85219-40-W-RP-001_(Rev_B).pdf

OLOKOLA GAS SUPPLY PROJECT PIPELINE FEED Constructability Study DOCUMENT NO. OKGS-NF2-038-RPT-CS-00001

B

11 DEC 06

Issued for Client Approval

FW

JP

RJL/FW

A

29 NOV 06

Issued for IDC

FW

JP

RJL/FW

REV

DATE

ORIG

CHK

APPR

ISSUE STATUS CODE

CONTRACTOR APPROVAL:

COMPANY APPROVAL:

DATE:

DATE:

COMPANY

CONTRACTOR document number: 85219-40-W-RP-001 COMPANY Document Number Project Management:

Project

Contract

Originator

Type

Discipline

Seq. No.

OKGS

NF2

038

RPT

CS

00001

Olokola Gas Supply Project

Constructability Study OKGS-NF2-038-RPT-CS-00001

Foreword The purpose of this Constructability Study is to identify vessels and areas of concern in conjunction with the installation of the export pipelines and infield flowlines for the Olokola Gas Supply Project.

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Table of Contents Page 1.

Introduction ................................................................................................................... 4 1.1 Project Description ............................................................................................ 4

2.

Scope ............................................................................................................................ 4

3.

Summary, Conclusions, and Recommendations .......................................................... 4 3.1 Summary ........................................................................................................... 4 3.2 Conclusions....................................................................................................... 5 3.3 Recommendations ............................................................................................ 6 3.4 Area of Concerns .............................................................................................. 7

4.

Terms and Definitions ................................................................................................... 8 4.1 Acronyms .......................................................................................................... 8

5.

Reference Materials ...................................................................................................... 8 5.1 Project Documents ............................................................................................ 8

6.

Installation Methodology ............................................................................................... 9 6.1 48 -inch Export Pipeline(s) ................................................................................ 9 6.2 In-field Flowlines >32” ..................................................................................... 10 6.3 Tie-In Spools ................................................................................................... 10 6.4 Wye Assembly................................................................................................. 11 6.5 Pipeline and Cable Crossings ......................................................................... 11 6.6 Pre-commissioning Export Pipelines and Infield Flowlines ............................. 12 6.7 Commissioning ................................................................................................ 17

7.

Vessel Matrix............................................................................................................... 18

Tables Table 1.1: Pipelay Installation Contractors - Export Pipelines (Vessels over 200T Tension) 19 Table 1.2: Pipelay Installation Contractor Matrix - Infield Flowlines....................................... 20

Appendices Appendix A Crossing MTO - Export Pipelines ....................................................................... 21 Appendix B Crossing MTO - Infield Flowlines........................................................................ 22

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1.

Introduction

1.1

Project Description This document was developed during pipeline FEED for the Olokola Gas Supply (OKGS) Project being executed by Chevron Nigeria Limited (CNL) offshore Nigeria in the Western Delta region. This document applies to both the export pipeline system that carries dehydrated gas and condensate from the Gas Production Platforms to the Olokola Liquefied Natural Gas (LNG) Plant and the infield flowline system that carries raw bulk flow between the Non-Associated Gas Wellhead Platforms and Gas Production Platforms.

2.

Scope The purpose of this Constructability Study is to evaluate the preliminary design of the export pipelines and infield flowlines associated with the Olokola Gas Supply Project (OKGS) to identify the type and capacity of the laybarge required for the project and also identify vessels that might be available to perform the work. The plan is to split the installation between export pipelines and in-field flowlines. The shallow water (63m to shore) and the line sizes (48” to 8”) eliminate considering J-lay; and limit the use of Reellay to the 8” produced water lines. The majority of the installation will be accomplished by use of the S-Lay installation method.

3.

Summary, Conclusions, and Recommendations

3.1

Summary The Olokola Field construction requires the installation of: •

30 risers, 64 pairs of various size flanges from 48” down to 8”, 36 spool pieces and 2 wye assemblies to connect approximately 370 miles of 10 various diameter pipelines to 2 production platforms, 10 each well head platforms and a riser platform and an onshore LNG facility.

•

Water depth ranges from 0 to 63m (206’); the majority in 6m (20’) to 18m (60’) of water.

•

There will be two installation contractors, 1 laying the 48”, 42” and 36” pipelines and 1 laying the pipelines 32” and less in diameter. There could be 2 or 3 dive boats to provide inspection and installation services as the pipelines are being laid. A Dive

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crew set up with a Saturation diving spread will be required for the deeper installations, over (200’).

3.2

•

There are 70+ pipeline crossings and 9+ cable crossings that will require protection with bridges, mattresses and/or sand/cement bags. The crossings will be installed prior to pipelay.

•

A separate vessel will be rigged up and dedicated for pre-commissioning and commissioning of all the pipelines/flowlines. Each pipeline contractor will be responsible for commissioning their individual work scope.

Conclusions 3.2.1

3.2.2

Export Pipelines •

The deep draft pipelay vessel with a static tensioning capacity of 275 to 325 metric tonnes (Te) and a stinger length between 67 to 109m is required for laying the 48” pipeline coated with 121mm concrete coating in water depth from 30 to 50m. This pipelay vessel with the above tensioning capacity and stinger length is capable of installing all other smaller diameter export pipelines.

•

To maintain a similar pipelay configuration as the dry installation, a flooded pipeline will require much higher tension that exceeds the tension limits of most available pipelay vessel. Alternatively, pipelay vessel selection may be based on the dry installation scenario and the installation contractor shall prepare a contingency procedure to ensure the safety of personal onboard, the pipelay vessel, and equipment in the event of a flooded pipeline. The pipeline structural integrity in such an event shall be considered secondary.

•

It is desirable to route the 48” pipeline in water depth less than 40m to avoid the scenario that only one or two pipelay vessels are capable of installing the pipelines.

•

The pipeline route curve radius should be 2000m or larger to accommodate the potential high seabed tension during pipelay.

Infield Flowlines •

Static tension capacity of 175 Te is required to lay the 26” flowline in 63m water. A pipelay vessel with the above tensioning capacity and stinger length is capable of installing all other infield flowlines.

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3.3

•

A shallow water pipelay vessel with static tensioning capacity of 100 Te and a stinger length around 40m may be able to lay the 26” pipelines to an intermediate water depth between 17m and 63m and the rest of the infield flowlines.

•

To maintain a similar pipelay configuration as in dry installation when a flowline is flooded it will require much higher tension and a shallow water pipelay vessel that is capable of handing both dry and wet installation may not be available for the Olokola Project. Alternatively, pipelay vessel selection may be based on the dry installation scenario and the installation contractor shall prepare a contingency procedure to ensure the safety of personnel the pipelay vessel and equipment in the event of flooded pipeline. The pipeline structural integrity in such an event shall be considered secondary.

•

The flowline route curve radius should be 2000m or larger to accommodate the potential high seabed tension during pipelay.

Recommendations The following are recommendations to the engineering efforts in the detailed design phase: •

Project specific seabed bathymetry and surface data along the pipeline/flowline routes are required for a detailed installation design.

•

Stress concentration due to the discontinuity of concrete weight coating should be included in the detailed installation engineering.

•

All export pipelines should be routed in water depth less than 40m to reduce the requirements on installation vessel and to bring in more competition to the tendering of installation work.

•

Installation contractors should be involved in the next phase to check the constructability of the Olokola export pipelines and infield flowlines using their vessels and equipment. Attention is required to look into the stinger roller reaction (single maximum and total load) during normal pipelay and pipeline laydown.

•

Dynamic pipelay analysis shall be performed in the detailed installation engineering to identify the maximum tension required for pipelay and the limiting sea states during installation.

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•

3.4

Consideration should be given to the provision of a SmartLay System to increase safety in the event of a wet buckle.

Area of Concerns The following are areas of concern: •

Shore pull tensions required for “breakout” under certain soil conditions should be carefully considered at the design stage.

•

Previous experience has shown that buoyancy bags attached by steel bands to the outside of the concrete coating sheared off not too far after touchdown as the pipe was pulled across the seabed. Recommend that a groove be put in the concrete in the coating yard when it is “green” and use 10mm steel cables instead of bands to attach the buoyancy bags. Special attention should be paid to the groove so that the cable can be pulled up tight, and hence not exposed to the stinger rollers and seabed during pipe pull. “A 1” x 1” groove shall be placed 1 meter from each end of 2325 joints of the line pipe to aid in attaching buoyancy to line pipe during shore pull.

•

The laying of a 48” pipeline is extremely weather sensitive.

•

Pipe lifting and movement are extremely dangerous operations, especially with large diameter concrete weight coated (CWC) pipe. It is imperative that all lifting/movement procedures are reviewed and agreed upon to ensure that safe methods are employed. Risk Assessments/Job Safety Analysis should be performed by contractor’s supervisors/operators prior to start of work.

•

The cut back of the CWC needs to be 38cm (15in.) (-0/+1) to ensure the Automated Ultrasonic Testing (AUT) equipment could fit to the pipe. The Fusion Bonded Epoxy (FBE) cut back needs to be 23cm (9in) min.

•

For FBE corrosion coating, a rough coat is recommended in order to help bond the concrete weight coating to the FBE.

•

Pipeline laydown (normal operation or contingency): large diameter pipeline may be over-stressed or rollers could possibly be over-loaded when the A&R head passes the stinger - this may be mitigated by stinger operation (lowering), adding buoyancy units, or using a section of sacrificial pipeline.

•

Pipelay initiation or laydown at platforms using start-up anchor - Geometry requirement for this operation will need to be checked to determine if pipelay can be done when the platforms are in place.

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•

Spool installation: confirm maximum length for spools - amount of platform overhang, spreader bar design requirement, diving operation limits.

•

Anchor handling: identify the vessel position/lay tension variation when repositioning anchors and the procedure to keep tension within the installation window. [Ref: 7].

•

Contingency: procedure in-place to address a ‘wet buckle’ case. Consideration should be given to the provision of a SmartLay System to increase safety in the event of a wet buckle.

4.

Terms and Definitions

4.1

Acronyms For the purposes of this report, the following acronyms are used: Acronyms A&R

Abandon and Recovery

AUT

Automated Ultrasonic Testing

CWC

Concrete Weight Coating

DSV

Dive Support Vessel

FBE

Fusion Bonded Epoxy

MAWP

Maximum Allowable Working Pressure

OKGS


OKLNG

Olokola Liquefied Natural Gas Plant

SOW

Scope of Work

Te

Metric Tonne

WD

Water Depth

WT

Pipe Wall Thickness

5.

Reference Materials

5.1

Project Documents 1.

OKGS-NF2-038-DES-PL-00001: Pipeline Design Basis

2.

OKGS-NF2-038-ANA-ME-00003: Installation Analysis – Export Pipelines

3.

OKGS-NF2-038-ANA-ME-00004: Installation Analysis – Infield Pipelines

4.

OKGS-CNL-038-SPC-PL-02023: Pipe Haul and Handing and Storage of Pipe, Valves and Fittings specification

5.

OKGS-CNL-038-SPC-PL-02027: Hydrotesting Specification

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6.

OKGS-CNL-038-SPC-PL-02062: Flooding and Leak Testing of Tie-In Spools

7.

OKGS-CNL-038-SPC-PL-02051: Anchor Handling Specification

6.

Installation Methodology

6.1

48 -inch Export Pipeline(s) 6.1.1

Shore Approach A double row of sheet pilings will be driven from high water mark on the beach to 4~5 m water depth and the material between the pilings will be removed by landbased equipment. An access channel will be dredged to 6 ~7 m water depth to allow shallow draft laybarge access to the cofferdam. A winch with sufficient capacity to pull the 48” coated pipeline from the installation vessel will be located onshore. The winch will be positioned to pull both pipelines without repositioning the winch. The shallow draft laybarge will setup adjacent to the end of the sheet piles, attach a pull-in wire to the pullhead and begin welding pipe with onshore winch pulling each section toward shore. When the pipe end reaches selected onshore location, the shallow draft laybarge will lay the 48” line to a water depth of approximately 15m and install laydown head and abandon pipeline if needed. The laybarge will move back to the sheet pile location, and duplicate pipe pull to shore and lay procedure to deeper water and laydown the 2nd 48” pipeline in 20m water depth if needed.

6.1.2

48-inch Okan GPP to OKLNG Export Pipeline(s) The laybarge will set up at the end of the 48” and retrieve pickup wire. A&R winch will be run through the stinger and attached to the laydown head and tension will be applied to retrieve pipeline along stinger and locate the pipeline in the welding station. The 48” laydown head will be removed, the pipe end beveled and pipelay will begin and continue at a rate of approximately 80 to 120 joints per day (vessel dependant). When the laybarge gets within 30m (100ft) of the Okan GPP Platform the laydown head will be attached and the pipeline abandoned to the seabed. The laybarge will move to the shallower water, retrieve the 2nd 48” pipeline and repeat the pipelay process to the Okan GPP Platform. The vessel will setup at the southeast side of the Okan GPP Platform to lay the 42” pipeline to EARP-B. The laybarge will utilize either: a bowstring to a platform leg, pile or an anchor for hold back to initiate tension on the pipeline pulling head. The laydown head will be placed in a predetermined target box in order to keep the tie-in spool at a maximum length of approximately 30m (100ft). The tie-in Page 9 of 22



spool will be installed at a later date. After the desired tension is reached additional joints of pipe will be welded on and the laybarge will move forward following x-ray approval and field joint application. A previously established pipe lay corridor for the placement of the flowline will be utilized to allow the flowline route between platforms to be accomplished by changing laybarge heading within pre-determined radius curvature. No intermediate fittings will be placed along the length of the pipeline. When the laybarge approaches the platform a laydown head will be attached and the pipe end placed in its target box under tension. The distance to the platform riser flange will be kept to a maximum length of 30m (100ft). 6.1.3

42” and 36” Pipelines

The larger laybarge will install the 42” and 36” pipelines in a similar manner as stated above. 6.2

In-field Flowlines 32” and less in diameter The installation of the infield lines will be accomplished by a smaller laybarge requiring less tension capacity. The smaller in-field flowlines will also use similar installation methodology.

6.3

Tie-In Spools The installation of the tie-in spools will be carried out by the respective EPC Contractor. All export pipelines and infield flowlines will have a tie-in spool connecting the riser to the pipeline/flowline or wye. For ease of installation, 2-swivel assemblies and 1misalignment swivel connection will be provided for each spool. This will allow for a swivel assembly at the bottom of the riser, and a second approximately mid-point of the spool. The misalignment swivel connection will be installed between the pipeline and spool. All spools will be pre-commissioned onshore to include: flooding/cleaning, gauging and hydrotest to 1.5 x design psig. At the riser end or Subsea wye, diver will take a measurement between each tie-in flange including the angle of the face of each flange. This metrology will be used to fabricate the spool piece that will be installed between the riser and the pipeline, flowline or wye. Fabrication/testing of the spools will be performed onshore. Pipeline mattresses and/or sand/cement bags should be placed under the riser tube turn for support and over top of the tube turn after tie-in to the pipeline and out from the platform approximately 15m (50ft) for protection from dropped objects. This distance may vary depending on the size of the riser tube turn.

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6.3.1

Option If the tie-in spool lengths can be reduced to a maximum length of 25 to 30m, they could be installed in one piece thereby reducing the number of flanges required and also reduce the installation time.

6.4

Wye Assembly The two wye assemblies weigh approximately 136 Te each, and will be placed by one of the installation vessels qualified in the weight range for the offshore lift. The installation vessel, with survey equipment onboard, will locate target box for the installation of the wye assemble and the vessel will be positioned with the crane in the optimum position for lift. Divers will perform pre-installation bottom survey and site preparation activities to ensure that the seabed in the area of the installation is clear and free of obstructions. The diver will also confirm that any existing pipelines in the vicinity are located. It is envisioned that the wye assemblies will be placed on piles due to the instability of the bottom soils. Vessel crane, with spreader bar and slings of pre-determined lengths, will place the pile template on the seabed. Piles will be driven to support penetration and the template will be removed. Elevation collars for positioning the wyes @ their desired elevation will be attached to each pile and tightened. Crane, with spreader bar and slings of predetermined lengths be attached to the wye assembly and the structure will be set over the piles and lowered to rest on the collars. If the bottom was found to be too soft to support the connecting spools, mattresses will have been placed to provide support. Divers will complete a bottom search and clear any installation devices, etc. Location and orientation will be confirmed by survey for the “As-built” final positioning of the Wye which will also include a video.

6.5

Pipeline and Cable Crossings There are 70+ pipeline crossings and 9+ cable crossing that will require protection with mattresses and/or sand/cement bags. The crossings will be installed prior to pipelay. A dedicated Dive Support Vessel (DSV) will be rigged up with survey equipment, diving spread, crane and sufficient deck space for mattresses. A bridge support will be placed over any existing pipelines that are in close proximity to one another. This layout will provide a more compact/efficient crossing. For individual crossings, the vessel will set up at the crossing location, where divers will probe for and establish the exact location of the existing pipeline. The diver will locate the perimeter area of crossing and conduct a bottom survey. Any damage to an existing pipeline will be noted and immediately

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reported to the Company representative. A minimum separation of 46cm (18in) between existing and new pipeline will be established. An “As-Built” survey of the crossing will note the center and perimeter of mattress coordinates. 6.6

Pre-commissioning Export Pipelines and Infield Flowlines 6.6.1

Flooding, Cleaning and Gauging It is proposed to flood, clean, and gauge offshore from a dedicated vessel via subsea hoses, filling the pipeline “wet end to wet end” with inhibited seawater. The proposed rate of flooding would be of the order of 22m3 per minute to achieve a minimum velocity of 0.35 m/s. The velocity in the 32” export pipeline would be greater using the same pumping spread, this being of the order of 0.5 m/s. The flood water would be treated with “standard offshore chemicals” to provide protection for 6 months exposure. It is proposed to flood, clean and gauge the four (4) export pipelines using the following five (5) pig train. •

Pig 1-Hi-Seal Bi-Directional Swabbing Pig, c/w pinger

•

300 linear meters of seawater

•

Pig 2-Hi-Seal Bi-Directional Cleaning Pig

•


•


•


•


•


•

Pig 5-Hi-Seal Bi-Directional Gauging-Cleaning Pig, c/w pinger

•

Chemically treated seawater – pipeline volume

Throughout the flooding and pigging operation the following minimum parameters would be recorded: •

Pig launch and reception times

•

Launch and reception pressures

•

Water flow rate

•

Ambient, seawater, and subsea temperatures

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Upon confirmation of the pig train reception the test end receiver would be removed and lifted to the surface, where the pigs would be removed and the gauge plate inspected. After confirmation of the integrity of the pigs and Gauge Plate are acceptable, the test end would be refitted subsea in preparation for the hydrotest. Photographic records would be taken of all received pigs. Consideration should be given to the provision of a Geometry-Caliper Pig Survey contingency, should a gauge plate be received damaged. 6.6.2

Hydrotesting Upon achieving the required test pressure the system would be allowed to stabilize to achieve temperature equilibrium within the test water. When the system is stabilized the test pressure will be re-established, and the test hold period commence. Pressures would be recorded every 10 minutes, along with pipe, ambient, and subsea temperatures. Upon successful completion of the test hold period, the respective pipeline would be depressurized. [Ref.5]. Upon completion of all hydrotesting the Pipelay Contractor would then commence the riser spool and wye piece tie-in program.

6.6.3

Leak Testing Upon completion of the tie-ins the topsides, risers, and spools would be toped up with inhibited seawater. All trapped air would be removed from the high points, and then pressurization would commence to achieve a test pressure of 1.1 x MAWP. Following the stabilization period the 8 hour test period would commence. Pressures would be recorded every 10 minutes along with pipe, ambient, and subsea temperatures. Upon successful completion of the Leak Test hold period the respective pipeline would be depressurized at a rate no greater than 2 barg per minute until zero pressure is achieved. [Ref 6].

6.6.4

Bulk Dewatering It is proposed to dewater the two 48” x 124.7km Okan GPP-OKLNG pipelines from onshore. For the 42” EARP-B and the 36” Funiwa GPP – EARP-B pipelines the optimum direction for dewatering would be from Okan GPP and Funiwa GPP respectively. From a pre-commissioning perspective the air-nitrogen spread would be located on the two main platforms, i.e., Okan GPP and the Funiwa GPP. The footprint required for this equipment is approximately 18m x 15m. This would be for all offshore dewatering, drying and nitrogen operations, but this may not be practical due to lack of space. If this is achievable it would eliminate the need for hose Page 13 of 22



transfers from the Vessel and the weather dependency of this operation. This would also make the operation more efficient by allowing the routing of air from a single static source to the respective main platform pipelines. The exceptions being the Meji and Sonam pipelines which would need to be dewatered from the satellites to accommodate the wye piece geometry. The bulk dewatering for the export pipelines would be achieved by the introduction of the following eight (8) pig train, which would be propelled at a velocity greater than 0.3 m/s. •

Pig 1-Hi-Seal Bi-Directional Swabbing Pig, c/w pinger.

•

500 linear meters of fresh water

•

Pig 2-Hi-Seal Bi-Directional Swabbing Pig

•

500 linear meters of freshwater

•


•

500 linear meters of dry oil free air at dewatering pressure

•


•


•


•


•


•


•


•


•

Pig 8-Hi-Seal Bi-Directional Swabbing Pig, c/w pinger

•

Dry oil free air - Pipeline volume

The fresh water would be introduced to act as a flush to remove the salt content of the seawater to an acceptable level < 200 ppm. The bulk dewatering of the Infield flowlines would be achieved by the introduction of the following six (6) pig train. •

500 linear meters of fresh water

•


•

500 linear meters of freshwater

•


•


•


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•


•


•


•


The pipeline test water would be offloaded overboard via an installed fabricated dumpline. The minimum size required would be a minimum of 8” diameter for the export system, and 6” for the In-field pipeline system. Upon reception of the dewatering pig train, the pigs would be removed in batches as dictated by the size of the pig receiver. Upon recovery of the pigs they would be inspected for wear and condition. Photographic records would be taken of all received pigs. Throughout all pigging operation the following minimum parameters would be recorded: •


•

Launch and Reception pressures

•

Air flow

•

Pipeline temperature

•

Terminal water flow rate

When the complete pig train has been removed the pipeline would be vented down to zero pressure via installed temporary silenced vents, located at each end of the pipeline. 6.6.5

Final Dewatering When each export pipeline has been depressurized, a second eight (8) pig train would be loaded and propelled through the pipeline at a velocity of between 0.5 – 1.0 m/s. The pig train will be as follows: •

Pig 1-Mediun Density Foam Pig

•


•


•


•


•


•


•


•

Pig 5-Hi-Seal Bi-Directional Swabbing Pig Page 15 of 22



•


•


•


•


•


•


•

Dry oil free air - Pipeline volume

When each infield flowline has been depressurized, a second six (6) pig train would be loaded and propelled through the flowline at a velocity of between 0.5 – 1.0 mls. The pig train would be as follows: •


•

500 linear meters of dry oil free air at de-watering pressure

•


•

500 linear meters of dry oil free air at de-watering pressure

•


•


•


•


•


•


•


•

Dry oil free air – Pipeline Volume

Upon reception of the final dewatering pig train, the pigs would be removed in batches as dictated by the size of the pig receiver. Upon recovery of the pigs they would be inspected for wear and condition and reported upon. Photographic records would be taken of all received pigs. Throughout all pigging operation the following minimum parameters would be recorded: •


•

Launch and Reception pressures

•

Air flow

•

Pipeline temperature

•

Terminal water flow rate Page 16 of 22



When the complete pig train has been removed the pipeline would be vented down to zero pressure in preparation for commissioning. 6.7

Commissioning Commissioning activities will include both the export pipelines and infield flowlines and be included in the contract for the each installation. 6.7.1

Air Drying – Export Pipelines & Flowlines Following depressurization, dry air will be flowed at the highest velocity achievable from the installed air spread to maximize the drying potential. The air drier units should be capable of a minimum dewpoint of -20°C. Dewpoint monitoring will be conducted to confirm the introduced air is consistently dry throughout. Terminal dewpoint monitoring will be performed with reading being taken every 3 hours in the early stages of drying and reduced to 30 minutes as the dryness level is reduced. Upon reaching a consistent dewpoint reading of the target temperature for 8 hrs, the system will be “shut-in” for a minimum of 12 hours while a soak test is performed. After the soak test period the complete pipeline will be subjected to a low pressure purge to evacuate at least two complete pipeline volumes. Throughout this operation dewpoint recording will take place continuously to confirm the dewpoint target is verified and consistent.

6.7.2

Nitrogen Purging and Packing The pipeline will be purged using nitrogen membrane technology utilizing the existing dry air spread. Nitrogen will be produced at the maximum flow and quality available from the air spread. The exiting air will be vented via a silenced vent, during which oxygen levels will be monitored continuously. When the terminal reading has reached the maximum nitrogen level achievable from the equipment, the vent would be isolated, so pressurization can commence. Nitrogen pressurization to 0.5 barg will proceed, at which point the injection will stop and all nozzles and connections isolated. The system will be labeled “Nitrogen Gas Pressure”, and a pressure gauge left open to indicate the contained pressure level.

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7.

Vessel Matrix Communications with Installation Contractors have identified various installation vessel(s) for the pipelay operation that are capable of performing the installation of the pipelines/flowlines. The 12, 8” and 6” flowlines could be installed by reel method, but at this stage none were offered. Offshore Contractors is a Nigerian contractor with equipment that appears suitable for the installation. Some of the contractors contacted have vessels that are capable of installing some/all the lines but are not interested in participating in the Project. Their comments as follows: McDermott – “We are aware of the Olokola Project however we are not currently active in the Niger Delta area and our strategic plans do not envision establishing a marine construction presence there in the near future.” Heerema – “No, we don’t do that type of work with our current equipment pool. We are limited to J-lay at the moment with 32” max and in deeper water segment only.” Subsea 7 – “Thank you; however at this time Subsea 7 would have to decline.” Horizon – “Our lay barge departed for Singapore last month so we have nothing to take on another job with. 48" is a little out of our range anyway.”

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Table 1.1: Pipelay Installation Contractors - Export Pipelines (Vessels over 200T Tension) GLOBAL Contact Information

Jim Gallagher

ACERGY

ALLSEAS

HYUNDAI

SAIPEM (SONSUB)

HYUNDAI

[email protected]

Barbara Thompson [email protected]

Johan Drost [email protected]

Clyde Evons [email protected]

K.S. Won [email protected]

K.S. Won [email protected]

Installation Vessel

Hercules

Seaway Polaris

Solitaire

Castoro Sei

HD-2500

HD-60

Dimensions(ft)

156.6m x 42.7m x 7.6m

137.2m x 39m x 9.1m

397m x 300m x 40.6m

143.5m x 64.5m x 29.8m

130m x 36m x 10.5m

186m x 35m x 15m

DP System

DPS-2

BV DY.MSA.MA.TA.RS- Class 3

DP- NMD Class 3/LRS DP (AAA)

4 azimuthal variable pitch.

N/A

N/A

Anchor Spread

Anchors (8 point mooring)


N/A




Diameter Capacity

S-Lay to 60-inches Reel lay to 18-inches

S-Lay to 60-inches J-Lay to 20-inches

S-Lay to 60-inches

S-lay to

S-Lay to 60-inches

S-Lay to 60-inches

Tensioner Capacity

544T

3 = 204T total

3 x 350T=1050T

3 = 330T

2 + 1 =226T

3 = 245T

A&R Winch Capacity

500T

150T

420T

330T

250T

300T

Crane Capacity

1800T fixed 1450T revolving

1,500T fixed 1,100T revolving

300T

2 x 134T ea



Stinger Configuration

1st section 61m 2nd section 35m

52m

Adjustable to 140m max

95m – 3 sections

83m – 1 section

Lay-ramp Location

Stb.

Center Slot

Center Slot

Stb.

Center Slot

Receive Pipe

Port

Port Or Stb.

Port Or Stb.

Port

Port

Pipe Storage On Board

24,000 tons

Double Jointing Capability

NO

NO

YES

YES

NO

YES

Welding System

Automatic & Manual

Automatic

Automatic

Semi-automatic

Automatic

Automatic & Manual

Working Draft

4.9m

4.8m to 5.8m (9.5m DP)

9.23m

10 – 14.5m

5.5m

8.5 – 10m

Horizon, McDermott, Subsea 7 and Heerema were contacted – no interest

Page 19 of 22



Table 1.2: Pipelay Installation Contractor Matrix - Infield Flowlines

Contact Information

Jim Gallagher [email protected]

Jim Gallagher [email protected]

Barbara Thompson [email protected]

Clyde Evons clyde.evons@saipemamerica .com

Johan Drost [email protected]

Henk Vastenholt [email protected]

Henk Vastenholt [email protected]

Roy Sijthoff [email protected]

Installation Vessel

DLB Iroquois

DLB Comanche

Seaway Orion

S 355

Tog Mor

Jascon 30

Jascon 25

Deepwater Caesar

Dimensions(ft)

122m x 30.5m x 9.1m

122m x 30.4m x 8.8m

84.5m x 27m x 4.8m

108m x 30m x 7.5m

111m x 27.4m x 6.1m’

111m x 30.5m x 6.7m

118.8m x 30.4m x 8.4m

146.5m x 128.6m x 30m’

DP System

None

None

None

None

None

DP-3

DP-Class 3

DPNMD Class 2

Anchor Spread






N/A

N/A

N/A

Diameter Capacity

S-Lay to 48-inches

S-Lay to 60-inches

S-Lay to 42-inches

S-Lay to 48-inches

S-Lay to 60-inches

S-Lay to 60-inches

S-Lay

S-lay to 42 inches

Tensioner Capacity

2= 200T total

1 x 75T

2 = 36T total

2 = 100T total

1 x 100T

1 x 100T

2 x 60T

3 x 137T =405T total

A&R Winch Capacity

200T total

79T

50T

110T

1 x 175T

100T

Crane Capacity

250 tons fixed 250 tons revolving


165T revolving


300T

300T

30.5m + 4-section pontoons

Single Section

Single Section

43m

55m

90m

Stb.

Center Slot

Port

Stb.

Lay ramp Location

Stb.

Receive Pipe

Port

SAIPEM (SONSUB)

ALLSEAS

OFFSHORE CONTRACTORS

GLOBAL

Stinger Configuration

ACERGY

OFFSHORE CONTRACTORS

GLOBAL

Port

HELIX

2 x 225T 800T

Pipe Storage On Board

300T

10,000T

Double Jointing Capability

NO

NO

NO

NO

NO

NO

NO

Welding System

Manual

Manual

Manual

Manual-Automatic (Optional)

Automatic

Manual

Automatic

Working Draft

4.3m

4.3m to 5.8m

3.3m

2.6m to 4.8m

3.15m

5m

6m

7.8m to 9m

Horizon, McDermott, Subsea 7 and Heerema were contacted – no interest

Page 20 of 22



Appendix A Crossing MTO - Export Pipelines Item

Nominal Diameter

Location

Number of Crossings Pipelines

Cables

Crossing Length (m)

Mattresses (1)

M1

Okan GPP – OKLNG (East)

48”

10

2

152

M2

Okan GPP – OKLNG (West)

48”

10

2

152

M3

EARP-B – Okan GPP

42”

3

3

48

M4

Funiwa GPP – EARP-B

32”

2

-

30

M5

Subtotal

382

Spares (10%)

38 Totals

---

30

7

Comments

420

Note: 1. Mattress dimensions: 5m x 2m x 150 mm thick, SG 2.2, articulated in all directions, with double – width and/or high density (SG ~3.0) edge blocks. Alternatively, 8’x20’x9”; weights typically circa 5000 kg in air and circa 2700 kg submerged.

Page 21 of 22



Appendix B Crossing MTO - Infield Flowlines Item

Nominal Diameter

Location

Number of Crossings Pipelines

Cables

Crossing Length (m)

Mattresses (1)

M1

Okan NWP-1 – Okan GPP

24

2

30

M2


20

1

15

M3


18”

1

15

M4


18”

3

45

M5

Meji NWP-1 – Meji Wye

24”

7

105

M6

North Apoi NWP-L – Funiwa GPP

20”

1

15

M7

Okubie NWP-B – Funiwa GPP

20”

3

45

M8

Sonam Wye– Okan GPP

26”

7

105

M9

Okan GPP Produced Waterline

8”

7

105

M10

Funiwa GPP Produced Waterline

6”

2

M11

2

32

Subtotal

512

Spares (10%)

51 Totals

---

34

2

Comments

563

Note: 2. Mattress dimensions: 5m x 2m x 150 mm thick, SG 2.2, articulated in all directions, with double – width and/or high density (SG ~3.0) edge blocks. Alternatively, 8’x20’x9”; weights typically circa 5000 kg in air and circa 2700 kg submerged.

Page 22 of 22

85219-40-W-RP-001_(Rev_B).pdf

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