An Introduction to Rotary System, Hoisting System and Circulatory System in Rotary Drilling Rig

Bahria University Department of Earth and Environmental Science (Islamabad Campus) Uzair Safi BS-GEOLOGY 6th

Table of Contents

An Introduction to Rotary Drilling Rig…………………………………. Page 1

1. The Rotary System………………………………………………… Page 2-3 Swivel……………………………………………………………. Kelly………………………………………………………………. Rotary drive……………………………………………………… Rotary table……………………………………………………… Drill pipe…………………………………………………………. Drill collars………………………………………………………. Drill bit…………………………………………………………….

2. The Hoisting System……………………………………………… Page 4-7 The derrick and substructure …………………………………. The block and tackle …………………………………………… The draw works………………………………………………….

3. The Circulatory System………………………………………….. Page 7-10 Circulating Equipment…………………………………………. Mud Circulation Process: ………………………………………

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An Introduction to Rotary System, Hoisting System and Circulatory System in Rotary Drilling Rig

An Introduction to ROTARY DRILLING RIG

Rotary drilling rigs are used for almost all drilling done today. A hole is drilled by rotating a bit to which a downward force is applied. Generally, the bit is turned by rotating the entire drillstring, using a rotary table at the surface, and the downward force is applied to the bit by using sections of heavy thick-walled pipe, called drill collars, in the drillstring above the bit. The cuttings are lifted to the surface by circulating a fluid down the drillstring, through the bit, and up the annular space between the hole and the drillstring. The cuttings are separated from the drilling fluid at surface. A sketch illustrating the rotary drilling process is shown in Fig.1

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Figure.1 - The Rotary Drilling Process

1. The Rotary System

The rotary system includes all of the equipment used to achieve bit rotation via various components. The main parts of the rotary system are as followed:

1. Swivel2. Kelly3. Rotary drive4. Rotary table5. Drill pipe6. Drill collars7. Drill bit

COMPONENTS:

1. The swivel supports the weight of the drillstring and permits rotation. The bail of the swivel is attached to the hook of the traveling block, and the gooseneck of the swivel provides a downward- pointing connection for the rotary hose.

Swivels are rated according to their load capacities.

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Kelly

Swivel


2. The Kelly is the first section of pipe below the swivel. The outside cross section of the kelly is square or hexagonal to permit it to be gripped easily for turning. Torque is transmitted to the kelly through Kelly bushings, which fit inside the master bushing of the rotary table. The Kelly must be kept as straight as possible to avoid wear off.

3. The Rotary Table is the principal component of a rotary or rotary machine, used to rotate the drill stem and support the drilling assembly. It has a beveled gear arrangement to create the rotational motion and an opening into which bushings are fitted to drive and support the drilling assembly.

4. The Drill pipes are heavy seamless tubing used to rotate the bit and circulate the drilling fluid. Joints of pipe 30 feet long are coupled together with tool joints.

5. The Drill collar is a heavy, thick-walled tube, usually steel, used between the drill pipe and the bit in the drill stem. It is used to put weight on the bit so that the bit can drill.

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Drill pipe

Drill collars

Drill bits


6. The Drill bit is a tool designed to produce a generally cylindrical hole (wellbore) in the earth's crust by the rotary drilling.

2. The Hoisting System

The function of the hoisting system is to provide a means of lowering or raising drill strings, casing strings, and other subsurface equipment into or out of the hole. Two routine drilling operations performed with the hoisting system are called making a connection and making a trip.

The principal components of the hoisting system are as followed:

1. The derrick and substructure 2. The block and tackle 3. The draw works

COMPONENETS:

2.1 The Derrick and Substructure:

The function of the derrick is to provide the vertical height required to raise sections of pipe from or lower them into the hole. The greater the height, the longer the section of

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pipe that can be handled and, thus, the faster a long string of pipe can be inserted in or removed from the hole. The most commonly used drillpipe is between 27 and 30 ft long.

In addition to their height, derricks are rated according to their ability to withstand compressive loads and wind loads. Allowable wind loads usually are specified both with the drillstring in the hole and with the drillstring standing in sections in the derrick. When the drillstring is standing in the derrick resting against the pipe-racking platform, an overturning moment is applied to the derrick at that point. Wind ratings must be computed assuming wind loading is in the same direction as this overturning moment. Anchored guy wires attached to each leg of the derrick are used to increase the wind rating of small portable masts. The American Petroleum Institute (API) has published standards dealing with derrick specifications and ratings. Substructure:

To provide working space below the derrick floor like for pressure control valves called blowout preventers, the derrick usually is elevated above the ground level by placement on a substructure. The substructure must support not only the derrick with its load but also the weight of other large pieces of equipment. The choice of design usually is governed by blowout preventer height and local soil conditions.

API recommends rating substructure load-supporting capacity accordingly:

The maximum pipe weight that can be set back in the derrick The maximum pipe weight that can be suspended in the rotary table.

The corner loading capacity (maximum supportable load at each corner).

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Substructure


A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. The pulleys are assembled together to form blocks. The principal function of the block and tackle is to provide a mechanical advantage, which permits easier handling of large loads.

The block and tackle is comprised of following components as:

a) The crown blockb) The traveling blockc) The drilling line

a. The Crown BlockAn assembly of sheaves or pulleys mounted on beams at the top of the derrick. The drilling line is run over the sheaves down to the hoisting drum.

b. The Traveling BlockAn arrangement of pulleys or sheaves through which drilling cable is reeved, which moves up or down in thederrick or mast.

c. The Drilling Line

In a drilling rig, the drill line is a multi-thread, twisted wire rope that is threaded or reeved through the traveling block and crown block to facilitate the lowering and lifting of the drill string into and out of the wellbore.

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Crown Block

Traveling Block


2.3 The Draw works

The draw works provide the hoisting and braking power required to raise or lower the heavy strings of pipe. The principal parts of the draw works are as followed:

Drum Brakes Transmission Catheads

The Drum transmits the torque required for hoisting or braking. It also stores the drilling line required to move the traveling block the length of the derrick.

The Brakes must have the capacity to stop and sustain the great weights imposed when lowering a string of pipe into the hole. Auxiliary brakes are used to help dissipate the large amount of heat generated during braking. Two types of auxiliary brakes commonly used are the Hydrodynamic type and the Electromagnetic type. For the hydrodynamic type, braking is provided by water being impelled in a direction opposite to the rotation of the drum. In the electromagnetic type, electrical braking is provided by two opposing magnetic fields. In both types, the heat developed must be dissipated by a liquid cooling system.

The draw works Transmission provides a means for easily changing the direction and speed of the traveling block. Power also must be transmitted to catheads attached to both ends of the draw works.

The Cathead is a spool-shaped attachment on a winch around which ropefor hoisting and pulling is wound.

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3. The Circulatory System

The circulating system consists of a range of equipment that works together to move drilling fluid (called mud) into and out of the hole being drilled. This drilling mud serves several purposes: it cools and lubricates the drill bit; it flushes cuttings and debris away from the face of the drill bit; and it coats the walls of the well to stabilize them.

Another critical function of the circulating system is to help control pressure within the well. The weight of the drilling mud can be adjusted to exert greater pressure at the bottom of the well than the pressure exerted by fluids (oil, gas, and water) in the surrounding rock. This control is necessary to prevent uncontrolled fluid flow into the well and to prevent the well walls from caving in, trapping equipment down hole.

Drilling mud can consist of any of the following mixtures:

• Water (fresh or saline) and clay (commonly bentonite) • Oil (diesel, mineral, or synthetic) and clay • Water with 10% oil, plus clay (emulsion) • A synthetic organic material and water •

3.1 Circulating Equipment

Mud circulates through many pieces of equipment, all of which play an important role. The drilling mud passes from the mud pump, the discharge line, the standpipe, the rotary hose, the swivel (or top drive), and the kelly (on rigs with a rotary- table system),

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the drill pipe, the drill collars, the bit, the annulus, the return line, the shale shaker, the desilter, the desander, the mud tanks, and the suction line (fig. 3.1).

3.2 Mud Circulation Process:

The Mud pump (Fig3.2a) takes mud from the mud tanks and sends it out a discharge line to a Standpipe(Fig3.2b). The standpipe is a steel pipe mounted vertically on one leg of the mast or derrick. Mud flows out of the standpipe and into the Rotary hose, which is connected to the Swivel on rotary-table system rigs or to the top drive. Mud goes down the Kelly on rigs with a rotary table; on rigs with a top drive, mud goes through passageways inside it. Once it leaves the kelly or the top drive, mud flows down the Drill stem, out the Bit. It does a sharp Uturn and heads back up the hole in the Annulus.The annulus is the space between the outside of the drill string and sides of the hole. As it flows up the annulus, the mud carries the cuttings made by the bit.

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Figure3.1 Components of a rig circulating system

Figure 3.2b Standpipe


Finally, the mud leaves the hole through a steel pipe called the "mud return line" and falls over a vibrating, screenlike device called the "shale shaker" (fig. 3.2c).

The shale shaker is appropriately named, for it rapidly vibrates or shakes as the mud returning from the hole falls over it. The shale shaker acts like a sifter and screens out the cuttings. The Mud and cuttings falling onto the shale shaker, removes the cuttings and the mud falls into a tank below the shaker. The Desanders removes fine particles, or solids, from drilling mud and the Desilters removes solids that are even smaller than those the desander removes(Fig3.2d). The Degasser is the equipment used to remove unwanted gas from the drilling fluid.

The circulating system is essentially a closed system. The system circulates the mud over and over throughout the drilling of the well. From time to time, however, crew members may add water, clay, or other chemicals to make up for losses or to adjust the mud's properties as the hole drills into new and different formations.

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Figure3.2c Shale shaker Figure3.2d Desander and Desilter


*END*

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An Introduction to Rotary System, Hoisting System and Circulatory System in Rotary Drilling Rig

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