PETE 628 Lesson 6

1
PETE 628Lesson 6

• Build Curve Design

Petroleum Engineering Department Texas AM
University
2
Outline

• Dogleg severity
• Single radius build curve - - No tangent
  section
• Complex tangent build curve - - Unequal
  build rates)
• The Ideal build curve
• Tangent section inclination...

3
Outline - contd

• Casing and drilling fluid programs
• Positive displacement mud motors (PDMs)
• Bit side forces - change in trajectory
• READ to page 46 in the TEXTBOOK
• HW 3 - Max. Tool Length - due 02-10-04

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Dogleg Angle
b
5
Dogleg Angle

• Total (3D) change in hole angle between two
  survey points in a borehole

• dogleg angle
• Ref. API Bulletin D20

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Dogleg Angle...
1

• Example
• Point 1 Point 2
  Change
• I1 20o I2 30o ?I 10o
• A1 70o A2 130o ?A 60o
• MD1 10,200 MD2 10,350 ?MD 150

2
7
Calculation of DL Angle

? dogleg angle
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Dogleg Severity, d

• Dogleg severity,
• ???????
• ????? ? (100/?MD) 25.93 (100/150)
• 17.29 deg/100 ft
• ( The dogleg severity is the dogleg angle over a
  measured depth of 100 ft )

9
Dogleg Severity - contd

• In general,
• the dogleg severity,

10
Single Radius Build Curve

• Problem Where should the KOP be located if
  the TVD at EOC is 10,000 ft, and there is no
  tangent section ?
• BUR 15 deg./100 ft
• Hole angle at start of build 5o
• Hole angle at end of build 92o

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Single Radius Build Curve, contd
R

I1
I2
?T
I1
R
I2
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Single Radius Build Curve - contd

• R 18,000/(??BUR) 382 ft (BUR 15)
• ?T R (sin I2 - sin I1)
• TKOP Tb - ?T
• 10,000 - 382 (sin 92 - sin 5)
• TKOP 9,652 ft

13
Complex Tangent Build Curve

• Problem Determine the depth of the kickoff
  point for a complex tangent build curve if
• Depth of target 9,200 ft
• First BUR 15 deg/100 ft
• Second BUR 12 deg/100 ft
• Tangent angle 45 deg.
• Length of tangent 120 ft
• I1 0 deg I2 90 deg

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Complex Tangent Build Curve, contd

R1
KOP
R2
Ltan
45
EOC
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Complex Tangent Build Curve, contd

R1
0o
R2
Ltan
90o
EOC
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Complex Build Curve - Solution

• R1 18,000/(? BUR1) 18,000/15 ? 382 ft
• R2 18,000/(? BUR2) 18,000/12 ? 477 ft
• First build section,
• ????TB1 R1 (sin I2 - sin I1)
• 382 (sin 45 - sin 0 ) 270 ft
• Tangent section,
• ????Ttan L cos I 120 cos 45 85 ft

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Complex Curve - Solution - contd

• Second build section,
• ????TB2 R2 (sin I2 - sin I1)
• 477 (sin 90 - sin 45) 140 ft
• TKOP TVD - ?TB1 - ?Ttan - ?TB2
• 9,200 - 270 - 85 - 140
• TKOP 8,705 ft

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Complex Tangent Build Curve, contd

8,705
R1 382
0o
270
R2 477
Ltan
85
90o
EOC
140
Depth of target 9,200 ft
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The Ideal Build Curve
R1
R2
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The Ideal Build Curve - contd

• First build section
• Design for maximum build rate based on
  probable range
• Determine ACTUAL build rate
• Second build Section
• Reduce build rate as needed to hit target by
  changing tool face angle

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Tool Face Angle (?)
? 0

• Example
• 20o build motor
• When tool face angle is zero,
• Angle build rate 20 deg./100 ft

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Tool Face Angle - contd
? -30
? 30

• When tool face angle 30 deg.
• Angle build rate 20 cos 30 17.3 deg/100 ft

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Optimum Tangent Angle
where K1 18,000/p for BUR in deg/100
ft
REF TEXT p.26
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Opt. Tangent Angle - contd

• Itan inclination of tangent, deg.
• If final well inclination, deg.
• BURMax maximum expected BUR
• BURMin minimum expected BUR
• Tb base of target
• Tt top of target
• NOTE K1 1,719 if BUR deg./30 m

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Target TVD at EOC

• where,
• Ttgt target TVD at EOC
• BURExp expected or planned BUR

REF TEXT p.26
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Tangent Section - Example

• Assumptions
• If 86 deg.
• BURMax 12 deg./100 ft
• BURMin 10 deg./100 ft
• BURExp 11 deg./100 ft
• K1 18,000/??? 5,729.58
• Base of target at TVD, Tb 10,020 ft
• Top of target at TVD, Tt 10,000 ft

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Optimum Tangent Angle

• Inclination of tangent section,
• Itan 52.01 deg.

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Target TVD at EOC

• Ttgt 10,009.09 ft

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Basic horizontal well casing programs

• No intermediate casing
• Intermediate casing to KOP
• Intermediate casing to EOC

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No Intermediate Casing

Bakken Shale North Dakota TVD - 3,250 m Lateral
- 762 m
245 mm
SALTS
14o/30 m
90o
140 mm
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Intermediate Casing to KOP

Swan Hills Alberta Jean Marie N.E. B.C.
245 mm
Sloughing Shale Lost Circulation Differential
Sticking
18o/30 m
178 mm
114 mm
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Intermediate Casing to EOC

Alberta - Deep Basin TVD - 2,780 m Lateral -
275 m
273 mm
Sloughing Shales
20o/30 m
90o
114 mm
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Casing and Drilling Fluid Program

Bakken Oil Well Use weighted invert oil mud
(oil is continuous phase) Casing cemented up
from EOC
9 5/8
Flowing Salt Zones
14o/100 ft
5 1/2
Pf 0.62 psi/ft
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Casing and Drilling Fluid Program
10 3/4

Cadomin Gas Well Use weighted invert mud to csg.
point. KCl-Water-Polymer mud in horizontal
Sloughing Shales Overpressured gas
20o/100 ft
7 5/8
0.35 psi/ft
4 1/2
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Csg. and drilling fluid program - contd

• Bakken oil well - N. Dakota
• Lateral hole 3,000 ft
• Production casing cemented up from EOC through a
  stage collar
• Cadomin gas well - Alberta
• No cemented liner
• Two stage cement job on intermediate casing

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Marker Beds

• Some marker beds will be continuous to a control
  well, and some will be discontinuous.
• The continuous marker may change depth relative
  to the target.
• Markers with isopachs constant to the zone are
  the most desirable ...

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Continuous vs. discontinuous marker beds.
Horizontal Well
Vertical Control Well
Horizontal Well
SHALE MARKER (continuous)
COAL - (discontinuous)
TARGET
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Marker bed dip angle is unequal to target dip
angle
t1 t2
Vertical Control Well
Horizontal Well
Horizontal Well
Itarget Imarker SHALE MARKER

t2
t1
TARGET
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Faults in uphole marker beds
Horizontal Well
Vertical Control Well
Horizontal Well

C
C
A
A
tAM tAM ? tAV tAV
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Discontinuous reservoirs
LATERAL VARIATION

VERTICAL VARIATION
FAULTS
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Target Zone is at Expected TVD
BUR 5o/100 ft
BUR 20o/100 ft

TARGET ZONE
EOC AT 90o TOP OF TARGET ZONE (from samples)
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Target Zone at Lower TVDdue to Formation Dip
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Cross Section of Mud Motors showing different
Lobe Patterns

STATOR
ROTOR
High Speed - Low Torque Motors
44
Cross Section of Mud Motors showing different
Lobe Patterns

HIGH TORQUE - LOW SPEED MOTORS
45
Conventional single-lobe downhole Mud Motor
DUMP VALVE
STATOR

ROTOR
UNIVERSIAL JOINT SHAFT
THRUST and RADIAL BEARINGS

DRIVE SHAFT
BIT
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Medium Radius Angle Build Assembly
NON-MAGNETIC DRILL COLLAR

MOTOR
17.3
CONNEC.-ROD HOUSING
3.2
BEARING ASSEMBLY
BENT SUB
6.3
MOTOR ASSEMBLY 26.8
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Combined Effect of Bent Sub and Bent Motor

BENT SUB
?1 1.5o

BENT MOTOR

?2 2.5o ? ?1 ?2 4.0o
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Bending Stresses at Kickoff
?
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Bending stresses at equilibrium
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Lateral forces on bit from kickoff to
equilibrium

FORCE ON BIT 1,000s of lbf

FEET DRILLED (MD)
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Kickoff in a soft homogeneous formation

R1
High Initial Dogleg BUR gtgt BUREXP
BUREXP REXP
Bottomhole Assembly will reduce Curvature
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Kickoff in a soft formation underlying a hard
formation

High Dogleg and Contact Point
Very Hard Siltstone
Sloughing
Very Soft Coal
Bottomhole Assembly will NOT wipe out Dogleg
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Bit shank wear in abrasive formation
Shank

Slow Bit Recipro.
Shank Wear
Bit Contact Force
Bit Cone

Gauge Cutting Structure
Abrasive, Hard Formation
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Dogleg Angle Equations