2. Rig Operations and Equipment

Habiburrohman abdullah 1

Rig Operations and Equipment

• Drilling Personnel

• Surface Drilling Equipment

• Subsurface Drilling Equipment

• Rig Selection

2

Drilling Personnel

3

Personnel Involved during Drilling

• The tool pusher. The drilling company provides a supervisor for the rig while the well is being drilled. At one time, this individual was called a tool pusher.

• The driller. The driller is directly in charge of the drilling four- or five-person rig crew and generally operates the draw works, the system of cables and pulleys used to run pipe into the hole and to pull pipe from the well.

4

Personnel Involved during Drilling

• The derrick worker. The derrick worker works high above the floor when the pipe is being pulled or run during regular operations. This position is commonly referred to as a derrick man.

• The floor workers. These personnel are also referred to as floor hands or roughnecks.

• Company representative.

• Third party personnel.

5

Drilling Rig Organization

Figure 1: Drilling Rig Organization6

Surface Drilling Equipment

7

Rig Power System

• Most rig power is consumed by hoisting & fluid circulating systems. • The early drilling rigs were powered primarily by steam. It become

impractical, because of high fuel consumption & large boiler plant required.

• Modern rigs are powered by internal combustion diesel engine & classified as :

- diesel electric type

- direct drive type

8

Rig Power System

Figure 2: Engine Power Output9

000,33

TP

HWQ dfi 000393.0

it Q

PE

N 2

P = Power output, hp

= angular velocity, rad/min

T = output torque, ft-lbf

33,000 ft-lbf/min/hp

Rig Power System

10

Where :

P [hp] shaft power developed by engine

[rad/min] angular velocity of the shaft

N [rev/min] shaft speed

T [ft-lbf] out-put torque

Qi [hp] heat energy consumption by engine

Wf [gal/hr] fuel consumption

H [BTU/lbm] heating value (diesel: 19,000 [BTU/lbm])

Et [1] overall power system efficiency

d [lbm/gal] density of fuel (diesel: 7.2 [lbm/gal])

33,000 conversion factor (ft-lbf/min/hp)

Rig Power System

• When the rig is operated at environments with non-standard temperatures (85 [F]) or at high altitudes, the mechanical horsepower equirements have to be modified. This modification is according to API standard 7B-11C:

a) Deduction of 3 % of the standard brake horsepower for each 1,000 [ft] rise in altitude above mean sea level,

b) Deduction of 1 % of the standard brake horsepower for each 10 ◦ rise or fall in temperature above or below 85 [F], respectively.

11

Hoisting System

• The main task of the hoisting system is to lower and raise the drillstring, casings, and other subsurface equipment into or out of the well.

• The hoisting equipment itself consists of: (1)draw works, (2) fast line, (3) crown block, (4) travelling block, (5) dead line, (6) dead line anchor, (7) storage reel, (8) hook and (9) derrick.

12

Hoisting System

Figure 3 : Hoisting System

13

Hoisting System

Figure 4: Making a connection14

Hoisting System

• “Making a connection”, the periodic process of adding a new joint of drillpipe to the drillstring as the hole deepens is referred.

• “Making a trip”, the process of moving the drillstring out of the hole, change the bit or alter the bottom-hole assembly, and lower the drillstring again into the hole is referred.

15

Hoisting System

Figure 5: Sketch of slips for drill pipe(a), drill collar(b) and casing(c)

16

Hoisting System

Figure 6: Tripping Out 17

Hoisting System

Figure 7: Lifting pipe at the rig floor 18

Hoisting System

• Sometimes the drillstring is not completely run out of the hole. It is just lifted up to the top of the open-hole section and then lowered back again while continuously circulating with drilling mud. Such a trip, called “wiper trip”, is carried out to clean the hole from remaining cuttings that may have settled along the open-hole section.

19

Hoisting System

Figure 8: Sketch of a drill pipe spinner 20

Derrick

• Derricks are classified (or rated) by the American Petroleum Institute (API) according to their height as well as their ability to withstand wind and compressive loads.

• The higher the derrick is, the longer stands it can handle which in turn reduces the tripping time. Derricks that are capable to handle stands of two, three or four joints are called to be able to pull “doubles”, “thribbles”, or “fourbles” respectively.

21

Derrick

Figure 9: Storage of doubles inside the derrick

22

Block and Tackle

• The crown block, the travelling block and the drilling line comprise the block and tackle which permits the handling of large loads. To lift and lower the heavy loads into and out of the borehole, the drilling line is strung multiple times between the crown and the travelling block

23

Block and Tackle

Figure 10: Block and tackle 24

Block and Tackle

• When no friction is assumed in the travelling and the crown block (constant tension in the drilling line), the hook load W creates a load to the drawworks with is equal the load in the fast line Ff which in turn depends on the number the line is strung n between the travelling and the crown block. This is expressed with:

W = n . Ff

25

Block and Tackle

• The input power Pi of the block and tackle is equal to the drawworks load Ff times the velocity of the fast line νf .

Pi = Ff . vf

• The output power or “hook power” Ph is given by the hook load times the velocity of the travelling block.

Ph = W . vb

26

Block and Tackle

Where:

EB = efficiency factor

n = no. of lines

nBE )98.0(

Figure 11: Efficiency factors for different tacklings

27

Number of Lines(n)

Efficiency(E)

6 0.874

8 0.841

10 0.810

12 0.770

14 0.740

Drilling Line

• The drilling line is a wire rope that is made of strands wounded around a steel core. It ranges in diameter from ½ to 2 inch. Its classification is based on the type of core, the number of strands wrapped around the core, and the number of individual wires per strand. Examples of it can be see in figure 12.

28

Drilling Line

Figure 12: Drilling Line 29

Drilling Line

• Since the drilling line is constantly under biaxial load of tension and bending, its service life is to be evaluated using a rating called “ton-mile”. By definition, a ton-mile is the amount of work needed to move a 1-ton load over a distance of 1 mile.

• When the drilling line has reached a specific ton-mile limit, which is mainly due to round trips, setting casings, coring and drilling, it is removed from service.

30

Drilling Line

• The ton-mile wear can be estimated by:

a) Round trip

b) Drilling operation

c) Coring operation

d) Running casing

31

Round Trip

Where:

Wb [lb] effective weight of travelling assembly

Ls[ft] length of a drillpipe stand

We [lb/ft] effective weight per foot of drillpipe

D [ft] hole depth

WC [lb] effective weight of drill collar assembly

less the effective weight of the same length of drillpipe

• It should be noted that the ton-miles are independent of the number of lines strung.

32

000,640,22

000,560,10

cb

esR

WWD

WDLDT

Drilling Operation

• drilling a section from depth d1 to d2.

Coring Operation

TR2 (ton mile), work done for one round trip at depth d2 where coring stopped

TR1 (ton mile), work done for one round trip at depth d1 where coring started33

123 datTdatTT RRd

122 RRc TTT

Running Casing

where:• Lcs [ft] ... length of casing joint• Wcs [lbm/ft] ... effective weight of casing in mud• D [ft] ... hole depth• Wb [lb] ... effective weight of travelling assembly

000,640,2000,560,10

)(5.0 bcscs

scWDWDLD

T

34

Drilling Line

• The drilling line is subjected to most severe wear at the following two points:

1. The so called “pickup points”, which are at the top of the crown block sheaves and at the bottom of the travelling block sheaves during tripping operations.

2. The so called “lap point”, which is located where a new layer or lap of wire begins on the

drum of the drawworks.

35

Drawworks

• The purpose of the drawworks is to provide the hoisting and breaking power to lift and lower the heavy weights of drillstring and casings. The drawworks itself consists of: (1) Drum, (2) Brakes, (3) Transmission and (4) Catheads, see figure 13.

• The drum provides the movement of the drilling line which in turn lifts and lowers the travelling block and consequently lifts or lowers the loads on the hook.

36

Drawworks

Figure 13: Drawworks 37

Drawworks

Where:

• Ph [hp] ... drum power output

• νf [ft/min] ... velocity of the fast line

• νb [ft/min] ... velocity of the travelling block

• W [lb] ... hook load• n [1] ... number of lines strung• E [1] ... power efficiency of the block and tackle system

bf vnv

E

vWP bh 000,33

38

Drawworks

• The input power to the drawworks is influenced by the efficiency of the chain drive and the shafts inside the drawworks. This is expressed with:

)1(

)1(

Kn

KKE

n

Where:• K [1] ... sheave and line efficiency, K = 0.9615 is an often used value.

39

Drawworks

• When lowering the hook load, the efficiency factor and fast line load are determined by:

n

n

LoweringK

KKnE

1

)1(

n

n

LoweringfK

KKWF

1

)1(

Where:

• Ff [lbf] ... tension in the fast line 40

Circulation System• The principle components of the mud circulation system are:

(1) mud pumps

(2) flowlines

(3) drillpipe

(4) nozzles

(5) mud pits and tanks (settling tank, mixing tank, suction tank)

(6) mud mixing equipment (mud mixing hopper)

(7) solid control equipment (shale shaker, degasser, etc.) see Figure 14.

41

Circulation System Schematic

Figure 14: Circulation System

42

Circulation System – Mud Pit

Figure 15: Mud Pit 43

Circulation System – Mixing Hopper

Figure 16: Mixing Hopper 44

Circulation System - Mud Pumps

There are two types of mud pumps in use today:

(1) duplex pump

(2) triplex pump

• Duplex Pump:

The duplex mud pump consists of two cylinders and is double-acting.• Triplex Pump:

The triplex mud pump consists of three cylinders and is single-acting.

45

Mud Pumps

Figure 17: Duplex Mud Pump Figure 18: Triplex Mud Pump46

Mud Pumps

Pumps are generally rated according to their:

1. Hydraulic power,

2. Maximum pressure,

3. Maximum flow rate.

• Since the inlet pressure is essentially atmospheric pressure, the increase of mud pressure due to the mud pump is approximately equal the discharge pressure.

47

Circulation System - Shale Shaker

When the mud returns to the surface, it is lead over shale shakers that are composed of one or more vibrating screens over which the mud passes before it is feed to the mud pits.

Figure 19: Shale Shaker

The Rotary System• The function of the rotary system is to transmit rotation to the drillstring and

consequently rotate the bit. During drilling operation, this rotation is to the right.• The main parts of the rotary system are:

(1) swivel

(2) rotary hose

(3) kelly

(4) rotary drive (master bushing, kelly bushing)

(5) rotary table

(6) drillstring

49

The Rotary System

Figure 20: Rotary System

50

The Rotary System

• Swivel

The swivel which established a connection between hook and kelly, has to be constructed extremely robust.

• Kelly

The kelly has a square or hexagonal cross-section and provides the rotation of the drillstring.

51

Rotary System

Figure 21: Swivel 52

Rotary System

• Rotary Drive

The rotary drive consists of master bushing and kelly pushing. The master bushing receives its rotational momentum from the compound and drives the kelly pushing which in turn transfers the rotation to the kelly.

53

Rotary System

Figure 22: Master & Kelly Bushing 54

Top Drive System

Top Drive System consist of :

(1) Crown Block

(2) Travelling Block

(3) Top Drive

(4) Drilling Line

Figure 23: Top Drive

55

Rig Selection

56

Rig Selection

• Following parameters are used to determine the minimum criteria to select a suitable drilling rig:

(1) Static tension in the fast line when upward

motion is impending

(2) Maximum hook horsepower

(3) Maximum hoisting speed

(4) Actual derrick load

(5) Maximum equivalent derrick load

(6) Derrick efficiency factor

57

Rig Types

• Rig can be categorized as land and marine rig. • Land rig :

(1) Cable tool

(2) Rotary rig (portable, standard derrick & conventional rig)• Marine Rig :

(1) Bottom supported : - Jackup

- Barge

(2) Floating rigs : - drillships

- semi-sumbersibles

58

Rig Selection

• Many design criteria are used in selecting the proper marine rig. Major criteria are as follows:

- water depth rating

- derrick & substructure capacity

- physical rig size and weight

- deck load capacity

- stability in rough weather

- duration of drilling program

- rig rating features, such as horsepower, mud mixing capacity

- exploratory vs development drilling

- availability & cost

59

Rig Selection

ffi vFP

W

Pv hb

WnE

nEEFd

1

Wn

nFde

4

4

11

nE

nE

F

FE

de

dd

60

Rig Selection

Where:• Fd [lbf] ... load applied to derrick, sum of the hook load,

tension in the dead line and tension in the fast line• Fde [lbf] ... maximum equivalent derrick load, equal to four

times the maximum leg load• Ed [1] ... derrick efficiency factor

61

Drilling Cost Analysis

• To estimate the cost of realizing a well as well as to perform economical evaluation of the drilling project, before commencing the project, a so called AFE (Authority For Expenditure) has to be prepared and signed of by the operator.

• Within the AFE all cost items are listed as they areknown or can be estimated at the planning stage. During drilling, a close follow up of the actual cost and a comparison with the estimated (and authorized) ones are done on a daily bases.

Drilling Cost Analysis

• Generally, an AFE consists of the following major groups:

(1) Wellsite preparation,

(2) Rig mobilization and rigging up,

(3) Rig Rental,

(4) Drilling Mud,

(5) Bits and Tools,

(6) Casings,

(7) Formation evaluation

Drilling Costs

• On of the most basic estimations of drilling costs is given by:

Where

• Cf [$/ft] ... cost per unit depth

• Cb [$] ... cost of bit

• Cr [$/hr] ... fixed operating cost of rig per unit time

• D [ft] ... depth drilled

• tb [hr] ... total rotation time during the bit run

• tc [hr] ... total non-rotating time during the bit run

• tt [hr] ... trip time

D

tttCCC tcbrbf

)(

Drilling Costs

• It has been found that drilling cost generally tend to increase exponentially with depth. Thus, the relationship as follow:

bDeaC Where

C [$/ft] ... cost per unit depth

D [ft] ... depth drilled

Drilling Time• The drilling time can be estimated based on experience and historical

penetration rates. Note that the penetration rate depends on:

(1) type of bit used

(2) wear of bit used

(3) drilling parameters applied (WOB, RPM)

(4) hydraulics applied (hydraulic impact force due to mud flow through nozzles)

(5) effectiveness of cuttings removal

(6) formation strength

(7) formation type.

Drilling Time• To estimate the drilling time, the so called “penetration rate

equation”,

• When the historical values of depth [ft] versus ROP [ft/hr] are plotted on a semilogarithmic graph paper (depth on linear scale), a straight line best-fit of the equation estimates the drilling time.

DaeKdt

dD2

Dad e

Kat 2203.2

2303.2

1

Drilling Time

• Here a2 is the reciprocal of the change in depth per log cycle of the fitted straight line, K is the value of ROP at the surface (intercept of fitted straight line at depth = 0 ft).

• The depth that can be drilled with each individual bit depends on

(1) bit condition when inserted,

(2) drilling parameters,

(3) rock strength

(4) rock abrasiveness.

Drilling Time

• Estimations of possible footages between trips can be obtained from historical data or applying equation:

where:• Di [ft] ... depth of the last trip• D [ft] ... depth of the next trip

DiabtLaa

D 2303.22

2

2303.2ln(303.2

1

Tripping Time

• Tripping time is also a major contributor to the total time spent for drilling a well. Tripping can be either scheduled (change of bit, reach of casing point, scheduled well-cleaning circulation) or on-scheduled, due to troubles.

• Following relationship can be applied to estimate the tripping time to change the bit. Thus the operations of trip out, change bit, trip in are included:

Tripping Time

where:

• tt [hr] ... required time for round trip

• ts [hr] ... average time required to handle one stand

• D [ft or m] ... length of drillstring to trip

• ls [ft or m] ... average length of one stand

D

l

tt

s

st 2

Subsurface Drilling Equipment

Subsurface Drilling Equipment

• Drill Bit• MWD tools• Mud Motor• Drill Collar• Heavy Weight Drill Pipe• Drill Pipe

• This chapter will be discussed further in upcoming class session.

END