DRILLING ENGINEERING
CHAPTER # 1
Rotary Drilling Rigs
Objective
To familiarize the student with
(1) the basic rotary drilling equipment and operational
procedures.
(2) introduce the student to drilling cost evaluation.
Drilling Team
 Large companies vs. small
 Specialized skills
 Service companies
Types of Wells
(1)
Wildcat Well: to discover new petroleum reservoir.
(2)
Development Well: exploit a known reservoir.
 Geological Group: recommends wildcat location.
 Reservoir Engg. Group: recommends development
 Drilling Group: designs and cost estimate.
 Tool pusher
 Driller
 Ass. Driller
 Derrickman (monkey board)
 2-3 rotary helpers (floormen – or – rough necks)
 Motor man
 Rig mechanics
Types of Wells...
 Rig electrician
 Company man
 Roust abouts
 Head roust about is the crane operator
 Mud engineer
 Casing crew
 Cementing service
 Legal Group: secures drilling rights
 Surveyors: establish and stake well location
 Drilling Contractor (Bid basis)
 Cost per Foot – drilling in area is routine.
 Cost per Day – unknown area
 Location Preparation
 Water Wells
Types of Wells...
• South Louisiana marshlands: inland barge
• Canadian Arctic Islands: man-made ice platform
• Extensive storage & Supply
• Manpower:
Contractor
Operator
Service Company
Consultants
1.1 Types of Drilling Rigs
Drilling and workover rigs come in a variety of shapes and
sizes with each having its own characteristics suited for a
particular job. Although there are many factors to be
considered in selecting the best rig for the job, a few are
especially critical. They are:






Surface location (land, inland water, offshore)
Estimated maximum hole depth
Horsepower requirements
Cost
Availability
As can be imagined, the selecting of drilling and workover
rigs is best accomplished by use of good, sound judgement
and engineering experience.
Rigs
Marine
Land
Bottom
Support
FLoating
Semi/
Submersible
Platform
Self Contained
Barge
Jackup
Tendered
Drill ship
Conventional
Jacknife
(Deeper)
Mobile
Portable
Mast (Small)
Common Types of Drilling Rigs
1. Land Rigs
As the name implies, these rigs are primarily used on
land; however, some have been transported offshore for
structure rig assignments. Most land rigs have to be
transported to location in sections, but some are selfcontained, permanently mounted on trucks. On location
they are usually set up on a board mat with a substructure
of 8 to 40 feet high, and a few are capable of drilling holes
to 30,000+ feet.
2. Inland Barges
Inland Barges are composed of two types:
a.
Barge mounted rigs
This type rig is capable of drilling in water depths from
0 to 12 feet. After being towed on location, the rig’s
hull is filled with water until it rests on bottom.
b. Posted barge mounted rigs
These type rigs have an upper deck supported by posts
from the lower hull. The deck contains all drilling
equipment and accommodations. Posted barges are
capable of drilling in water depths from 0 to 20 feet.
The rig is towed on location and the lower hull filled
with water to secure it on bottom.
3. Submersible Rigs
These rigs are towed on location and are capable of working
in water depths from 18 to 70 feet. They are composed of an
upper deck and lower hull connected by beams. On some
types a large bottle, or something similar, is located on each
corner of the rig for stability. These bottles, as well as the
lower hull itself, are filled with water to set the rig on bottom
and stabilize against movement.
4. Jack-up Rigs
These rigs are normally towed on location, but a few are selfpropelled. They are composed of an upper deck supported by
either three or more legs attached to mats or spud cans and are
capable of working in water depths from 30 to 350 feet.
These mats or cans rest on the ocean floor with the deck
jacked up into drilling position. There are two common types
of jack-up rigs; Bethlehem and Letourneau. The former uses
stabilized column legs attached to mats while the latter uses
three, truss-type legs mounted on spudcans.
5. Semi-Submersible
These rigs can be towed on location, or some types are selfpropelled. They are capable of drilling in water depths of
20 to 2,000+ feet. The rig itself remains stationary in the
drilling position by a series of anchors (usually two
connected at each corner of the rig) positioned on the ocean
floor at a distance away from the rig. It should also be
noted that some Semis can be used as a submersible rig.
6. Drill Ships
Drill ships are self-propelled drilling vessels capable of
drilling in water depths of 18 to 2,000+ feet. There are two
basic types of drill ships - one that positions itself with
anchors and one that uses dynamic positioning.
7. Structure Rigs
Structure rigs are mounted on a fixed platform with all
drilling equipment secured on deck. The rig itself is
capable of changing positions on the structure;
however, the structure is permanently based and
designed to last many years. Structures are capable of
being set in water depths of 10 to 850+ feet. Structure
set-ups usually follow a successful exploratory program
in order that many development wells can be drilled
from one location. These wells are almost always
directional.
Rotary Drilling Process
•
Rotary table rotates the drill string
 Downward force applied to the bit
 Cuttings are lifted to the surface by circulating a fluid
down the drill string.
Main Component Parts of a Rotary Rig are:2.
3.
4.
5.
Power System
Hoisting System
Fluid Circulating System
Rotary System
Well Control System
6.
Well Monitoring System
1.
A Rotary Drilling Rig
1.2 Rig Power System
 Most power consumed by :
hoisting system and fluid circulation
 Not used at same time
 Total power requirements 1000 – 3000 hp
 Old days steam
 Now internal combustion diesel engines types (1) dieselelectric type (electric motors), (2) direct-drive type (gearschains) depending on power method.
Power-System Performance Characteristics
Are stated in terms of:
1.
2.
3.
Output horse power
Torque
Fuel consumption for various engine speeds
P
=
 T = 2N.F.r
Where,
P

T
N
=
=
=
=
shaft power (hp)
2N, Angular velocity of the shaft (engine speed), rad/min
output torque (lb-ft)
Rev./min
(1.1)
Power-System Performance Characteristics …...
 Overall power efficiency determines the rate of fuel
consumption (Wf) at a given engine speed.
 Heating values (H Btu/lbm) of various fuels for internal
combustion engines are shown in Table 1.1.
Fuel
Diesel
Gasoline
Butane
Methane
Density (lbm/gal)
7.2
6.6
4.7
--
Heating Value H(Btu/lbm)
19,000
20,000
21,000
24,000
• Heat energy to the engine Qi
Qi = Wf.H (hp)
(1.2)
Et = P /Qi = Energy Output / Energy Input
(1.3)
Et = overall power system efficiency
Example 1.1: A diesel engine gives an output torque of
1,740 ft-lbf at an engine speed of 1,200 rpm. If the fuel
consumption rate was 31.5 gal/hr, what is the output
power and overall efficiency of the engine?
The annular velocity, , is given by
=2(1,200) = 7,539.8 rad/min.
The power output can be computed using Eq. 1.1:
P=  T
7,539.8(1740) ft  lbf / min

= 397.5 hp
33,000 ft  lbf / hp
Solution:
Since the fuel type is diesel, the density  is 7.2 lbm/gal
and the heating value H is 19,000 Btu/lbm (Table 1.1).
Thus, the fuel consumption rate is wf is
wf = 31.5 gal/hr (7.2 lbm/gal)
1hour 

 60 min utes 
= 3.78 lbm/min
The total heat energy consumed by the engine is given by Eq.
1.2:
Qi= wf H

3.78lbm / min( 19,000 Btu / lbm )( 779 ft  lbf / Btu )
33,000 ft  lbf / min/ hp
= 1,695.4 hp.
Thus, the overall efficiency of the engine at 1,200 rpm given
by Eq. 1.3 is
P
397.5
Et 

= 0.234 or 23.4% Answer
Qi 1695.4
1.3 Hoisting System
Function:
Used to lower or raise drill strings, casing string and other
subsurface equipment into or out of hole.
Principal Components:
1. Derrick and substructure
2. Block and tackle
3. Draw works
Functions of Derrick:
1. Provides vertical height required to raise sections of pipe.
2. Rated according to their ability to withstand compressive
loads and (wind loads)
Components of Block and Tackle:
1. Crown block
2. Travelling block
3. Drilling line
Components of
the hoisting
system
Principal Function:
To provide a mechanical advantage which permits easier
handling of large loads.
Load supported by travell ing block

Load imposed on the draw works
M
W
Ff
M= Mechanical advantage
F = tension in the fast line
The ideal mechanical advantage that assumes no friction in
the block and tackle can be determined from a force analysis
of the travelling block.
n Ff= W
Mi =
W
n
W /n
Input power of block and tackle = pi
Pi = Ff Vf
(1.5)
Ff = draw works load
Vf = velocity of fast line
Ph = output power of the hook load
Pn = W.Vb
(1.6)
W = travelling block load
Vb = velocity of travelling block
Vb 
Vb 
Vf
n
Vf
h
Ph (nFf )  (V f / n )
E

1
Pi
Ff V f
no friction
Power efficiency is
E
W
Ff n
actual system
Tension in the fast line
W
Ff 
Eh
(1.7)
Eq. 1.7 is used to select drilling line size.
Fd
= W + Ff + Fs
Fd
Fs
= load applied to the derrick
= tension in the lead line
Fd  W 
W W
 1  E  En 

W

En n
En


fast
dead
(1.8a)
(1.8b)
Example 1.2: A rig must hoist a load of 300,000 lbf. The
drawworks can provide an input power to the block and
tackle system as high as 500hp. Eight lines are strung
between the crown block and traveling block.
Calculate
(i) the static tension in the fast line when upward motion is
impending,
(ii) the maximum hook horsepower available,
(iii) the maximum hoisting speed,
(iv) the actual derrick load
(v) the maximum equivalent derrick load, and
(vi) the derrick efficiency factor.
Assume that the rig floor is arranged as shown in Fig 1.17.
Solution:
(i) the power efficiency of n=8 is given as 0.841 in Table 1.2.
The tension in the fast line is given by Eq. 1.7.
W 300,000
Ff 

 44,590lbf
En 0.841(8)
(ii) The maximum hook horsepower available is
Ph = E.I = 0.841 (500) = 420.5 hp
(iii) The maximum hoisting speed is given by

 33,000 ft  lbf / min
 420.5hp
hp
Ph 

vb 

W
300,000lbf








= 46.3 ft/min
To pull a 90-ft stand would require
t
90 ft
 1.9 min
46.3 ft / min
(iv) The actual derrick load is given by Eq. 1.8b
 1  E  En 
Fd  
W
En


 1  0.841  0.841(8) 
 
(300,000)
0.841(8)


= 382,090 lbf
(v) The maximum equivalent load is given by Eq. 1.9
84
n4
Fde  
(300,000)  450,000lbf
W 
8
 n 
(vi) The derrick efficiency factor is
 Fd  382,090
 
Ed  
 0.849 or 84.9% Answer
 Fde  450,000
Drawworks
Provide the hoisting and braking power required to raise or
lower the heavy strings of the pipe.
Principle Parts
• The drums
• The brakes
• The transmission
• The catheads
1.4 Rotary System
Main Parts:
1. Swivel
2. Kelly
3. Rotary Drive
4. Rotary Table
5. Drill Pipe
6. Drill Collar
1. Swivel:
Supports the weight of the drillstring and permits
rotation i.e. Bail and Gooseneck.
2. Kelly:
Square or Hexagonal to be gripped easily. Torque is
transmitting through kelly bushings. Kelly saver sub is
used to prevent wear on the kelly threads.
Rotary System…...
3. Slips:
During making up a joint slips are used to prevent
drillstring from falling in hole.
4. Rotary Drive:
Provides the power to turn the rotary table.
* Power Sub: can be used to connect casing.
5. Drill Pipe:
Specified by (a) Outer Diameter
(b) Weight per foot
(c) Steel grade
(d) Range Length
Range
1
2
3
Length (ft)
18 to 22
27 to 30
38 to 45
Rotary System…...
* Tool Joint:
Female is called Box.
Male is called Pin.
* Upset :
Thicker portion of the pipe.
* Internal upset: Extra thick.
* Thread Type:
Round, tungsten carbide hard facing.
6. Drill Collar:
Thick walled heavy steel pipe used to apply weight to the bit.
* Stabilizer Subs : Keep drill collars centralized.
* Capacity : Volume per unit Length.
Ap 
Aa 
As 

4

4

4
d
2
= Capacity of pipe
( d 2  d12 ) = Capacity of annulus
2
2
( d1  d 2 ) = Displacement
(1.13)
(1.14)
(1.15)
Rotary System…...
Capacity and displacement nomenclature
Rotary System…...
Example 1.4: A drillstring is composed of 7,000 ft of 5-in.,
19.5-lbm/ft drillpipe and 500 ft of 8-in. OD by 2.75-in ID
drill collars when drilling a 9.875-in. borehole. Assuming
that the borehole remains in gauge, compute the number
of pump cycles required to circulate mud from the
surface to the bit and from the bottom of the hole to the
surface if the pump factor is 0.178 bbl/cycle.
Solution:
For field units of feet and barrels, Eq. 1.13 becomes
2

  2  2  gal  bbl  12in   d
bbl / ft
Ap   d in. 


  
3 
4
  231in.  42 gal  ft   1,029.4 
Rotary System…...
Using Table 1.5, the inner diameter of 5-in., 19.5 lbm/ft
drillpipe is 4.276 in.; thus, the capacity of the drillpipe is
4.2762

 0.01766 bbl ft
1,029.4
And the capacity of the drill collars is
2.752

 0.00735 bbl ft
1,029.4
The number of pump cycles required to circulate new
mud bit is given by

0.01776(7,000)  0.00735(500)bbl  719cycles .
0.1781bbl cycle
Rotary System…...
Similarly, the annular capacity outside the drillpipe is given by
9.8752  52

 0.0704 bbl ft
1,029.4
And the annulus capacity outside the drill collars is
9.8752  82

 0.0326 bbl ft
1,029.4
The pump cycles required to circulate mud from the bottom
of the hole to the surface is given by

0.0704(7,000)  0.0326(500)  2,858cycles
0.1781bbl cycle
Answer
Components of the rotating system
1.5 Circulating System
Components:
1.
2.
3.
4.
Mud Pumps
Mud Pits
Mud Mixing Equipment
Contaminants Removal Equipment
Pumps:
Reciprocating Positive Displacement Piston Pumps.
• Two-Cylinders - Duplex (Double Acting Forward-Backward)
• Three-Cylinders - Triplex (Forward only Single Acting)
Duplex
Heavy
Bulky
High Output Pressure
Pulsation
Require more Maint.
Triplex
Light
More Compact
Lower
Without Pulsation
Cheaper to Operate
Therefore majority of new pumps are Triplex.
Circulating System…...
Advantages
(1) Ability to move high solid content fluids
(2) Ability to move large particles
(3) Ease to operation and maintenance
(4) Reliability
(5) Ability to operate over wide range of pressure s and flow
rates by changing the diameters of the pump liners and pistons.
Overall Pump Efficiency =Mechanical Efficiency x Volumetric Efficiency
Em= Mechanical Efficiency ~ 90%
Ev= Volumetric Efficiency ~ 100%
Two Circulating pumps are installed on the rig.
• Shallow portion both are used.
• Deeper portion one is used.
Circulating System…...
Components of the circulating System.
Circulating System…...
Circulating System
Circulating System…...
Pump Displacement
(1) Double Acting
Figure 1.25 (a)
dr = Piston rod diameter
dL= Liner diameter
Ls= Stroke Length (Stroke = one complete pump revolution).
Forward Stroke Volume Displaced = (/4) dL2 Ls
Backward Stroke Volume Displaced = (/4) (dL2 - dr2 ) Ls
(for one Cylinder)
Total Volume =Fp= 2 Ls(/4) (2LL2 - Lr2 ) . Ev
(1.10)
(for two Cylinders)
Fp= Pump factor or pump displacement cycle.
Example 1.3: Compute the pump factor in units of barrels
per stroke for a duplex pump having 6.5-in. liners, 2.54in. rods, 18-in. strokes and a volumetric efficiency of
90%?
Solution:
The pump factor for a duplex pump can be determined
using Eq 1.10:
Fp = 2 Ls(/4) (2LL2 - Lr2 ) . Ev
= (/2) (18) [ 2(6.5)2 - (2.5)2] . (0.9)
= 1991.2 in.3 /stroke
or = 0.2052 bbl/stroke.
Answer
Circulating System…...
(2) Triplex Acting
Figure 1.25(b)
Fp= 2 (/4) dL2 Ls. Ev
(1.11)
q=flow rate = Fp . N
(Where N = no. of cycles per unit time)
Pumps are rated for
1. Hydraulic Power
2. Maximum Pressure
3. Maximum Flowrate
P  q
PH 
1714
PH = Pump Pressure, hp
∆P = Increase in pressure, psi
q = Flow rate (gal/min)
∆P cannot more than 3500 psi
(1.12)
Circulating System…...
Flow conduits between pump and drill string include:
1.
2.
3.
4.
5.
Surge chamber (Pulsation Damper)
4 or 6 inch heavy-walled pipe connecting the pump to
a pump manifold located on the rig floor.
Standpipe and rotary hose.
Swivel
Kelly
Go over EXAMPLE 1.3.
Contaminant Removal
1.
2.
3.
Circulating System…...
Shale shaker for coarse rock cuttings
Hydrocyclones and decanting centrifuge for fine particles.
Degasser
Gas as a drilling Fluid (Air, Natural gas)
1.
2.
3.
4.
5.
Penetration rate is higher than water especially when
formation is strong and extremely low K.
Water flow is a problem.
Isolate by injecting
(a) Low Viscosity Plastic
(b) Silicon Tetrachloride
(c) Using Packers
Min. annular velocity is 3000 ft/min for injection pressure.
Use Foam.
1.6 Well Monitoring System
Parameters displayed
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Depth
Penetration rate
Hook Load
Rotary Speed
Rotary Torque
Pump Rate
Pump Pressure
Mud Density
Mud Temperature
Mud Salinity
Gas content of mud
Hazardous gas content of air
Pit Level
Mud Flow Rate.
* Centralized well monitoring system
* Mud Logger
* Subsurface well-monitoring and data telemetry systems
(mud pulser).
1.7 Well Control System
Function:
Prevents the uncontrolled flow of formation fluids from the
wellbore.
Kick:
Flow of formation fluids in the presence of drilling fluid
(blowout).
Uses:
1. Detect the Kick
2. Close the well at the surface.
3. Circulate the well under pressure to remove
formation fluids and increase density.
4. Move drillstring under pressure.
5. Divert flow away from rig personnel and equipment.
Kick Detection During Drilling Operation
Well Control System…...
Kick Detection:
a. Pit volume indicator
b. Flow indicator
c. Hole fill up indicator (during tripping)
d. Count the pump strokes.
BOP (Blow Out Preventer)
Multiple BOP’S used in series: BOP Stack
Ram Preventers
Pipe Rams
Blind Rams :
Shear Rams:
Semi circular openings which
match diameter of pipe
Closes the hole, no pipe present.
Blind rams that shear the pipe.
Working press: 2000, 5000, 10000, 15000 psig.
Annular Preventers (Bag-type): Rubber Ring
BOPE:Closed hydraulically or using screw-type locking.
Well Control System…...
Accumulators
High pressure hydraulic system used to close the BOP.
* Fluid Capacity : 40, 80 120 gal.
* Max. Operating Pressure : 1500-3000 psig.
* has a small pump independent of rig power.
Strip Pipe
Lower pipe with preventer closed. Must be able to vary
closing pressure using pressure regulating system.
Drilling Spool
Placed between ram preventers
(1) provide space for stripping
(2) flowline attached to it.
Well Control System…...
Kill Line
conduit used to pump into the annulus.
Choke Line
Diverter Line
Conduit used to release fluid
from the annulus.
Drilling Spools
Must be large enough to allow next casing to be put in
place without removing the BOP.
Casing Head (Braden Head)
Attached to BOP, welded to the first string of casing
cemented in the well.
Control Panel
To operate the BOP stack. RSRRS
Well Control System…...
Rotating Head
Seals around the kelly at top of BOP stack, used for drilling with
slight surface pressure at annulus.
Kelly Cock
Close the flow inside kelly.
Internal Blowout Preventers
Prevents flow inside drill string.
Adjustable Choke
Used during Kick circulation, controlled from a remote panel on
the rig floor.
Sufficient pressure must be held against the well by the choke so
that the bottomhole pressure in the well is maintained slightly
above the formation pressure.
* Working Press Systems: 2000,3000,5000,10000,15000 psig.