EXERCISE 17 Answer questions about the text
1. What is the main principle of fluid movement?
2. What is the bottom hole flowing pressure?
3. What is the wellhead pressure?
4. What is the static pressure?
5. Is the pressure within a column of fluid greater at the bottom or at the top of the column?
6. What is the hydrostatic pressure?
7. How great should reservoir pressure be to allow fluid flow up the well bore?
8. What does the flow rate of oil and gas depend on?
9. How does the energy of gas and salt water influence on oil production?
EXERCISE 18 Are the following statements true or false? Correct the false ones with the right information and discuss your answers with a partner.
1. When the well is drilled into a hydrocarbon reservoir and open at the surface, the area in the vicinity of the well bore becomes an area of high pressure.
2. The pressure within a column of fluid increases with depth and is greater at the top of the column than at the bottom.
3. In order for fluids to flow up the well bore, the reservoir pressure must be greater than the total of the hydrostatic and atmospheric pressure.
4. Oil can move and lift itself from reservoirs through wells to the surface.
5. Energy in the gas or the salt water furnishes the force to drive the oil through and from the pores of the reservoir into the wells.
EXERCISE 19 Connect the terms with their definitions.
| 1. Permeability | a) the pressure at surface, when the well is flowing |
| 2. Viscosity | b) the change of pressure with depth |
| 3. The bottom hole flowing pressure | c) the pressure is directly related to the depth and the density of the fluid |
| 4. The wellhead or flowing tubing pressure | d) a combination of depositions geographically related to the same area and dependent upon a favorable tectonic structure. |
| 5. Static tubing pressure | e) the pressure at the well bottom when fluids are flowing into the well |
| 6. Hydrostatic pressure | f) the pressure at the surface, when the well is shut-in and fluids are not flowing through the tubing |
| 7. The hydrostatic gradient | g) easiness with which fluid can move through porous rock. It means numerous channels for oil and gas migration |
| 8. Oil and gas field | h) easiness with which oil can be poured. It means thick oil |
EXERCISE 20 Choose the word that doesn’t suit in each group.
· High, low, well, bottom hole flowing, flowing tubing, static tubing
· Tubing, well, well bore, well bottom, pressure, depositions
· Drill, flow, move, shut-in a well, open
· Oil, gas, pressure, salt water, energy
EXERCISE 21 Give the English equivalents to the following word combinations.
1. Проницаемость
2. Ствол скважины
3. Давление на забое скважины
4. Давление на поверхности
5. Давление в подошве столба
6. Давление в коллекторе
7. Вязкости жидкости
8. Нефтяные и газовые месторождения
EXERCISE 22 Read and translate the text.
Water-Drive Reservoirs
Where the formation containing an oil reservoir is fairly uniformly porous and continuous over a large area compared to the size of the oil reservoir itself, vast quantities of salt water exist in surrounding parts of the same formation often directly in contact with the oil and gas reservoir. These tremendous quantities of salt water occur under pressure and provide a great additional store of energy to aid in producing oil and gas.
The energy supplied by the salt water comes from expansion of the water as pressure in the petroleum reservoir is reduced by production of oil and gas. This effect is slight for any small quantity, but becomes of great importance when changes in reservoir pressure affect enormous volumes of salt water that are often contained in the same porous formation adjoining or surrounding a petroleum reservoir.
The expanding water moves into the regions of lowered pressure in the oil and gas saturated portions of the reservoir caused by production of oil and gas and retards the decline in pressure. In this way, the expansive energy in the oil and gas is conserved. The expanding water also moves and displaces oil and gas in an upward direction out of lower parts of the reservoir.
By this natural “Water-Drive” process the pore spaces vacated by oil and gas produced are filled with water, and oil and gas are moved towards the well.
The “Water-Drive” is generally the most efficient oil-production process. Oilfields where “Water-Drive” is effective are capable of yielding recoveries ranging up to 50 percent of the oil originally in place, depending on:
1. The physical nature of the reservoir rock and of the oil.
2. The care exercised in producing the wells.
3. The rate of oil and gas production from the field or reservoir.
These factors also greatly affect the oil-recovery efficiency in the case of “Gas- Cap-Drive” reservoirs. However, rate of production seems to exert only minor effect on oil recoveries obtainable from “Dissolved-Gas-Drive” type fields except where conditions are favorable for gas caps to form.
In many cases reservoirs may possess the possibilities for either “Water Drive” or “Gas Drive”. In such event, the kind of operation and total rate of production will determine which type of drive will actually be effective, and accordingly will greatly affect the oil recovery.