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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.

        1. 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 mierofissures 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.

            1. Find in Тех! 1 English equivalents for the following:

промивання струменем води, протитиск, кріплення долота, маеловловлювач, гсилостійкий, точка замерзання, вічна мерзлота, буровий насос, привідний глибинний двигун, устя свердловини.

            1. Speak about the purpose of drilling.

            2. Name at least seven demands that drilling fluids must meet.

            3. 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, hydroearben-base solution, gaseous active agent, aerated drilling fluid, high bottom hole temperature.

            1. 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 letter 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 argil lites;

d hydrogel-base suspensions; с emulsions of the "oil in water" type.

              1. Nonaqueous-base drilling fluids:

a degassed oil and petroleum products; b multicomponent hydrocarbon-base solutions; с recovered emulsions of the "water in oil" type.

              1. Gaseous active agents (air, natural gases, exhaust gases of internal combustion engines).

              2. 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, carnalite, heavily salinized argillaceous rocks) and deeply occurring argillites in wells with a high bottom hole temperature.

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