graduation project (petroleum)

1. Graduation Project
Drilling Technology
Team Leader
Team Members
2019 – 2020

2. ACKNOWLEDGMENTS
In the present world of competition there is a race of existence in which those are
having with to come forward succeed. Project is like a bridge between theoretical
and practical working. With this willing I joined this particular project. First of all,
I would like to thank the supreme power the Almighty God who is obviously the
one has always guided me to work on the right path of life. Without his grace this
project could not become a reality. Next to him are my parents, whom I am greatly
indebted for me brought up with love and encouragement to this stage. I am feeling
oblige in taking the opportunity to sincerely thanks to Mr. Farhad Kaka Amin
and special thanks to my worthy teacher of (Production) Mrs. Shajwan Azad ,
moreover, I am highly obliged in taking the opportunity to sincerely thanks to all
the staff members of (Hawler institute for Oil & Gas) for their generous attitude
and friendly behavior. At last I am thankful to all my teachers and friends who
have been always helping and encouraging me though out the year. I have no
valuable words to express my thanks, but my heart is still full of the favors
received from every person.

3. ABSTRACT
Drilling is one of the stages of oil exploration, carried out after the prospecting
phase, and involves all the operations done since the beginning of the well to its
delivery, (to the production team). The objective of this study is to analyses and
characterizes exactly the major processes performed during the drilling of an oil
well. These are processes that involve a high investment and financial risk, where
safety and efficiency are key words and crucial for an economic viability. The
correct sizing of these processes, the way they are guided and run, becomes the key
to a drilling´s success. It is in this context that the analysis of procedures and the
operational issues relating to these processes, become extremely important for the
oil industry, and for society, since oil is the main source of energy today,
contributing to the formulation of best practices and improvement of the drilling
technology. For a better understanding of all operations, the main equipment used
in the drilling of a well is, covered first, and only after, drilling operations are
properly mentioned. The drilling program and the completion of a well is,
presented at the end, which describes in detail all operations, including how to
proceed in case of the abandonment of a well.

4. No. Contents of the first chapter Page
1. Introduction 1
1.1 Drilling 2
1.1.1 Type of drilling rig 2
1.1.2 Drilling craw 3
1.2 Component of drilling rig 3
1.2.1 Hoisting system 4
1.2.1.1 Substructure 4
1.2.1.2 Derrick 5
1.2.1.3 Crown block 5
1.2.1.4 Travelling block 6
1.2.1.5 Hook 6
1.2.1.6 Draw works 7
1.2.1.7 Drilling line 7
1.2.1.8 Cathead 8
1.2.1.9 Air hoist 8
1.2.1.10 Drill line spool 9
1.2.2 Rotating system 9
1.2.2.1 Top drive 9
1.2.2.2 Swivel 10
1.2.2.3 Kelly 11
1.2.2.4 Kelly bushing 11
1.2.2.5 Master bushing 11
1.2.2.6 Rotary table 12
1.2.2.7 Drill string 12
1.2.2.8 Drill pipe 12
1.2.2.9 Heavy weight drill pipe 13
1.2.2.10 Drill color 13
1.2.2.11 Sub 14
1.2.2.12 There are basically three types of drilling bit 14
1.2.3 Power system 15
1.2.3.1 SCR 15
1.2.3.2 Diesel tank 15
1.2.4 Circulation system 16
1.2.4.1 Drilling fluid major direct function of drilling fluid 17
1.2.4.2 Mud pumps 17
1.2.4.3 Divert Mud flow to kill lines in case of kill or lost circulation 17
1.2.4.4 Stand Pipe 18
1.2.4.5 Rotary hose 18
1.2.4.6 Mud return 18
1.2.4.7 Shale Shake 19
1.2.4.8 Desander 19
1.2.4.9 Desilter 19
1.2.4.10 Degasser 20
1.2.4.11 Mud gas separator 20
1.2.4.12 Reserve Pit 20
1.2.4.13 Drilling fluid 21

5. No. Contents of the second chapter Page
2. Casing 22
2.1 Types of Casing Strings 22
2.1.1 Caisson pipe (26 to 42 in. OD) 23
2.1.2 Conductor pipe (7to 20in. OD) 23
2.1.3 Surface casing (17-1/2 to 20 in. OD) 23
2.1.4 Intermediate casing (17-1/2 to 9-5/8 in. OD) 23
2.1.5 Production casing (9-5/8 to 5 in. OD) 24
2.1.6 Liners 24
2.2 Cementation 25
2.2.1 Primary Cementation 25
2.2.2 Main Functions 25
2.2.3 Primary Cementing Techniques 25
2.2.4 Stage Cementation: Reasons 26
2.2.5 Liner Cementation 26
2.2.6 Secondary Cementation 27
2.2.7 Reasons for setting cement 27
2.3 Measurement While Drilling (MWD) 27
2.3.1 Survey sensor 28
2.3.2 Gamma-ray Sensor 28
2.3.3 Resistivity Sensor 28
2.3.4 Temperature Sensor 28
2.3.5 Downhole WOB/Torque 28
2.3.6 Turbine RPM 28
2.4 Logging while drilling (LWD) 29
2.5 Completion 29
2.5.1 Open Hole Completion 30
2.5.2 Conventional Perforated Completion 30
2.5.3 Sand Exclusion Completion 30
2.5.4 Permanent Completion 30
2.5.5 Multiple Zone Completion 31
2.5.6 Drainhole Completion 31
2.6 Wellhead 31
2.7 Blowout Prevention System 32
2.7.1 Choke manifold 32
2.7.2 Accumulator 33
2.7.3 Diverter System 33
2.8 Xmasstree system 33
2.8.1 Main components of Christmas tree 33
2.8.2 Christmas tree function 34
2.9 Drilling Problems 34
2.9.1 Stuck Pipe/Pipe Sticking 34
2.9.2 Lost Circulation 34
2.9.3 Shale Problem/Borehole Instability 35
2.9.4 Prevention of Sloughing Shale 35
2.9.5 Mobile Formation 35
2.9.6 Prevention Action 35
2.9.7 Under gauge Hole 36
2.9.8 Kick and Blowout 36

6. 2.9.9 Causes of Kick/Blowout 36
2.9.10 One critical function of drilling fluid 36
2.9.11 The effects of blowout are: 36
Discussion 37
Conclusions 38
References 39

7. Figure Figure Page
Figure 1.1: Hoisting System 4
Figure 1.2: Substructure 4
Figure 1.3: Derrick 5
Figure 1.4: Crown block 5
Figure 1.5: Travelling block 6
Figure 1.6: Hook 6
Figure 1.7: Draw works 7
Figure 1.8: Drilling Line 8
Figure 1.9: Wire Rope Construction Line 8
Figure 1.10: Cathead 8
Figure 1.11: Air hoist 8
Figure 1.12: Drill line spool 9
Figure 1.13: Rotating system 9
Figure 1.14: top drive 10
Figure 1.15: Swivel 10
Figure 1.16: Kelly 11
Figure 1.17: Kelly bushing 11
Figure 1.18: Master bushing 11
Figure 1.19: Rotary table 12
Figure 1.20: Drill string 12
Figure 1.21: Drill pipe 13
Figure 1.22: Heavy Weight Drill pipe 13
Figure 1.23: Drill color & Drill pipe 13
Figure 1.24: Types of Sub 14
Figure 1.25: Types of bit 14
Figure 1.26: Power system 15
Figure 1.27: SCR 15
Figure 1.28: Diesel tank 15
Figure 1.29: Principal components 16
Figure 1.30: Mud pumps 17
Figure 1.31: Divert Mud flow 17
Figure 1.32: Stand pipe 18
Figure 1.33: Rotary hose 18
Figure 1.34: Mud return 18
Figure 1.35: Shale shake 19
Figure 1.36: Desander 19
Figure 1.37: Desilter 19
Figure 1.38: Degasser 20
Figure 1.39: Mud gas separator 20
Figure 1.40: Reserve pit 20
Figure 1.41: Circulation system 20
Figure 2.42: Type of casing string (1) 22

8. Figure 2.43: Type of casing string (2) 24
Figure 2.44: Cementing 25
Figure 2.45: Cementing process 26
Figure 2.46: Cementing Applications 27
Figure 2.47: Gamma-ray Sensor 28
Figure 2.48: Wellhead 31
Figure 2.49: Blowout Prevention 32
Figure 2.50: Choke manifold 32
Figure 2.51: Accumulator 33
Figure 2.52: Xmasstree system 33
Figure 2.53: Components of Christmas tree 33
Figure 2.54: Lost Circulation 34
Figure 2.55: Kick and Blowout 36
Table Table Page
Table 1: Type of wire rope construction 8
Table 2: The difference between MWD and LWD 29

9. Drilling Technology
Chapter One Page 1
1. INTRODUCTION
Oil plays a vital role in the development of day-to-day societies, being, considered as the main
strategic product of today’s global energy. Due to the continuous development of society, the
demand for energy is increasing, resulting in the need to explore and produce more and more. It
is in this context that the oil industry is a strategic sector in the fundamental functioning of
modern economies. The problem is that, with this increased consumption, more accessible oil
reserves are depleted at a fast pace and it becomes necessary to explore new areas where the
complexity and the risk of operations are larger, requiring knowledge, technologies and
personnel. There are also further questions about the impact caused on an environment, which
makes the challenge of the oil industry to not only overcome the structural complexity of the
areas explored, but to also be, produced in a sustainable way. Thus, the analysis of operations
conducted during the drilling of an oil well is extremely important, and contribute to the
improvement of the technology used and the implementation of best practices in future
operations.

10. Drilling Technology
Chapter One Page 2
1.1 Drilling
The driller will start drilling from the bottom of the conductor casing going deeper into the
ground. Drilling fluid known as ‘mud’ will be pumped down through the inside of the drill pipe
and out through nozzles in the drill bit. This will force any cuttings up and out of the top of the
conductor in the same way as in the jetting process. Most surface holes are drilled using sea
water if offshore. Forcing the cuttings up and out of the bore will keep the drill string from
getting jammed and keep the wellbore clean.
1.1.1 Types of drilling rig
In general, rotary rigs can be distinguished into:
A- Onshore rigs (Land rigs)
1- Conventional rigs
 Small land rigs,
 Medium land rigs,
 Large land rigs,
2- Mobile rigs:
 Portable mast,
 Jackknife,
B- Offshore rigs (Sea)
1- Bottom anchored rigs
 Artificial Island
 TLP,
 Submersible,
 Jack up,
 Concrete-structured, etc,
2- Floating rigs
 Drillship,
 Semi-submersible,
 Barge

11. Drilling Technology
Chapter One Page 3
1.1.2 Drilling Craw
Hoisting system
Rotary system
Power system
Circulating system
Well control system
Well Monitoring system
``

12. Drilling Technology
Chapter One Page 4
1.2.1 Hoisting System
Function:
The hoisting system is the set of equipment necessary to lower or raise drill strings, casing
string and other subsurface equipment into or out of hole.
Principal Components
1- Substructure and Derrick
2- Crown block
3- Travelling block
4- Draw works
5- Drilling line
1.2.1.1 Substructure
The substructure is the supporting base for the derrick, the drawwork sand the rotary table,
and constitutes the working floor for operations, or drilling floor, being elevated with respect
to ground level. The substructure is a reticular structure of steel beams that can easily be
dismantled, and rests on concrete foundations or on a base of wooden planks around the
cellar.
Its height varies from a few metersupto10 min the large strings
Figure 1.1: Hoisting System
Figure 1.2: Substructure

13. Drilling Technology
Chapter One Page 5
1.2.1.2 Derrick
The derrick is an open framework structure of steel beams, whose function is to hold the
ensemble of sheaves at its top, known as the crown block, on which all of the items of
equipment operated in the well or on the drilling floor are suspended.The height of the
derrick must be such as to permit the vertical movement of the travelling block for a
distance greater than the equivalent of one stand. For example, to handle a stand of
3drillpipes (about 27 m long) the derrick has to be about 40 m high. The derrick is designed
to resist the loads tripped in and out of the well in the operating phases, which induce both
static and dynamic stresses.Every derrick has a rated load capacity, defined by API
(American Petroleum Institute) standards, which establish the maximum hook load.
1.2.1.3 Crown block
An assembly of sheaves mounted on beams at the top of the derrick / mast and over which
the drilling line is reeved. The crown block bears the load applied at the hook and its
function is to reduce the wire rope tension required to pull the tubular material used to drill
the well. It at the top of the rig consists of a set of sheaves (usually from 3 to 7) supported
by a framework of steel beams.
Figure 1.3: Derrick
Figure 1.4: Crown block

14. Drilling Technology
Chapter One Page 6
1.2.1.4 Travelling block
Consists of another set of sheaves ( one fewer than for the crown block ) , mounted on an
axis connected to the hook. The number of sheaves in the crown and travelling block is
chosen on the basis of the rated capacity of the tower and the rate of pulling , which is
inversely proportional to the number of lines of wire rope connecting the travelling block
and the crown block.
1.2.1.5 Hook
The high-capacity J-shaped equipment used to hang various other equipment, particularly
the swivel and Kelly, the elevator bails or top drive units. The hook is attached to the
bottom of the traveling block and provides a way to pick up heavy loads with the traveling
block. The hook is either locked (the normal condition) or frees to rotate, so that it may be
mated or decoupled with items positioned around the rig floor, not limited to a single
direction.
Figure 1.5: Travelling block
Figure 1.6: Hook

15. Drilling Technology
Chapter One Page 7
1.2.1.6 Draw works
The draw works is the machine that transmits the power to operate the equipment in the
well. The basic components of the draw works are an engine, one or more drums containing
a steel cable, and the brakes. The main brake is a strongly-built, band brake, used to stop
the drill string as it is being lowered, or to release it slowly during drilling. Normally a
hydraulic brake and an electromagnetic brake are used, although these cannot stop the
hoisting drum completely and they cannot be used alone.
1.2.1.7 Drilling Line
The drilling line contained in the hoist drums consists of helically-wound steel-wire strands
around a plastic, vegetable fiber or steel core. The first end of the drilling line (fast line) is
wound around the hoist drum, after which it passes alternately over the sheaves of the
travelling block and of the crown block, while the other end (deadline) is anchored to an
element of the substructure. The tension of the line is measured on this anchorage, and this
makes it possible to calculate the weight of the equipment suspended from the hook (e.g.
drill string, casing, etc.). Through being wound around the drum and over the block
sheaves, the line is subject to wear and tear, to weakening of the wires (due to local
overheating) and to fatigue due to cyclical variations of tension in the winding over the
sheaves and the drum. One method of assessing the state of wear and tear of the drilling line
is visual inspection, but this is uncommon because of the uncertainty involved, the practical
difficulties and the time required. Slipping and cutoff, is performed when a given value of
the work carried out by the line has been reached.
Figure 1.7: Draw works

16. Drilling Technology
Chapter One Page 8
Table 1: Type of wire rope construction
Shallow 1” to 1-1/8” diameter
Deep 1-1/4” to 2” diameter
Contruction 6 x 19 S or 6 x 21 S or 6 x 25 FW, RRL, IPS or EIP, IWRC
1.2.1.8 Cathead
The cathead disused to lift heavy
objects and to pull on the tongs
when making up the drill pipe.
1.2.1.9 Air hoist
An air hoist or tugged is a safer
way to lift heavy objects.
Figure 1.8: Drilling Line
Figure 1.9: Wire Rope Construction Line
Figure 1.10: Cathead
Figure 1.11: Air hoist

17. Drilling Technology
Chapter One Page 9
1.2.1.10 Drill line spool
The drilling line is stored on a spool Periodically, some of the drilling line is cut off at the
draw works and additional line is pulled off the spool to replace the cut line.
1.2.2 Rotating System
Function
The system of rotation is intended to cause the drill string to rotate.
Principal Components
1- The rotary table
2- Kelly or Top Drive
3- Kelly Bushing
4- Master Bushing
1.2.2.1 Top drive
The top drive is a relatively recent piece of equipment, introduced towards the mid-1980s,
grouping together in a single unit the equipment for connecting the drill pipes, rotation of
the drill string and circulation of the fluid
The top drive unit is suspended from the hook and is guided by two vertical rails fixed to
the derrick, which provide the reactive torque necessary to prevent the rotation of the
whole complex and to allow free vertical movement.
Figure 1.12: Drill line spool
Figure 1.13: Rotating system

18. Drilling Technology
Chapter One Page 10
The use of the top drive instead of the rotary table offers numerous
advantages, including:
 Possibility of ‘drilling by stands’ (adding the pipes by stands, and not individually)
allowing greater control of drilling.
 The reduction of the time required to connect the pipes, with less risk of accidents for
drilling operators.
 The possibility of performing the trip-out operation while circulating mud and rotating
the string (back reaming), impossible with the rotary table and useful for preventing
the drill string from becoming stuck.
 The possibility of obtaining longer cores, as intermediate connections are eliminated.
1.2.2.2 Swivel
The rotary tool that is hung from the hook of the traveling block to suspend the drill string
and permit it to rotate freely.
It also provides connection for the rotary hose and provide passageway for the flow of
drilling fluid in to the drill stem.
Figure 1.14: top drive
Figure 1.15: Swivel

19. Drilling Technology
Chapter One Page 11
1.2.2.3 Kelly
The Kelly is a pipe of square or hexagonal section that transmits the motion of the rotary
table to the drill string.
It receives this motion from the Kelly bushing, to which it is joined through a sliding
coupling, so that it can move vertically.
1.2.2.4 Kelly Bushing
A device that when fitted to master bushing transmits torque to the kelly and
simultaneously permits vertical movement of the Kelly to make hole.
1.2.2.5 Master Bushing
A device that fits into the rotary table to accommodate the slips and drive the kelly bushing
so that the rotating motion of the rotary table can be transmitted to the Kelly.
Figure 1.16: Kelly
Figure 1.17: Kelly bushing
Figure 1.18: Master bushing

20. Drilling Technology
Chapter One Page 12
1.2.2.6 Rotary table
The rotary table makes the drill string rotate and supports its weight during operations or
during the connection of a new drill pipe, when it cannot be borne by the hook
1.2.2.7 Drill string
The drill string is an assemblage of hollow pipes of circular section, extending from the
surface to the bottom of the hole. It has three functions:
It takes the drilling bit to the bottom of the hole, while transmitting its rotation and its
vertical load to it.
It permits the circulation of the drilling fluid to the bottom of the hole.
It guides and controls the trajectory of the hole.
1.2.2.8 Drill Pipe
The drill pipes are hollow steel pipes of various types, with two tool joints welded at their ends.
They are standardized according to API standards and classified on the basis of their length
(usually about 9 m), their outside diameter, their linear weight and their steel grade.
The most common drill pipes are the Following: 3.50'' (13.30lb/ft.) , 4.50'‘ (16.60lb / ft. )
and 5'' (19.50 lb. /ft.)
Figure 1.19: Rotary table
Figure 1.20: Drill string

21. Drilling Technology
Chapter One Page 13
API range length (ft.)
1- 18-22
2- 27-30
3- 38-45
1.2.2.9 Heavy Weight Drill pipe
To avoid the danger of breaks in the drill string, a short stretch of intermediate heavy-wall
or heavy-weight drill pipes is inserted.
Similar in appearance to a drill pipe, HWDP has the following different dimensional
characteristics; the tube wall is heavier about 1” thick in most sizes, the tool joints are longer,
and the tube section has a larger diameter at mid length to protect the pipe from wear.
1.2.2.10 Drill color
The heavy, thick-walled tube steel, used between the drill pipe and the bit in the drill stem
to provide pendulum effect to the drill stem and to provide weight on bit.
The drill collars have a thick wall, are made out of solid steel bars, rounded externally,
bored on the inside and with threaded ends directly on the body, with threading analogous
to that used for ordinary pipes.
The drill collars are 9 to 13 m in length and their outside diameter is between 3.125'' and
14''.
Figure 1.21: Drill pipe
Figure 1.22: Heavy Weight Drill pipe
Figure 1.23: Drill color & Drill pipe

22. Drilling Technology
Chapter One Page 14
They are also standardized (API), with the most common diameters being 9.50'', 8'' and
6.50''.
Drill collars made of nonmagnetic steel also exist, and are used in directional drilling so
as not to influence the sensors that measure the earth’s magnetic field.
They are manufactured with stainless steels (alloys of K-Monel type) or with chrome-
manganese steel alloys.
1.2.2.11 Sub
A short, threaded piece of pipe used to adapt parts of the drilling string that cannot
otherwise be screwed together because of difference in thread size or design.
 These consist of:
 Bit Sub
 Crossover Sub
 Kelly Saver Sub
 Lifting Sub
 Bent Sub
1.2.2.12 There are basically three types of drilling bit
1. Drag Bits
2. Roller Cone Bits
3. Diamond Bits
Drag bits: used in soft formations such as sand or clay.
Roller cone bit: used in very soft formation to very hard formation.
Diamond bit: used in hard formation.
Figure 1.24: Types of Sub
Figure 1.25: Types of bit

23. Drilling Technology
Chapter One Page 15
1.2.3 Power system:
In a drilling site power is needed to run the machines driving the main components of the
rig, such as the draw works, the pumps, the rotary table and the engines of the various
auxiliary facilities (compressed air, safety systems, centrifugal pumps, lighting, services,
etc.) Internal combustion engine or a turbine that is the source of power for driving
equipment on the Rig.
1.2.3.1 SCR
Power and electrical control room
1.2.3.2 Diesel tank
Fuel tank for generator
Figure 1.26: Power system
Figure 1.27: SCR
Figure 1.28: Diesel tank

24. Drilling Technology
Chapter One Page 16
1.2.4 Circulation system
Function
A major function of the fluid circulating system is to remove the rock cuttings from the
hole as the drilling progresses
Principal Components
1- Mud Pump
2- Pump Manifold
3- Standpipe
4- Swivel
5- Drill string
6- Annulus
7- Return Line
8- Shale Shaker
9- Desander
10- Desilter
11- Degasser
12- Mud Pit
Circulating System
There are a number of main objectives of this system
 Cooling and lubricating the drill bit.
 Controlling well pressure.
 Removing debris and cuttings.
 Coating the walls of the well with a mud cake.
The circulating system consists of drilling fluid, which is circulated down through the
well hole.
The most common liquid drilling fluid, known as 'mud', may contain clay, chemicals,
weighting materials, water and oil.
The circulating system consists of a starting point, the mud pit, where the drilling fluid
ingredients are stored.
Mixing takes place at the mud mixing hopper, from which the fluid is forced through
pumps up to the swivel and down all the way through the drill pipe, emerging through the
drill bit itself.
From there, the drilling fluid circulates through the bit, picking up debris and drill
cuttings, to be circulated back up the well, traveling between the drill string and the walls
of the well (also called the 'annular space').
Once reaching the surface, the drilling fluid is filtered to recover the reusable fluid.
Figure 1.29: Principal components

25. Drilling Technology
Chapter One Page 17
1.2.4.1 Drilling Fluid Major direct function of drilling fluid
 To keep hole free of cuttings.
 To exert sufficient hydrostatic pressure on the formation.
 To prevent walls from caving.
 To cool & lubricate the drill string.
 To reduce friction between the hole and the drill string.
 To help suspend the weight of the drill string and casing.
 To deliver hydraulic energy to the formation under the bit.
1.2.4.2 Mud pumps
A large, high-pressure reciprocating pump used to circulated the mud on a drilling rig.
With 2 or 3 pistons (duplex or triplex pumps), may be single–or dual acting, and receive
their power from an electric motor in dependent from other uses.
1.2.4.3 Divert Mud flow to kill lines in case of kill or lost circulation
Figure 1.30: Mud pumps
Figure 1.31: Divert Mud flow

26. Drilling Technology
Chapter One Page 18
1.2.4.4 Stand Pipe
The vertical pipe rising along the side of the derrick or mast, which joins mud pump
manifold to the rotary hose.
1.2.4.5 Rotary hose
A large-diameter (3 – to 5 -in. inside diameter), high-pressure flexible line used to
connect the stand pipe to the swivel. This flexible piping arrangement permits the kelly
(and, in turn, the drill string and bit) to be raised or lowered while drilling fluid is pumped
through the drill string. The simultaneous lowering of the drill string while pumping fluid
is critical to the drilling operation.
1.2.4.6 Mud return
The passageway of the drilling fluid as it comes out of the well.
Figure 1.32: Stand pipe
Figure 1.33: Rotary hose
Figure 1.34: Mud return

27. Drilling Technology
Chapter One Page 19
1.2.4.7 Shale Shaker
An equipment the uses a vibrating screen to remove cuttings from the circulating fluid in
rotary drilling operations.
1.2.4.8 Desander
A centrifugal device for removing sand from the drilling
fluid to prevent abrasion of the pumps.
1.2.4.9 Desilter
Also a centrifugal device for removing free particles of silt from the drilling fluid to keep
the amount of solids in the fluid at the lowest possible point.
Figure 1.35: Shale shake
Figure 1.36: Desander
Figure 1.37: Desilter

28. Drilling Technology
Chapter One Page 20
1.2.4.10 Degasser
1.2.4.11 Mud gas separator
1.2.4.12 Reserve Pit
A waste pit, usually an excavated earthen-walled pit.
Figure 1.38: Degasser
Figure 1.39: Mud gas separator
Figure 1.40: Reserve pit
Figure 1.41: Circulation system

29. Drilling Technology
Chapter One Page 21
1.2.4.13 Drilling fluid
Types of drilling fluid
1- Water-base Muds
2- Oil-base Muds
1- Water-base Muds
The term water-base mud refers to any drilling fluid where the continuous phase, in
which some materials are in suspension and others are dissolved, is water. Thus any
water-base mud system consists of a water phase, inert solids, a reactive solids phase and
chemical additives. Each of these parts contribute to the overall mud properties.
The individual contributions are:
Water: create initial viscosity.
Inert solids (low-gravity solids like sand and chert and high-gravity solids like barite and lead
sulfides): produce required mud weight.
Reactive solids (low-gravity solids like bentonite and attapulgite clays): cause further
viscosity and yield point.
Chemical additives (mud thinners like phosphate, chrome, lignosulphonate, lignite's, and
surfactants, and mud thickeners like lime, cement and polymers): aid to control viscosity,
yield point, gel strength, fluid loss, pH-value, filtration behavior.
2- Oil-base Muds
Opposite to water-base muds where water is the continuous phase, at oil-base mud
systems crude or diesel oil forms the continuous phase in the water-in-oil emulsion. In
this way oil-base mud can have as little as 3% to 5% or as much as 20% to 40% (invert
emulsions) water content.
Oil-base mud systems are applied when:
1- Drilling sensitive production zones or problem shales,
2- Drilling salt sections and formations that contain hydrogen sulfide,
3- Danger of stuck pipe problems,
4- Drilling at bottom hole temperatures that are permissible by water-base muds.
Low-gravity solids content has to be monitored closely when drilling with oil-base muds
since at this environment solids do not hydrate which causes low-gravity solids contents
to exceed nacceptable levels often. This results in reduction of penetration rate, formation
damage and increase in risk of differential sticking.

30. Drilling Technology
Chapter Two Page 22
2. Casing
Casing is large diameter pipe that is assembled and inserted into a recently drilled section
of a borehole. Similar to the bones of a spine protecting the spinal cord, casing is set
inside the drilled borehole to protect and support the well stream he lower portion is
typically held in place with cement.
Functions of Casing
Casing that is cemented in place aids the drilling process in several ways:
1- Prevent contamination of freshwater well zones.
2- Prevent unstable upper formations from caving-in and sticking the drill string or forming
large caverns.
3- Provides a strong upper foundation to use high-density drilling fluids to continue drilling
deeper.
4- Isolates different zones, that may have different pressures or fluids - known as zone
isolation, in the drilled formations from one another.
5- Seals off high pressure zones from the surface, avoiding potential for a blowout.
6- Prevents fluid loss into or contamination of production zones.
7- Provides a smooth internal bore for installing production equipment.
2.1 Types of Casing Strings
There are different types of casing for different functions and drilling conditions.
They are run to different depths and one or two of them may be omitted depending on the
drilling conditions. They are:
1- Caisson pipe
2- Conductor pipe
3- Surface casing
4- Intermediate casing
5- Production casing
6- Liners
Figure 2.42: Type of casing string (1)

31. Drilling Technology
Chapter Two Page 23
2.1.1 Caisson pipe (26 to 42 in. OD)
 For offshore drilling only.
 Driven into the sea bed.
 It is tied back to the conductor or surface casing and usually does not carry any load.
 Prevents washouts of near-surface unconsolidated formations.
 Ensures the stability of the ground surface upon which the rig is seated.
 Serves as a flow conduit for the drilling mud to the surface
2.1.2 Conductor pipe (7to 20in. OD)
 The outermost casing string.
 It is 40 to 500 ft in length for onshore and up to 1,000 ft for offshore.
 Generally, for shallow wells OD is 16 in. and 20 in. for deep wells.
 Isolates very weak formations.
 Prevents erosion of ground below rig.
 Provides a mud return path.
 Supports the weight of subsequent casing strings.
2.1.3 Surface casing (17-1/2 to 20 in. OD)
 The setting depths vary from 300 to 5,000 ft.
 10-3/4 in. and 13-3/8 in. being the most common sizes.
 Setting depth is often determined by government or company policy and not selected
due to technical reasoning.
 Provides a means of nippling up BOP.
 Provides a casing seat strong enough to safely close in a well after a kick.
 Provides protection of fresh water sands.
 Provides wellbore stabilization.
2.1.4 Intermediate casing (17-1/2 to 9-5/8 in. OD)
 Also called a protective casing, it is purely a technical casing.
 The length varies from 7,000 to 15,000 ft.
 Provides isolation of potentially troublesome zones (abnormal pressure formations,
unstable shales, lost circulation zones and salt sections).
 Provides integrity to withstand the high mud weights necessary to reach TD or next
casing seat

32. Drilling Technology
Chapter Two Page 24
2.1.5 Production casing (9-5/8 to 5 in. OD)
 It is set through the protective productive zone(s).
 It is designed to hold the maximal shut-in pressure of the producing formations.
 It is designed to withstand stimulating pressures during completion and workover
operations.
 A 7-in. OD production casing is often used
 Provides zonal isolation (prevents migration of water to producing zones, isolates
different production zones).
 Confines production to wellbore.
 Provides the environment to install subsurface completion equipment.
 Provides protection for the environment in the event of tubing failure during production
operations and allows for the tubing to be repaired and replaced.
2.1.6 Liners
 They are casings that do not reach the surface.
 They are mounted on liner hangers to the previous casing string.
 Usually, they are set to seal off troublesome sections of the well or through the producing
zones for economic reasons (i.e. to save costs).
 Drilling liner
 Production liner
 Tie-back liner
 Scab liner
 Scab tie-back liner
Figure 2.43: Type of casing string (2)

33. Drilling Technology
Chapter Two Page 25
2.2 Cementation
Oil well cementing is the process of mixing slurry of cement and water and displacing it
down the casing, tubing or drill pipe to a pre specified point in the well
1- Primary cementing → Casing Cementation
The cementing takes place soon after the lowering of casing is called primary cementation.
2- Secondary cementing
Any other operations where cement is pumped in a well either during drilling operation or in
production phase
2.2.1 Primary Cementation
We need to pump cement in a well
• An oil/gas well is completed in stages.
• Each stage is secured /completed by lowering a suitable size steel pipe (casing).
• The casing pipes are held in its position by an adequate length of cement bond between
pipe and annulus.
• Cement is mixed with water to form a cement slurry of desired density and pumped into
the pipe and displaced in the annulus between casing and open hole.
2.2.2 Main Functions
• Bond and support the casing
• Protect the casing from corrosion.
• Protect the casing from shock loads
• Sealing-off problematic zones.
• Restrict fluid movement between formations
2.2.3 Primary Cementing Techniques
1. Single stage cementation
2. Multi stage cementation
3. Liner cementation
Figure 2.44: Cementing

34. Drilling Technology
Chapter Two Page 26
It is the most common technique
Normally accomplished by pumping one batch of cement down the casing between two
rubber plugs.
The bottom plug is placed in the casing, followed by cement slurry.
When the batch of cement has been pumped into the casing, a top plug is released.
The top plug is pumped down until it lands on the top of float collar, thus completing the
cement job.
2.2.4 Stage Cementation: Reasons
1- Down hole formations unable to support hydrostatic pressure exerted by a long column
of cement
2- To cement wells having two or more zones of interest separated by long intervals
3- Limitations of cementing equipment's
4- Cementing of high pressure gas zones & water producing horizons.
2.2.5 Liner Cementation
A liner is a standard string of casing, which does not extend all the way to surface, but is
hung off inside the previous casing string.
Figure 2.45: Cementing process

35. Drilling Technology
Chapter Two Page 27
2.2.6 Secondary Cementation
Any Cementing operation other than Primary cementing Operation (Casing/ Liner
Cementation) is referred to as “Secondary Cementation”
2.2.7 Reasons for setting cement
1. To stop lost circulation during drilling.
2. Directional drilling and side tracking.
3. To plug back a depleted zone.
4. Abandonment.
Applications
1. Supplement a faulty primary cement job.
2. Reduce water/oil, water/gas, or gas/oil ratio.
3. Repair casing leaks.
4. Stop lost circulation in open hole while drilling.
5. Supplement primary cement around a liner by squeezing the top of the liner (during
primary cementation)
6. Sealing leakage of the liner top (in case of failure after primary cementation).
7. Abandonment of single zones.
2.3 Measurement While Drilling (MWD)
MWD is the process by which certain information is measured near the bit and transmitted
to surface without interrupting normal drilling operations. The type of information may be:
a- Directional data (Inclination, Azimuth, Toolface)
b- Formation characteristics (Gamma-ray, Resistivity logs)
c- Drilling parameter (Downhole WOB, Torque, rpm)
Figure 2.46: Cementing Applications

36. Drilling Technology
Chapter Two Page 28
2.3.1 Survey sensor
1- Gamma-Ray Sensor
2- Resistivity Sensor
3- Temperature Sensor
4- Downhole WOB/ Torque
5- Turbine RPM
6- Standpipe Pressure Transducer
2.3.2 Gamma-ray Sensor
Gamma-rays are emitted by radioactive elements such as isotopes of potassium, thorium and
uranium. With this it is possible to identify shale zones
2.3.3 Resistivity Sensor
Resistivity is a measure of the formation’s resistance to the flow of electric current. The
response from the formation will depend on the fluid content. (Oil and gas act as insulator)
2.3.4 Temperature Sensor
Monitors the annulus mud temperature. The sensing element may be a strip of platinum
whose electrical resistance changes with temperature.
2.3.5 Downhole WOB/Torque
Made by a system of sensitive strain gauges mounted on the bit. The strain gauges will
detect axial forces for WOB and torsional forces for torque.
2.3.6 Turbine RPM
Consists of a 2-in. diameter probe that is placed very close to the top of the rotating turbine
shaft. As the shaft rotates, an electric coil within the probe picks up voltage pulses due to the
magnets. By counting the number of pulses over a certain interval, the turbine speed in rpm
can be calculated.
Application of MWD
1- Directional Surveying
2- Formation Evaluation
3- Drilling Parameter
Figure 2.47: Gamma-ray Sensor

37. Drilling Technology
Chapter Two Page 29
2.4 Logging while drilling (LWD)
Is an oilfield service that provides a tool within the drill string that transmits real time
formation information. The LWD tools are located near the end of the drill string. The
measurements recorded provide drilling engineers with critical well information so they may
make time sensitive decisions about future well operations.
LWD provides important well information on porosity, resistivity, acoustic waveform, hold
direction and weight on bit. These measurements can be used to calculate ROP (rate of
penetration) which is important in determining the speed at which the well is being drilled.
Data is transmitted to the surface by pulses through the mud column.
Table 2: The difference between MWD and LWD
LWDMWD
DensityInclination, azimuth, tool face
PorosityRotational speed of the drill string
ResistivitySmoothness of that rotation
Acoustic-caliperType and severity of any vibration downhole
Inclination at the drill bit (NBI)Downhole temperature
Magnetic resonanceTorque and weight on bit
Formation pressureMud flow volume
2.5 Completion
Well completion commonly refers to the process of finishing a well so that it is ready to
produce oil or natural gas. In essence, completion consists of deciding on the characteristics
of the intake portion of the well in the targeted hydrocarbon formation. There are a number
of types of completions, including:
Open Hole Completion
Conventional Perforated Completion
Sand Exclusion Completion
Permanent Completion
Multiple Zone Completion
Drainhole Completion
The use of any type of completion depends on the characteristics and location
of the hydrocarbon formation to be mined.

38. Drilling Technology
Chapter Two Page 30
2.5.1 Open Hole Completion
Open hole completions are the most basic type and are used in formations that are unlikely
to cave in. An open hole completion consists of simply running the casing directly down
into the formation, leaving the end of the piping open without any other protective filter.
Very often, this type of completion is used on formations that have been ‘acidized’
2.5.2 Conventional Perforated Completion
Conventional perforated completions consist of production casing being run through the
formation. The sides of this casing are perforated, with tiny holes along the sides facing the
formation, which allows for the flow of hydrocarbons into the well hole, but still provides a
suitable amount of support and protection for the well hole. The process of perforating the
casing involves the use of specialized equipment designed to make tiny holes through the
casing, cementing, and any other barrier between the formation and the open well. In the
past, 'bullet perforators' were used, which were essentially small guns lowered into the well.
The guns, when fired from the surface, sent off small bullets that penetrated the casing and
cement. Today, 'jet perforating' is preferred. This consists of small, electrically-ignited
charges, lowered into the well. When ignited, these charges poke tiny holes through to the
formation, in the same manner as bullet perforating.
2.5.3 Sand Exclusion Completion
Sand exclusion completions are designed for production in an area that contains a large
amount of loose sand. These completions are designed to allow for the flow of natural gas
and oil into the well, but at the same time prevent sand from entering the well. Sand inside
the well hole can cause many complications, including erosion of casing and other
equipment. The most common methods of keeping sand out of the well hole are screening or
filtering systems. These include analyzing the sand experienced in the formation and
installing a screen or filter to keep sand particles out. The filter may be either a type of
screen hung inside the casing, or a layer of specially-sized gravel outside the casing to filter
out the sand. Both types of sand barriers can be used in open holes and perforated
completions.
2.5.4 Permanent Completion
Permanent completions are those in which the components are assembled and installed only
once. Installing the casing, cementing, perforating, and other completion work is done with
small diameter tools to ensure the permanent nature of the completion. Completing a well in
this manner can lead to significant cost savings compared to other types.

39. Drilling Technology
Chapter Two Page 31
2.5.5 Multiple Zone Completion
Multiple zone completion is the practice of completing a well so that hydrocarbons from two
or more formations may be produced simultaneously, yet separately. For example, a well
may be drilled that passes through a number of formations as it descends; alternately, it may
be more effective in a horizontal well to add multiple completions to drain the formation
efficiently. Although it is common to separate multiple completions so that the fluids from
the different formations do not intermingle, the complexity of achieving complete separation
can present a barrier. In some instances, the different formations being drilled are close
enough to allow fluids to intermingle in the well hole. When it is necessary to prevent this
intermingling, hard rubber 'packing' instruments are used to maintain separation among
different completions.
2.5.6 Drainhole Completion
Drainhole completions are a form of horizontal or slant drilling. This type of completion
consists of drilling out horizontally into the formation from a vertical well, providing a
'drain' for the hydrocarbons to empty into the well. In certain formations, drilling a drainhole
completion may allow for more efficient and balanced extraction of the targeted
hydrocarbons. Drainhole completions are more commonly associated with oil wells than
with natural
2.6 Wellhead
The wellhead consists of the pieces of equipment mounted at the opening of the well to
manage the extraction of hydrocarbons from the underground formation. It prevents leaking
of oil or natural gas out of the well, and also prevents blowouts caused by high pressure.
Formations that are under high pressure typically require wellheads that can withstand a
great deal of upward pressure from the escaping gases and liquids. These wellheads must be
able to withstand pressures of up to 20,000 pounds per square inch (psi)
gas wells.
Figure 2.48: Wellhead

40. Drilling Technology
Chapter Two Page 32
2.7 Blowout Prevention System
Function
Blow Out Preventers (BOPs), are large valves located on the well head during drilling
operations, able to fully shut-in the well in just a few tens of seconds, whatever the working
conditions, the function of the well control system is to prevent the uncontrolled flow of
formation fluids from the wellbore.
Principal Components:
1. Annular Blowout Preventer
2. Ram Blowout Preventer
3. Diverter
4. Drilling Spools
5. Manifold, Valves and Sensors
6. Accumulator
7. Inside BOP
BOP stack consists, starting from below, of:
1- One or more spools for connection to the wellhead
2- A dual function ram preventer
3- A single-function ram preventer
4- An annular blow out preventer
5- A lateral tube which conveys the outgoing mud from the well to the shaker.
2.7.1 Choke manifold
The arrangement of piping and special valves, called chokes, through which drilling mud is
circulated when the blowout preventers are closed to control the pressures encountered
during a kick.
Figure 2.50: Choke manifold
Figure 2.49: Blowout Prevention

41. Drilling Technology
Chapter Two Page 33
2.7.2 Accumulator
The storage device for nitrogen pressurized hydraulic fluid, which is used in operating the
blow out preventers.
2.7.3 Diverter System
The diverter is a large, low pressure, annular preventer equipped with large bored is charge
flow lines. This type of BOP is generally used when drilling at shallow depths below the
conductor.
2.8 Xmasstree system
The set of valves, spools & fittings connected to the top of the well to isolate, direct and
control the flow wellbore fluids.the control valves, pressure gauges and chokes assembled at
the top of the well to control the flow of oil and gas after the well has been drilled and
completed.
2.8.1 Main components of Christmas tree
Pressure gauge
T-Cap
Swab valve
Primary wing valve
Kill wing valve
Choke
Upper master valve
 Lower master valve
Figure 2.51: Accumulator
Figure 2.53: Components of Christmas tree
Figure 2.52: Xmasstree system

42. Drilling Technology
Chapter Two Page 34
2.8.2 Christmas tree function
 Safety barrier
 Safely stop produced or injected fluid
 Injection of chemicals to well or flow line
 Allow for control of down hole valves
 Allow for electrical signals to down hole gauges
 To bleed of excessive pressure from annulus
 Regulate fluid flow through a choke
 Allow for well intervention
2.9 Drilling Problems
 Stuck pipe
 Lost circulation
 Borehole instabilities
 Mobile formation
 Under gauge hole
 Kicks and blowout
2.9.1 Stuck Pipe/Pipe Sticking
Definition: When part of the drill pipe or collars are stuck in the hole If pipe cannot be
rotated or pulled and circulation is good, then pipe is probably wall stuck
Causes of pipe sticking:
a. Differential/wall sticking
b. Mechanical sticking
c. Key seating
2.9.2 Lost Circulation
One of the major problems in drilling operation.
Occurred in almost every formation and at virtually all depths.
Occurs when hydrostatic pressure of mud exceeds the breaking strength of the formation.
Definition: Partial or complete loss of drilling fluid during drilling, circulating or running
casing.
Figure 2.54: Lost Circulation

43. Drilling Technology
Chapter Two Page 35
Type of Lost Circulation
1- Those types inherent in the formation: porous, permeable, and unconsolidated
formations cavernous or irregular formations natural fractures in formations (faults,
joints, fissures)
2- Those openings caused by poor drilling practices: induced fractures caused by high
mud weights or pressure surges
2.9.3 Shale Problem/Borehole Instability
Shale: sedimentary rock form by deposition and compaction of sediments contain clays, silt
water, quartz, feldspar compact or unconsolidated rock depend on water content Definition
of shale problem/borehole instability: a condition where the shale section containing
bentonite or other hydratable clays which continually absorb water from the mud, expands,
swell & slough into the hole
Whole instability resulting from drilling shale sections Other terms: sloughing shale,
heaving shale, running shale
2.9.4 Prevention of Sloughing Shale
Use suitable mud system to inhibit hydration (high Ca & K content, OBM, oil emulsion,) to
decrease the tendency of mud to hydrate water sensitive clays Increase circulation rate for
more rapid removal of particles Increase mud density for greater wall support (Phyd > Pf)
Decrease water loss of mud Avoid fast trips or swabbing of the hole Keep flow properties &
annular velocity at such a level as to insure good hole cleaning
2.9.5 Mobile Formation
A salt or shale can squeeze into the well bore because it is being compressed by the
overburden forces the deformation results in a decrease in the well bore size, causing
problems running BHA’s, logging tools and casing and stuck pipe A deformation occurs
because the mud weight is not sufficient to prevent the formation squeezing into the well
bore Once broken, the hole will become enlarge
2.9.6 Prevention Action
Identify salt dome monitor mud chlorides and mud resistivity maintain sufficient mud
weight select an appropriate mud system that will not aggravate the mobile formation plan
frequent reaming/wiper trips particularly for this section of the hole slow trip speed before
BHA enters the suspected area minimize the open hole exposure time of these formations

44. Drilling Technology
Chapter Two Page 36
2.9.7 under gauge Hole
Drilling hard abrasive rock wears the bit and the stabilizer gauge and results in a smaller
than gauge hole When a subsequent in-gauge bit is run, it encounters resistance due to the
under gauge section of hole If the string is run into the hole quickly without reaming, the bit
can jam in the under gauge hole section
This mechanism normally occurs:
− After running a new bit
− After coring
− When a PDC bit is run after a roller cone bit
− When drilling abrasive formations
2.9.8 Kick and Blowout
Kick: An entry of formation fluids (gas, oil or water) into the wellbore during drilling
Blowout: Uncontrolled flow of formation fluids (gas, oil or water) from the wellbore
Kick and blowout can occur when hydrostatic pressure of mud is lower than the formation
pressure
2.9.9 Causes of Kick/Blowout
Drilling into high pressure zones (abnormal pressure) swabbing when coming out of the hole
improper hole fill-up on trips lost circulation during drilling or cementing
2.9.10 One critical function of drilling fluid
When formation pressure is more than hydrostatic pressure, a kick occurs. An uncontrollable
kick may cause a catastrophic blowout - perhaps the worst disaster during drilling operation.
2.9.11 The effects of blowout are
 Loss of life.
 Loss of drilling equipment (including the rig).
 Loss of the well.
 Loss of oil and gas reserves.
 Damage to the environment.
Figure 2.55: Kick and Blowout

45. Drilling Technology
Chapter Two Page 37
DISCUSSION
When a drilling project is commenced, two goals are governing all aspects of it.
The first is to realize the well in a safe manner (personal injuries, technical
problems) and according to its purpose; the second one is to complete it with
minimum cost. Thereto the overall costs of the well during its lifetime in
conjunction with the field development aspects shall be minimized. This
optimization may influence where the well is drilled (onshore - extended reach or
offshore above reservoir), the drilling technology applied (conventional or slim-
hole drilling) as well as which evaluation procedures are run to gather subsurface
information to optimize future wells.

46. Drilling Technology
Chapter Two Page 38
CONCLUSIONS
Drilling is one of the best methods available to obtain crude oil and gas from
sedimentation. It is important to weigh the advantages and disadvantages of
each drilling method since this may differ according to the drilling site.
Directional drilling proved to be the most effective. Various drill bits are also
available and chosen according to the type of sediment being drilled. Hybrid
drill bits were found to be the most useful. Cost of drilling is expensive,
therefore it is vital to inspect conditions at which drilling would take place so
that maximum crude oil and gas can be produced with minimum cost.

47. Drilling Technology
Chapter Two Page 39
References
1. Dr. Claude B. Reed. 2006. Laser Rock Drilling. History Channel.
Interview.1.5.2006.
2. Dr. Claude B. Reed. 2009. Laser Oil and Gas Well Drilling. Argonne
National Laboratory.
3. Dr. Reimer, P. 2009. World Petroleum Council.
4. Gene C. n.d. Drilling and Well Construction.
5. Graves, R. M., and O'Brien, D. G. 1998. StarWars Laser Technology
Applied to Drilling and Completing Gas Wells.
6. John H. Berry. n.d. Drilling Fluids Properties & Functions.
7. Nitters, G., Pittens, B. & Buik, N., 2016. Well Stimulation Techniques for
Geothermal Projects in Sedimentary Basins, New York: IF Technology.
8. Schlumberger Oilfield Glossary
http://www.glossary.oilfield.slb.com/
9. Statoil, Fact sheet Njord
http://www.statoil.com/en/OurOperations/ExplorationProd/ncs/njord/Pages/
default.aspx
10.History of Drilling. (n.d.). Retrieved September 16, 2014.
http://www.rigsinternational.com/ our-offer/history-of-drilling