Rolling cutter type. Cutting tools of this type have been improved by using roller bearings on the spindles, on which the cutting elements rotate, and by building them as fully assembled units.
The cutting elements are hard-faced with tungsten carbide to assure long service and high footage. These bits are used in any formations as well as in very hard, abrasive formations.
Sometimes the tooth may be replaced by a peg of hard facing metal. Bits have a nozzle for discharging the drilling fluid. The nozzle sizes vary from 7 to 22 mm.
The unique design of this tool represents a new and revolutionary approach to drilling. This is no ordinary bit, but the result of years of experience, careful engineering and many months of actual drilling to iron out flaw's in design. The result is a bit which will offer the driller positive performance in formations and situations where other bits will fail.
The unusual angle-mounted cutter heads produce a rolling - cutting motion which is unexcelled for formation cutting, and the powerful flushing action through the center of the bit insures that the cutting head will always have a clean surface to work on, even in sticky formations.
Diamond bits. Diamond bits are normally used in hard formations and drill by scrapping action of the stones which protrude from a steel matrix. The spiral water ways on the bit serve to channel the drilling fluid around and pick up the cuttings. A bit such as this
may contain as much as 900 carats of industrial diamonds. The advantages of these bits are their high penetration capacity and drilling speed.
Core bits. In addition to these tools, which are designed to remove the entire cross-section of the hole with the assistance of the circulating fluid, may be added bits which cut circumferential channels or kerfs, leaving the center as a core to be removed in a properly constructed core barrel.
Core barrels are of three main types: single-tube, double-tube and the swivel type double tube tool. All are hollow tubes which accept the solid cylindrical core of rock cut by the annular-type bit. The drilling rig begins to make hole and as it does the bit, cuts into formation and causes a round portion of it to slide into the core barrel, which is located immediately above the bit. When a specified number of feet are cut, the barrel is brought to the surface and the core is unloaded.
3 Supply a heading for Text 1.
4 Give English equivalents of the following:
типи доліт, подрібнення породи, мати певні механічні та абразивні властивості, класифікувати, середня твердість, ріжуче- абразивний, тягучість породи, одна площина, поступово, колона обсадних т руб.
§ Make a written translation of the following:
As regards the principle underlying the breaking up of the rock all boring bits may be classified as follows:
1 Bits producing fragmentation and chipping (shearing), destined to drill non-abrasive and abrasive rocks of medium hardness, and also hard tough and very tough rocks.
2 Bits of the cutting-abrasive type of action intended for drilling in rocks of medium hardness and also in alternating layers of high-plastic little viscous rocks and those containing rocks of medium hardness and even hard ones.
6 Speak about general types of bits.
Unit 6 Rroller Bits
1 Learn the meaning of the following words, word-combinations and word groups:
roller, jet, weld, forge, wrist, rotate, bearing, cutter, thread. Hush, crush, type, use, hole, industry, sectional, fit out, rock-breaking member, outside, tool, top, allow, passage, provide.
2 Read and translate Text 1: Text 1
In the course of a more than 60-year long history marking the progress in the design of roller bits, use in the drilling practice have found bits with a single, two, three, four and six rollers. Today, however, most widely used are three-roller bits, some of whose type is shown in Fig. 6.1. From among roller bits of other types in use are presently the single-roller cutter ones.
For full hole drilling the industry puts out largely sectional three-roller jet bits (Fig. 6.2) made by welding together three forged sections 3, about whose wrists 5 rotate on bearings 6 and 7 roller cutters 4 fitted out with rock-breaking members. Once the sections are welded together outside (male) tool joint thread 1 is cut at the top end of the bit. To allow for the passage of the drilling fluid the bit is provided with flushing holes 2.
The bits are manufactured with single, two, three and four- cone roller cutters. When the bit rotates clockwise the cutters roll over the bottom hole counter-clockwise and accomplish a complicated rotary motion. As a result, the rock-breaking components of the roller cutters strike the rock and thus crush and chip it off. Therefore, as concerns the principle of rock disintegration, roller bits belong to the class of bits of crushing-chipping action.
Fig. 6.2 Sectional three-roller jet bit
Fig. 6.1 Three-roller bit |
There exist two patterns of roller cutters arrangement in the bit:
- with the roller cutters axes intersecting the bit axis at one point;
- with the roller cutters axes displaced towards the direction of the bit rotation, parallel to a position in which their axes intesect the bit axis. Such a displacement of the axes over length is termed positive.
The first design pattern was laid at the basis of the CT, T, T3, TK, TK3, K and OH types of the bit, while bits of the M, M3, MC, MC3, C and C3 types were constructed by following the second pattern.
3 Supply a heading for Text 1.
4 Find in Text 1 English equivalents for the following:
широко застосовувати, тркрізцеве долото, зварювати, поршневий палець, бур, різьба, буровий розчин, промивати струменем рідини, за годинниковою стрілкою, проти годинникової стрілки, виготовляти, здійснювати, належати до, пересікати, зміщення, дробляче-сколюючий.
5 Make a plan to Text 1 and retell it.
6 Describe a sectional three-roller jet bit using Figure 6.2.
Unit 7 Diamond - Set Bits
1 Learn the meaning of the following words., word-combinations and word groups:
diamond-set bit, secure, occur, shape, helical, radial, radially-stepped, periphery, surface, steel, attachment, sinter, alloy, bort, array, layer, diverse, fabrication, require, exposure, crack, penetration, lack, wear, adjust, gap, entrain, minute, discharge, annular, cool, overheat, reduction, sludge, catcher, trap, velocity, extraneous, tip, scavenge, wing.
2 Read Text 1:
Text 1 Diamond-Set Bits
Diamond-set bits secure an effective disintegration of nonabrasive and little abrasive rock of medium and great hardness, especially when these occur at a considerable depth.
They are made with variously shaped surface of the contact sectors fitted out with diamonds, with helical (lug. 7.1), radial (Fig. 7.2) and radially-stepped (Fig. 7.3) arrangement.
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Fig. 7.1 Bits with helical arrangement |
Fig. 7.3 Bits with radially-stepped arrangement |
The peripheral part in the bits of all types forms in the well wall a spherical surface with varying radius of the sphere that changes into a cylindrical surface.
The diamond-set bit consists of a shaped diamond-carrying head and a steel body with an attachment tool joint thread.
The head is usually made by pressing and sintering a mixture of specially selected powderlike hard alloys. Before pressing bort crystals are arrayed in a compression mould according to a preassigned pattern. After pressing, and sintering the diamond crystals are firmly fixed inside the external layer of the head.
By employing diverse materials for the fabrication of the matrix that comes from sintering the mix, the required exposure of diamonds during operation of the bit in the bottom hole is achieved.
When excessively exposed, the diamonds crack and break, while with an insignificant exposure the needed penetration of the diamonds into the rock will be lacking and the; drilling will prove ineffective.
In drilling hard and tough rocks, the wear of the matrix is more intensive and therefore it should be made more wear-resistant, for this will preclude the excessive exposure of the diamonds. In rocks of medium hardness the mater ial of the matrix is less susceptible to wear and, therefore, it should be made less wear-resistant.
By adjusting the extent of diamond exposure one can also ensure a continual gap between the matrix and the rock during operation of the bit in the bottom hole.
As a result of this, on leaving the flushing holes of the bit, the drilling fluid can pass all over and along the gap. entrain the minutest particles of the drilled out rock, discharge them into the radial or radial-helical channels running betv/een the contact sectors and then farther on into the annular space.
An intensive flushing of the bottom nole during drilling operation is needful also for cooling the diamond grains, for with an excessive overheating the diamonds can lose their hardness and become subject to graphitization.
In full-hole drilling of oil and gas wells, the cLiamond-set bits are made in sizes 2-3 mm less than the corresponding sizes of roller cutter bits. The reduction of their diameters is due to the need for creating conditions that would favour a change over to drilling with diamond-set bits after the roller ones, in which, as a rule, the diameter decreases as the bit gets worn out.
Apart from bits whose contact surfaces are fitted out with comparatively big diamonds arrayed in a single layer, in drilling rocks of medium hardness use is made of impregnated diamond-set bits whose shaped head made of thoroughly interm xed powderlike hard alloy materia! with crushed (fragmented) and fine-grained diamonds.
To raise the performance capacity of diamond-set bits, particular attention is to be paid to the preparation of the well bore and its bottom hole. Therefore, when drilling with the last three-five roller bits, a metal cutting and sludge catcher is set up above the turbodrill (electrodrill), or, with rotary drilling, at a distance of 10-12 m from the bit, to trap metallic fragments (pieces of hard alloy, broken roller teeth, etc.) and sludge.
A sharp reduction of the ascending stream velocity of the drilling fluid above the catcher ensures a satisfactory clearing of the bottom hole of extraneous objects which could have caused destruction of the diamonds and the matrix of the diamond-set bit.
3 Give English equivalents of the following:
алмазне долого, спіральний, радіальний, сталева основа, порошкоподібний, технічний алмаз, форма для лиття, піддавати дії, тріскати, проникати, запобігати, щілина, найдрібніші частки, надмірне перегрівання, екплуатаційна спроможність, зламаний зубець.
4 Find in Text 1 five sentences with non-finite forms of the verb, define their functions and translate the sentences into Ukrainian.
5 Write 8-10 questions covering the main idea of Text 1.
6 Explain the difference between diamond-set bits with helical, radial, and radially-stepped arrangement using Figures 7.1, 7.2, 7.3.
7 Learn the meaning of the following words, word-combinations and word groups:
application, drilling fluid, assure, scavenge, soft rock, medium-hard rock, hard rock, consist of, wing, weld, row, chamfer, rotation, reinforce, tooth, precede, edge, granular, plane, periphery, equal, provide, headpiece, elongated wing, grind, gauge.
8 Read Text 2:
Text 2 Hard Alloy Bits
Alongside bits faced with natural diamonds, bits tipped with extra-hard alloys have lately found application in sinking of deep wells.
In these bits the drilling fluid is brought to the bottom hole of the well along six flushing holes, thus assuring proper scavenging of
the bottom hole from the drilled out rock and cooling of the contact sectors.
In drilling alternating soft, medium-hard, and hard rocks, hard alloy-tipped bits shown in Fig. 7.4 are employed in some districts of the USA. These bits consist of a body and six short wing welded to it in two vertical rows. The contact surfaces of radially running wings are chamfered at 30° in the direction of bit rotation and reinforced with hard alloy teeth. The teeth are pressed into the holes in such a manner as to have every subsequent row lie at a higher level than the preceding one by one third of the tooth depth. The intervals between them and the front edges of all the wings are surfaced with a granular hard alloy.
The side planes of the wings are reinforced with hard alloy teeth and a layer of agranular hard alloy. The bit has four flushing holes, one of which directs the fluid to the centre of the bottom hole and the other three to its periphery over a distance equalling two thirds of the radius from the axis of the bit. The jet bits are provided with special headpieces.
When drilling in soft rocks, the bit breaks up the rock by cutting it with three elongated wings. In drilling off hard and tough rocks, the bit grinds and disintegrates the rocks, like this is done by diamond-set bits, but with higher specific loads on the bottom hole face, this owing to the rows of teeth arranged at different height from the bottom hole face.
Once the first row of the teeth has been worn out, the second and then the third row set to work of breaking up the rock. At this time the borehole walls are being gauged simultaneously by six wings.
9 Make a written translation of Text 2.
10 Describe hard-material bits of the cutting-abrasive action ty pe using Figure 7.4.
CONTROL TASKS
1 Answer the questions:
1 What is the chill bit intended for?
2 How are boring bits classified as regards the principle
underlying the breaking up of the rock?
3 How are boring bits subdivided as regards their purpose?
4 What are the most widely used bits?
5 What are the shapes of roller cutters?
6 What are the patterns of roller cutters arrangement in the bit?
7 What do diamond-set bits secure?
8 What do diamond-set bits consist of?
9 What do hard alloy bits consist of?
10 What is the difference between diamond-set bits and hard alloy bits?
2 Give English equivalents of the follo wing:
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3 Give Ukrainian equivalents of th e following:
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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 There exist two types of bits each one of which is designed for disintegration of rocks possessing definite mechanical and abrasive properties.
2 When the bit rotates counter-clockwise the cutters roll over the bottom hole clockwise and accomplish a complicated rotary motion.
3 Diamond-set bits secure an effective disintegration of nonabrasive and little abrasive rock of medium and great hardness, especially when these occur at a considerable depth.
4 When excessively exposed, the diamonds crack and break, while with an insignificant exposure the needed penetration of the diamonds into the rock will be lacking and the drilling will prove ineffective.
5 The contact surfaces of radially running wings are chamfered at 35° in the direction of bit rotation and reinforced with hard alloy teeth.
5 Make a written translation of the following:
By employing diverse materials for the fabrication of the matrix that comes from sintering the mix, the required exposure of diamonds during operation of the bit in the bottom hole is achieved.
When excessively exposed, the diamonds crack and break, while with an insignificant exposure the needed penetration of the diamonds into the rock will be lacking and the drilling will prove ineffective.
In drilling hard and tough rocks, the wear of the matrix is more intensive and therefore it should be made more wear-resistant, for this will preclude the excessive exposure of the diamonds. In rocks of medium hardness the material of the matrix is less susceptible to wear and, therefore, it should be made less wear-resistant.
By adjusting the extent of diamond exposure one can also ensure a continual gap between the matrix and the rock during operation of the bit in the bottom hole.
As a result of this, on leaving the flushing holes of the bit, the drilling fluid can pass all over and along the gap, entrain the minutest particles of the drilled out rock, discharge them into the radial or radial-helical channels running between the contact sectors and then farther on into the annular space.
PART 3 MUD TECHNOLOGY
Unit 8 Purpose and Classification of Drilling Fluids
1 Learn the meaning of the following words, word-combinations and word groups:
drilling fluid, suspend, precipitation, flushing, hydraulic, fracturing, microfissure, greasing, plug, crust, penetration, permafrost rock, brine water, adjustment, facilitate, impede, mud pump, bottom drive engine, meet the requirements, raw material, suspension, emulsion, solution, exhaust gases, internal combustion engine, foam.
2 Read and translate Text 1:
Text 1
At the first stage marking the progress of rotary drilling the key function of the drilling fluid was continual removal from the well bottom hole and its bore of the drilled- out rock cuttings. At present its functions have been broadened and demands on its composition and properties increased.
In boring the drilling fluid should:
1 provide for an effective and complete clearing of the bottom hole of the drilled- out particles and for their evacuation to the ground surface;
2 hold suspended the drilled-out particles and prevent their precipitation onto the bottom hole face after flushing (circulation) has been discontinued;
3 help augment the stability of the rocks making up the bore hole walls;
4 produce on the borehole walls a counter-pressure sufficient to bar the ingress of formation fluids. This pressure, however, should not be too high to avoid a sharp fall in the effectiveness of drilling and hydraulic fracturing of rocks, or microfissuring and absorption loss of the fluid;
5 properly cool friction surfaces, above all the bits;
6 provide for an adequate greasing of friction surfaces, especially of bit supports, even in the presence of great contact pressures between them;
7 not impair oil trapping properties of producing horizons;
8 possess bridging or plugging properties, e.g. form in the pores and microfissures of the borehole walls a thin, dense and little permeable crust firmly bound with the rocks and barring penetration thereto not only of the drilling fluid proper but of its filtrate, as well;
9 be highly heat-resistant in sinking high-temperature wells and have a low freezing point, as well as low thermal conduction when drilling in permafrost rocks;
10 be sufficiently inert to the action of drilled-out rock cuttings and mineralized brine waters, but lend itself relatively readily to chemical treatment when undergoing adjustment of its properties;
11 facilitate or not impede the disintegration of the bottom hole rock with the bit;
12 as far as possible contain no components capable of exerting a strong abrasive action on the equipment;
13 protect drilling equipment and tools against corrosion;
14 be easily e nough handled by mud pumps;
15 largely consist of cheap and non-deficient materials.
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:.
3, Supply a heading for Text 1.
4 Find in Text 1 English equivalents for the following:
промивання струменем води, протитиск, кріплення долота, маеловловлювач, теплостійкий, точка замерзання, вічна мерзлота, буровий насос, привідний глибинний двигун, устя свердловини.
5 Speak about the purpose of drilling.
6 Name at least seven demands that drilling fluids must meet.
7 Learn the meaning of the following words, word-combinations and word groups:
diversity, geological conditions, water-base drilling fluid, salt brine, hydrogel-base suspension, nonaqueous-base drilling fluid, degassed oil product, hydrocarbcn-base soludon, gaseous active agent, aerated drilling fluid, high bottom hole temperature.
8 Read Text 2:
Text 2
Various requirements that are to be met by the quality and composition of the drilling fluid in actual drilling, the diversity of geological conditions and the presence of a suitable raw material, all this led to the appearance of several types of the drilling fluid. The fetter may be classed into the following groups:
1 Water-base drilling fluids:
a water (fresh, sea, salt brine); b clayey suspensions;
с natural suspensions appearing on drilling of non-argillaceous rocks and argillites;
d hydrogel-base suspensions; с emulsions of the "oil in wafer" type.
2 Nonaqueous-base drilling fluids:
a degassed oil and petroleum products; b multicomponent hydrocarbon-base solutions; с recovered emulsions of the "water in oil" type.
3 Gaseous active agents (air, natural gases, exhaust gases of internal combustion engines).
4 Aerated drilling fluids and foams.
In sinking of wells, water-base fluids enjoy the greatest popularity, with gaseous agents and aerated fluids coming next. Nonaqueous-base drilling fluids are most often than not employed in dealing with special problems and also in drilling off plastic flow- prone rocks (bischofite, camalite, heavily salinized argillaceous rocks) and deeply occurring argillites in wells with a high bottom hole temperature.
9 Supply a heading for Text 2.
10 Speak about four types of the drilling fluids.
11 Translate the following sentences into English using the words and expressions from Text 1 and Text 2.
1) При бурінні промивальна рідина повинна забезпечувати ефективне і повне очищення забою від вибурених частинок і винесення їх на поверхню;
2) Промивальна рідина створює на стінки свердловини протитиск, достатній для запобігання притоку пластових рідин і газів.
3) Проте цей тиск не повинен бути надто високим, щоб уникнути різкого зниження ефективності буріння, а також гідравлічного розриву порід або розкриття природних мікротріїцин і поглинання промивальної рідини.
4) Промивальна рідина передає енергію від бурових насосів, встановлених на поверхні, вибійному двигуну при турбінному бурінні.
5) Гіри бурінні свердловин найбільш широко застосовують рідини на водній основі, а також газоподібні агенти і аеровані рідини.
Unit 9 Water-Base Drilling Fluids
1 Learn the meaning of the following words, word-combinations and word groups:
penetrate, viscosity, permeable, rigidity, wetting, humidify, prevent, contribute, cave, dense, differential, average, suspend, stick, sediment, saturate, pipe, inhibitor, delay, oxidative, trap, aqueous, inherent, brine, dilution, lattice, montmorillonite, cell, tetrahedron, dispersion, apt, swell, bulk up, pellet, suspend, treating, alkali, piercing, intersaline, subsaline, starch.
2 Read Text 1:
Text 1 Water
In many areas most readily obtainable and cheap natural liquid is fresh or mineralized water. This is why it was precisely water that was used during the initial period marking the development of rotary drilling.
Water cools the bit and friction surfaces of the drilling shall better than other lieuids. At a sufficiently high flow rate, it can very effectively remove the drilled-out rock cuttings from the bottom hole and from the bore of the well. Water is satisfactorily cleared from fragments of the drilled-out rock even in comparatively simple water- settling systems since it is devoid of thixo-tropic properties. When the
coefficients of formation pressure abnoimality Ca < 1. the hydrostatic pressure of the water column in the well proves sufficiently great to avert the influx of formation fluids.
Being the lightest among the liquids under consideration, water exerts lesser pressure on the bottom hole face. It penetrates freely the voids and microfractures in the rock, preventing closure of the latter, and thus facilitates breaking up the face with the bit. Therefore with water flushing the rock breakdown speed is higher than in flushing with other fluids of the group under r eview.
Inasmuch as viscosity and density of water are insignificant, flushing with water requires less power than with other fluids of the group. Thanks to low viscosity of water, its flow is always turbulent, which makes for better removal of fragments from the well and decreases the possible development of a loose crust of drilled- outparticles on the permeable sections of:he borehole walls. Furthermore, the use of water helps improve working conditions of the drilling crew, for in this caise there is no need to prepare hundreds of cubic metres of drilling fluid.
But water is not a universal drilling fluid. A number of important shortcomings restrict its usage. It is krown that the rigidity of some rocks on their wetting is affected quite noticeably; they acquire the ability of plastic flow' under much 1 ower stresses than in the nonhumidified state. Water is not only incapable of preventing humidification, but actually contributes to it. Low viscosity of waiter facilitates its gaining access into the minutest pores of unstable rocks, which accelerates their deformation and caving.
With water circulation, no dense crust of the solid-phase fine particles forms on the permeable walls of the borehole, the one that is capable of offering high resistance to filtration of the drilling fluid i nto the surrounding rocks. Even with a smalI pressure differential water is easily filtered through fine pores in the rock. On the other hand, in drilling off of highly porous and especially fissured rocks with the coefficient of abnormality less than unity the water can be absorbed very quickly. Experience teaches us that, on the average, the volume flow rate of w/ater used in drill ing is 6-8 times superior to that of other fluids in the group under consideration. This must obviously be taken account of in choosing the type of the drilling fluid, since the greater flow rate may result in an increased cost of the well. An intensive loss of water can also lead to an inadequate cleanout of the well from the drilled-out rock fragments (cuttings).
Water does not possess thixotropic properties and therefore cannot hold suspended solid particles at rest. Once circulation is discontinued the drilled-out fragments partly stick to projections in the borehole walls and partly settle down onto the bottom hole face. The sediment of drilled-out fragments amassed near face can, while getting compacted, block the drilling string, especially when there are clayey particles amidst these fragments. In running in a new' bit and lifting a worn one from the bottom hole the well has to be flushed more thoroughly, for otherwise the bit and the bottom drive engine can get silted by the sediment.
Water easily dissolves many chemogenic rocks and becomes saturated with salts. For this reason, its corrosive action on the drill pipes and equipment may figure as a very serious factor indeed. To protect equipment against corrosion - inhibitors (substances capable of delaying or preventing oxidative chemical reactions) have to be added to water. As a rule, water affects adversely the oil trapping properties of producing horizons.
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