14 Deflection Methods

Directional Drilling

Deflection Methods

Alignments

Tool Orientation

Sperry Drilling Services

2007

• Selection of kick-off / sidetrack options • open hole

• cased hole

• Direction of sidetrack relative to original hole

• wellbore separation

• Kick-off point selection • formation hardness • stability • casing condition

• Nudging needed ?

Issues …

Kick-off / Sidetrack Options

•

Open hole kick-off or sidetrack

from open hole bottom cement plug [off whipstock]

•

Cased hole sidetrack

through milled casing section, or casing window (off whipstock)

Sidetracking a Vertical Well

kick-off / tie-on point

original wellbore survey stations new wellbore TD new target no preference in direction

Sidetracking a Deviated Well

kick-off / tie-on point

original wellbore survey stations TD sidetrack, new borehole Preferred direction :

on low side of original wellbore

new target

Deflection Tools

Rotary assembly : - Gilligan tool

- jetting

Steerable assembly : - from open hole bottom

- from whipstock, set to

- cement plug, or

- packer - via milled casing section

The Gilligan Tool

bending

• Emergency method of deflection • The drillpipe bends under the WOB and

points the bit to an arbitrary direction • Stabilizers increase the effectiveness

direction of deflection DC

1 joint of drillpipe

near-bit stabilizer (optional) / bit sub WOB

stabilizer (optional)

Jetting Needs a Deflection Bit

Smith Tool type BHDJ rock bit

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 • 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

Bit Displacement (1)

Lateral distance from the BHA centerline to the bit center

B

D

= L

t

x sin

θ [in]

where : Lt (in) length from bend to bit

θ (°) bend angle

_______________________________________ Example :

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 Bd

θ

Lt Bent sub

Bit Displacement (2)

Lateral distance from the motor centerline to the bit center

B

D

= L

t

x sin

θ [in]

where : Lt (in) length from bend to bit

θ (°) bend angle

_______________________________________ Example :

9 5/8” Sperry-Drill, 6/7 lobe, 5.0 stage Lt = 129.4” θ = 1.5° BD = 129.4 x sin 1.5 = 3.39 in Bd

θ

Lt

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

Bit Interference

B

_i

= B

_D

+ 0.5(D

_M

+D

_B

)-D

_H

[in]

where : BD (in) bit displacement DM (in) OD of the motor DB (in) bit size DH (in) hole size Dm

Db Dh

Bit Interference – Bent Sub

Bi = BD + 0.5(DM +DB)-DH

= 10.41 + 0.5(9.625 + 12.25) - 12.25 = 9.098 in

Bd= 10.41 (in) bit displacement Dm = 9.625 (in) OD of the motor Db = 12.25 (in) bit size Dh = 12.25 (in) hole size

Dm Db Dh Bi Bd Bent sub

Fsside force at the bit

Bit Interference – Bent Housing Motor

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

BD = 3.39 (in) bit displacement DM = 9.625 (in) OD of the motor DB = 12.25 (in) bit size DH = 12.25 (in) hole size

Dm

Db Dh

Bi BH

Fsside force at the bit

Side Force Calculation

3 t L 0 . 3 c S i B s F = × × where S_c=I×E Bi bit interference, in

Sc stiffness coefficient, lb/in2

Lt distance of bend from bit, in

Fs side force, lbf

I moment of inertia, in4

E modulus of elasticity, 29 x 106 _psi

Do outside diameter, in Di inside diameter, in and ⎟⎟_⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ₋ =₆₄D4_o D4_i I π

Side Force at Bit - Examples

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 :

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

Kick-off in Open Hole

The bit, motor and stbilizers form 3 contact points for a defined circular path

3-point geometry applies

no wall contact at the bend 1 2 3 WOB resultant force side force

Sidetracking from Cement Plug

Time drilling : 4-5 in/hr progress low WOB

monitor cement to formation cuttings ratio 50% cement 50% formation 100% cement 100% formation cmt plug

WOB resultant_force side force

Window must not start at casing coupling Open the window from

here

CCL

Set 100-150ft cmt plug

and dress it place f

o r t h e w in d o w

Preparations for

Running a Whipstock

Alternatively, a packer could be set below the casing coupling

Bottom Trip Whipstock

bottom trip trigger

cement plug window casing collar drill collar orienting sub UBHO starter mill shear pin whipstock slips hinge

Stiffback Whipstock

bottom trip trigger

cement plug shear pin

whipstock

slips no hinge

This whipstock might be set upside down

PackStock Whipstock

key for orientation window casing collar orienting stinger packer drill collar orienting sub UBHO starter mill shear pin whipstock slips hinge

PackStock Whipstock

stinger sits on key key for orientation pin sheared slips activated window casing collar whipstock tilted back

Packer + Whipstock

window casing collar packer drill collar orienting sub UBHO starter mill shear pin whipstock slips hinge high pressure hose

Starter Mill

the bolt comes to here

Mill with Drilling Cutters

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

String Mills for Dressing the Window

Note the blade’s left hand spiralling and barrel shape

The Shape of the Window

top bottom

Result of a surface experiment

The Shape of the Window

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

top

bttm

HS

HS ± 30°

Orientation of the Whipstock

Note : for LS orientation use stiffback whipstock ! the tip must rest

Roll-off Compensation

HS planned direction 5-10° whipstock face after setting

Retrievable Whipstock Detail

tip of the whipstock

slot

hook from HOMCO

Milling must not start at casing coupling !

Mill away about a joint length

CCL

Set a cmt plug to here

remo

ve ca

sin

g

Preparations for

Casing Section Milling

Start here

Clean the hole from steel debris

Mill a Section of the Casing

casin

g

remo

ved

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

Fill the Open Section

with Cement

casin g remo ved casin g remo ved

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

Dress off the Cement

casin

g

remo

Sidetrack the well via the open section

Sidetrack

Orient the assembly

100% cement

100% formation

Tricone Bit for Drilling Abrasive Formations

Low friction inserts on bit legs Shaped, active gauge cutters

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.

DBS Hypersteer Bit

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.

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

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.

Toolface Direction with Bent Motor

or Turbine

• Represents the orientation of the bent sub or the bent housing on a mud motor • The TF direction could be :

– 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)

Toolface Direction with Bent Sub

and Bent Motor or Turbine

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

Bent Sub Alignment to the Motor Toolface

If bent sub is used on top of a bent housing motor : The motor toolface and bent sub scribeline has to be lined up !

cut off direction of bend on bent sub

direction of bend on motor toolface scribeline

shims

MWD to Motor Toolface Alignment

scribeline chalkmark A B MWD HOC mud motor or turbine toolface offset

Why do we need this? TFO

A B

Sensor Configuration in Electronic Survey Systems

Gy By Gx Bx TF Acceleration vectors

Magnetic field vectors Gz

Bz

The toolface must be pointing in the X direction ! probe axis

Gravity toolface : Gx,Gy Magnetic toolface : Gx,Gy,Gz

Bx,By,Bz

The X Direction Marked on Hang-off Collars

Gx Bx

Gy By

TF

The machined notch is called “scribeline” index key

Measuring the Toolface Offset with Protractor

chalkmark mtr toolface position

MWD scribeline

Measuring the Toolface Offset

scribeline chalkmark 360 OD AB TFO DC × π × =

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

TFO (toolface offset) is measured in degrees (degrees) 360 AA AB TFO= × (degrees) A B MWD HOC mud motor or toolface offset TFO A B

Toolface Offset Calculation - Example

° = × = × = 360 33.6 3 . 50 7 . 4 360 AA AB TFO TFO A B Distances measured :

AA = 50.3 in (8 inch hang-off collar) AB = 4.7 in

scribeline motor

toolface

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

Magnetic North Referenced Toolface Direction

Magnetic Toolface (MTF) • Used if inclination is < 5-8º • Referenced to Magnetic North • Less accurate than high-sideTF

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

MN

E TF

High-side Referenced Toolface

Gravity Toolface (GTF) • Referenced to the high-side

(direction) of the borehole • Used if inclination is >5-8º • Given as X° Right or Left from

the HS HS

Note : the toolface direction is LEFT from HS here MN

E TF

high side

Magnetic Toolface vs. High-side Toolface

HS MN E TF HS or hole direction MTF GTF

HS 20L AZ 135 MN HS 170° MN 37R MTF 110 GTF ? E MN HS GTF ? AZ 315 MN MTF ?

Toolface Examples

MTF ?

Drilling a Deviated Well

Drilling modes :

• 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 Resulting curvature : rotated L oriented L rotated L rotated DLS oriented L oriented DLS DLS + × + × =

Required Oriented Ratio

Roriented oriented length ratio to total drilled

Loriented length of hole drilled oriented

Ltotal length of hole drilled (total)

Note : enter drop rate as negativ number rotated DLS oriented DLS rotated DLS required DLS total L oriented L oriented R − − = =

Tool Alignment vs. Orientation

Alignment

• Where is the toolface position ? - on fixed housing : marked

- on adjustable bent housing : where the numbers met • 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

• Orient the motor toolface when on bottom - compensate for reactive torque

- adjust toolface direction as drilling progresses

Calculation of the Required Toolface Setting

For Wellpath Correction

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

A B B A+ B A−

The Ragland Diagram

ΔAZ I2 ΔTF DL 0

Scales !

Note : DLS or BUR = DL / ΔMD HS is gravity highside I1 HS Ragland Diagram ΔAZ I1 I2

Building Inclination and Changing Direction

DL HS

I

2

> I

1 Ragland Diagram 0 ΔTF ΔAZ I1 I2

Dropping Inclination and Changing Direction

DL HS

I

2

< I

1 Ragland Diagram 0 ΔTF ΔAZ = 20.17° I2 =13.6° ΔTF = 110°

Example

Note : Complete the change while drilling 100 ft with 110° GTF resulting in DLS = 5°/100 ft DL = 5° HS I1 =14.5° 0 Ragland Diagram Δ

AZ = 0

I2 ΔTF = 180° DL

Dropping Inclination without Changing Direction

HS

I

₂

< I

₁ I1 Ragland Diagram 0 Δ

AZ = 0

I1 I2 ΔTF = 0° DL

Building Inclination without Changing Direction

HS

I

₂

> I

₁

Ragland Diagram

ΔAz I2 ΔTF DL 0 Note : ΔTF > 90° ! I1 HS

Changing Direction without Changing Inclination

Ragland Diagram

I

2

= I

1 ΔAz_max I2 ΔTF DL 0 Note : ΔTF > 90° ! I1 HS

Maximum Direction Change

Ragland Diagram

Calculation :

deg I DL sin a AZ 1 max ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = Δ Example

:

DL = 5° I1 = 14.5° ° = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = Δ 20.17 5 . 14 5 sin a AZmax

TF = 90 +

ΔAZmax GTF = 90 + 20.17 = 110° from HS 2 2 1 2

I

DL

I

=

−

°

=

−

=

I

DL

13

.

6

I

2 2 1 2

I

2

< I

1

Note : the maximum direction change causes inclination drop

Polar Graph Paper

The Ouija-board

DL circles initial inclination final inclination direction change TF rotation from HS Note :

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

Ouija Board Calculation

(DrillQuest)

Projection to target TVD

Direction to the Side of the Target

recent position, P N direction to target center

φ

Δφ Δφ R TC d left right

Inclination to the End of the Target

TC ΔTVD recent position d1 d2 dTC ΔMDTC ΔMD1 ΔMD2 R IN1 IN2 INTC P near far