14 Deflection Methods

Sperry Drilling Services

2007.1

Issues … •

Directional Drilling

Selection of kick-off / sidetrack options • •

•

Deflection Methods Alignments Tool Orientation

Direction of sidetrack relative to original hole •

•

wellbore separation

Kick-off point selection • • •

•

open hole cased hole

formation hardness stability casing condition

Nudging needed ?

Sperry Drilling Services 2007

Sidetracking a Vertical Well Kick-off / Sidetrack Options

survey stations

• Open hole kick-off or sidetrack from

kick-off / tie-on point

open hole bottom cement plug [off whipstock]

new wellbore original wellbore

• Cased hole sidetrack through milled casing section, or casing window (off whipstock)

TD new target no preference in direction

Deflection Tools

Sidetracking a Deviated Well

Preferred direction : on low side of original wellbore

Rotary assembly :

Steerable assembly : - from open hole bottom

kick-off / tie-on point survey stations

- Gilligan tool - jetting

sidetrack, new borehole

original wellbore

- from whipstock, set to - cement plug, or - packer - via milled casing section

new target TD

Directional Drilling – Deflection Methods

Page 1


2007.1

WOB

The Gilligan Tool DC

Jetting Needs a Deflection Bit Smith Tool type BHDJ rock bit

stabilizer (optional) • Emergency method of deflection • The drillpipe bends under the WOB and points the bit to an arbitrary direction

bending 1 joint of drillpipe

• Stabilizers increase the effectiveness

near-bit stabilizer (optional) / bit sub direction of deflection

Bit Displacement (1)

The Mechanism of Deflection with Bent Element •

A bent element in the bottom hole assembly displaces the bit from the borehole centerline

•

The bit displacement results in bit-borehole interference

Bent sub

Lateral distance from the BHA centerline to the bit center

BD = Lt x sin θ [in] Lt

θ •

The interference creates side force acting on the bit

•

The side force pushes the bit sideways, thus it drills axially and laterally, too

•

As the assembly drills, the curvature of the wellbore is increasing until the side force is significant

•

At equilibrium build rate (curvature) the side force becomes 0, and the curvature is not increasing further

Bd

Lt

Lt (in) length from bend to bit θ (°) bend angle

Bit Interference

Bd

Distance the bit would displace beyond the wall of the wellbore if not constrained by formation. Dh Dm

_______________________________________ Example : 9 5/8” Sperry-Drill, 6/7 lobe, 5.0 stage Lt = 129.4” θ = 1.5°

θ

BD = 129.4 x sin 1.5 = 3.39 in


9 5/8” Sperry-Drill, 6/7 lobe, 5.0 stage Lm = 32.14 ft Lt = 32.14 + 1.0 = 33.14 ft = 397.68” θ = 1.5° BD = 397.68 x sin 1.5 = 10.41 in

Lateral distance from the motor centerline to the bit center

where :

Lt (in) length from bend to bit θ (°) bend angle

_______________________________________ Example :

Bit Displacement (2)

BD = Lt x sin θ [in]

where :

Db

Bi = BD + 0.5(DM +DB)-DH [in] where : BD (in) DM (in) DB (in) DH (in)

bit displacement OD of the motor bit size hole size

Bi

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2007.1

Bent sub

Bit Interference – Bent Sub Bd = 10.41 (in) Dm = 9.625 (in) Db = 12.25 (in) Dh = 12.25 (in)

Bit Interference – Bent Housing Motor


BD = 3.39 (in) DM = 9.625 (in) DB = 12.25 (in) DH = 12.25 (in)


Dh

Dh

Bi = BD + 0.5(DM +DB)-DH = 10.41 + 0.5(9.625 + 12.25) - 12.25 = 9.098 in

Dm

Bi = BD + 0.5(DM +DB)-DH = 3.39 + 0.5(9.625 + 12.25) - 12.25 = 2.077 in

BH

Dm Db

Db

Fs side force at the bit Bd

Bi

Bi

Side Force at Bit - Examples

Side Force Calculation B × S × 3. 0 Fs = i c L3 t

where

4 − D 4 ⎞⎟ Sc = I × E and I = π ⎛⎜⎜Do i ⎟⎠ 64 ⎝

Fs side force at the bit

Assuming a 9-5/8"Sperrydrill with 3" equivalent ID : moment of inertia I = 4173 in4 stiffness coefficient SC = 12.102 x 109 bit to bend distances Lt = 397.7 and 129.4 in Side forces at the bit :

Bi Sc Lt Fs I E Do Di

3

bit interference, in stiffness coefficient, lb/in2 distance of bend from bit, in side force, lbf moment of inertia, in4 modulus of elasticity, 29 x 106 psi outside diameter, in inside diameter, in

Bent sub on top of a straight motor = 5,252 lbf Motor with bent housing ------------- = 34,803

Sidetracking from Cement Plug

Kick-off in Open Hole

Time drilling :

The bit, motor and stbilizers form 3 contact points for a defined circular path 3-point geometry applies

4-5 in/hr progress low WOB monitor cement to formation cuttings ratio

side force 100% cement

no wall contact at the bend

2

WOB

50% cement 50% formation

resultant force

1


WOB

side force resultant force

100% formation

cmt plug

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2007.1

Preparations for Running a Whipstock

CCL

drill collar

Bottom Trip Whipstock

orienting sub UBHO Window must not start at casing coupling

casing collar starter mill

place for the window

Open the window from here

Set 100-150ft cmt plug and dress it

shear pin

whipstock

window

hinge slips bottom trip trigger

Alternatively, a packer could be set below the casing coupling

cement plug

Stiffback Whipstock

drill collar

PackStock Whipstock

orienting sub UBHO casing collar starter mill

shear pin

This whipstock might be set upside down

shear pin

whipstock

whipstock

no hinge

hinge

slips

window

slips orienting stinger

bottom trip trigger cement plug

PackStock Whipstock

packer

drill collar orienting sub UBHO

key for orientation

Packer + Whipstock casing collar

casing collar

starter mill

shear pin

high pressure hose

whipstock tilted back pin sheared window

window

whipstock hinge slips packer

slips activated stinger sits on key

key for orientation


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2007.1

Starter Mill

Mill with Drilling Cutters

the bolt comes to here

PDC cutters allow the mill to drill some distance out of the window Note the blade’s left hand spiralling !

The Shape of the Window

String Mills for Dressing the Window

bottom

Result of a surface experiment

top

Note the blade’s left hand spiralling and barrel shape

The Shape of the Window

Orientation of the Whipstock top

HS HS

± 30°

An other surface experiment. Note the twisting shape of the window.

the tip must rest on the casing wall

bttm


Note : for LS orientation use stiffback whipstock !

Page 5


2007.1

Roll-off Compensation HS

Retrievable Whipstock Detail 5-10° tip of the whipstock

planned direction whipstock face after setting

slot

hook from HOMCO

Preparations for Casing Section Milling

CCL

Mill a Section of the Casing

Milling must not start at casing coupling !

Clean the hole from steel debris

casing removed

Mill away about a joint length

remove casing

Start here

Set a cmt plug to here

Fill the Open Section with Cement

Dress off the Cement

Set an overlapping cmt plug Wait on cement for sufficient time !


casing removed

casing removed

Drill and dress the cement below the top of the milled section (~10ft)

Page 6


2007.1

Sidetrack

Tricone Bit for Drilling Abrasive Formations

Orient the assembly

Shaped, active gauge cutters

Sidetrack the well via the open section

100% cement

Low friction inserts on bit legs 100% formation

DBS Hypersteer Bit

DBS Hypersteer Bit

Designed for the push-the-bit rotary steerable systems. Aggressive, short gages are appropriate for high dogleg requirements. These bits are also designed with longer, more passive gauges where hole quality is of concern.

Designed for point-the –bit rotary steerable systems. Generally feature longer, more passive gauge lengths. Like the others, they are optimized to match the mechanical system, the formation, and the required dogleg severity.

DBS Fulldrift Bit

Toolface Direction with Bent Sub and Straight Motor or Turbine bent sub The direction of bend is marked with a scribe-line (machined groove)

Common bend angles : 0.25 – 0.50 - 0.75 – 1.00° etc.

The extended gauge of the bit matches the requirements of the Geo-Pilot system, providing excellent steerability, hole quality, and low vibration level.


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2007.1

Toolface Direction with Bent Motor or Turbine

Toolface Direction with Bent Sub and Bent Motor or Turbine

bent sub •

Represents the orientation of the bent sub or the bent housing on a mud motor

•

The TF direction could be :

The bent sub scribeline has to be aligned with the motor / turbine toolface !

– Magnetic North referenced … “Magnetic Toolface” (MTF) given as Azimuth – High Side referenced … “Gravity Toolface” (GTF) given as X degrees Right or Left (… from the recent hole direction known from the last survey)

MWD to Motor Toolface Alignment

Bent Sub Alignment to the Motor Toolface If bent sub is used on top of a bent housing motor : MWD HOC

A B

The motor toolface and bent sub scribeline has to be lined up !

offset

chalkmark

toolface

scribeline

A

B

scribeline

TFO

cut off direction of bend on bent sub

mud motor or turbine Why do we need this? shims

direction of bend on motor

Sensor Configuration in Electronic Survey Systems

toolface

The X Direction Marked on Hang-off Collars

probe axis

Gy

Gx Magnetic toolface : Gx,Gy,Gz Bx,By,Bz

Acceleration vectors

Gz

Gy By

Gravity toolface : Gx,Gy

index key

By

Bx

Magnetic field vectors

Gx Bx

Bz TF

TF

The toolface must be pointing in the X direction ! The machined notch is called “scribeline”


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2007.1

Measuring the Toolface Offset Measuring the Toolface Offset with Protractor MWD HOC

A

A

B

scribeline

B

TFO offset

chalkmark

TFO =

MWD scribeline

chalkmark mtr toolface position

or

mud motor

AB × 360 (degrees) ODDC × π

TFO = AB × 360 (degrees) AA

Note : AB distance is in the same units as AA or ODDC toolface

TFO (toolface offset) is measured in degrees

Toolface Offset Calculation - Example Magnetic North Referenced Toolface Direction Distances measured : AA = 50.3 in (8 inch hang-off collar) AB = 4.7 in

MN A

B TFO

4.7 TFO = AB × 360 = × 360 = 33.6° AA 50.3

Magnetic Toolface (MTF)

TF

• • •

scribeline

motor toolface

Used if inclination is < 5-8º Referenced to Magnetic North Less accurate than high-sideTF

E

Note : check the method of angle measurement with the directional drilling company !

Note : The toolface direction is mechanically transferred to the survey tools

Magnetic Toolface vs. High-side Toolface

High-side Referenced Toolface Gravity Toolface (GTF) HS

MN

•

TF high side

• •

Referenced to the high-side (direction) of the borehole Used if inclination is >5-8º Given as X° Right or Left from the HS

E

Note : the toolface direction is LEFT from HS here


HS

MN TF MTF

HS or hole direction GTF

E

Note : the HS could be referenced to either magnetic- or true North !

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2007.1

Toolface Examples Drilling a Deviated Well MN 20L

AZ 315 MN

HS

HS

Drilling modes :

MTF ?

GTF ?

• Oriented – the TF is set to the required direction and drilling performed without drillstring rotation • Rotated – the drillstring is rotated, the hole drilled is straight E

Resulting curvature :

DLS = MTF ?

AZ 135 MN

37R

DLSoriented × Loriented + DLSrotated × Lrotated Loriented + Lrotated

MTF 110 GTF ?

HS 170° MN

Tool Alignment vs. Orientation

Required Oriented Ratio Alignment

•

DLSrequired − DLSrotated L Roriented = oriented = L total DLSoriented − DLSrotated

Roriented

Loriented Ltotal

oriented length ratio to total drilled length of hole drilled oriented length of hole drilled (total)

Calculation of the Required Toolface Setting For Wellpath Correction

•

Adjust position of bent subs, kick pad(s) to motor toolface

•

Align survey instrument to bent sub / motor toolface

•

Measure toolface offset to MWD

Orientation

•

Note : enter drop rate as negativ number

Where is the toolface position ? - on fixed housing : marked - on adjustable bent housing : where the numbers met

Orient the motor toolface when on bottom - compensate for reactive torque - adjust toolface direction as drilling progresses

Vectorial Sum and Difference

• The Ragland – diagram • Polar graph paper • The Ouija board (slide rule) • Computer programs (Pluto, DrillQuest)

A −B

B

A +B A


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2007.1

The Ragland Diagram

Building Inclination and Changing Direction I2 > I1

Scales !

I2

I2 DL

ΔAZ

ΔAZ ΔTF

I1

0

DL

HS

ΔTF

I1

0

HS

Note : DLS or BUR = DL / ΔMD HS is gravity highside Ragland Diagram

Ragland Diagram

Dropping Inclination and Changing Direction

Example

I2< I1

.6° I 2 =13

I2 DL

ΔAZ = 20.17°

ΔAZ

ΔTF = 110° HS

HS

ΔTF

I1

0

DL = 5° I1 =14.5°

0

Note : Complete the change while drilling 100 ft with 110° GTF resulting in DLS = 5°/100 ft Ragland Diagram

Ragland Diagram

Dropping Inclination without Changing Direction

I2< I1

I2 > I1

ΔTF = 180°

ΔAZ = 0 I2 0

Building Inclination without Changing Direction

ΔAZ = 0 I2

DL

I1

ΔTF = 0°

DL HS 0

I1

Ragland Diagram


HS

Ragland Diagram

Page 11


2007.1

Changing Direction without Changing Inclination

Maximum Direction Change

I2

I2 = I1

I2

DL

DL

ΔAz

ΔAzmax ΔTF

I1

0

HS

Note : ΔTF > 90° !

I1

0

ΔTF

HS

Note : ΔTF > 90° !

Ragland Diagram

Ragland Diagram

Polar Graph Paper

Calculation : Δ

⎛ DL ⎞ ⎟⎟ deg AZ max = a sin ⎜⎜ ⎝ I1 ⎠ TF = 90 + ΔAZmax

I2 = I12 − DL

2

Example :

DL = 5° Δ

I1 = 14.5°

⎛ 5 ⎞ AZmax = a sin ⎜ ⎟ = 20.17° ⎝ 14.5 ⎠

GTF = 90 + 20.17 = 110° from HS 2 I2 = I12 − DL = 13.6°

I2 < I1

Note : the maximum direction change causes inclination drop

The Ouija-board

Ouija Board Calculation (DrillQuest)

initial inclination

direction change

TF rotation from HS

DL circles

final inclination

Note : The Ouija-board is based on the same vector calculations as the Ragland diagram


Projection to target TVD

Corr. run length

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2007.1

Inclination to the End of the Target

Direction to the Side of the Target

P

recent position left R TC

N

IN1 INTC IN2

d direction to target center

φ

Δφ Δφ

recent position, P

right

ΔTVD

ΔMD2

ΔMDTC

ΔMD1

R

d1 dTC d2 near


far TC

Page 13

14 Deflection Methods

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