1. Drilling Engineering 2 Course (2nd Ed.)

2. 1. the Survey of a Well
2. Calculating the Survey of a Well
3. Deflection Tools and Techniques
4. Hydraulic Method (Jetting)
5. Mechanical Methods

3. 1. Whipstock Running Procedures
2. Adjustable bent sub above motor
3. Motor housing with one or two bends
4. Offset Stabilizer on Motor
5. While Drilling Techniques
A. Data Transfer

5. Open Hole Whipstock Running
Procedures
The procedures for running the whipstock
can be summarized as follows:
A whipstock is to be selected according to
the wedge needed to effect the desired deflection.
A bit that is small enough
to fit in the hole with the chosen whipstock is selected.
The whipstock is attached to the bottom of the drillstring
by means of a shear pin.
Having run into the hole, the drillstring is rotated
according to the survey information,
until the tool-face of the whipstock is oriented
in the desired direction.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 5

6. Open Hole Whipstock Running
Procedures (Cont.)
By applying enough weight,
the chisel point is set firmly into the formation or cement plug
• to prevent the whipstock from rotating.
Additional weight is applied
to shear the pin that holds the drill collar to the wedge.
Rotation can then begin.
A small diameter pilot hole is drilled
to a depth of about 15 [ft] (4.5m) below the toe of the whipstock
at which point the whipstock-stop reaches the top collar
of the whipstock.
The pilot hole is then surveyed
to make sure that it has been drilled in the right direction.
After the pilot hole has been surveyed,
the bit and the whipstock are tripped out.
A hole opener is then run
to ream out the pilot hole to the full size hole.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 6

7. Casing Whipstock Running Procedures
The running steps for a casing whipstock
can be summarized as:
The casing whipstock packer with anchor device
is run to the kick-off point.
The alignment key is oriented using a gyro survey,
so that the whipstock will land in a unique position,
where the side track is needed.
The casing packer is set
to provide a base for the whipstock.
The whipstock is attached to a starting mill
by means of a shear pin and run in hole.
The whipstock is landed in the pre-oriented packer
by means of a lock-sub (mule-shoe stinger), and
thereby oriented in the desired direction.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 7

8. Casing Whipstock Running Procedures
(Cont.)
Weight is applied to break the shear pin
thereby freeing the starting mill off the whipstock.
The string is then rotated
to mill the casing to create the window.
Once the window has been cut,
the mill is replaced by a smaller sidetracking bit which is forced
by the whipstock through the window outside the casing.
A pilot hole can then be drilled.
After drilling the pilot hole,
the bottom hole assembly is pulled out and
replaced by an assembly of string and watermelon mills
• to make the window large enough
to accommodate a conventional bottom hole assembly.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 8

9. Cons and pros of whipstock technique
The whipstock’s biggest advantage is that
it provides a controlled hole curvature at the onset,
while distributing the side force
over the length of the whipstock body.
Whipstocks can also be run
at any depth in any kind of rock although
they are best suited for use in very hard rock
where jetting and mud motor deflecting techniques
are generally ineffective.
The main disadvantage of the whipstock is
the necessity to drill the pilot hole and then trip out
to change the smaller bit to one of the wellbore diameter.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 9

10. Downhole Motor With Bending Device
The most common
deflection technique
currently in use involves
running a downhole motor
which drives the bit
without rotating
the drill string.
Two different types of
downhole motors have
been developed,
the positive displacement
mud motor and
the mud turbine.
To create a change in the
trajectory,
downhole motors require a
deflection device.
The deflection is provided
either by a special sub
placed above the motor,
called a bent sub, or
by introducing a deflection
at the bottom section or
below the motor.
(steerable bottom hole
assembly)
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 10

11. Bent Sub
A bent sub is about two feet long
having the axis of the lower pin
connection machined
slightly off vertical.
 The amount of this so called
“offset angle”
• varies between 0.5 and 3.0◦.
The direction
in which the tool is deflected,
called “tool face”,
 is marked by a reference line
on the outer surface of the sub.
The bent sub itself
is connected
to a motor below it and
to an orienting sub above it.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 11

12. Making the Deflection
Once the assembly is run to the bottom of
the hole, the bent sub is oriented using the
orienting sub and a survey tool.
 After orientation, mud circulation is started
which initiates the operation of the mud motor
and drives the bit without rotating the drill
string.
The amount of deflection produced
is mainly a function of
 the offset, the length and stiffness of
the motor, and the hardness of the formation.
Typically, this type of assembly
is engaged in drilling until
the hole inclination reaches about 20◦.
 At this point the motor and the bent sub are
pulled out of the hole, and
 the building rotary assembly is engaged to
complete the building section of the hole.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 12

14. Steerable Bottom Hole Assembly
The increased application of downhole motors and
turbines as deflection tools has led to
the concept of having an adjustable component
with the bottom hole assembly that is
capable of altering the well path
without having to pull out of the hole
in order to change the bottom hole assembly.
Such a steerable drilling system is comprised of
a bit, a steerable motor, MWD tools and stabilizing unit(s).
The three categories of commercially available
steerable systems are:
adjustable bent sub above the motor,
motor housing with one or two bends, and
offset stabilizer on motor.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 14

15. conventional bent subs vs.
multi-angle bent-sub
The conventional bent subs with fixed angle
have the disadvantage that
they cannot be run in the hole in a straight position coaxial
to the string axis and therefore, cannot be used in rotary drilling.
Thus, the advantage of
a down hole adjustable deflection device is that
it can be run in the hole coaxially and the required
amount of deflection can be controlled from the surface.
 This makes directional drilling more efficient and less time consuming.
The multi-angle bent-sub
associated with a downhole motor allows for drilling of
the complete build up zone and of
the constant angle zone with the same bottom hole assembly.
Here the bent sub angle is controlled from the surface.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 15

16. The adjustable bent sub
The adjustable bent sub consists of
an upper and a lower sub that are connected
by an offset conical swiveling joint.
The axis of the conical joint is tilted
with respect to the main axis of the tool.
The lower sub is constructed so that
it is able to rotate at an angle that is
slightly offset from the vertical axis.
Initially the tool is made up so that
the upper and the lower subs are aligned.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 16

18. Bent housing vs. adjustable bent sub
when the deflecting device
is placed
on the top of
a downhole motor,
it introduces the deflection
at a distance far enough
from the bit to create
a considerable bit offset.
 The amount of
bit offset introduced
by the bent subs prohibits
rotating of the drill-string.
 Under this circumstance
drilling proceeds in
sliding or orienting mode only.
Building a bent house
at the lower end of a positive
displacement motor itself
introduces a deflection which
is much closer to the bit and
therefore, more effective than
what is possible
with the bent sub on
the top of the motor.
This means that a bent
housing will provide
a larger turn than a bent sub
of similar size and deflection.
The bent housing motor
assembly can be used
in steering mode
as well as in rotary mode
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 18

19. double-tilted universal joint housing
The bit offset
in the bent house assembly
can be reduced further
without affecting
the bit tilt angle
by introducing a second tilt
in the opposite direction
to the first one.
 Here the body of the motor
is brought back into a position
aligning with the borehole
axis.
When the rotary table is
engaged while the downhole
motor is in the hole,
bit offset is negated and
the assembly
drills straight ahead
to maintain inclination and
direction.
Such a deflecting unit is
known as double-tilted
universal joint housing
(DTU).
The DTU joint housing
develops a minimum bit offset
to give
the navigation drilling system
a full steering capability.
A bit angle of 0.25 to 0.78◦
is adequate to provide
directional control
using the DTU.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 19

20. straight hole drilling
The rotation of the
bending motor housing
for straight hole drilling
causes a slightly over
gauged hole and
that creates a “step” when
the drilling switches from
rotary to orient mode or
vice versa.
Therefore,
the smaller the bit offset,
the less the bit will cut with
its side, and the smaller
the size of the step.
Cutting with the bit face
extends bit life and
optimizes
the rate of penetration.
Similarly,
by keeping the motor
concentric to the hole,
rotary drilling
proceeds smoothly
without excessive
rotational bending
to the assembly.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 20

21. the step problem
A limitation with
all steerable systems is that
the stabilizers hang on
to the hole wall at a step,
and hence
reduce the weight on bit.
Although this step can
happen with a conventional
rotary assembly,
it is more common
with steerable systems
because the diameter of
the hole drilled in rotary mode
is slightly larger than the part
drilled in orienting mode.
The magnitude of
this step depends on
the formation hardness,
stability and
the build rate of the system.
To minimize
the step problem,
the near bit stabilizer
 should be under-gauged and
 should have
shallow nose heel angles.
The step size
can be further reduced
by minimizing
the build rate of the system.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 21

24. The deflection below the turbine
The positive displacement motor can use
either a bent sub above the motor or
have the housing (bend housing) below it.
The deflection below the turbine is provided by
a special stabilizer with an under-gauge blade,
known as offset stabilizer, and
is located on the turbine near the bit.
The under-gauge blade is considered
to be the tool face.
It is oriented in the same way as
the bent sub and the bent house.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 24

25. Procedure
When the drill-string is not rotated,
the turbine drives the bit along a predefined course
which is given by the under-gauge blade orientation.
The greater the stabilizer offset
(higher under-gauge blade),
the greater the rate of build,
but the amount of offset is limited.
Once the wellbore is brought back
onto the planned trajectory,
the drillstring can be rotated.
Rotating the offset stabilizer
results in a slightly over-gauge hole.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 25

27. While Drilling Techniques
With
“while drilling techniques”,
the direction of
the wellbore,
condition of the drillstring
as well as the formations
that have been penetrated
can be measured and
the measurements
transferred to the rig-site
while drilling.
While drilling sensors
are typically
mounted at the BHA as
close as possible to the bit.
Depending on the
drillstring configuration,
the distance between
the bit and the measuring
devices can be as little as
10 [ft] (3m).
In this way,
the measurements taken
are somewhat behind
the bit and depending on
the penetration rate,
are recorded
with some lag-time.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 27

28. While drilling systems
While drilling systems generally consist of
a power system,
measuring sensors and
a telemetry system for data transfer.
The power system can be either based
on a battery, a turbine or a combination of them.
Batteries have the advantage that
no circulation is needed to carry out measurements,
thus while tripping, control logs can be run.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 28

29. Measurement While Drilling
The term “measurement while drilling” (MWD)
refers to the while drilling measurement of
directional parameters (MD, inclination, azimuth)
as well as certain drilling parameters like
WOB, downhole torque, temperature, etc.
The sensor to perform these measurements are
three orthogonal fluxgate magnetometers and
three accelerometers.
The use of gyroscope navigated MWD
offers significant benefits over navigation sensors.
They offer greater accuracy and
are not susceptible to inference from magnetic fields.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 29

30. Operating temperature of MWD
The drilling parameters measured with MWD tools
are aimed to increase the drilling efficiency (stick-slip),
be applied to detect
abnormal formation pressures or any kind of hole problems.
Most MWD tools can operate at tool-temperatures
up to 150 ◦C, some sensor work up to 175 ◦C.
It should be noted that
the tool-temperatures are generally about 20 ◦C
less than the formation temperatures,
measured by wireline logs which is
caused by the cooling effect of mud circulation.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 30

31. Operating pressure and shock load
of MWD
Downhole pressures create less problems for MWD
tools than downhole temperatures.
Most MWD tools are designed
to withstand up to 20,000 [psi] which is rarely encountered.
MWD tools are most sensitive to shock and vibrations.
Torsional shock, created by stick-slip
have been found to be able to cause tool failure,
lateral shocks which can be magnitudes higher than axial
shocks, can be reduced by the use of jars.
Normally sensors measure MWD shock loads
constantly and transmit them to the rick.
There the driller can manipulate the drilling parameters
to keep them in acceptable limits.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 31

32. Logging While Drilling
The term “logging while drilling” (LWD)
refers to the while drilling measurements
of wireline equivalent parameters like
resistivity,
porosity,
density and
sonic logs.
When these parameters are known,
“geosteering” can be performed
where the trajectory of the well is “re-designed”
according to the actual formation’s position and shape.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 32

34. Introduction
Since the amount of data measured by while
drilling techniques can be large,
mostly not all measurements are continuously
transferred to the rig.
Data that are not transferred are commonly
stored and retrieved at the following trip.
Several different systems have been developed to
transfer the measured data to the surface,
the “mud pulse telemetry”
is the by far most often applied on.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 34

35. different mud pulse systems
Three different
mud pulse systems are
commercially available
today:
Positive pulse system:
creates a momentary
flow restriction
(higher pressure than
the drilling mud volume)
in the drillpipe.
It is the most often
applied one
(since it is easiest to
achieve even for extended
reach wells.)
Negative pulse system:
creates a pressure pulse
lower than that of
the mud volume by
venting a small amount of
high pressure drillstring
mud from the drillpipe of
the annulus.
Continuous wave system:
creates a carrier
frequency that is
transmitted through
the mud and encoded
data using phase shifts of
the carrier.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 35

36. signal to noise range
When the signals reach the surface,
they are retrieved by transducers
that are located on the standpipe and
send to computers at the site for further evaluation.
The data transmitted are overlayed with noise
where the mud pumps are the main source.
Other parameters that influence
the “signal to noise range” are:
what mud type and bit type are in use,
the length of the well and
the drilling parameters applied itself.
Spring14 H. AlamiNia Drilling Engineering 2 Course (2nd Ed.) 36

37. 1. Dipl.-Ing. Wolfgang F. Prassl. “Drilling
Engineering.” Master of Petroleum
Engineering. Curtin University of Technology,
2001. Chapter 9