ch2 rig components (student copy)

7/26/2019 CH2 Rig Components (Student Copy)

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PETROLEUM ENGINEERING DEPARTMENT

UNIVERSITI TEKNOLOGI PETRONAS

DRILLING ENGINEERING by Muhammad Aslam Md Yusof 1

Chapter 2: Rig Components

POWER SYSTEM

ENGINE TERMINOLOGY

Horsepoweris a unit of work established by James Watt in 1870. Watt defined one horsepower as

the ability to do 33,000 ft-lbf of work per minuteor 550 ft-lbf of work per second. This is also the

power necessary to raise one ton a distance of feet in one minute, assuming no friction.Engine horsepoweris a measure of the theoretical characteristics of an engine. Brake horsepower

(BHP) is the actual horsepower of the engine and also the only measurable horsepower, after

deducting the internal friction losses of an engine. It is usually determined from the force exerted on

a friction brake or dynamometer connected to the drive shaft.

Torqueis defined as a force around a given point, F applied at a radius, R from that pointor in much simpler word as the twisting force of the engine. Note that the unit of torque, T is

.

Efficiency factor(describes the power losses from the prime movers to the end-use equipment,which can be expressed as follows:

Where energy output is from the prime mover and energy input is the amount remaining for actual

usage after some losses. The system losses result from friction, gears, and belt and line losses.

Fuel TypeDensity

Heating Value Diesel 7.2 19000

Gasoline 6.6 20000

Butane 4.7 21000Methane - 24000

Table 2.1: Heating value of various fuel types

POWER SYSTEM CALCULATIONS

Generally, the main characteristics of power system performance are engine output or brake

horsepower (BHP), heat energy input, overall power system efficiency and fuel consumption for

different engine speeds.


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From basic calculations, work, W is the product of force, F and distance, D ;

The power, P , can be expressed as;

Where t is time .For a rotating shaft;

Where N is number of revolutions per minute (rpm)

Thus, the horsepower, HP (hp) is given by

Hence, to rearrange the equation it give the engine output or BHP, BHP (hp);

Where

angular velocity

, T is the output torque,

Or

Heat energy input, (hp);

Where is fuel consumption rate in and H is the heat value of fuel in .The overall efficiency factor is defined as the energy output over energy input and yields;


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Example 2.1

Based on the data given, determine the output power, BHP and overall efficiency, Output torque from a diesel engine, Engine speed, Fuel type = DieselFuel consumption rate, Unit conversion factors:

Answer:


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Example 2.2

In a drilling operation major power supply is required by the hoisting system, rotary system,

circulation system and mud cleaning equipment. If the output horsepower required by the top drive

is 2200 hp, the hoisting system is 2000hp, the circulation system 2400hp, cleaning equipment 300hp

and 20% of all is required for additional facilities, calculate the diesel consumption for a 25 day

drilling operation and casing operation (in gallons). The overall engine efficiency,, is 15% andtransmission efficiency, , is 85%. Other data;

Heat value of fuel, Density of fuel,

Answer:


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EXERCISES

1. Calculate the overall efficiency, , for the following conditions:A diesel engine has an output torque, Engine speed, Density of fuel, Fuel consumption, Heat value of fuel,

Answer: 13.3%

2. A diesel engine gives an output torque of at an engine speed of . Ifthe fuel consumption rate was , what is the output power and overall efficiency ofthe engine?

Answer: 331.29 hp and 19.24%

3. The total power consumed by different equipment on a land rig is 7000hp. If the rig is

operating for a period of 25 days, how much diesel fuel will be required? The overall engine

efficiency and transmission efficiency are 20% and 95% respectively.


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CIRCULATING SYSTEM

MAJOR COMPONENTS

Circulating system can be described as the blood of the drilling operation. This is because, all its

major components especially drilling mud is flowing throughout the entire drilling operation. It

travels from (1) the mud tanks (2) to the mud pumps, (3) through the surface connections, (4) to the

drill string, (5) then to the bit, (6) up the annulus, (7) to the mud cleaners and (8) back to the suction

tank. This is to remove drill cuttings from the hole as the drilling progresses and also to clean the

wellbore, to cool and to lubricate the bit and also to transmit hydraulic horsepower to the bit. The

major components of the circulating system are;

Mixing equipment

Pits

Mud cleaners

Mud pumps

MIXING EQUIPMENT

The drilling mud mixing equipment;

Hopper; mud chemicals and solids are poured through the hopper, which is connected to a

high shear jet. Due to the jet action, the mud chemicals are homogeneously mixed.

Mud gun & Agitators; the resulting mud is again vigorously agitated with a mud gun and

then directed to the suction tank. In the suction tank, mud is further kept in motion with

mechanical agitators. This is done to prevent solid settlement. Before the mud is delivered

to the main pump it is charged by a centrifugal pump to give the mud a pressure of 80-90

psi.

PITS

It is usually a series of large steel tanks, all interconnected and fitted with agitators to maintain the

solids, used to maintain the density of the drilling fluid, in suspension. Some pits are used for

circulating (e.g. suction pit) and others for mixing and storing fresh mud. Most modern rigs have

equipment for storing and mixing bulk additives (e.g. barite) as well as chemicals (both granular and

liquid). The mixing pumps are generally high volume, low pressure centrifugal pumps.


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MUD CLEANERS

Solid control or cutting separation can be done by using one or more methods of solid separation;

Settling

Screening

Hydrocyclone

Rotating centrifuge

While settling and screening methods are the mainly the mechanism of shale shaker by using

gravitational force, hydrcocyclone and centrifuge, however, achieve higher rates of separation by

using centrifugal forces than can be obtained by gravitational settling. Cutting can divide into four

sizes which are;

Category Size Example

Colloidal 2 or less Bentonite, clays and ultra-fine drill solids

Silt 2 to 74 Barite, silt and fine drill solids

Sand 74 to 2000 Sand and drill solids

Gravel More than 2000 Drill solids, gravel and cobble

Shale Shaker

The most important cutting separation equipment is shale shaker, a vibrating screen separators used

to remove drill cuttings from the mud. It is the first line of defense against solids accumulation in

mud cleaning equipment or solid removal chain. A modern shale shaker works by removing about

100% of solids greater than 74microns. The shale shaker cannot remove silt and colloidal size solids.

Thus, it requires dilution and other equipment to control the ultra-fine drill solids.

There are three basic types of shale shakers that are widely use in the industry which are;

The circular-motion shaker; an older design and produces lowest centrifugal force, or G-

force.

The elliptical-motion shaker;a modified circularmotion type in which the center of gravity

is raised above the deck and counter weights are used to produce an egg-shaped motion

that varies in both intensity and throw as solids move down the deck.

The liner-motion shaker;use two circular-motion motors mounted on the same deck. The

motors are set for opposite rotation to produce a downward G-force and an upward G-force

when the rotations are complementary, but zero G-force when the rotations are opposed.


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Sand trap

It is a settling pit located directly after the shale shaker. It can gather the larger particles that can

plug or damage the next solid removal equipment if a screen develops a hole of if the shaker is

bypassed. It use gravitational force acting on the particle for settlement, thus this compartment

should never be stirred or used as suction for discharge for hydrcyclones.

Hydrocyclone (Desander and Desilter)

Hydrocyclone is a static device, closed vessel that applies centrifugal forces to incoming liquid so

that it can classify or separate heavy and light components in the liquid. It is designed to convert

incoming liquid velocity into rotary motion. A centrifugal pump feeds a high volume of mud

through a tangential opening into the large end tunnel-shaped hydrocyclone. When the proper

amount of head pressure is used, it spins the mud in the cyclone and creates centrifugal force in

the mud. A a result, higher mud solids move outward toward the wall of the cyclone where they

agglomerate and spiral down the wall to the outlet at the bottom of the vessel. Light components

like liquid, however, move toward the axis of the hydrocyclone where they move up toward the

outlet at the top. Thus, all hydrocyclones operate in a similar manner, whether they are used as

desanders, desilters or clay ejectors.

Desander is required to remove those abrasive solids in the mud that can be done by the shale

shaker and also to avoid over load on the desilters. It normally use 6-in internal diameter or larger.

Larger desander has the advantage of larger volumetric capacity (flow rate) per hydrocyclone but

has some disadvantage of making wide particle size cuts in range of 45 to 74 micron. In order to get

the best result, it is required to have proper head pressure at the inlet.

Normally, a 4-in internal diameter hydrcyclone is usually used for desilting. Desilter is needed to

remove cuttings with size of 15 to 35 microns. Since barite falls into the same size range as silt

(refer to the cutting size table above), it alos will be separated from the mud by desilter. Because of

this, desilter is rarely used on the mud weight above than 12.5ppg. Moreover, desander and

desilter are widely used while drilling surface hole and when the low density mud is used.


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Mud Cleaner

A mud cleaner, basically will remove sand size drill solids from the mud and it somehow can retain

the barite. Firstly, the mud is passing through the desilter, and then screens the discharge through

a fine-mesh shaker. The larger solids trapped on the screen are discarded leaving the mud and

solids that pass through return into the circulation. Generally, 97% of barite particles are less than

74-micron in size. Thus, most of the barite will be discharged by the hydrocyclone and moving

through the screen and returned into the mud system. In other words, we can say that mud

cleaner is a backup to the shale shakers and in order for a mud cleaner to be an effective cutting

separator equipment, the screen size must be finer than the screen size on the shale shaker.

Centrifuge

Basically, a centrifuge is solid-control equipment that able to remove fine and ultrafine solids. In

normal industrial practice, a decanting-type centrifuge is used to increase the forces causing

separation of the solids by increasing centrifugal force. It consists of a conical, horizontal steel bowl

rotating at a high speed, with a screw shaped conveyor inside. Mud feeds into one end and the

cuttings are separated and moved up the bowl by a rotating scroll to exit at the other end. Even

though it principle is quite similar to hydrocyclone, there is a key difference between these two

equipment. The centrifuge is dynamic separator that is able to apply much more centrifugal force

than hydrocyclone thus remove finer materials while the hydrocyclone is passive separator capable

of applying modest amounts of centrifugal force.

On the rig site, this mud cleaning equipment arrangement is really important to get maximum

separation efficiency. The mechanical equipment is set up based on the particle size that it will

remove. In addition, although a degasser or mud-gas separator is technically a not solid removal

device, it needs to be located after the shale shaker since the centrifugal pumps and other solid

control equipment do not operate efficiently in existence of gas in the mud. Thus, the proper

arrangement for mud cleaning equipment is per below;

1. Shale shaker

2. Sand trap

3. Degasser

4. Desander

5. Desilter

6. Mud Cleaner

7. Centrifuge

8. Cutting dryer (if using oil-based mud, to recover the mud before the dumped the cuttings)


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Figure 1: Example of mud cleaning system (courtesy of

https://reader009.{domain}/reader009/html5/0328/5abba8e0621ff/5abba8e70ac1c.jpg)

MUD PUMPS

At least two slush pumps are installed on the rig. At shallow depths they are usually connected in

parallel to deliver high flow rates. As the well goes deeper the pumps may act in series to provide

high pressure and lower flow rates. Positive displacement pumps are used (reciprocating pistons) to

deliver the high volumes and high pressures required to circulate mud through the drill string and up

the annulus. There are two types of positive displacement pumps which are;

Duplex pump (two cylinders)double acting (pump on the up-stroke and down-stroke)

Triplex pump (3 cylinders)single acting (pump on the up-stroke only)

Triplex pumpor three-cylinder pump is a single acting pump only on forward piston stroke. It means

that when the piston moves forward, it will pump and suction happen when the piston moves in

backward direction. Triplex pump system needs three different cylinders, one each while the duplex

pump requires only single cylinder unit. This pump are the most common type of pump used in well

service activities since it require less maintenance, light, compact, cheaper than duplex pump and

generally is capable of handling many fluid types including corrosive fluids, abrasive fluids and

slurrys containing relatively large particulates.


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Duplex pumpor two cylinders pump is a double acting pump. For every movement of the piston it

will result in pumping and suction. For example, while the piston moves forward, both suction and

pumping occur simultaneously and separately at both ends. Same thing goes when the piston moves

backward. Even though the duplex pump is cheaper and has higher efficiency than triplex pump, it

requires high cost of maintenance and also difficult to maintain.

Figure 2: Triplex (three-cylinder pump) design

Figure 3: Duplex (two-cylinder pump) design


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CIRCULATING SYSTEM CALCULATIONS

Theoretical displacement on the forward stroke, the volume displaced is;

Where is liner diameter and is stroke length . Similarly, on the return stroke;

( ) Where is piston diameter Taking into account of both strokes, the total volume displaced for a complete cycle by a pump,

can be expressed as; ( ) For a triplex pump, the piston diameter does not affect the pump output because the piston

discharges in one direction. The total volume displacement for single-acting triplex pump can be

expressed as;

() Considering a volumetric efficiency, the total volume displacements for both pumps are;

() ( ) () ()

The pump displacement per cycle is also known as pump factor. The pump flow rate, is the product of total volume displacement per cycle, and pump speed, in cyclesper minute (in oilfield, 1 complete pump revolution = 1 stroke, hence pump speed is usually given in

strokes per minute).

Hydraulic horsepower of a pump, is given by;

Where is pump pressure


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Example 2.3

Calculate the pump factor in units of barrel per stroke for a duplex pump below

Stroke length 17

Rod diameter 2.5Liner diameter 6.5

Volumetric efficiency 90%

Unit conversion factors:

Answer:


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Example 2.4

A triplex pump with 6.5 liners, 2.5 rods and 18 strokes is operating at 150 cycles per minute and a

discharge pressure of 4000 psig.

a) Determine the pump factor in gal per cycle at 100% volumetric efficiency

b) Calculate the flow rate in gal per min

c) Compute the pump power developed during the operation

Answer:


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Example 2.5

A double-acting duplex piston pump with 6.5 liner, 2.5 rod and 17 stroke was operated at 4,000

psig and 20 cycles/min for 10 minutes with the suction pit isolated from the return mud flow. The

mud level of the suction pit, which is 6.5 ft wide and 20 ft long, was observed to fall 20 during this

period. Compute (a) volumetric pump efficiency, (b) pump factor and, (c) the hydraulic horsepower

developed by the pump.

Answer:


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EXERCISES

1. A triplex pump with 16 in stroke is operating at 4000psig and 20 cycles per minute. If the

volumetric efficiency of the pump is 80% and the horsepower of the pump is 350hp.

Calculate the piston/liner diameter for this pump.

Answer: 7.579 in

2. A double-acting duplex pump with 6.5 liners, 2.5 rods, and 18 strokes was operated at

3000 psig and 20 cycles/min for 10 minutes with suction pit isolated from the return mud

flow. The mud level in the suction pit, which is 7 ft wide and 20 ft long, was observed to fall

18 during this period. Compute the pump factor, volumetric pump efficiency, and hydraulic

horsepower developed by the pump.

Answer: 7.854 gal/cycle; 0.82; 274.9 hp

3. Consider triplex pump having 6-in liner and 11- in, strokes operating at 120 cycles/min and a

discharge pressure of 3000 psig. Calculate (1) pump factor in units of gal/cycle at 90%

volumetric efficiency (2) flow rate in gal/min (3) hydraulic horsepower developed.

Answer: (1) 3.635 gal/cycle (2) 436.2 gal/min (3) 763.5 hp


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HOISTING SYSTEM

MAJOR COMPONENTS

The main function of hoisting system is provide means of lifting and lowering drill string, casing

string, and other subsurface equipment into the wellbore during drilling activities and also helps the

replacement of the drilling line when it was subjected to wearing. Two routine works carried out by

using the hoisting system are making a connection and making a trip.

The major components of hoisting system are;

Drawworks

Derrick and substructure

Block and tackle

DRAWWORKS

Drawworks, primary hoisting machinery can be described as the heart of the rig. It provides a

means of raising and lowering the travelling block. The main components of modern drawworks are;

Hoisting drum & motor

Brakes (main brake and auxiliary brake)

Transmission

Catheads

The drawworks consist of wire-rope drilling line winds on the large revolving drum and extends over

a set of sheaves in the top of derrick, known as the crown block and down to another sheaves

known as travelling block. A large drilling hookis suspended at the end of the travelling block use to

suspend the drill string. This is allowing the drill string to be moved up and down as the drum turns.

There are two segments of the drilling line known as fast line and dead line. The fast line is the

wire rope drilling line that winds on the drawworks drum to the crown block. The drilling line then

enters the sheaves of the crown block and is makes several passes between the crown block and

traveling block pulleys for mechanical advantage. One end of the line then exits the last sheave on

the crown block and is anchored to a derrick leg on the other side of the rig floor. This section of

drilling line is called the "dead line" because it does not move.


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Figure 4: Schematic design of hoisting system (After Adam T Bourgouyne et al, 1991)

BLOCK AND TACKLE

Block and tackle is the main link between the drawworks and pipe or casing and consists of;

Crown block

Travelling block

Drilling lines (fast line and dead line)

The main principal function of block and tackle is to provide a mechanical advantage, M to allow

easier handling of large loads. It can be defined as;

Where is the load supported by travelling block or hook load and is the load imposed on thedrawworks (tension in the fast line).

Under a static condition, consider a free body diagram in Figure 4, in ideal mechanical advantage

condition where there is no friction in pulleys, the tension in the drilling line is constant. So, hook

load, is supported by the fast lines (i.e. by each of the strung lines through the travelling block). Itgives;

Or

Where is the number of lines strung throughout the crown block and the travelling block. Thenumber of lines is chosen based on the loading condition.


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Table 1: Average efficiency factors for block and tackle system (After Adam T Bourgoyne et al)

Number of lines, Efficiency, 6 0.874

8 0.841

10 0.810

12 0.770

14 0.740

Note that dead-line load is carried by dead-line anchor and the fast-line load is carried by the

hoisting drum.

The input power, of the block and tackle is given as;

Where is the fast-line velocityThe output power or power supplied to the hook, can be expressed as;

Where is the travelling block velocity. The movement of the fast line by a unit distance tends toshorten each of the strung lines between the block and tackle by times the unit distance, thus;

Block and tackle efficiency is the ratio between output power to input power. In an ideal condition

where no friction in the block and tackle system, the efficiency if unity.

However, there is power loss due to friction and other factors in real system. Thus, the approximate

value of average efficiency for the block and tackle system can be referred in Table 1. Using the

value, the actual tension in the fast line for a given load can be determined by using;


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Thus, the fast-line tension gives;

Note that after some or total part of the drill string immersed in the drilling fluid, the weight of the

drill string is reduced because there is upward force that keeps the drill string afloat. Buoyancy

factoris the factor used to consider loss of weight because of the immersion in drilling mud.

Whereis the mud weight in ppg andis the steel density either or .Moreever, under a dynamic condition, the fast-line tension and dead-line tension are illustrated in

Figure 5.

The tension in the successive fast-lines is equal to load imposed on the drawworks, times thesheave efficiency factor,and the tension in the last line is the tension in the dead-line, .The normal value for sheave efficiency, is 0.9615.

So, the load supported by the travelling block, can be expressed as;

Solving this, the tension in the fast-line yields, ;

Considering the block and tackle efficiency, the tension in the dead-line gives;


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Figure 5: Effect of friction on the efficiency of the hoisting system (After H Rabia)

Basically, the number of lines is depending on the load to be supported by the hoisting system and

also the tensile rating of the drilling line used. After certain drilling period, the drilling line becomes

worn and must be replaced. To maintain a good drilling line while drilling, a regular practice known

as slip and cut operation has been practiced in the industry. It is a periodically replacement of a

segment of the drilling line wrapped around the crown block and the travelling block to avoid any

drilling line fatigue. The slipping the drilling lineinvolves losing the dead line anchor and placing a

few feet of new line in service from the storage reel. Cutting the drilling linemeans removing the

line from the drum and cutting off a section of the line from the end.

The slip and cut operation at specific period is determined by the ton-mile calculation. It is a method

introduced to measure the work done by the drilling line by quantifying the cumulative product of

the loaf lifted (in tons) and the distance lifted of lowered (in miles).

Ton-mile is calculated for

Round trip

Drilling or connection

Setting casing

Coring

Short trip


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ROUND TRIP TON-MILE

It is total of the work done by travelling block, drill pipe and drill collar when running and pulling the

drill string from the well.

i. work done by travelling assembly, Where is the weight of travelling assembly, is the length of each stand and is the number ofstand.

Note that to run a stand in the hole, the travelling block has to move a distance of

approximately. Similar amount of work is required to pull the stand out of the hole. Thus totalwork done by travelling assembly is given by;

Assuming , so

ii. work done by drill pipe,

Where

Taking into account the buoyancy factor affecting the weight of drill pipe, the work done by drill pipe

is;

[( ) ( )] Where is buoyant weight of the drill pipe.Assuming the friction loss is the same in going into the hole as in coming out, the work done in lifting

the drill pipe is the same as in lowering, so for a round trip, the work done is equal to

[( ) ( )]


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iii. work done by drill collar,

Where

is the correction for the added work done in lowering and lifting assembly because drill

collars and bit weigh more per foot than drill pipe (previously it is assumed the weight of drill pipe

was run to bottom of the hole).

( )

It yields,

( )

Thus, the total work done for a round trip is given by

( )

Rearrange the equation it gives;

Or

DRILLING OPERATIONS TON-MILE

To calculate the ton-mile in drilling operations,

it has to consider the work performed

during the operation;

a) drill ahead length of the Kelly

b) pull up length of the Kelly

c) ream ahead length of the Kelly

d) pull up length of the Kelly to add single or double

e) put Kelly in rat hole

f) pick up single or double

g) lower drill stem in hole

h) pick up Kelly


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Note that for operations (a) and (b) equal for 1 round trip, operations (c) and (d) equal for 1 round

trip, operations (e), (f) and (h) is equal to round trips, and operation (g) equals to round trips.

If thus the ton-miles for drilling operations;

Where is the ton-miles for one round trip at depth (shallower depth) and is the ton-milesfor one round trip at depth (deeper depth).If operations (c) and (d) are omitted, it gives

If top drive is used,

If reaming is done between connections with a top drive then,

SETTING CASING OPERATIONS TON-MILE

The ton-miles for setting casing operations,is given by;

Since no extra weight from the drill collar, the ton-miles for setting casing operations;

Where is the buoyant weight of casing and is the casing joint length.SHORT TRIP OPERATIONS TON-MILE

The ton-miles for short trip operations, is given by;

Where is the ton-miles for one round trip at depth (shallower depth) and is the ton-milesfor one round trip at depth

(deeper depth).


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DERRICK AND SUBSTRUCTURE

Derrick or Mast is an elevated structure (usually of metal construction) on a drilling rig to provide the

vertical height necessary for the hoisting system to raise and lower the pipe. All the drilling rigs

construction must follow the requirement API standard 4A. This is to ensure the rig is capable to

handle all loads, including maximum drilling loads and weight of pipe set in the derrick. In the

meantime, the derrick also must be able to withstand winds loads acting horizontally and also the

compressive loading. In industrial practice, the selection of drilling rig is based on the rig usage such

as drilling activities, workover or servicing.

Figure 6: API standard 4A derrick size classification

For the normal drilling operation, the pipe is requires to be handled in stands (3 joint of connected

pipe is about 90 ft height). Hence, for older rig usually requires 123 ft of derrick height.

However, in the modern drilling operation nowadays, the height of derrick normally requires

additional height to accommodate the top drive system. Most widely used size is API 19 which

provides 146ft height and 30ft square base with pipe racking capacity of 160 stands of 5ft drill pipe.

The derrick can be classed into two types which are;

Standard derrick

Portable derrick and mast


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The load applied on the derrick,is the total of hook load,, the fast-line tension,and the dead-line tension, and the;

In a static condition, given that the fast-line tension is and dead-line tension is ityields;

Noted that the load on the rig is not distributed equally over all four derrick legs because the dead

line is anchored to one of the leg and the drawworks is situated on one side of the derrick floor. The

load distribution for each derrick leg is shown in the Table 2.

Figure 7: Illustration of drilling lines on the rig floor

The dead-line affects only the leg A to which it is anchored. Besides that, the leg C and leg D would

share the full load of fast-line tension. The leg B only loaded with the hook load during the drilling

operation. It is important to know that at block and tackle efficiency exceed 0.5, the load exerted on

leg A is greater than other legs. Since the derrick will fail if any leg failed, it is convenient to define

the maximum equivalent derrick load,which is equal to four times the maximum leg load (legA),.


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Table 2: Distribution of load on the derrick leg

Load on each derrick leg

Load

sourceLoad Leg A Leg B Leg C Leg D

Hook

Load

Fast-line

- -

Dead-

line - - -

Total load

( )

( )

Noted that derrick efficiency, is used to evaluate various drilling line arrangement.


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Example 2.6

A rig must hoist a load of 450,000. The drawworks can provide an input power to the block andtackle system as high as 450 . Eight lines are strung between the crown block and travelling block.Calculate:

a) The static tension in the fast line when upward motion is impending,b) The maximum hook horsepower available,c) The maximum hoisting speed,d) The actual derrick load,e) The maximum equivalent derrick load,f) The derrick efficiency factor,

Answer:


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Example 2.7

Ten lines are strung between the crown block and travelling block, and the dead line is anchored to a

derrick leg on one side of the v-door, as shown in the figure below. The rig must hoist a load of

500,000, calculate the load distribution on the derrick legs A, B, C and D.Answer:


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EXERCISES

1. Calculate the fast-line tension when lifting a 500,000 load for 6, 8, 10, 12 and 14 linesstrung between the crown block and travelling block.

Answer: , , , , ,2. A rig must hoist a load of 200,000. The drawworks can provide an input power to the

block and tackle system as high as 800 . Eight lines are strung between the crown blockand travelling block. Calculate:

a) The static tension in the fast line when upward motion is impending,Answer: 24961

b) The maximum hook horsepower available,(Answer: 648 hp)c) The maximum hoisting speed, (Answer: 106.9 )d) The actual derrick load, (Answer: 244691)e) The maximum equivalent derrick load,(Answer: 280000)f) The derrick efficiency factor, (Answer: 0.874)

3. Eight lines are strung between the crown block and travelling block, and the dead line is

anchored to a derrick leg on one side of the v-door, as shown in the figure below. The rig

must hoist a load of 400,000, calculate the load distribution on the derrick legs A, B, C andD.

Answer: , ,

REFERENCES

1. Bourgoyne, A.T., M. E. Chenevert, K. K. Millheim, and F. S. Young. 1986. Applied Drilling

Engineering. SPE Tectbook Series, Vol. 2. Crittendon, B. C. 1959.2. https://reader009.{domain}/reader009/html5/0328/5abba8e0621ff/5abba8f73e577.jpg

ch2 rig components (student copy)

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