This document provides definitions and applications of directional drilling. It discusses how directional wells are used to access reservoirs beneath obstacles or property lines. Deflection tools like whipstocks and bent subs are used to change a well's trajectory. Positive displacement motors and turbine motors are the two types of mud motors used to rotate drill bits for directional drilling. The three main well profiles are defined as: Type I "build and hold", Type II "build, hold, and drop", and Type III "continuous build". Examples are given of how to design each type of directional well based on input parameters.

1. JAMES A.
CRAIG

2. Table of Contents
 Definitions
 Applications of Directional Drilling
 Deflection Tools
 Mud Motors
 Types of Well Profile

3. Definitions
 Directional drilling is the process of directing the
wellbore along some trajectory to a predetermined
target.
 Deviation control is the process of keeping the
wellbore contained within some prescribed limits
relative to inclination, horizontal excursion from the
vertical, or both.

4. Applications
 History
 Interests in controlled directional drilling began about
1929 after new and later accurate means of measuring
hole angle was introduced during the development of
Seminole, Oklahoma field.
 In the early 1930’s the first controlled directional well
was drilled in Huntington Beach, California.
 Controlled directional drilling was initially used in
California for unethical purposes, that is, to
intentionally cross property lines.

5.  In 1933, during the development of the Signal Hill field
in Long Beach, California, several wells were drilled
under the Sunnyside Cemetery from locations across the
streets surrounding the cemetery.
 In 1934, it was used to kill a wild well, Madeley No.1, near
Conroe, Texas.

6. Typical offshore
development platform
with directional wells

7. Developing a field under a city
using directionally drilled wells

8. Drilling of directional
wells where the reservoir is
beneath a major surface
obstruction

9. Sidetracking
around a fish

10. Using an old well to explore for
new oil by sidetracking out of the
casing and drilling directionally

11. A relief well drilled to intersect the
uncontrolled well near the bottom

12. Salt dome drilling (direct the well
away from the salt dome to avoid
casing collapse problems)

13. Fault drilling through a steeply
dipping, inclined fault plane.

14.  Other applications include:
 To reach multiple targets
 Horizontal drilling
 To reach thin reservoirs (using horizontal and
multilateral drilling)
 To avoid gas or water coning problems

15. Deflection Tools
 The wellbore can be deflected from its current
position using any of the following:
 Whipstocks
 Jetting bit
 Bent subs with downhole motors

16. Whipstocks
Advantages
•It provides a controlled hole curvature
at the onset
•Can be run at any depth in any kind of
rock and very useful in hard rock
where others fail
Disadvantage
•It is necessary to drill the pilot hole
and then trip out to change the smaller
bit to one of the wellbore diameter.

18. Jetting bit
Advantages
•Several attempts can be made to initiate deflection without
pulling out of hole
•A full gauge hole can be drilled from the beginning
Disadvantage
•The technique is limited to soft-medium formations
•Severe dog-legs can occur if the jetting is not carefully
controlled
•On smaller rigs there may not be enough pump capacity to
wash away the formation

20. Bent subs with downhole motors
 The bent sub is run directly above the motor and its pin is
offset at an angle of 1 – 3 degrees.
 Deflection of the wellbore occurs when drilling is carried
out with no surface rotation to the drillstring.
 The drill bit is forced to follow the curve of the bent sub.
 The degree of curvature depends largely on the bent sub
offset angle and the OD of the motor.
 When the required angles (inclination and/or azimuth) are
obtained, this BHA is tripped out to be replaced with a
rotary assembly.

22. Steerable motors
 The motor is designed with an in-built bent housing below
the motor section; usually the connecting rod housing.
 The bent housing angle is usually 0.25 – 1.5 degrees.
 The use of steerable motors with the correct drill bit and
BHA reduces the number of round trips required to
produce the desired inclination/azimuth.
 It can be used in either :
 Oriented mode (sliding)
 Rotary mode

23. Oriented (Sliding) mode
•The drillstring remains
stationary (rotary table or
top-drive is locked) while the
drill bit is rotated by the
motor.
•The course of the well is only
changed when drilling in
sliding mode as the drill bit
will now follow the curvature
of the motor bent housing.
Rotary mode
•Steerable motor becomes
“locked” with respect to
trajectory and the hole
direction and inclination are
maintained while drilling.

24. Bit offset:
Steerable motor
vs. PDM with bent
sub

25. Mud Motors
 There are two types of mud motors:
 Turbines
 Positive displacement motors (PDM)

26. Turbine motor
 The turbine motor consists of:
 A multistage blade-type rotor and stator sections. The
number of rotor/stator sections can vary from 25 to 50.
 A thrust bearing section and a drive shaft.
 The rotor blades are connected to the drive shaft and
are rotated by mud pumped under high pressure.
 The stator deflects the mud onto the rotor blades.
 Rotation of the rotor is transmitted to the drive shaft
and drill bit.

28. Positive displacement motors (PDM)
 A PDM consists of:
 Power section (rotor and stator)
 By-pass valve
 Universal joint
 Bearing assembly

29.  Power section
 The PDM consists of a helical steel rotor fitted inside a
spirally-shaped elastomer moulded stator.
 Mud flowing under pressure fills the cavities between
the dissimilar shapes of the rotor and stator and under
the pressure of mud, the rotor is displaced and begins to
rotate.
 The rotor actually moves in an elliptical shape. This
eccentric movement is converted to true circular motion
by a universal joint assembly.

31.  By-pass valve
 This valve allows the drilling fluid to by-pass the mud
motor allowing the drillstring to fill during tripping in
and drain when making a connection or pulling out of
hole.
 The valve operates by a spring which holds a piston in
the upper position.
 In this position, ports in the by-pass valve are open
allowing mud to flow in or out of the drillstring.
 At 30% of recommended flow rate, the piston is forced
down, closing the ports and directing flow through the
mud motor.

33.  Universal Joint:
 A Connecting Rod assembly is attached to the lower
end of the rotor.
 It transmits the torque and rotational speed from the
rotor to the drive shaft and bit.
 Universal joints convert the eccentric motion of the
rotor into concentric motion at the drive shaft.
 Bearing and Drive Shaft Assembly
 The drive shaft is a rigidly-constructed hollow steel
component.
 It is supported within the bearing housing by radial
and axial thrust bearings

34. Types of Well Profile
 Type I
 Build and Hold
 Type 2
 Build, Hold and Drop.
 Returns to vertical after dropping – S-shape.
 Does not return to vertical after dropping – Modified S-
shape.
 Type 3
 Continuous Build

35. KOP
TYPE III
TYPE II
TYPE I
BUILD & HOLD BUILD – HOLD & DROP CONTINUOUS BUILD

36. Type I – build and hold
 Information needed:
 Surface co-ordinates
 Target co-ordinates
 TVD of target
 TVD to KOP
 Build-up rate

40. Type II – build, hold and drop
 Information needed:
 Surface co-ordinates
 Target co-ordinates
 TVD of target
 TVD to KOP
 TVD at end of drop-
off (usually end of
well)
 Build-up rate
 Drop-off rate
 Final angle of
inclination through
target.
 Because Type II have 2 curves,
2 radii need to be calculated
and compared with the total
departure, D3.
 These quantities are then used
to calculate the maximum
possible inclination angle at
end of build-up curve.

41. D3 > (R1 + R2) D3 < (R1 + R2)

42. Type III – continuous build
 Used for salt dome
drilling.
 For planning appraisal
wells.
 Information needed:
 Surface co-ordinates
 Target co-ordinates
 One parameter from:
 Maximum
inclination angle
 TVD to KOP
 Build-up rate

43. Design a directional well with the following
restrictions:
• Total horizontal departure = 4,500 ft
• True vertical depth (TVD) = 12,500 ft
• Depth to kickoff point (KOP) = 2,500 ft
• Rate of build of hole angle = 1.5 deg/100 ft
• Profile type: Type I well (build and hold)

44. (i) What is the maximum hole angle
required.
(ii)What is the total measured
depth (MD)?
q

45. ft
820
,
3
5
.
1
000
,
18
r1 


0
r2 
 
ft
000
,
10
500
,
2
500
,
12
D
D 1
4




ft
500
,
4
x4 
Maximum
Inclination
Angle

46. 46













500
,
4
)
820
,
3
(
2
500
,
4
)
820
,
3
(
2
000
,
10
500
,
4
000
,
10
tan
2
2
2
1
-

3
.
26
max 
q

















q 
4
2
1
4
2
1
2
1
4
2
4
1
4
1
max
x
)
r
r
(
2
x
)
r
r
(
2
)
D
D
(
x
D
D
tan
2

47. 47
ft
395
)
26.3
cos
-
3,820(1
)
cos
1
(
r
x 1
Build


q



ft
4,105
395
500
,
4
xHold




ft
265
,
9
L
105
,
4
sin
L
Hold
Hold



q

Measured Depth of
Well

48. 48
Hold
rad
1
1 L
r
D
MD 
q


ft
518
,
13
MD 
265
,
9
180
26.3
3,820
2,500 





 

