I Learn the words:

1. slips - клинья, плашки

2. wedge - клин

3. toothed - зазубренный, зубчатый

4. to grip - зажимать, захватывать

5. recovery - извлечение, добыча

6. temporary - временный

7. to displace - вытеснять

8. water drive - водонапорный режим (вытеснение нефти нагнетаемой водой)

9. primary - главный, первичный

10. gas cap drive - режим газовой шапки

11. expansion - расширение

12. to dissolve - растворять

13. solution - раствор

14. to expel - вытеснять, исключать

15. maintenance - поддержание

16. desirable - желаемый

17. beneficial - благоприятный

18. to retain - удерживать, сохранять

19. injection - нагнетание

20. loss - потеря

22. secondary - вторичный

23. common - обычный, общий, распространенный

24. ordinary - значительный

25. artificial - искусственный

26. to employ - применять, использовать

27. water flooding - заводнение

28. favorable - благоприятный

29. to flush - вымывать, промывать

30. to push - толкать

II Translate the text: Geological Considerations in oil and gas recovery methods

After the discovery of an oil and gas field the most important objective is the recovery of the maximum possible amount of oil and gas in the reservoir. The maximum recovery of oil and gas from a reservoir depends upon a number of factors, many of which are of a geological nature.

Recovery Mechanisms. Oil itself has no inherent energy; it is therefore necessary to displace oil from sand by either water or gas. Oil may be displaced from sand by any one or a combination of three mechanisms, as follows:

1. Water drive, in which the oil is displaced by water rising from below. Water drive is generally the most efficient primary or natural oil recovery mechanism.

2. Gas cap drive, in which a free gas cap is present but with no water encroachment. The displacement action of the downward expansion of gas will drive oil out of the sand. A high recovery is possible by this mechanism.

3. Dissolved gas drive, in which there is no water en encroachment and no free gas present. The release of pressure will cause gas to come, out of solution and expel part of the oil and most of the gas from the reservoir. A large amount of oil is left in the sand. This is the least efficient of the primary or natural recovery mechanisms.

Pressure Maintenance. The retention of pressure in a reservoir will tend to preserve the desirable original physical characteristics of the oil with resulting beneficial effect upon its recovery. In some fields the pressure is retained by an effective water drive. In gas cap drive fields and dissolved gas drive fields there is a gradual loss in pressure resulting in high gas-oil ratios and a loss in oil recovery.

The common methods of pressure maintenance are water injection and gas injection into the reservoir. The pressure is held as near as possible to the original reservoir pressure.

Secondary Recovery. The amount of oil originally in the reservoir which is not recoverable by natural recovery mechanisms and by ordinary pumping methods is considerable. It is estimated the amount ranges from 15 to 75 per cent, depending upon the type of natural recovery mechanism and other factors. It is possible to recover a large part of the oil left in the reservoir by secondary recovery methods.

Secondary recovery is the recovery of oil and gas by any method, such as artificial flowing or pumping that may be employed through the joint use of two or more wells. Liquids or gases are injected into the common reservoir through one or more injection wells, and the oil and gas are produced through other wells by flowing or pumping.

The secondary recovery method most commonly employed at the present time is water flooding.

Water Flooding. Water flooding is the most efficient method of secondary recovery if structural and sand conditions are favorable. The secondary source of energy is water under pressure. The water, which is injected into the reservoir under pressure, operates essentially as a flushing agent, pushing the oil ahead of it. Water flooding operations have been very successful in certain fields. The structure of the area should be gently 'dipping and without faults. Permeability should be uniform and the reservoir rock continuous.

Experiments have shown that a residual oil content of from 15 to 25 per cent will remain in the reservoir sand after it has been wetted by water, as in a water flooding operation. It is possible therefore to determine by a thorough study of cores the approximate amount of oil which can be recovered by water flooding. An additional recover as large as that obtained during natural flow is possible if the connate water saturations are high.

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