Any successful system of drilling oil wells must provide, first of all, a means of fracturing or abrading the rocky formations that must be penetrated to reach the oil reservoir, and, second, it must provide a means of excavating Ihe loosened material from the well as drilling proceeds. In addition, provision must be made for preventing the walls of the well from caving and for sealing off water and gas. Wells are usually intended to be vertical or nearly so. The well must, of course, be deep-enough to reach the oil reservoir, and it should be of adequate cross section to permlit the introduction and operation of a pumping device of sufficient capacity to make operation of the well profitable.
3 Translate the following words and word combinations and use them in the sentences of your own:
устя свердловини, забій свердловини, експлуатаційна колона груб, обвал породи, обсадні труби, цільновигягнена труба, з’єднання муфтою, закупорити, арматура, закриття свердловини, опорна свердловина, розвідувальна свердловина, пошукова свердловина, продуктина свердловина.
4 Pick out from Text 1 all the sentences containing Modal Verbs and translate them in to Ukrainian.
5 Write 8-10 questions covering the main idea of Text 1.
6 Learn the meaning of the following words, word-coinbinations and word groups:
cable tool drilling, percussion drilling, rotary drilling, explosion drilling, thermal drlling, flexodrilling, vibrational drilling, core drilling, drilling rig, lubricate, install, drawworks, assembly, derrick, mount, implement, wedge, rope, rod, bucket, drill collar, water course, nozzle, annular, tank, stem, shaft, twist-off, fishing, hoisting, reducing gear, spindel, hollow, gear clutch, clamping, swivel, feeding, hose, storing drum, inject, search, core sample, kelly pellet core head, drag bit,core barrel, core breaker.
7 Read Text 2: Text 2 Methods of Drilling
Drilling oil and gas has become widespread and universal. The bit has drilled the Arctic tundra and the deserl sand, the ocean depth and the mountain top, the open plain and the city square. Almost all types of conditions have been met, yet almost every day there is somehting new in drilling. People like challenges and one of the greatest challenges is drilling.
There are some general methods of drilling oil wells each with its peculiar advantages. They are Cable Tool or Percussion Drilling, Rotary Drilling, Flxplosion Drilling, Thermal Drilling, Flexodrilling, Vibrational Drilling, and Core Drilling.
Rotary drilling comprises two types:
1) the engine on the surface - rotary drilling;
2) the engine at the bottom of the well - (the engine is attached to the lower end of the drill pipe) t urbodrilling and electrodrilling.
As petroleum becomes harder to find and is located much deeper when it is found, so the drilling industry keeps up with the need and builds bigger and more efficient equipment to dig down to the oil.
Modern drilling equipment is consolidated and classified under the term of a drilling rig.
A drilling rig is not a single unit, but is composed of a series of integrated parts which work together to keep the bit on bottom.
Rotary drilling bits effectively cut through the crust of the earth. The drill string, made of tough steel pipe, turns the bit and channels the drilling fluid down to lubricate it and carry the cuttings away. The bit must be replaced when it wears out and there has to be a connection between the surface and the bit on bottom.
On any rig there are a large number of water, mud and air lines, which must be installed. Rigs are built to certa in capacities, depending on the size of the drawworks. They will drill effectively to a given depth, varying with the size of the drill pipe used, the size of the pump and weight of the casing to be run. They are usually specialized for a particular area.
At present the assembly of the drilling equipment and derrick is done by the industrial method. The drilling equipment is mounted on three metal platforms, which are moved from one oil well location to another, as need arises.
Percussion drilling. This is the most primitive and most efficient way of drilling, which is implemented by a wedge bit. The wedge bit is fixed on a steel rope or metallic rods by means of which the bit is made to give successive blows on the formation.
When sufficient cuttings are accumulated on the bottom, a special bucket with a valve extracts the cuttings from the hole. Nowadays there are special transportable rigs for percussion drilling. In the USA 10 % of the total drilling is implemented by this method.
Rotary drilling. The rotary drilling method is comparatively new. The idea of this method was introduced into life in 1901. In the rotary method, the hole is drilled by a rotating bit to which a force is applied. The bit is fastened to, and rotated by, a drill string, composed of drill pipe and drill collar, with new sections of joints being added as drilling progresses.
The cuttings are lifted from the hole by the drilling fluid which is continuously circulated down the inside of the drill string through water courses or nozzles in the bit, and upward in the annular space between the drill pipe and the bore hole. At the surface the returning fluid (mud) is diverted through a series of tanks or pits which afford a sufficient period to allow cuttings separation and any necessary treating. Periodically the drill pipe must be removed from the hole in order to replace the bit.
Power in rotary drilling is transmitted from the surface to the bit through the drilling string and considerable part of the power is wasted in idle rotation of the drilling string. Power losses depend upon many factors, e. g. length and diameter of the stem, specific gravity of the mud.
Rotary drilling is used in different geological conditions: in unstable formations, zones of loss of circulation, water-gas bearing layers of high pressure. Rotary drilling makes it possible to use any agent such as air, gas, mud (with a specific gravity more than 2.3 gr/cm3 and highly viscous). It is also possible to use jet bits and bits of small diameters.
The major disadvantages of rotary drilling are as follows:
1 Surface equipment must be of high power, a great part of it being waisted in rotating the drill shaft and operating of the surface equipment.
2 Drill pipes must be of high quality.
3 Hydraulic horsepower of pumps is not always used completely.
4 The installations are very noisy which makes working conditions hard.
Drilling by the turbine method. In turbine drilling the bit is
rotated by a turbodrill attached to the lower end of the drill string. The turbodrill is powered by a multiple-stage hydraulic turbine, which is driven by the drilling fluid. Power on the bit can be kept constant as the hole goes down. Standard rotary equipment is used, and the turbine and rotary methods are interchangeable.
Turbine drilling demonstrates such benefits as:
1 Fast penetration.
2 Elimination of twist-off and other fishing and lost-hole hazards.
3 Reduced drill pipe and tool joint wear.
4 Lower mud consumption than in rotary drilling.
5 Reduced rig wear.
Turbine drilling is safe, fast and efficient, and will substantially reduce well cost. The turbodrill provides a hydraulic drive for the bit at the bottom of the hole and obviates the necessity for constant rotating the drill pipe. The turbodrill depends solely upon hydraulic power of the stream of drilling fluid to rotate the bit.
Turbine drilling can be accurately described as hydraulic rotary drilling. Drill-pipe weight and required stream power are the main criteria in selecting the rig for turbine drilling. Steam or power rigs with adequate hoisting and pump capacities are equally suitable. The turbodrill is made up in the drill string immediately above the bit. No drill collars are carried adove the tool. However, the drill collars should be carried when the desired bit load exceeds the weight of the turbodrill. Selection of the proper drill pipe is of great importance. The drill stem should have the highest attainable hydraulic efficiency, in order that fluid power losses in the mud-circulating system may be kept to minimum.
Conventional rotary drilling mud and mud control are used on turbodrill run. A mud-line screen is carried at the pump outlet to drop out large particles which might get past the pumps and a strainer is provided above the bit to keep cuttings from being carried into the turbodrill by back flow when drill pipe connections are made. Conventional rock bits are used.
The risk of twisting off the drill pipe, or leaving drill pipe or drill collars in the hole because of a joint backing off, is eliminated in turbine drilling. The danger of tool-joint and drill collar connection failure is greatly reduced, because the drill stem turns very slowly and is under greatly reduced stress.
Bit failure should be less frequent, since the turbodrill provides a hydraulic shock absorber for the bit. The danger of a fishing job caused by caving or heaving of the formation still exists, but is probably reduced because the drill stem turns more slowly and does less damage to the hole wall.
Since turbodrill cuttings are fine and annular mud flow is faster and more uniform, the danger of lost circulation may be reduced. The turbodrill turns the bit at speeds ranging from 500 to 1000 r. p. m, which are not high enough to do any damage, and it is believed that the lighter drilling loads tend to reduce bit wear.
Hole deviation has never been a problem with the turbodrill. It is believed that the turbine drilling combination of relatively light bit load and high bit speed will usually produce a straight hole. The new design of the spiral turbodrill provides for the reduction of the revolutions to 300 per minute. The use of the multi-stage turbodrill results in higher penetrating power at a lower capacity of the pump, which enables drilling greater depth.
Electrodrilling. The electric motors (1.500 r. p. m) were provided with a reducing gear for decreasing the revolutions of the bit. Main elements of an electrodrill are:.the electromotor in oil bath and spindel to transmit rotation and power to the bit; the electric motor is
provided with a hollow shaft for circulating drilling fluid through to the bit.
The shaft is thin-walled, calculated not for axial loading but for torque only. Thus, it is provided with a spindle - a short, thick-walled, strong shaft on ball bearings or rubber supports. Ball bearings are lubricated by oil from the oil bath; rubber is lubricated by drill fluid in the chamber (not oil).
A gear clutch connects the shah of the motor and the spindel The electrodrill is powered by means of a special 3-line cable, constantly fixed in each drill pipe; the ends of the pipes cany clampings providing electrical contacts. An electrical swivel is fixed under the swivel to transmit electric power to the bottom hole motor. The fluid is circulated through the drill pipes.
Electrodrilling has technical and economic advantages over both rotary and turbodrilling:
1 Energy is transmitted to the bottom of i:he hole regardless of either the depth of the well or quantity and quality of the circulating fluid.
2 Since the drill pipes do not rotate and fluid pressure is not high, the life of pipes is considerably increased and, hence, steel consumption per one meter of drilling is decreased. High pressure pumps are not required.
3 Automation of the process is simplified, feeding of the bit is mechanized: a bottom hole inclinometers fixed over the drill makes it possible to measure constantly inclination of the well.
4 Application of both heavy mud and air for well circulation is possible.
Electrodrilling without application of drill pipes.. Time for round trips is considerably reduced. The string consists of the bit, drill collars, spindel, reducing gear, slush pump at the bottom hole for local circulation, electric motor, short tube for cuttings and 3-phase cable. The weight of the surface equipment is about 20 tons. No pumps are required on the surface, a low r ate of penetration is on the minus side of the method.
Flexodrilling. A new method of drilling - drilling on flexible drillstem (flex-stem) was put forward about 40 years ago. The drillstem is a continuous, flexible hose manufactured in long lengths.
Mud is pumped through the flex-stem. Either one turbodrill or electrodrill may drive the bit which is fixed several meters below the drill collars to create weight on bit. The strong point of this method is in economy of expensive steel pipes and save in time for round trips. When the bit is pulled out, the flex-stem is wound in the storing drum.
Vibrational drilling. Vibrational drilling combines rotary and percussion drilling. There are three types of vibrators: mechanical with a drive from an electric motor or electromagnetic device, a hydraulic vibrator with a drive from a hydraulic turbine and an air or pneumatic vibrator.
A bottom hole vibrator with the drive is fixed on the string next to the bit or over the drill collars. It transmits strong vibrations to the rotating bit: 100 impacts per min, 13 tons strong, which increase rate of penetration many times. The disadvantages of this method are: lack of durability of vibrators and high rate of failures of the drill pipes.
Explosion drilling. A special device automatically feeds the drill string with explosive charges which are delivered to the bottom hole by the circulating fluid. Exposive drilling is believed to be used at different depths in hard formations. It will considerably reduce time for round trips.
Thermal drilling. Special thermal drilling rigs attained wide spread acceptance in drilling shallow wells in hard formations. Burning up kerosine or diesel fuel in oxygen at the bottom of the hole provides temperature 2500°C. The drilling string consists of two rows of pipes. The fuel is piped to the nozzle where it bums up and the gas and vapour mixture attains the velocity of 1800 m/sec. The nozzles are water cooled. The disintegration of the formation occurs due to the high temperature and the high speed of the gas injected into the bottom of the well.
Core drilling. Structural drilling is aimed at the study of the geological structure of an area, at plotting structural maps of a horizon, at the search of reservoir rocks. To solve these problems it is necessary to have a required number of samples of mother rock along the total depth of drilling. This is achieved by drilling structural wells and wild cats.
Core drilling is such a type of rotary drilling in which formation is destroyed not upon the entire area of the bottom but in a circular way. This produces a column of mother rock which is called a core sample. Structural drilling is done from some tens of meters up to several thousand meters in depth. Rigs for core drilling may be of a rotary type and a spindel type. Flotation is transmitted from the rotary table through the kelly or less frequently from the spindel.
Four kinds of drilling tools are used in core drilling:
1 Hard alloy core heads for semi-hard and hard formations.
2 Diamond core heads for extra-hind formation.
3 Pellet core heads for igneous rocks.
4 Roller bits and sometimes drag bits.
Core equipment for core drilling includes core head, core barrel, drill pipe, kelly. For ordinary drilling the core barrel is replaced by drill collars. There are single and double core barrels. In the first case the fluid goes between the core and the inside wall of the pipe. In the second case it goes in the annular area.
The turbobit is used in turbodrilling for the recovery of the core sample. The turbobit comprises the drill bit, the core breaker, the core barrel and turbodrill with a hollow shaft. The use of the turbobit enables the recovery of the core sample in a core barrel to the surface without pulling out of the drill pipe and bit.
8 Find in Text 2 English equivalents for the following:
канатне буріння, ударне буріння, роторне буріння, вибуховий спосіб буріння, термічне буріння, буріння на гнучких шлангах, вібраційне буріння, колонкове буріння, бурова установка, бурова іишка, неробочий хід, питома вага, гідромоніторне долото, гідравлічна потужність, турбобур, поломка бурильних труб, ловильні роботи у свердловині, піднімання інструменту, амортизатор, оберт за хвилину, шариковий підшипник, спуск- підйом інструменту, буровий насос, гнучкий кабель, продуктивний пласт, материнська порода, пустотілий вал, грунтоноска, виловлювати.
9 Make a written translation of the following:
Rotary drilling is used in different geological conditions: in unstable formations, zones of loss of circulation, water-gas bearing layers of high pressure. Rotary drill ing makes it possible to use any agent such as air, gas, mud (with a specific gravity more than 2.3 gr/cnr’ and highly viscous). It is also possible to use jet bits and bits of small diameters.
The major disadvantages of rotary drilling are as follows:
1 Surface equipment must be of high power, a great part of it being
waisted in rotating the drill shaft and operating of the surface
equipment.
2 Drill pipes must be of high quality.
3 Hydraulic horsepower of pumps is not always used completely.
4 The installations are very noisy which makes working conditions hard.
10 Describe in brief each method of drilling.
11 Working in pairs test each other’s ability to describe advantages and disadvantages of each method of drilling.
Unit 17 Drilling Equipment
1 Learn the meaning of the following words, word-combinations and word groups:
rig, derrick, substructure, drawworks, mud pump, crownblock, swivel, rotarybhose, mount, support, pier, spool, hoisting, brake, slip, coil, kelly joint, suspend, trip, reciprocating, piston, duplex, failure, fatigue, drill collar, hollow shaft, furnish, conduit, seamless, hexagonal, fitting, bushing, suspension.
2 Read Text 1: Text 1 Drilling Equipment
Rotary drilling equipment is complex and the basic rig components are:
1 Derrick or Masts
2 Substructures
3 Drawworks
4 Rotary table
5 Mud pumps
6 Prime movers
7 Auxiliary equipment - crownblock, swivel, hook, bits, rotary hose, drilling line and etc.
Derricks. Derrick is a four-sided, pyramidal structure of square cross section. The function of the derrick is to provide the vertical dearence necessary to the raising and lowering of the drill string into and out of the hole during the drilling operations. It must be of sufficient height and strength to perform these duties.
Derricks are of two general types, standard and portable. A standard derrick is of belted construction and must be assembled part by part.
A portable derrick or mast is one capable of being erected as a unit. The derrick is mounted on a substructure. Derricks are constructed from 18 to 53 meters high. Drilling derricks are usually 40; 42; 53 meters high.
To facilitate rapid assembly of drilling equipment and moving from one well location to another, the derrick may be replaced by a braced mast of unitary construction. Usually the mast will be designed to facilitate disassembly or folding of component parts, small and light enough to be moved on trucks or tractors.
Such masts can be moved into a new location and made ready for drilling service in but a fraction of the time ncccessary for erection of a standard steel derrick.
Portable masts were first developed for drilling to comparatively shallow depths - as great as 2,286 m - and were seldom more than 256 m in height; but more recently, larger and better designed masts have been used in deep drilling operations. Recent designs provide a structure 39; 41 or 43 m high, capable of supporting loads as great as 500 tons and of conducting drilling operations to depths of 4.570 m or more.
Substructure. The substructure is the support on which the derrick rests. This must be of sufficient strength to support the anticipated loads with adequate safety factors.
Substructures vary in size, depending on the type and weight of the drilling equipment above them and on the amount of control devices that they will contain. Substructures may be pier, concrete and metal.
Drawworks. The drawworks is the principal tool of equipment on a rotary rig. It is the control centre from which the driller operates the rig. It houses the drum v/hich spools the drilling line during hoisting operations end allows feed-off during drilling. A large draw works can sometimes weigh up to 40 tons.
Brakes. The brake is an important part of drawworks design. Brakes on a drilling rig permit the driller literally to stop on a dime and handle the travelling block and drill string with comparative ease. The hydraulic brake works on the principle of fluid transmission and retards the speed of the drill pipe descending in the hole sufficiently to allow the slips to be set.
The electro-magnetic brake requires electrical excitation by an outside current. The breaking effect is controlled by the amount of electrical current admitted to the magnetic coils of the unit. These auxiliary braking units provide ample means to enable the driller to lower the drill string safely into the well bore.
Rotary table. Rotary table has two primary functions:
1 It transmits the rotation to the drill string by turning the kelly
joint.
2 It suspends the pipe weight during connections and trips. The table is chain-driven through the draww'orks, although a smaller, separate engine is sometimes used as an independent unit.
Mud pumps. The function of the mud or slush pumps is to circulate the drilling fluid at the desired pressure and volume. The pump used for this service is the reciprocating piston, double-acting, duplex type. The term «double-acting» denotes that each side of the piston does work, while «duplex» refers to the number of pistons - two.
Mud pumps providing high pressure and high capacity are used in drilling. The capacity of a mud pump attains several hundred horsepower. The pump is driven by an electrical or diesel engine. One - three mud pumps are employed in the w^ell-location.
Prime movers. There are four general groups of prime movers - diesel, steam, internal combustion or diesel-electric each giving a certain advantage for certain working conditions. The prime mover selected for a rig must be able to meet certain specifications.
It must be corvenient to move. Becoming more and more widely accepted is the diesel-electric combination. Diesels are used to power generators which supply electricity to electric motors on the rig. They are being used especially on off-shore installations, where floor space is at a minimum.
Drilling string. The drill string is an extremely expensive rig component and must be replaced periodically. Most drill-string failures are due to material fatigue which has been aggravated by corrosion and improper care and handling.
The drilling string provides means of senting the bit on bottom, of turning it, and of providing it with drilling fluid to clear away the cuttings.
Just above the bit are the drill collars. Hollow shafts of toughest alloy steel, the drill collars weigh from a hal f ton to more than two tons each. The number of these drill collars in the drilling string may range from 2 to 20 or more - whatever number is required weight on the bit to make it cut. Between the top of the drill collars and the surface is the drill pipe.
l he drill pipe furnishes the necessary length for the drill string and serves as a conduit for the dri lling fluid.
Drill pipe sections (or joints) are hollow, seamless tubes manufactured from high grade steel. To form a strong union between pipes, each is equipped with tool joints. The tool joints are attached to the pipe after its manufacture.
At the point where the tool, joints are attached to the pipe, the latter has a thick wall called the upset to give more strength to the assembly.
The main diameter sizes of drill pipes are 89; 114; 127; 140; 147; 168 mm. When drilling is in progress the quality of the drill pipes is periodically checked by examination, pressure-testing and sometimes fault detaction. The defective pipes are removed. In recent years besides steel pipes light alloy drill pipes are being used. Light-weight pipes make it possible to reduce the round trip time considerably and to use lighter capacity drilling rigs.
Kelly joint. The kelly joint is the topmost joint in the drill string. It is commonly square but may be hexagonal. The kelly passes through fitting, properly shaped bushings in the rotary table allowing the rotation of the table to be transmitted to the entire drill string. This is its primary function. In addition the kelly joint supports the
drill string in suspension. The upper end of the kelly is connected with the swivel.
3 Give English equivalents of the following:
бурова вишка, лебідка, помпа бурового розчину, головний двигун, буровий шланг, поперечне січення, бурова колона, монтувати, свая, піднімання інструменту, подача інструменту у свердловину, робоча труба, рейс опускання-иіднімання, ланцюгова передача, двигун внутрішнього згорання, втомлюваність металів, порожнистий вал, безшовна труба, високолегована сталь, дефектоскопія, час операції опускання-піднімання, перевідник.
4 Pick out from Text 1 all the verbs in the Passive Voice.
5 Give definitions of derrick, substructure and drawworks using Text 1.
6 Find, read and translate the sentences in Text 1 in which we learn about brakes and mud pumps.
7 Working in pairs test each other’s ability to describe the main functions of the basic rig components.
Unit 18 Auxiliary Drilling Equipment
1 Learn the meaning of the following words, word-combinations and word groups:
crown block, travelling block, withstand, exert, pull, collapse, screw, top stand, suspend, pulley, tong, slip, slips, wrench, make up tong, swing, handling.
2 Read Text 1:
Text 1 Auxiliary Equipment Crown block. The crown block is situated at the top of the derrick. The drilling line, which is attached to the drum of the drawworks, goes from there to the crown block. The derrick serves as a support for the crown block and travelling block, and must be able to withstand the strain of the weight of the pipe as it comes out of the hole.
Sometimes the pipe becomes stuck and the driller attempts to work it loose with the drawworks. If he exerts a pull greater than the capacity of the derrick, then it will collapse, since the amount of load on hook is device controlled.
Swivel. The swivel is the connection between the slush pumps and the drill string. It also functions as a universal joint, allowing the drill string to turn while mud is passing through it. From the swivel the mud goes to the kelly, which is screwed on the top stand of drill pipe in the drill string. The swivel is suspended on a hook.
Travelling block and hook. The travelling block is merely the travelling pulley assembly which connects the drilling line to the hook and swivel. This may be combined with the hook as a unit, or they may be separate parts.
Mechanization elements. Located on the derrick floor near the rotary table are the tongs and slips. The tongs are large wrenches, which are used to tighten or loosen the drill pipe and drill collars.
Two sets of tongs are used, the lead or make up tongs and the back-up tongs. They are counter-balanced by a weight under the derrick floor. A line passes from the weight to a pulley in the derrick and back down to the tongs. This balances their weight and allows the operators to swing them with no difficulty. Power tongs and slips have now been developed to the point where they may be installed as standard equipment. Operating by hydraulic pressure or by air pressure, they eliminate much of the fatigue resulting from handling the mechanical tongs, and thus reduce the possibility of accidents.
Power slips are designed to fit around the drill pipe in the rotary table, and serve to prevent its slipping into the hole while making a connection or making a trip. The use of power slips also reduces fatigue, and provides faster performance in making connections and trips.
3 Make a written translation of the following:
Mechanization elements. Located on the derrick floor near the rotary table are the tongs and slips. The tongs are large wrenches, which are used to tighten or loosen the drill pipe and drill collars.
Two sets of tongs are used, the lead or make up tongs and the back-up tongs. They are counter-balanced by a weight under the derrick floor. A line passes from the weight to a pulley in the derrick and
back down to the tongs. This balances their weight and allows the operators to swing them with no difficulty. Power tongs and slips have now been developed to the point where they may be installed as standard equipment. Operating by hydraulic pressure or by air pressure, they eliminate much of the fatigue resulting from handling the mechanical tongs, and thus reduce the possibility of accidents.
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