2 Giive English equivalents of ithe following:

розчинення	бурильний розчин
луг	дисперсія
водовіддача	захисний одяг
сивушні оливи	опір тертя
поверхнево-активна речовина	розчин на нафтовій основі

3 Match the terms with their definitions:

1 carboxymethyl cellulose	a) serve to bind calcium and magnesium ions and to improve the wettability of clays
2 caustic soda	b) reduce the coefficient of friction and keep down the intensity of the rock-breaking tools wearout
3 soda ash	c) a high-molecular powder­like agent of a white or cream colour, readily soluble in water
4 soluble glass	d) a colourless crystalline mass, readily soluble in water
5 phosphates	e) a white-coloured powder, difficultly soluble in cold water, bu: with rising temperature its solubility improves
6 lubricating additives	f) a vitreous mass of an unstable composition, readily soluble in water

4 Tell whether each of the following statements is true or false according to the text. Correct the false statements to make them true:

1. The drilling fluid transmits power from mud pumps installed on the ground surface to the bottom drive engine in turbodrilling and also to the face of the bottom hole.

2. Water cools the bit and friction surfaces of the drilling shaft worse than other liquids.

3. Water is a universal drilling fluid.

4. Caustic soda doesn't cause burns on the body surface and blindness when it gets into eyes.

5. The properties of the mud fluid undergo changes in the course of drilling.

5 Make a written translation of the following:

Mud fluids other than the water-base ones are intended largely for drilling in producing formations, when water-base muds act adversely on the productivity; in core-drill sampling, when there is a need for obtaining rock specimens uncontaminated with the filtrate (to determine the actual presence of oil, the content of connate water and permeability); in piercing argillites and schistous clays prone to lose their rigidity and to crumble (or collapse) under the effect produced by the water-base mud filtrate; in sinking high- temperature (hot) wells and, not infrequently, in cases of high coefficients of the formation pressures abnormality, when it becomes difficult to keep in good condition a water-base mud fluid; in drilling over chemogenic deposits, which are readily soluble in water-base drilling fluids. Fluids other than water-base ones may be also utilized in overhauling the wells and for temporary closing-in of the latter.

PART 4

DRILLING METHODS AND DRILLING EQUIPMENT

Unit 16 Methods of Drilling

1. Learn the meaning of the following words, word-combinations and word groups:

well head, inch, oil string, proceed, caving, encounter, exclude, casing, screw, socket, joint, segregate, seal off, cement, fitting, valve, cosing- in, attach, key hole, exploratory well, wild cat, producing well, fracture, abrade, penetrate, loosen.

2. Read and translate Text 1:

Text 1 Description of an Oil Well

In general, an oil well is similar to any other borehole drilled for the purpose of producing water or other fluids.

The well bore length exceeds many times its diameter. The opening of the well bore at the surface is called the well head, and its lower part the bottom hole. The depth of an oil well is controlled by the depth at which oil is found.

The diameter of a well varies. A deep well has a diameter at the surface of about 16-18 inches, which diameter is reduced progressi­vely to about 6 inches at the bottom. The diameter of the oil string depends on the expected productivity of the well.

As drilling proceeds, subsurface waters or formations of a caving nature are often encountered. To exclude such water from the well and to hold back the caving formations, the well is lined with steel tubes known as casing.

The number of strings of casing and their diameter is controlled by local conditions and by the depth to which the well is to be drilled.

Oil-well casing is usually made of solid drawn tubes with screwed and socketed joints. There may be within the well bore several strings of casing: the surface casing, the intermediate or protective string and the oil string.

In cases where the oil is struck at high pressures or where it is essential that all upper water shows, must be permanently sealed off or segregated from each other, each string of casing is cemented in place.

The necessary valves and fittings, known as the "Christmas Tree" for closing-in oi' controlling the production, are attached to the inner or oil string of casing.

There are different kinds of oil wells depending on the purpose for which they are drilled, such as: key holes, exploratory wells, wild cats, producing wells or producers, seismic wells and etc.

Any successful system of dril ling 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 permit 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, цільновигяїнена 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-combinations and word groups :

cable tool drilling, percussion drilling, rotary drilling, explosion drilling, thermal drlling, fl ex od rilling, 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, P^xplosion 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) turbodrilling 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 ol 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 pen strating 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 shaft 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 rate 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 burns 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-hard 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 юшка, 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.

8. 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 metre than 2.3 gr/cm ' 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.

8. Describe in brief each method of drilling.

9. 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 - erownbloek, swivel, hook, bits, rotary hose, drilling line and etc.

Derricks. Derrick is a four-sided, pyramidal structure of square ;ross 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 £.nd 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 drawworks, 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 well-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 convenient 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 siring 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 handlling.

The drilling string provides means of setting 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.

The 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 bsing 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.

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.

1. Make a plan to Text 1 and retell it.

2. Learn the meaning of the following words, word-combinations and word groups:

cementing, seal., slurry, truck, squeeze, tank, strata, perforation, attachment, shoe, cementing collar., cementing plug, stop-ring, drillable plug.

3. Read Text 2:

Text 2 Casing and Cementing

The «wrapping» for the hole is called casing. It is a heavy steel pipe which seals off the hole from cave-ins, and is in turn wrapped in cement, which protects the casing from corrosion, prevents migration of fluids from one formation to the other, and prevents pollution of the-oil and gas produced.

Placing the cas ng accurately is a job requiring skill and expe­rience. When the casing is set in the proper location, it must be held there, which is the job of the cement. The cement seals the annular space between the casing and the walls of hole. Casing is run in the hole in much the same manner as drill pipe, but it is a great deal larger in diameter.

Casing, like drill pipe, varies in lengths. The number and size of the casing strings used vary with the area, depth and the choice of the operation. Note that three separate casing sizes are indicated: the surface pipe, the intermediate string and the oil string.

Each casing string is cemented in place by a slurry pumped down the-pipe and up the annulus between the casing and the open hole. The cement is then allowed to set for several hours before drilling or other operations are recommended.

Cementing units, cement mixers, tracks with cement and high pressure line, and cement head are used for pumping and squeezing the cement. The cementing unit is a heavy lead capacity truck with two pumps mounted on it: a high pressure pump for pumping cement and fluid and a second pump for supplying water to the cement mixer.

A cement mixing unit is a truck with a metal container for dry cement mounted on it. Behind this container there is a special tank in which cement is mixed with water, that is the cement slurry is being obtained. The water supply is measured precisely, the result of which is that a slurry of any desirable specific gravity may be obtained .

After the cement sets electirometric work for determination of the quality of cement behind the siring of casing is carried out.

The string of casing is tested for hermetization after which gusher fitting is mounted on the well head and a series of perforations is made opposite the oil. or gas productive stratum. Casing strings are designed to withstand three principal types of loading: tensile load, collapse pressure and burst pressure.

Before casing is run in the hole, certain attachments may be ad­ded to it. They are: the guide plug (shoe), the thick wall cementing collar, the shoe, the cementing plug, the reverse valve, the stop-ring. When all the casing is set, then cementing operations begin, The casing and cementing crew connects a series of hoses to the top of the well, and pumps cement down the hole and up mound the annular space between the casing and the wall of the hole.

A drillable plug is inserted immediately follo wing the last of the slurry and drilling fluid is pumped behind this plug to the bottom of the hole.

This procedure forces the cement into the space between the casing and well wall. The cement is allowed to set and is tested: the plug is drilled through, and drilling operations are again underway.

Threaded joint and welded joint connections are applied to casing. Welded joint casing is usually used in gas wells.

4. Give English equivalents of the following:

проміжна колона труб, експлуатаційна колона груб, цементувальна головка, цементувальний аїрегат, питома вага, фонтанна арматура, розривне зусилля, зминання, тиск розриву, заливочна пробка, нарізне з'єднання, зварне з'єднання.

5. Make a written translation of the following:

Cementing units, cement mixers, tracks with cement and high pressure line, and cement head are used for pumping and squeezing the cement. The cementing unit is a heavy load capacity truck with two pumps mounted on it: a high pressure pump for pumping cement and fluid and a second pump for supplying water to the cement mixer.

A cement mixing unit is a truck with a metal container for dry cement mounted on it. Behind this container there is a special tank in which cement is mixed with water, that is the cement slurry is being obtained. The water supply is measured precisely, the result of which is that a slurry of any desirable specific gravity may be obtained.

6. Describe the processes of casing and cementing using Text 2.

7. Learn the meaning of the following words, word-combinations and word groups:

scratcher, centralizer, spring, filter cake, spud, blowout, preventer, ram, packing, casing hanger, flow line, connection, pressure gauge, flow bean, choke, bypass line, pay zone, perforating gun, jet-type perforator, shaped charge, jet, fire, bullet.

8. Read Text 3:

Text 3

Centralizers and scratchers. Centralizers and scratchers serve as invaluable aids in cementing a well. Centralizers are heavy spring steel guides which fit around the outside of the casing. They serve to keep it centered in the hole, thus permitting a good cementing job If they were not used, then the casing might be lying against one side of the hole and would not be properly centered. As the centralizers aid in centering the casing, so scratchers remove the mud filter cake that has been deposited on the wall of the well bore. If the filter cake were not removed, then it would act as a barrier between the cement and the formation.

Once the scratchers are installed on the casing, they are operated by one of two methods. The casing may be spudded to allow the scratchers to remove the wall cake, or it may be rotated, which ac­complishes the same result when special scratchers are used. The wall cake may also be removed by either hydraulic or chemical means.

Blowout preventers. It is not always possible to predict the exact magnitude of pressures which will be encountered in the drilling of a well. Consequently, it is not uncommon to encounter pressures greater than those imposed by the drilling fluid, with the result that formation fluids flow into the bore hole and eventually to the surface. This effect is called a blowout and is one of the most feared and expensive accidents which can occur in well drilling.

The main function of blowout preventers is to furnish a means of closing off the annular space between the drill pipe and casing. Blowout preventers may be universal and ram type with mechanical, electrical and hydraulic drive. Steel rams with rubber packing are the basic elements of blowout preventer.

Christmas tree. When all these operations have been finished: casing set and cemented, then the Christmas Tree is installed. The Christmas Tree is the equipment above ground that controls the flow of oil or gas from the well. Included in the assembly are casing hangers, flow line connections, pressure gauges, valves, and flow- beans or chokes. Bypass line are installed so that the flow of oil or gas may be switched for line repairs and the choke may be changed without interruption of production.

Perforating. When casing and cement have been set in the pay zone, there must be some opening made to allow the oil and gas to pass into the well bore. On some formations, the perforating gun is used, while on others the jet-type perforator is more adaptable. It. fires shaped charges which accomplish penetration by jets of high- temperature, high-velocity gases. The perforating gun fires bullets through the casing and cement to open passages for flow of oil and gas. It is fired electrically from the surface through-cable. 12 Make a written translation of the following:

It is not always possible to predict the exact magnitude of pressures which will be encountered in the drilling of a well. Consequently, it is not uncommon to encounter pressures greater than those imposed by the drilling fluid, with the result that formation fluids flow into the bore hole and eventually to the surface. This effect is called a blowout and is one of the most feared and expensive accidents which can occur in well drilling.

13. Put 5 questions to Text 3.

14. Find, read and translate the sentences in Text 3 in which we learn about Christmas Tree.

15. Learn the meaning of the following words, word-combinations and word groups:

fishing, break down, "etrieve, twist, jamming, cone, wedge, wrench, hammer, loose, taper tap, thread, diengage, overshot, intact, grapple, spear, grasp, junk, barrel, hollow, catcher, deflection, angle, whipstock, rearmer, knuckle joint., concave, groove, inclination, balltype.

13. Read Text 4:

Text 4

The term fishing, applies to all operations concerned with retrie­ving of equipment or other objects from hole. One of the most com­mon causes of fishing is the failure of the drill string. The weight and torque applied to it can cause it to twist in two while in the hole.

Another common cause of fishing is the jamming or loss of a cone on the rotary bit. Occasionally, a bit may fail, or a cone may drop off the bit and be wedged in the bottom of the hole.

A wrench, hammer, or other tool may be accidentally dropped in the hole. Before any more drilling can be done, these tools must be recovered, leaving the hole clean and ready for the bit.

There is always the possibility that the pipe will come stuck in the hole. When it cannot be worked loose, it is necessary to remove the pipe above the tight spot and fish the remainder from the hole with the help of special tool.

Fishing tools. Fishing tools are quite numerous. Among the first fishing fools were rotary taper taps and die collars. The tap is run into the fish and rotated until sufficient threads are cut for a firm hold. Their principal disadvantage was the fact that they could not be disengaged, but remained with the fish.

Overshot. One of the most common tools, used for fishing today is the overshot When a twist-off occurs, the in-tact portion of the drill string is taken from the hole and the overshot is lowered in.

This device fits over the fish in the hole; the grapple engages the pipe and enables it to be removed from the hole. Hole-pipe clearance must be sufficient to accomodate the wall thickness of the overshot. Modern overshots have a releasing mechanism to be used if the fish cannot be pulled.

Spears. These devices pass inside the fish, grasping its inner wall with expending slips, which can be set or released by rotating the •)ipe. Spears are generally used when the hole clearance will not olerate an overshot. Their principal advantage is their releasing (lechanism. Small items of junk such as bit teeth, cones, or other small pieces of steel may be retrieved with a permanent magnet run on the drill pipe.

Junk basket. The junk basket is prob&bly the next most commonly used tool. When a cone is last of a bit or when tools are accidentally dropped in the hole, a junk basket can be used to retrieve them.

I

The junk basket is built with a long hollow inner barrel. The bottom of the basket is built much the same as a core bit, and serves the same purpose. The junk basket is lowered to the bottom of the hole and is set over the article to be recovered. The drill string is rotated, causing the bit to cut a small core in the formation. A catcher brings both the core and the article above it to the surfacc, enabling drilling to proceed. Fishing magnet can be used for the same purpose.

Directional drilling. Control of the course of a well during the process of drilling is of vital importance. For diverse reasons it is frequently neccssary or desirable to finish a well at some point away from a straight line drawn vertically below the rotary table. For this purpose a technique called "directional drilling" has been developed. The system has been used in starting wells under a derrick location on land and drilling away from a straight hole into a producing sand beneath the sea or to reach points situated some distance away, horizontally, from the starting point. In this event, the well must be lirectionally controlled during the progress of drilling from the iurface location to the point selected for penetration of the producing formation. This will involve use of devices to achieve deflection of the well in the desired direction and at a suitable angle from the vertical to reach the point selected for penetrat ion of the reservoir rock. The art of directional drilling has so far progressed that a well may be drilled into a given stratigraphic horizon within a few feet of the point selected and the entire course of the well may be kept within a predetermined hypothetical cylinder of intervening formation not more than 25 ft in diameter.

Directional drilling method has been likewise frequently helpful in straightening crooked holes and in drilling around tools that fishing jobs have been unable to clear out of the hole.

Directional drilling may be used profitably in exploration work in a new field.

The tools that have been developed for the purpose of changing the direction of a well are: whipstocks, knucle joints and special drilling bits and reamers.

Whipstocks. A whipstock is along, slender steel wedge with a concave groove on its inclined face, supported in the well in such a position that the drilling tool is deflected from the previous course of the well towards the direction in which the inclined grooved surface faces.

Whipstocks are of two general types, removable and fixed. The removable one is withdrawn from the hole with the drill pipe, while the fixed type stays in the hole as a permanent installation.

Knuckle joint. A knuckle joint is a special type of drill support designed to deflect the well without using a whipstock. It incorporates a balltype universal joint, connected to and rotated by the drill pipe, which allows the bit to drill at an angle to the axis of the drill column. The knuckle joint is oriented on bottom so that the tool points in the direction in which it is desired to drill.

13. Give English equivalents of the following:

піднімати інструмент із свердловини, гаєчний ключ, звужене місце, мітчик, ловильний дзвін, поломка бурильних труб, пристосування для розчеплення, клини для захоплення труб, корзина для сміття, колонкове долото, труботримач, з різних причин, направлене буріння, продуктивний пласт, викривлена свердловина, дефлектор, жолобчатий, шарнірного типу.

13. Describe the main fishing tools using Text 4.

14. Find, read and translate the sentences in Text 4 in which we learn about directional drilling.

JO Read Text 5:

Text 5 Offshore Drilling Equipment

The primary difference between land and water drilling installa­tions occurs in the supporting structure for the rig and its auxiliary equipment. Other rig components are similar to those used in land drilling with added emphasis on operational ease.

Drilling for oil under water has introduced many new problems to the industry. To set up a rig in a shallow lake or a marsh, the sub­mersible barge serves as a foundation. The rig is assembled on it, and the entire unit is towed by tug to the location. When it is in place, valves are opened, flooding the barge and causing it to sink in position. Once drilling is completed, the water is pumped from the barge, allowing to be moved to the next location.

The mobile drilling platform with supporting legs is widely used in offshore drilling today. When on location, the legs are lowered to the ocean floor and the floating platform is elevated above the water by means of hydraulic jacks.

A second type of mobile drilling platform consists of a deck sec­tion containing the rig elevated above a floating section by means of supporting legs. When the floating section is flooded it will sink to the ocean floor and provide support to the main platform.

After drilling operations are completed, the unit is then refloated and moved to the next drilling site.

Some of these platforms provide sufficient area for living quar­ters, necessary storage space, and the complete drilling unit. Other platforms of smaller dimension necessitate the use of a floating barge or tender which contains the major portion of the drilling equipment, storage space, and drilling crew accomodations. The mud system is contained on the tender. Mud is pumped from the tender through the circulating cycle and then back to the tender. On the newer drilling tenders, the power source - diesel engine driving electric generators - is located on the tender and power is delivered to the electric motors on the platform by cable.

When drilling on a man-made structure is completed, the drilling equipment is removed, and the platform is used for production equipment to bring the oil to the surface and to control the flow.

When wells were first drilled- off-shore, boats were the sole means of transportation between the land and the rig. This could mean a daily trip for the crews and other personnel sometimes lasting six or seven hours. To this discomfort was added the disadvantage of seasickness when rough weather w as encountered. Helicopters are pro­ving to have a permanent place in off-shore drilling, for they furnish a convenient and rapid means of transportation between the shore and the installation at sea.

21. Give English equivalents of t he following:

морське буріння, болото, баржа, що сама занурюється, буксир, тягнути на буксирі, наповнювати водою, стійка, плавучий, домкрат, баркас., забезпечувати.

21. Make a written translation of the following:

Some of these platforms provide sufficient area for living quar­ters. necessary storage space, and the complete drilling unit. Other platforms of smaller dimension necessitate the use of a floating barge or tender which contains the major portion of the drilling equipment, storage space, and drilling crew accomodations. The mud system is contained on the tender. Mud is pumped from the tender through the circulating cycle and then back to the tender. On the newer drilling tenders, the power source - diesel engine driving electric generators - is located on the tender and power is delivered to the electric motors on the platform by cable.

21. Make a plan to Text 5 and retell it.

CONTROL TASKS

1 Answer the questions:

1. What are some general methods of drilling oil wells?

2. How are the cuttings lifted from hole in rotary drilling?

3. What are the benefits of the turbine drilling method?

4. What methods of drilling does vibrational drilling combine?

5. In what way does core drilling diffeir from rotary drilling?

6. What is derrick and what is its function?

7. What are tool joints ued for?

8. What is the Christmas free and what does it control?

9. What does the term "fishing"' apply to?

10. What is directional drilling?

ZGive English equivalents of the following:

роторне буріння

експлуатаційна колона труб

обсадні труби

пошукова свердловина

колонкове буріння бурова вишка

ловильні роботи у свердловині

продуктивна свердловина ударне буріння

шариковии підшипник

бурова помпа

буровий нілані"

головний двигун лебідка

поломка бурильних труб піднімання інструменту

вертлюг

робоча груба

бурова колона

гаєчний ключ

пружина

рідкии цемент

манометр

труботримач

морське буріння

кулевий перфоратор направлені; буріння

забійний двигун

3 Match the terms with their definitions:
1 Christmas Tree	a) a method of drilling that combines rotary and percussion drilling
2 percussion drilling	b) the connection between the slush pumps and the drill string
3 rotary drilling	c) the necessary valves and fittings for closirig-in or controlling the production
4 derrick	d) a secial type of drill support designed to deflect the well without using a whipstock
5 drill string	e) devices that pass inside the fish, grasping its inner wall with expending slips which can be set or released by rotating the pipe
6 knuckle joint	f) the control centre from which the driller operates the rig
7 spears	g) the most primitive and the most efficient way of drilling which is implemented by a wedge bit
8 vibrational drilling	h) an extremely expensive rig component that must be replaced periodically
9 drawworks	i) a four-sided pyramidal structure of square cross section
10 swivel	j) the way of drilling when the hole is drilled by a rotating bit to which a force is applied

4. Tell whether each of the following statements is true or false according to the text. Correct the false statements to make them true:

   1. The number of strings of casing and their diameter is controlled by local conditions and by the depth to which the well is to be drilled.

   2. in turbine drilling the bit is rotated by a turbodrill attached to the upper end of the drill string.

   3. There are two types of vibrators: mechanical with a drive from an electric motor or electromagnetic device and an air or pneumatic vibrator.

   4. The function of the derrick is to provide the horizontal clearence necessary to the raising and lowering of the drill string into and out of the hole during the drilling operations.

   5. The function of the mud or slush pumps is to circulate the drilling fluid at the desired pressure and volume.

5. Make a written translation of the following:

Directional drilling. Control of the course of a well during the process of drilling is of vital importance. For diverse easons it is frequently necessary or desirable to finish a well at some point away from a straight line drawn vertically below the rotary table. For this purpose a technique called "directional drilling" has been developed. The system has been used in starting wells under a derrick location on land and drilling away from a straight hole into a producing sand beneath the sea or to reach points situated some distance away, horizontally, from the starting point. In this event, the well must be directionally controlled during the progress of drilling from the surface location to the point selected for penetration of the producing formation. This will involve use of devices to achieve deflection of the well in the desired direction and at a suitable angle from the vertical to reach the point selected for penetration of the reservoir rock. The art of directional drilling has so far progressed that a well may be drilled into a given stratigraphic horizon within a few feet of the point selected and the entire course of the well may be kept within a predetermined hypothetical cylinder of intervening formation not more than 25 ft in diameter.

P ART 5

COMPLICATIONS IN THE COURSE OF DRILLING

Unit 19 Circulation Loss

1. Learn the meaning of the following words, word-combinations and word groups:

blowout, lost circulation, tight hole, drill collar, gas cutting, swabbing, quebracho, kelly valve, permeable, fractured, cavernous, fibrous, flaky, reinforcing plug., handling, regain, waiting technique, blind drilling, floating, mud cap.

2. Read and translat e Text 1:

Text 1 Difficulties Encountered in Drilling

Blowout is a dangerous and expensive accident in oil-well drilling operations. Blowouts may result from insufficient drilling- fluid density, caused perhaps by gas-cutting. Or, they may occur as a result of failure to keep the hole full of fluid, a situation created by withdrawing the drill column from the well or as a result of lost circulation.

A "tight" hole ;>r clay "balled up'" on the drill collar and bit may create a swabbing, O" suction effect on the format below as the drill column is withdrawn, thus developing an abnormal pressure differential that allows high-pressure gas to enter the well.

To avoid such situations in drilling through high-pressure gas- bearing formations, close attention should be given to the physical properties of the drilling fluid, maintaining high density by addition of heavy mineral, low viscosity by addition of quebracho or phosphates, and good wallbuilding properties by addition of bentonite.

Prompt countermeasures should be taken to deal with lost circulation. Additional fluid should be pumped into the well to compensate for displacement;, as the drill column is withdrawn, maintaining the well full of fluid at all times.

If possible, operations that create high differential pressures be­tween the formation and the well should be avoided.

In drilling into high-pressure formations, ths well should always be equipped with a blowout preventer and kelly valve which can be closed in the event that a blowout should occur. Thus, the well may be shut in until appropriate measures may be taken to control it. J Put questions to each part of Text 1 and retell it in English. 4 Read Text 2:

Text 2 Lost Circulation

Lost circulation is one of the oldest and most common problems of rotary drilling. It may occur to any depth anywhere, particularly in deep wells. Circulation loss is a common difficulty in drilling through unusually permeable, fractured, fissured, or cavernous formations.

Fluid loss to the formations becomes excessive and in extreme cases will fail to return to the surface so that drill cuttings are not removed from, the well. In general, lost circulation may be divided into two classes: first, losses to highly porous or cavernous forma­tions; and second losses created by poor drilling techniques.

It is important to locate the interval within which circulation loss isoccuring before undertaking remedial measures .

Circulation loss may often be remedied by addition of fibrous, flaky, or coarse granular materials and reinforcing plugs to the drilling luid, perhaps with additional benionite to increase viscosity, and wall-building properties. The true value of any material can be determined only from its performance in the field.

There are three fundamental approaches to the problem of hand­ling lost circulation: preventive methods, special drilling methods, and attempting to regain circulation after it has been lost.

The waiting technique has been found helpful in preventing and overcoming serious lost circulation. At the first indication of lost circulation, drilling and circulation are stopped. The bit is pulled up to a point of safety, and the hole is permitted to remain quiet for a period of 4 to 8 hours. After such waiting periods, drilling maybe resumed without further loss.

There are areas that have; cavernous and open-fissured zones that simply do not permit conventional rotary drilling. Blind drilling with

no returns at the surface, and cable tools have been used for these conditions. In blind drilling, water is pumped down to cool the bit and to carry the cuttings away but no returns are brought to the surface. Sometimes the cuttings are carried into the loss zone and have been known to cure the loss and get returns.

An important variation of this dry drilling is the use of a floating mud cap to balance the formation fluid pressure with the drilling and hydrostatic pressure. This is done by carefully pumping fluid into both the annulus and the drill pipe.

5. Pick out from Text 2 five sentences containing the verbs in Passive Voice and translate them.

6. Make a plan to Text 2 and retell it.

7. Learn the meaning of the following words, word-combinations and word groups:

showing, caving-in, crumble, stick, drilling string, rend, jointing, clearance, restoration, acceleration, flushing, round trip, balling, adjustment, viscidity, yield point, absorption, fissure, traverse, seal off, plugging material, annulus, plug up, cuttings, slurry, plugging mixture, bed, harden, overlap, packer.

5. Read Text 3:

Text 3

In the course of drilling there arise diverse complications: absorption (circulation loss) of drilling fluid or of cement slurry, oil-gas and water showings, caving-in and crumbling of rocks, stickings and tight pulls of the drilling string and others. In many cases it is easier to avert the occurrence of a trouble than to eliminate it. Quite frequently one complication developing in the well and not eliminated quickly enough becomes aggravated by other types and, at times, occasions the appearance of new troubles. Therefore, great attention should be given to prevention and quick elimination of developing complications. Circulation losses occur:

• when the rock has open fractures, caverns and other major channels, and the pressure exerted by the mud on the borehole walls exceeds the formation pressure in a given horizon;

• when pressure exerted by the mud on the borehole walls is high enough to open up closed microfractures existing in a given rock, or to rend it and thus cause the development of new fractures.

Mud absorption increases the total consumption of the drilling fluid required for sinking a well; the rate of its deepening is slowed down, for the drilling crew is forced to spend a part of their working hours in preparing and treating an additional volume of the mud fluid, which increases the cost of drilling.

In the event of circulation loss the level of the mud fluid settles several scores and even hundreds of metres below the mouth of the well. Because of this the backpressure on the borehole walls declines and this can give rise to an inflow of brine water and gas coming from a horizon with a higher coefficient of abnormality. It is important to forestall the development of circulation loss and, if it occurs, to control it as quickly as possible.

Natural jointing, cavernosity, firmness of rocks and formation pressures are factors common to nature, they are outside the power of man and cannot possibly be controlled in the course of drilling. To preclude and eliminate absorption in the first of the above named cases it is necessary that the resistance of natural fractures and channels to spreading of mud fluid over and along them be in excess of the difference between the pressure exerted by this mud on the walls of the fractures and the formation pressure in a given horizon.

An analysis shows that circulation loss may be attributed to the following causes:

• an increased density of the mud fluid surpassing the limit;

• excessively high hydrodynamic pressure arising during backwash of the well along the section from the absorbing horizon to the mouth of the well and occasioned by a high flow velocity, too small a clearance between the pipe string and the borehole wall, or an improper choice of rheological properties for the drilling fluid;

• high hydrodynamic pressure at the time of re-established circulation, caused by an elevated gel strength of the mud;

• high hydrodynamic pressure arising during an attempt at a very quick restoration of circulation and conditioned by the inertia of the drilling fluid;

• high hydrodynamic pressure developing when running in a pipe string at a great speed, or with excessive acceleration;

• high hydrody lamic pressure arising during flushing of the well, or in the course of round trips, if the pipe string or the bit becomes subject to balling.

With known pressure gradients of rock fracturing and abnormality coefficients (factors), it is possible in many cases to forestall the above troubles through proper control and adjustment of the drilling fluid properties (by reducing density, gel strength and the yield point, plastic viscidity), by restricting the speed and acceleration in round trips and also by an adequate choice of the casing program.

With absorption ensuing when drilling in a fissured or cavernous rock one must, if necessary, minimize the circulation loss through adjusting mud properties (by reducing density, additing plugging materials, raising viscosity), quickly traverse the whole of the difficult zone and then, if needed, seal it off with some or other plugging material, or as the last resort, by means of the casing string.

If several absorption horizons may be opened up in the course of drilling a well, the question of sealing off each individual horizon before drilling in the next one, or of sealing operations to be effected following the opening of all or several horizons is decided upon by taking account of the circulation loss intensity and its influence on the technical arid economic efficiency of boring operations (drilling rate, the cost of well).

When a horizon with a high absorption intensity is drilled in, the outflow of mud to the ground sur face stops altogether, its level in the well goes down and settles at a depth of tens and even hundreds of metres from the well mouth. In this case the intensity of the circulation loss can be determined by means of special investigations only. Circulation losses of such a great intensity are commonly referred to as complete, or catastrophic.

The following are the measures used for eliminating circulation losses:

• the density of the drilling fluid is reduced, through aeration, for instance;

• the flow velocity of the mud fluid in the annulus is brought down, especially if the clearance between the borehole walls and the pipe string is insignificant;

• a certain volume of mud fluid with high gel strength and rapid structurization is squeezed into the absorption horizon and the well is left alone for a few hours;

• a small amount of fibrous or granulated materials is added to the mud fluid to plug up joints and fissures less than 1-2 mm wide and channels with an equivalent diameter of 4-5 mm;

• boring is done without allowing the mud fluid to escape to the day surface, and it is presumed that the drilling cuttings by entering the channels and fissures of the absorption horizon gradually plug them up;

• a certain volume of quick-setting cement slurry or of some other low-density plugging mixture, often with an addition of fibrous or granulated materials, is forced into the absorption formation;

• coarse-grained inert materials (sand, gravel, etc.) are washed into large channels, cracks and caverns to plug them up and to achieve a significant diminution of the absorption intensity, these being then cemented with a quick-setting plugging mixture;

• high-molecular compounds capable of becoming polymerized upon contact with formation water, hardening and tightly plugging up the absorption channels, are squeezed into the bed;

• absorption zones are overlapped with case pipes (as a last resort).

The method of the circulation loss elimination or a combination of such methods is chosen depending on the specific absorption intensity and with due regard for a possible technical and economic effect they may yield. If the well opens up several highly intensive absorption zones, the best result is, as a rule, achieved when each zone is sealed off individually, being preliminarily isolated from other pervious horizons by means of a packer.

9. Fiind in Text 3 English equivalents for the following:

запобігати, усувати, ліквідовувати, посилювати, перевищувати, протитиск, передбачати, переважати, зворотний потік води, відновлювати, операція опускання-піднімання, утворення сальників, градієнти тиску розриву порід, герметично заробляти, тампонуючий матеріал, тампонуюча суміш, у крайньому випадку, за допомогою, швидкість буріння, вартість свердловини, пластова вода, щільно закупорювати, канал поглинання.

9. Find in Text 3 Infinitive constructions and translate them into Ukrainian.

10. Find in Text 3 conditional sentences and translate them into Ukrainian.

11. Make a written translation of the following:

The method of the circulation loss elimination or a combination of such methods is chosen depending on the specific absorption intensity and with due regard for a possible technical and economic effect they may yield. If the well opens up several highly intensive absorption zones, the best result is, as a rule, achieved when each zone is sealed off individually, being preliminarily isolated from other pervious horizons by means of a packer.

9. Translate the following sentences into English using the words and expressions from Text 3.

   1. При поглинанні у багато разів збільшуються загальні витрати промивальної рідини.

   2. Іноді при зниженні рівня рідини оголюються стінки свердловини, складені нестійкими породами.

   3. Природна тріщинуватість, кавернозність, міцність гірських порід і пластовий тиск: - це природні чинники, незалежні від волі людини, тому управляти ними в процесі буруння неможливо.

   4. Щоб запобігти поглинанню промивальної рідини, дуже важливо знати величини градієнтів тиску розриву і коефіцієнти аномальності продуктивних та всіх інших горизонтів, розкритих свердловиною.

   5. Поглинання великої інтенсивності звичайно називають повним, або катастрофічним.

10. Supply a heading for Text 3.

11. Imagine that you are asked to make a report on measures used for eliminating circulation losses. Write the main points of your report and illustrate each point with the material from Text 3.

Unit 20

Gas-, Oil-, and Waiter-Showings

1. Learn the meaning of the following words, word-combinations and word groups:

hoisting, single-cone roller bit, diamond-set bit, balled up bit, tool joint, pressure differential, permeability, bulk, menace, influx, overflow, breakdown, blowout, reliability, sediment, foliation, rupture, sinking of the well, check valve, stand idle, fluid jet, union, hook up, batch, stand pipe.

2. Read and translate Text 1:

Text 1

The formation fluids and gases can enter the well, first and foremost, in the event when formation pressure even in one of the horizons is higher than the pressure exerted on it by the mud fluid. The inflow of fluids and gases can take place when a bed displaying an elevated abnormality factor is being drilled in, with poor control over the density and degassing of the mud fluid, with the mud level in the well going down as a result of the circulation loss, or when hoisting a pipe string without addition of the mud, with a rapid hoisting of a pipe string (especially with a diamond-set or a single-cone roller bit, with a balled up bit or tool joints, .with a packer, etc.).

The inflow intensity depends upon the pressure differential, the permeability of the bed area adjoining the well bore, the properties of formation fluids and gases, as well as on other factors, and quite frequently the inflow is very significant.

A certain amount of formation fluids and gases gain access into the drilling fluid together with drilling breaks. Their bulk is roughly proportional to the drill speed iri rock. The formation gas can also force its way into the well owing to diffusion via permeable walls of the borehole. As a rule, the inflow intensity of the formation fluids and gases is not high and does not present any menace, provided there are no lengthy intervals in the mud circulation and the mud undergoes proper degassing on the surface. In case of protracted intermissions in circulation a certain amount of gas can enter the mud fluid from the top portion of the gas-bearing sand.

The influx of non-gassy or little gassy formation fluids (commonly brine water) becomes ostensible by the overflow through the mouth on discontinued flushing, and, at times, even in the course of it, as well as by an increased volume of mud in the receiving tanks of the circulating pumps.

The gas-oil-water showings not only stand in the way of proper drilling, but are causative of breakdowns and accidents. In the case of intensive gas-oil showings, instances of demolished wellhead and drilling equipment, of explosions and fires are of not infrequent occurrence.

To prevent the influx of formation fluids and gases into the well, as well as of blowouts and uncontrolled flow it is necessary:

• to tightly seal the wellhead with preventors, keep an eye on their good working order and proper performance., to check on the reliability of their control system and to correct the disclosed defects in good time;

• to exercise control over the quality of the drilling mud leaving the well. Starting from the moment of nearing a horizon displaying a significantly elevated abnormality factor, one must continually control the density of the mud leaving the well and its gas content;

• to use mud fluids with low water loss (not more than 2-3 cm³ in 30 min), as low gel strength as possible, zero daily sediment and an insignificant yield point, when opening up horizons with a materially elevated abnormality factor (especially gas-bearing ones);

• to increase the density of the mud in the well to a level high enough for maintaining a slight excess pressure in the well over the formation pressure, but invariably below that at which is possible foliation (or rupture) of rocks and absorption of the mud, prior to opening up horizons with an elevated abnormality factor;

• to degas the mud fluid leaving the well; in the event of a considerable increase in the gas content it is advisable to suspend the sinking of the well and, without stopping to flush it, replace the gassy mud with a fresh one with a higher density;

• to keep at the drill rig a spare amount of mud fluid of the quality matching that required for drilling in horizons with an increased abnormality factor, this amount comprising not less than two-three-fold volume of the well;

• to pour into the well additional amounts of the drilling fluid, when pulling up a pipe string, at a rate sufficient to always keep its level near the wellhead;

• to set up a check valve in the bottom part of the drilling string;

• not to allow the well to stand idle for long periods of time without flushing it; in the course of round trips intermediate flushings lasting for 1-1.5 cycles every 500-1000 m are necessary.

A best means for removing gas from the drilling fluid are vacuum degassers. It is also expedient to utilize them for removing air from the mud fluid when this is entrained into the latter, in some types of chemical treatment and also in boring attended by flushing with aerated muds.

When adding mud into the well at the time of the pipe string hoisting it is advisable to make use of automatic units.

If it becomes impossible to preclude the inflow of formation fluids and gas and a blowout occurs, with the drilling string inside the well, one must close the preventer without delay, direct the fluid jet escaping from the well via a side branch pipe of the wellhead hookup equipped with a union and pump in, through the drill pipes, a non-gassy drilling fluid of a higher density so as to raise the pressure on the horizon above the formation pressure level and thus stop the inflow. In case of a blowout with no drilling string in the well an attempt is to be made at running in quickly at least a few stands of drill pipes, then close the preventer and start forcing in a weighted mud fluid. If it is impossible to lower the pipes, the preventer is then to be closed and a batch of mud squeezed into the well through the side branch pipe of the hookup.

3. Find in Text 1 conditional sentences and translate them into Ukrainian.

4. Give English equivalents of the f ollowing:

сальник на долоті, перепад тиску, загроза, аварія, розшарування, поглиблення свердловини, проміжне промивання, зв'язка ланцюгів, промивальна рідина, що обважнює, труба-стояк.

3. Make a w ritten translation of the following:

A certain amount of formation fluids and gases gain access into the drilling fluid together with drilling breaks. Their bulk is roughly proportional to the drill speed in rock. The formation gas can also force its way into the well owing to diffusion via permeable walls of the borehole. As a rule, the inflow intensity of the formation fluids and gases is not high and does not present any menace, provided there are no lengthy intervals in the mud circulation and the mud undergoes proper degassing on the surface. In case of protracted intermissions in circulation a certain amount of gas can enter the mud fluid from the top portion of the gas-bearing sand.

3. Supply a heading for Text 1.

4. Find,, read a»id translate the sentences in Text 1 in which we learn what to do if it is impossible to preclude the inflow of formation fluids and gas and & blowout occurs.

5. Working in pairs test each other's ability to describe measures for preventing the influx of formation fluids and gases into the well.

Unit 21

Crumbling and Caving-in of Rocks, Narrowing of the

Well Bore

1. Learn the meaning of the following word?;, word-combinations and word groups:

caving, debris, viscosity, velocity, funnel, reaming, swabbing, caved interval, redrilling, lapse of time, spud, suspend, logy, remedy, scrape off, sheath, keyseated portion, keyseating, keyseated interval, fishing.

2. Read and translate Text 1:

Text 1 Caving and Freezing of the E»rill Column

Caving zones and sections in which the formations tend to sque­eze into the well are often the source of serious trouble. Sometimes caving can be prevented by the use of the correct type of mud fluid, but once a bad cave has occurred it is not easy to correct the trouble, or to overcome the difficulties arising through in. The drilling debris is carried from the well by the returning mud circulation, the carrying capacity being a function of the viscosity of the: fluid and the velocity of the flow-stream.

If excessive caving occurs, the area of the annul us outside the drill pipe is increased, and therefore the velosity of the circulating fluid over this zone is decreased. As soon as the speed is reduced below a critical point, the debris can no longer be carried upwards in the flow-stream, but settles around the bottom of the "funnel" caused by the cave.

In extremely bad cases the cave must be filled up with cement and a new hole drilled through it before drilling can proceed.

Sometimes it is necessary to keep reaming out the well and to insert casing to shut off the zone as soon as possible.

Caving of the walls with the dri 11 pipe on bottom will present a more serious problem. In this case, the drill column may be so thoroughly buried that it cannot be manipulated freely and is apt to become permanently frozen in the hole. This results usually from improper mudding of the walls or the swabbing effect of the drill column in a tight hole.

If freezing (or cave-in of the rock) has not stopped circulation altogether it might be possible to wash away the caved-in rock by pumping in fluid under high pressure.

The drill column may then be raised cautiously with slow rota­tion until the bit is above the caved interval. If the caved interval is of considerable thickness, it may be impossible to free the drill column and it must then be parted above the caved interval and the lower part sidetracked in subsequent redrilling. The drill column may be also released through shooting inside it. Hydrogen chloride solution, water and oil are employed to release frozen tools. The fluid is pumped into the freeze zone and a little above. When after a lapse of time the tool has been spudded up and down it may be raised to the surface Freezing of the drill column in the well may bring serious difficulties and should be avoided by all possible means.

When formations containing considerable heavy clay are being drilled, they may be penetrated more rapidly than the material can be hydrated or suspended in the drilling fluid and a mass of clay will accumulate on the drilling bit and about the drill collar. The drill column becomes "logy" and is difficult to manipulate in the well. In trying to lift it, the clay is perhaps further compacted and compressed until it becomes fast in the hole. The remedy for this condition is obviously a slower rate of penetration or greater volume rate of circulation of drilling fluid. In other cases, owing to use of poor quality of drilling fluid in a very permeable, low-pressure formation, thick clay cake may form on the walls of the well, restricting the annular space between the wall of the hole and the drill column.

In drawing out drill pipe from the well, the large-diameter drill collar and bit may scrape off some of this material so that it accumulates above the drill collar and freezes the column in the hole. To avoid this condition, a drilling fluid of better colloidal value should be used, forming a thinner wall sheath.

The most common cause of frozen drill pipe is drawing the drill collar up into a keyseated portion of the hole. Keyseating may result in a soft formation where drill pipe under tension is operated. To avoid this, the keyseated intervals should be reamed.

Another cause of frozen drill pipe is found in the settling of drill cuttings and heavy minerals suspended in drilling fluid when circulation is interrupted. To avoid this difficulty, a drilling fluid of proper thixotropic properties should be used that will gel and suspend the drill cuttings when circulation fails.

If the column cannot be freed by such methods, resort must be had to fishing procedures.

3. Find in Text 1 the sentences containing modal verbs and translate them into Ukrainian.

4. Make a written translation of the following:

When formations containing considerable heavy clay are being drilled, they may be penetrated more rapidly than the material can be hydrated or suspended in the drilling fluid and a mass of clay will accumulate on the drilling bit and about the drill collar. The drill column becomes "logy" and is difficult to manipulate in the well. In trying to lift it, the clay is perhaps further compacted and compressed until it becomes fast in the hole. The remedy for this condition is obviously a slower rate of penetration or greater volume rate of circulation of drilling fluid. In other cases, owing to use of poor quality of drilling fluid in a very permeable, low-pressure formation, thick clay cake may form on the walls of the well, restricting the annular space between the wall of the hole and the drill column.

5. Speak about causes of frozen drill pipe.

6. Write a summary of Text 1.

7. Learn the meaning of the following words, word-combinations and word groups:

efflux, traverse, confine, resilient, brittle, exposure, after-effect, residual, swell, cohesion, bulk up, jointy, crumble, filter cake, ascend, descent, mounting, backwash, avert, augment, fluctuation, fatigue, overlap.

8. Read Text 2:

Text 2

Drilling is sometimes attended by crumbling and caving-in of the rock and narrowing of the well bores, this manifesting itself in rising pressure in the mud pumps during flushing, in efflux to the day surface of a large quantity of sand and of fairly big rock fragments, and also in an appreciably greater effort needed to raise the pipe string.

One of the causes responsible for this trouble is a changed stress state in the rock traversed by drilling.

In a naturally occurring rock any of its elementary volume is subjected to confining pressure, with side pressure Ps acting on its walls in the horizontal plane. On drilling in the rock the side (lateral) pressure against the borehole walls decreases from Ps down to the pressure exerted by the mud fluid column. This results in a changed stress state in the area in and around the well bore.

If the stresses iri the walls and in the area around the well bore turn out to be greater than the strength of the resilient-brittle rock, this will begin disintegrating and crumbling into the well bore. In case of a plastic-brittle or a highly plastic rock, it will undergo plastic deformation and be squeezed into the well bore as soon as the stresses in the walls and around the well bore area surpass the yield limit. The after-effects of tectonic processes (crumbling of rocks, jointing, residual stresses) reduce the resistance of rocks to disintegration and thus act as a contributing factor to the emergence of crumbling, caving, and also to the narrowing of the well bores.

The diminished strength and, consequently, stability can be due to swelling of some, chiefly argillaceous, rocks following penetration therein of the mud filtrate and weakening of the cohesion forces between partic les of the rock skeleton. The bulking up rate depends upon the mineralogical composition of the rock and chemical composition of the filtrate.

In traversing jointy and crumpled rocks the well bore not infrequently gets narrowed owing to the mud wetted fragments of crumbling and drilled-out rocks sticking to the walls. Within intervals composed of permeable rocks the narrowing is caused by the formaition of a thick fi lter cake on the walls, especially in cases of long delayed flushing and utilization of a high filter-loss mud.

Because of crumbling and caving-in of the rocks the well bore gets enlarged locally (through formation of caverns); the transport of crumbled and drilled-out rock to the: ground surface becomes rather difficult, since the speed of the ascending current (up-bole velocity) and its lifting force diminish; drill pipe failures, particularly in rotary drilling, become more frequent, for in the cavernous zone the deflection and, consequently, the bending stress are on the increase. In view of the danger of the drill pipes breakdown the drilling weight has to be reduced and this brings on the diminishment of the drilling rate. The time and means spent in flushing the well prior to withdrawing the worn-out bit and in its working and flushing during descent of the new bit go up. Caving-in of the rock and narrowing of the well bore bring forth a mounting pressure in the pumps at the time of flushing due to an increase of hydraulic resistances at the sites of contraction and, occasionally, the backwash of the well becomes infeasible altogether.

In case of crumbling rocks and narrowing of the well bore the magnitude of the force necessary to move the drill pipe string may have to be increased quite impressively. Occasionally," the movement of the string is made fully impossible, for the arising stresses exceed the strength of the pipes' material.

In many instances a trouble: of this kind can be averted by augmenting the pressure acting against the borehole walls, i.e. practically through increasing the density of the mud fluid.

Therefore, to preclude the occurrence of this kind of troubles one should utilize drilling fluids that do not wet the rock, or, in an extreme case, muds with a very low water loss and of such composition that their filtrate would not produce any appreciable and rapidly diminishing strength and stability of the rocks. It is, for example, expedient to make use of lime-bituminous drilling fluids and also of some inverted emulsions arid suspensions with hydrogels as their base, as the dispersion medium practically does not filter out from them and fails to humidify the rock.

Moreover, an effective measure would be to lower the frequency and amplitude of the hydrodynamic pressure fluctuations. When the fatigue faiiure of the borehole walls appears to be the principal cause of troubles, it is sometimes advisable to change the casing program of the well and to overlap the danger zone with a casing column.

9 Translate the following sentences into English using the words and expressions from Text 2.

1) Після розкриття породи бічний тиск на стінки стовбура

свердловини зменшується.

2. Наслідки тектонічних процесів знижують опірність породи руйнуванню.

3. Величина і швидкість набухання породи залежать від мінералогічного складу породи і хімічного складу фільтрату.

4. Через небезпеку поломки бурильних груб доводиться зменшувати навантаження на долото, а це призводить до зменшення швидкості буріння.

5. Для запобігання ускладнень потрібно використовувати промивальні рідини тільки з малою водовіддачею і такого складу, щоб їхній фільтрат не викликав помітного зменшення міцності і стійкості порід.

   10. Supply a heading for Text 2.

   11. Divide Text 2 into logically complete parts and give each a subtitle.

   12. Working in pairs test each other's ability to describe the principal causes of crumbling and caving-in of rocks and narrowing of the well bore.

Unit 22

Sticking of Drilling and Casing Strings

1. Learn the meaning of the following words, word-combinations and word groups:

hoist, tight pull, tightening, sticking, elaborate, eliminate, exorbital, asunder, aggravate, breakdown, emergence, furrow, deflect, tool joint, balling, filter cake, ascending, abrupt, disrupt, scour, threaded pipe joint, adhesiveness, coarse-dispersion, curtail, sludge trap, lubricating additive, surfactant.

2. Read and translate Text 1:

Text 1

To hoist a pipe string out of the well, it becomes necessary on many occasions to apply a force that is appreciably (10-20 per cent and more) in excess of the weight of the string itself. Such phenomena are known by the name of tight pulls or tightenirigs.

Sometimes, to start off the string and bring it up to the ground surface an effort closely approaching the ultimate one that the strength of the pipes permits and even surpassing it has to be applied. Such tight pulls are called stickings. A sticking is a [rouble arising out of non-observance of the drilling technology or ^f an improper consideration of features specific for the geological structure of the deposit, lithological composition and properties of [he rocks, while elaborating the technology of drilling. At times, in in attempt at eliminating sticking exorbitant forces are applied and the string breaks asunder. In this case the sticking is aggravated by a breakdown. For this reason, stickings are often classified as breakdowns.

There exist several causes responsible for tight pulls and stickings of drilling and casing strings. They are:

1. High excessive pressure of the mud column with a substantial water loss.

2. Emergence of furrows (furrowing) in the borehole walls, made up of insecure rocks, especially along the section of a heavily deflected bore. Such furrows are usually cut in the borehole walls with tool joints during round trips.

3. Caving-in and crumbling of rocks.

4. Balling consisting of thick filter cake pieces torn off the borehole walls during movement of the pipe string.

5. Balling that consists of drilling breaks falling out of the ascending stream of the mud fluid due to an abrupt drop of its speed at the sites of a sizable enlargement of the well bore (in caverns, for example), or because of disrupted normal circulation (for instance, as a result of scoured threaded pipe joints).

6. Blevated adhesiveness of some filter cakes.

The principal measures aimed at preventing tight pulls and stickings include: the use of muds with a low (not more than 3-5 cm³ per 30 min) water loss and the minimum possible contcnt of a coarse-dispersion solid phase; low excess pressure in the well; prevention of furrowing, first of all, by considerably curtailing the number of round trips; a thorough clearing of the drilling fluid on the surface and the use of bottom hole sludge traps to remove large- sized drilling breaks from the stream near the hole face; observance of measures designed to preclude earlier reviewed complications; lowering adhesiveness of filter cakes by emulsification of the drilling fluid through the addition of lubricating additives, or some surfactants.

3. Pick out from Text 1 the sentences containing the verbs in the Passive Voice and translate (hem.

4. Translate the following sentences into English using the words and expressions from Text 1.

1. Для підйому колони труб зі свердловини необхідно докласти зусилля, що значно перевищує вагу самої колони.

2. Іноді при спробі усунути прихват докладають надмірних зусиль, і колона обривається.

3. Через сильне ущільнення кірки в зоні контакту, проникнення у цю зону фільтрату промивальної рідини утруднено.

4. Жолоби у стінках свердловини звичайно виробляються бурильними замками під час сгіуско-підйомних операцій.

5. Коли буріння припинено, бурильну колону слід систематично провертати ротором і не залишати її на довгий час у спокої.

   5. Supply a heading for Text 1.

   6. Make a plan to Text 1 and retell it,,

   7. Find, read and translate the sentences in Text 1 in which we learn about the causes responsible for tight pulls and stickings of drilling and casing strings.

Unit 23 Deep Well Drilling 1 Learn the meaning of the following words, word-combinations and word groups:

depletion, mantle, yield point, reamer, drill collar, shear stress, coat, melt, thermorésistant, drawworks, hp- horsepower, plunger-type pump, piston, bottom hole engine, jet engine, drill stem, round trip, reel up, directed blasting, reject.

2 Read and translate Text 1:

Text 1 Deep Well Drilling

Ever growing depletion of oil arid gas pools at small depths and growing demand for oil and gas create an urgent need for deep well drilling.

Deep well drilling has already become a very acute problem in many oil producing countries. Deep drilling covers a wide scope of problems to solve and which are not necessarily those connected with exploration for oil and gas alone, but also with the study of formations of the earth crust and underlying upper mantle and with the discovery of new materials including thermonuclear materials. Wells, deeper than 4500 m, are classified as deep wells. Such wells are drilled now in many countries. In 1938 the deepest well's depth was 4573 m. In 1949 the record was raised up to 62:55 m. Later 8000 m wells are drilled in different parts of the world, production being done at the depth as much as 7000 m. Some geologists claim that they see no reason why oil cannot be found at depths from 12000 to 24000 m. That is why the problem of superdeep drilling has been arisen.

Drilling of wells from 4500 to 8000 m has solved many prob­lems related to ultra deep drilling. Ultra deep drilling once mastered will help to discover oil and gas not only in new oil bearing areas but in old, well equipped and construct ed areas.

In view of drilling deeper than 10000 m there have been created new sorts of steel for drill pipes with yield point more than 95 kg/mm² and for casing more than 140 kg/mm .

In the process of drillin g of deep wells wi th the use of bits, roller type reamers and rubber stabilizers are fixed along the drill collars in order that deviation of the hole may be prevente d.

Weight applied on bit in this case is around 30 to 40 tons. The length of drill collars in deep rotary drilling reach 300 m; pump pres­sure at 6000 to 7000 m may vary from 125 to 250 atm.

A circulation cycle of mud is sometimes 9 to 10 hours. It should be noted that in deep well drilling under high temperatures the best results were attained in the case of muds with a low hard particles content: oil base muds, emulsion muds with CMC and graphite stable chromelygnosuJphate muds. Muds treated with surface active reagents with low percentage of nitrogen and 6 per cent of oil are also used.

3. Make a written translation of the following:

Deep well drilling has already become a very acute problem in many oil producing countries. Deep drilling covers a wide scope of problems to solve and which are not necessarily those connected with exploration for oil and gas alone, but also with the study of formations of the earth crust and underlying upper mantle and with the discovery of new materials including thermonuclear materials. Wells, deeper than 4500 m, are classified as deep wells. Such wells are drilled now in many countries. In 1938 the deepest well's depth was 4573 m. In 1949 the record was raised up to 6255 m. Later 8000 m wells are drilled in different parts of the world, production being done at the depth as much as 7000 m. Some geologists claim that they see no reason why oil cannot be found at depths from 12000 to 24000 m That is why the problem of superdeep drilling has been arisen.

3. Divide Text 1 into logically complete parts and give each a subtitle.

4. Put questions to each part of Text 1 and retell it in English.

5. Read and translate Text 2:

Text 2 Some Perspectives of Drilling Wells up to 15.000 m

Drilling up to 15000 m is considered feasible provided a number of problems are solved. The main problem is the heat barrier. Scien­tists presume that at approximately 15000 m the temperature of formations can average from 230 to 470°C. Pressure difference at such depths may vary from 1600 to 1900 atm.

High temperature may harmfuly affect physical and mechanical properties of mud, strength of the walls of a well, work of bit, ce­menting operations and geophysical experiments in a well.

Nowadays there are muds which remain stable under temperatures up to 260°C. However, according to some publications the use of water base muds in the conditions of higher temperatures will not be expedient. Control of water filtration under these conditions will also be difficult.

In order to reduce hydraulic losses in the annulus it is necessary to have minimum static shear stress. A thermally treated metal coat on a bit will presumedly melt arid under the influence of different loads the roller's teeth will deform which necessitates more effective cooling of the bit. It is natural that specific conditions of superdeep wells will necessitate applipation of special therrnoresistar t cementing materials and cementing units for pressures of 1000 atm and higher.

In superdeep drilling drawworks and pumps are most important elements of equipment. There are drawworks with a maximum drum load 45 tons. After partial improvement such drawworks can be incorporated into superdeep drilling.

Mud pumps must have around 1800 hp and ensure continuous circulation of the well at 350 atm. Plunger-type pumps ensuring better sealing of the piston in the cylinder are considered prospective for high depths.

Drilling up to 15000 m and deeper may require reconsideration of many problems in drilling, and probably will require new methods of drilling. Such methods of drilling as explosive drilling, flexodrilling and bottom hole engines are very interesting and prospective for superdeep drilling.

Explosive drilling may prove rather efficient in drilling highly hard formations. The gist of this method lies in destruction of for­mations by explosive charges, which are endlessly fed to the bottom. The use of atomic and jet engines can be foreseen for superdeep dril­ling.

Research institutions of many countries work at the problem of drilling without steel pipes with the help of a strong flexible drill- stem. Mud is pumped to the bottom through this stem. The bit may re­ceive rotation from an electrodrill or a turbodrill. The advantage of this method is in saving steel pipes. It also facilitates round trips and reduces their time. When the bit is being pulbd out the flex-stem is reeled up.

It should be noted also that in superdeep-drilling aside from first class powerful machinery and advanced technology of drilling there will arise necessity in skilled, highly qualified specialists in drilling.

7. Speak about the perspectives of deep well drilling.

8. Speak about the problems tha t deep drilling is used to solve.

9. Write a summary of Text 2.

CONTROL TASKS

1 Answer the questions:

1. What can cause the blowout?

2. What measures can be taken to avoid lost circulation?

3. Where and when do circulation losses occur?

4. What are the results of excessive caving?

5. What problems is deep drilling used to solve?

6. What are the most common causes of frozen drill pipe?

7. What does the inflow intensity depend on?

8. What should be done to prevent the inlfux of formation fluids and gases into the well?

9. What causes crumbling, caving-in of the rock and narrowing of the well bores?

10. What are the causes responsible for tight pulls and stickings of drilling and casing strings?