Unit 7 Diamond - Set Bits
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.
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 (Pig. 7.1), radial (Fig. 7.2) and radially-stepped (Fig. 7.3) arrangement.
Fig.
7.1 Bits with helical arrangement
Fig.7.2
Bits with radial 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 between 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 diamond-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.
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, екилуатаційна спроможність, зламаний зубець.
Find in Text 1 five sentences with non-finite forms of the verb, define their functions and translate the sentences into Ukrainian.
Write 8-10 questions covering the main idea of Text 1.
Explain the difference between diamond-set bits with helical, radial, and radially-stepped arrangement using Figures 7.1, 7.2, 7.3.
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.
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.
Figure 7.4 - Hard-material bits of the cutting-abrasive action type