Fluid Flow

Fluids move from regions of high pressure to regions of low pressure. 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 low pressure. If the reservoir has sufficient permeability, oil and gas flow from all directions into the well bore. When fluids are flowing into the well the pressure at the well bottom is called the bottom hole flowing pressure. The pressure at surface, when the well is flowing, is called the wellhead or flowing tubing pressure. The pressure at the surface when the well is shut-in and fluids are not flowing through the tubing is called the shut-in or static tubing pressure.

The pressure within a column of fluid increases with depth and is greater at the bottom of the column than at the top. This principle can be demonstrated by the change you feel on your ears when you dive to the bottom of a swimming pool. The pressure is directly related to the depth and the density of the fluid, and is called hydrostatic pressure.

For a given height of a column of fluid, the hydrostatic pressure of liquids is much greater than the hydrostatic pressure of gas. For example, the change of pressure with depth (called the hydrostatic gradient) is about 1.0 Kpa/m in gas. In oil the gradient varies from 8.0 to 9.0 Kpa/m.

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. The flow rate of oil or gas into the well bore depends on the permeability of the reservoir rock, the area of flow into the well bore and the viscosity of the fluid.

Oil and gas energy drives

Oil and gas reservoirs and fields have also been classified according to the type of natural energy and forces available to produce the oil and gas. At the time oil was forming and accumulating in reservoirs, pressure and energy in the gas and salt water associated with the oil was also being stored which would later be available to assist in producing the oil and gas from the underground reservoir to the surface. Oil cannot move and lift itself from reservoirs through wells to the surface. It is largely the energy in the gas or the salt water (or both) occurring under high pressures with the oil that furnishes the force to drive or displace the oil through and from the pores of the reservoir into the wells.

The words to be memorized:

1. Drill– бурить

2. Flow– фонтанировать

3. Flowrate – уровень притока, «расход»

4. Hydrostatic gradient– гидростатический градиент

5. Shut-in a well –закрыть скважину

6. Tubing – насосно-компрессорные трубы (HKT)

7. Well, hole – скважина

8. Wellbore– ствол скважины

9. Wellbottom– забой скважины

10. Bottom hole flowing pressure – забойное динамическое давление

11. Bottom hole- забойное

12. Wellhead– устье скважины

13. Buttom– подошва

14. Depositions – залежи

15. Development – разработка (месторождения)

16. Gas cap – газовая шапка

17. Permeability factor – коэффициент проницаемости

18. Pores – поры

19. Reservoir – коллектор

20. Residual – остаточный

21. Impermeablecaprock– непроницаемая покрывающая порода

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.

Permeability	the pressure at surface, when the well is flowing
Viscosity	the change of pressure with depth
The bottom hole flowing pressure	the pressure is directly related to the depth and the density of the fluid
The wellhead or flowing tubing pressure	a combination of depositions geographically related to the same area and dependent upon a favorable tectonic structure.
Static tubing pressure	the pressure at the well bottom when fluids are flowing into the well
Hydrostatic pressure	the pressure at the surface, when the well is shut-in and fluids are not flowing through the tubing
The hydrostatic gradient	easiness with which fluid can move through porous rock. It means numerous channels for oil and gas migration
Oil and gas field	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.