 44 53 60 47 35 26 32 34 23 23 11 12 22 16 18 16 846

100 – 200 49 58 65 76 89 81 62 69 86 96 130 102 68 51 27 30 48 53 39 20 31 34 20 13 38 1435

200 – 400

400 – 600 2 2 2 2 4 4 2 2

2 1 1 6 3 5 3 1

1 1

44

600 – 1000 1 2 1

1000 1500 3

Total

1500 2000 1

71 94 135 154 218 179 133 153 192 200 248 215 150 123 107 109 120 105 82 43 59 69 50 48 72 3129

5 6

2 2 3 3 5 11 7 2 5

1 1 3 3 63

1 3 3 1 3 1 3 2 1 2 1 24

1 2 1 2

1 1

2 3 12

2

* Note that the numbers of wells are 12% higher than in Table 5.2, page 41 because different sources of information have been used.

Table 6.4 Development wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/) Spud year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

< 50 9 12 14 15 26 39 35 41 56 58 41 47 58 35 58 91 29 26 37 42 35 34 42 39 15 934

Number of wells drilled within water depth range (m)* 50 – 100 – 200 – 400 – 600 – 1000 100 200 400 600 1000 1500 11 129 10 127 18 105 14 75 15 81 2 16 93 2 3 60 20 82 32 87 14 83 1 1 14 67 2 1 37 68 1 31 81 5 26 108 3 36 110 1 2 37 134 3 67 175 5 11 53 170 9 4 64 173 12 7 51 130 1 12 36 148 5 5 39 203 5 12 47 151 5 13 2 2 43 110 3 8 2 33 106 10 3 767 2856 69 83 6 2

1500 2000

* Note that the numbers of wells are 6% higher than in Table 5.2, page 41 because different sources of information have been used.

Total 149 149 137 104 124 150 98 143 175 157 125 153 175 172 207 265 287 262 293 236 229 293 262 205 167 4717


Page: 61

Table 6.5 and Table 6.6 present the water depth specific no. of exploration and development wells drilled in Norwegian waters. Table 6.5

Exploration wells drilled in Norwegian waters vs. water depth

Spud year 50 – 100

<50 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Table 6.6 Spud year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Total

Number of wells drilled within water depth range (m) 100 – 200 – 400 – 6001000 – 200 400 600 1000 1500

9 8 18 6 12 3 5 4 9 11 19 21 10 10 4 6 7 13 4 3 1 1 2 6 1 193

1

1

13 22 19 14 12 16 13 16 7 14 12 13 11 11 12 25 5 19 11 5 7 16 10 11 8 322

20 13 15 22 29 34 24 19 13 9 15 22 23 14 10 9 19 19 11 15 16 19 7 7 9 413

Total 1500 – 2000

1 3 2 1 1 1

1 1

1 3

2 1

2 2 1

1

16

5

1 1 2

1

7

1

Development wells drilled in Norwegian waters vs. water depth Number of wells drilled within water depth range (m) 50 - 100 100 - 200 200 - 400 400 - 600 21 10 5 9 13 12 25 25 35 34 27 31 25 31 38 26 26 29 28 16 18 26 26 30 31 597

7 6 18 15 21 36 25 23 20 29 25 23 50 48 40 43 61 42 47 60 79 89 73 66 51 997

3 8 10 11 26 42 40 56 64 64 72 88 85 67 69 56 761

Total

1

1

2

28 16 23 24 34 48 50 48 55 66 60 64 86 105 120 109 143 135 139 149 185 200 167 165 138 2357

42 43 52 42 53 53 43 42 31 35 46 57 45 35 27 40 32 55 29 24 27 39 22 26 18 958

Page: 62


6.3 Shut-in Wellhead Pressure Related Exposure Data All data for the US GoM OCS wells stems from (/1/). Only data for wells that are completed as producers are included. For the Norwegian wells the main source of information has been a list of HPHT wells from NPD combined with the NPD Borehole list. For the UK wells no pressure related data is presented.

6.3.1 US GoM OCS Drilling Wells The shut-in wellhead pressure exposure data for drilling wells (both development and exploration wells) are all based on the first production well test carried out on the well. In US GoM OCS many exploration wells are completed as producers (see Table 5.1). It should also be noted that many development wells are not completed as producers, because they are dry. Since the shut-in wellhead pressures have been recorded more frequent the last 5 to 10 years than the previous years it was selected to only include data from wells that have been spudded after January 1988 Development drilling There were in total 1417 development wells listed with a shut-in wellhead pressure on the first well test after completion.

In Figure 6.6 the development wells shut-in wellhead pressures have been plotted against the well depth.


Page: 63

Development wells Shut-in pressure v.s. well depth, sorted 24000 22000 20000

n i - 18000 t u ) h i 16000 S s / ) p14000 t ( e e e 12000 f ( r u h t s s 10000 p e e r p 8000 d l l 6000 e W 4000 2000 0

0

10

20

30

40

50

60

70

80

90

Cumulative percent Shut-in test pressure (psi)

Figure 6.6

True vertical depth (ft)

Expon. (True vertical depth (ft))

Development wells shut-in wellhead pressures plotted against well-depth

Exploration drilling There were in total 508 exploration wells listed with a shut-in wellhead pressure on the first well test after completion.

In Figure 6.7 the exploration wells shut-in wellhead pressures have been plotted against the well depth.

Page: 64


Exploration wells Shut-in pressure v.s. well depth, sorted 24000 22000 20000 n i t 18000 u h ) i 16000 S s / ) p t ( e e 14000 e 12000 f ( r u h t s s 10000 p e e r p 8000 d l 6000 l e W 4000 2000 0

0

20

40

60

80

100

Cumulative percent Shut-in test pressure (psi)

True vertical depth (ft)

Expon. (True vertical depth (ft))

Figure 6.7 Exploration wells shut-in wellhead pressures plotted against well depth

When looking at Figure 6.7 it is important to note that the number of wells drilled is based on only the exploration wells that have been completed as producers and listed wi th a well test with a positive pressure. If looking at the Mobile area, 33 exploration wells have been drilled to more than 20000 feet (6100 meters) in the period 1980 - 1996. These wells are likely all HPHT (more than 10000 psi) wells. In the Destin Dome Blocks six wells have been drilled in the same formation as the Mobile wells. In the Pensacola one well has been drilled. In addition 401 exploratory wells have a well depth between 16000 – 20000 feet. By reviewing the test pressures for development wells drilled in the same block and evaluating shut-in test pressure and the well spud dates, at least 57 of these were likely to be HPHT wells (close to 10000 psi or above). Further, some of the wells drilled to less than 16000 feet have been HPHT wells. It is then likely that it has been drilled in the range of 100 to 200 exp loration HPHT wells in the US GoM OCS in the period 1980 - 1998.

6.3.2 Norwegian Drilling Wells The number of HPHT wells drilled in Norway is shown in Table 6.7. The data from before 1996 stems from the NPD daily drilling report system (DDRS). The data from 1996 and later stem from the report ”Utvikling i risikonivå norsk sokkel”, hovedrapport, Fase 6 – 2005,www.ptil.no .


Table 6.7

Page: 65

Number of HP/HT wells drilled in the Norwegian waters sorted on years o

No. of HPHT wells (>690 bar and/or > 150 C) Exploration Production 3 2 2 0 3 3 8 7 9 5 3 2 3 4 5 1 2 1 4 2 2 3 3 2 2 1 2 10 3 20 76 41

Year 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Total

6.3.3 US GoM OCS Wells in Production The pressure exposure data for production wells are based on all the well test s with a listed shutin wellhead pressure in the period 1980 – 1996 (/1/). Totally 48264 tests were listed with a positive wellhead shut-in pressure. Many well tests were not listed with well test pressures. The distribution of well tests in four different pres sure ranges is presented in Table 6.8. Table 6.8

Pressure ranges in production wells in US GoM OCS wells

Pressure range below 6000 psi (414 bar) 6000 – 8000 psi pressure 8000 – 10000 psi more than 10000 psi (690 bar) Total

No. of well tests 46928 926 336 74 48264

Relative distribution 97,23 % 1,92 % 0,70 % 0,15 % 100,00 %

In Figure 6.8 the development wells shut-in wellhead pressures have been plotted against the well depth.

Page: 66


Figure 6.8 All well tests performed 1980-1996 and listed with a shut-in wellhead pressure

6.4 Production Rates and Gas Oil Ratio Data, US GoM OCS This section is based on MMS Ogor A files from 1980 – 1999 (/1/). These files list the well individual production amount (gas, oil and water) for each month. Only the December data each year has been used to reduce the amount of information to handle

6.4.1 Production Rates Figure 6.9 and Figure 6.10 show the production rate for the US GoM OCS oil and gas wells respectively. The production rate data has been grouped in two different groups, the 80-ties and the 90-ties.


Page: 67

200 180

Daily Oil Volume in the 80's

160

Average 80's

) y a 140 d / 3 m120 ( n o i t 100 c u d 80 o r p l i 60 O

Daily Oil Volume in the 90's Average 90's

40 20 0

% 0

% 0 1

% 0 2

% 0 3

% 0 4

% 0 5

% 0 6

% 0 7

% 0 8

% 0 9

% 0 0 1

Perecentage of oil wells Figure 6.9 Oil well production rates, US GoM OCS wells, 1980 - 1999

The number of wells in production in the December month was slightly higher in the 90's than in the 80's. The average produced amount of oil was 41 m3/day in the 90's and 36 m3/day in the 80's per oil well that produced in the December month. In the end of the 90's some wells have experienced flow-rates of more than 3000 m3/day. The highest flow-rate seen was 5600 m3/day (or approximately 35 000 bbls). The wells are only those wells categorized as oil wells in the MMS files (some of them were only producing gas, and no oil). Nearly 99% of these wells have also produced gas, in average 13013 Sm3/day. Water production was also listed for 88% of these wells. On average for all wells the water production was 49.5 m3/day, i.e. more water was produced than oil.

Page: 68


500000 Daily Gas Volume 80's

450000

Daily Gas Volume 90's

) y 400000 a d / 3 350000 m S ( 300000 n o i t 250000 c u d 200000 o r p 150000 s a G100000

Average 80's Average 90's

50000 0 % 0

% 0 1

% 0 2

% 0 3

% 0 4

% 0 5

% 0 6

% 0 7

% 0 8

% 0 9

% 0 0 1

Perecentage of gas wells Figure 6.10 Gas well production rates, US GoM OCS wells, 1980 - 1999

The number of wells in production in the December month was slightl y higher in the 90's than in the 80's. The average produced amount of gas was 108 000 Sm3/day in the 90's and 124 000 Sm3/day in the 80's per gas well that produced in the December month. The best producers 3 produced nearly one million Sm /day. The wells are only those wells categorized as gas wells in the MMS files (some few of them were only producin g oil, and no gas). Approximately 66% of these gas wells also produced oil, in average 7.3 m3/day for all the wells. Water production was 3 also listed for 67% of these wells. In average for all wells the water production was 18.2 m /day.

6.4.2 Gas Oil Ratio The gas oil ratio data has been grouped in two different groups, the 80-ties and the 90-ties.


Page: 69

4000 3500 GOR 80's (Sm3/Sm3) 3000

GOR 90's (Sm3/Sm3)

3 2500 m S / 2000 3 m S 1500 1000 500 0 % 0

% 0 1

% 0 2

% 0 3

% 0 4

% 0 5

% 0 6

% 0 7

% 0 8

% 0 9

% 0 0 1

Perecentage of oil wells Figure 6.11 Well test GOR data sorted on period 100000

80000

) 3 60000 m S / 3 m S ( 40000

GOR 90's (Sm3/Sm3) GOR 80's (Sm3/Sm3)

20000

0 % 0

% 0 1

% 0 2

% 0 3

% 0 4

% 0 5

% 0 6

% 0 7

Perecentage of gas wells

% 0 8

% 0 9

% 0 0 1

Figure 6.12 Well test GOR data sorted on period

6.5 Workover Frequency Exposure Data Very little statistical material related to number of workovers carried out exists. From the SINTEF study "Reliability of Surface Controlled Subsurface Safet y Valves, Phase III", SINTEF report STF 75 F89030, it was observed 498 workovers on a total of 7790 well years. The data was mainly collected in the period 1985 - 1989 for North Sea wells. This gives in average:

Page: 70


15.6 well years per workover The NPD Annual reports from 1980 to 83 lists the number of workovers carried out the actual year alongside the number of production wells. A total of 88 workovers were listed and a total of 731 production well years. This gives in average: 8.3 well years per workovers In the autumn 2001 a search in the NPD Daily Drilling Report System (DDRS) was carried out. The search criteria specified: •

•

•

Traditional type of equipment was used (i.e. the permanently installed drilling rig and not a coiled tubing or snubbing unit). The main operation was Workover Sub operation was completion string (i.e. involved pulling of the completion string).

Each well that had at least on occurrence with the above combinations within one year was counted as a workover. This means that if two workovers were carried out the same year it will be counted as one workover only. On the other hand if the workover starts in December one year and is completed in January the next year it will be counted as two workovers. This count of workovers has been possible for the period after 1995 when NPD introduced some new codes in the DDRS. Seventy-six workovers were carried out in the year 2000. The result from this count for the years 1996 to 1999 is shown in Table 6.9. Table 6.9 Year 1996 1997 1998 1999 Total

Workover frequencies in Norwegian waters No. of workovers 56 72 86 59 273

No. of production wells

No. of inject- Sum no. of No of well years per ion wells wells workover

580 612 624 854

189 194 211 259

769 806 835 1113

13.7 11.2 9.7 18.9

2670

853

3523

12.9

It seems that the workover frequencies related to conventional workovers has decreased since the beginning of the 1980-ties when comparing with the above results. It is recommended that 10.6 well years per workover is used for the estimates related to blowout/well release frequencies per workover operation. This value will represent the average for the period 1980 - 2000.

6.6 Wireline Frequency Exposure Data Very little statistical material related to number of wireline runs exists. To establish an estimate for wireline exposure data, experience from the Ekofisk field in 1992 has been used. In 1992, 135 wells were in service (production and injection). A total of 220 wireline jobs were carried out. If in average each wireline job includes 2.5 wireline runs a total of 550 wireline runs were carried out for the 135 wells. This gives in average:


Page: 71

4.2 wireline runs per well year or 1.7 wireline jobs per well year It is important to note that the Ekofisk field mainly has wireline retrievable SCSSVs, and not tubing retrievable SCSSVs that most operators prefer when completing new wells today. It should further, be noted that most likely several minor incidents (small gas releases) during wireline jobs have never been recorded as blowouts.

6.7 Coiled Tubing and Snubbing Exposure Data Table 6.10 lists the number of coiled tubing and snubbing workovers that have been carried out in the Norwegian waters in the period 1984 - 1995. The NPD Daily Drilling Report System (DDRS) was used to extract the dat a. The data may not be exact because the DDRS did not include a specific code for these operations before 1995. The results are based on a search in the activity description for all production wells stored in the database. Coiled tubing and snubbing activities during regular drilling and completion are not included in Table 6.10. Coiled tubing and snubbing operations carried out, as a part of a conventional workover, is included. These operations should not have been included because they were only a sub-operation during a conventional workover. Therefore the activity level as listed in Table 6.10 probably is 10 – 20% higher than the real figures. Table 6.10 Coiled tubing and snubbing workover exposure data for the Norwegian sector of the North Sea, 1984 - 1995 Year 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 Total

Snubbing workovers 1 5 5 7 8 12 4 15 28 21 33 49 188

Coiled tubing workovers 0 1 3 5 3 13 16 13 19 32 38 48 191

In the autumn 2001 a search in the NPD Daily Drilling Report System (DDRS) was carried out. The search criteria specified that either a snubbing or a coiled tubing unit was used. The main operation was Workover and the sub operation was not specified. Each well that had at least on occurrence with the above combinations within one year was counted as a snubbing workover or a coiled tubing workover . This means that if two operations were carried out the same year it will be counted as one operation only. On the other hand if the operation starts in December one year and is completed in January the next year it will be counted as two operations. If dedicated snubbing or coiled tubing units are used in association with a conventional workover they will be regarded as separate operations, i.e. the total number of operations indicated in Table 6.11 may be

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some higher than the real figures. The result from this count for the years 1996 to 2000 is shown in Table 6.11. Table 6.11 Coiled tubing and snubbing workover exposure data for the Norwegian sector of the North Sea, 1996 - 2000 Year 1996 1997 1998 1999 2000 Total

Snubbing workovers 42 39 32 30 24 167

Coiled tubing workovers 83 81 83 49 50 346


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7. Overall Blowout/Well Release Frequencies Only overall blowout/well release frequencies for the different operational phases have been calculated. If required, analyses that are more detailed can be carried out by using the information presented in the various tables in the previous sections and/or the SINTEF Offshore Blowout Database. The listed frequencies in this section are based on the experience from US GoM OCS, UK and Norway in the period 1980-01-01 - 2005-01-01 only. The blowout frequencies during the different operational phases are presented in Table 7.1 to Table 7.6. The four blowouts listed with the phases “Unknown” and Unknown drilling” are not included. Please also note that blowouts caused by external loads are disregarded when calculating the blowout/well release frequencies. Table 7.1

Blowout/well release frequencies during completion (based on Table 4.4, Table 5.1, Table 5.2, and Table 5.4)

No. of completions No. of incidents per incident per completion Blowout (surface flow) 20 328 9 2171 0.00046 Blowout (underground flow) 20 328 0 0 Well release 20 328 6 3256 0.00031 Diverted well release 20 328 0 0 Total 20 328 15 1302 0.00077 * Based on total number of wells completed in Table 5.1, number of developments wells drilled in Table 5.2, and Table 5.4. Category

Table 7.2

No. of completions* No. of incidents

Blowout/well release frequencies during development drilling (based on Table 4.4 and Table 5.11)

Type of incident Blowout (surface Deep flow) Shallow Blowout Deep (underground flow) Shallow Diverted well Deep release Shallow Deep Well release Shallow Total Category

No. of dev. wells drilled 22 833 22 833 22 833 22 833 22 833 22 833 22 833 22 833 22 833

No. of incidents 8 22 3 1 0 16 5 2 57

No. of drilled wells per incident 2854 1038 7611 22833 1427 4567 11417 401

No. of incidents per drilled well 0.00035 0.00096 0.00013 0.00004 0 0.00070 0.00022 0.00009 0.00250

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Table 7.3


Blowout/well release frequencies during exploration drilling (based on Table 4.17, Table 5.1, Table 5.2, and Table 5.4) Type of incident

Category

Deep Blowout (surface flow)

Shallow Total Deep

Blowout (underground flow) Shallow Total Diverted well release

Shallow Total Deep

Well release Shallow Total Unknown

Deep Total Deep

All Shallow Total exploration drilling

Table 7.4

Exploration No. of. wells No. of No. of drilled wells No. of incidents well type drilled incidents per incident per drilled well Appraisal 6257 9 695 0.00144 Wildcat 7505 13 577 0.00173 Appraisal 6257 8 782 0.00128 Wildcat 7505 14 536 0.00187 Unknown 1 13762 45 306 0.00327 Appraisal 6257 0 0 Wildcat 7505 7 1072 0.00093 Appraisal 6257 0 0 Wildcat 7505 0 0 13762 7 1966 0.00051 Appraisal 6257 2 3129 0.00032 Wildcat 7505 7 1072 0.00093 13762 9 1529 0.00065 Appraisal 6257 3 0 Wildcat 7505 3 0 Unknown 2 Appraisal 6257 2 3129 0.00032 Wildcat 7505 2 3753 0.00027 13762 9 1529 0.00065 Appraisal 6257 1 6257 0.00016 Wildcat 7505 0 0 13762 1 13762 0.00007 Appraisal 6257 13 481 0.00208 Wildcat 7505 23 326 0.00306 Unknown 1 Appraisal 6257 11 569 0.00176 Wildcat 7505 22 341 0.00293 Unknown 1 13762 71 194 0.00516

Blowout/well release frequencies during production (based on Table 4.4 and Table 5.17). Blowouts caused by external loads (storm, fire etc.) are disregarded

No. of well years in service Blowout (surface flow) 211 142 Blowout (underground flow) 211 142 Diverted well release 211 142 Well release 211 142 Total 211 142 Category

Table 7.5

No. of incidents 7 1 0 2 10

No. of well years per No. of incidents per incident well year 30163 0.000033 211142 0.000005 0 105571 0.000009 21114 0.000047

Blowout/well release frequencies during well workover (based on Table 4.4, Table 5.17 and Section 6.5)

No. of No. of workover per No. of incidents per incidents incident workover Blowout (surface flow) 19 920 20 996 0.00100 Blowout (underground flow) 19 920 0 0 Diverted well release 19 920 0 0 Well release 19 920 17 1172 0.00085 Total 19 920 37 538 0.00186 * Based on in average one workover per 10.6 production well years (Section 6.5) Category

No. of workovers*


Table 7.6

Blowout/well release frequencies during wireline (based on Table 4.4, Table 5.17 and Section 6.6)

No. of wireline No. of No. of wireline jobs jobs* incidents per incident Blowout (surface flow) 358 941 4 89735 Blowout (underground flow) 358 941 0 Diverted well release 358 941 0 Well release 358 941 4 89735 Total 358 941 8 44868 * Based on in average 1.7 wireline jobs per production well years (Section 6.6) Category

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No. of incidents per wireline job 0.000011 0 0 0.000011 0.000022

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Sintef Blowout

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