What is an Oil and Natural Gas Reservoir?

 

Oil and natural gas were formed from the remains of prehistoric plants and animals. Hundreds of millions of years ago, prehistoric plant and animal remains settled into the seas along with sand, silt, and rocks. As the rocks and silt settled, layer upon layer piled up in rivers, along coastlines, and on the sea bottom. Geologic shifts resulted in some of these layers being buried deep in the earth. Over time, the layers of organic material were compressed under the weight of the sediments above them, and the increasing pressure and temperature changed the mud, sand, and silt into rock and the organic matter into petroleum. This rock containing the organic matter that turned into petroleum is referred to as source rock. The oil and natural gas is contained in the tiny pore spaces in these source rocks, similar to water in a sponge.

Over millions of years, the oil and gas that formed in the source rock deep within the earth moved upward through tiny, connected pore spaces in the rocks. Some seeped out at the surface of the earth. But most of the petroleum hydrocarbons were trapped by nonporous rocks or other barriers that would not allow it to migrate any further. These underground traps of oil and gas are called reservoirs. Reservoirs are not underground "lakes" of oil; reservoirs are made up of porous and permeable rocks that can hold significant amounts of oil and gas within their pore spaces. The properties of these rocks allow the oil and natural gas within them to flow through the pore spaces to a producing well.

Some reservoirs may be only hundreds of feet below the surface. Others are thousands, and sometimes tens of thousands of feet underground. In the U.S., a few reservoirs have been discovered at depths greater than 30,000 feet (9.15 km). Many offshore wells are drilled in thousands of feet of water and penetrate tens of thousands of feet into the sediments below the sea floor.

Most reservoirs contain oil, gas, and water. Gravity acts on the fluids to try to separate them in the reservoir according to their density, with gas being on top, then oil, then water. However, other parameters, such as fluid/rock properties and solubility will restrict complete gravitational separation. When a well produces fluids from a subsurface reservoir, typically oil and water, and often some gas will be recovered.

The larger subsurface traps are the easiest deposits of oil and gas to locate. In mature production areas of the world, most of these large deposits of oil and gas have already been found, and many have been producing since the 1960s and 1970s. The oil and gas industry has developed new technology to identify and access smaller, thinner bands of reservoir rock that may contain oil and gas. Improved seismic techniques (such as 3D seismic) have improved the odds of correctly identifying the location of these smaller and more difficult to find reservoirs. There is still a lot of oil and gas left to be discovered and produced. Future discoveries will be in deeper basins, and in more remote areas of the earth. There will also be a lot of small reservoirs found in existing oil and gas areas using advanced technologies.

 

2. Answer the questions on the text:

 

1) What rock is referred to as source rock?

2) Where are oil and natural gas contained?

3) How are petroleum hydrocarbons trapped?

4) What is an oil reservoir?

5) What rocks is a reservoir made of?

6) How deep below the surface are the reservoirs?

7) Why are oil, gas and water separated in a reservoir?

8) What is there on top of a reservoir?

9) What factors restrict complete gravitational separation?

10) What deposits are the easiest to locate?

11) Why are new technologies being developed?

12) What techniques have improved the odds of correctly identifying the location

of smaller reservoirs?

13) Where will future discoveries of oil and gas take place?

 

3. Give English equivalents of the following word-combinations from the text:

 

накапливаться слой за слоем, со временем, называться нефте-материнской породой, мельчайшее поровое пространство, перемещаться дальше, морские скважины, в зависимости от плотности, растворимость; территории, где давно ведется добыча (нефти/газа), распознавать и доходить до, более тонкие пласты, усовершенствованная техника, отдаленные территории,

4. Complete the sentences in coloumn A choosing the correct ending from column В:

А

1) Oil and natural gas were formed from ...

2) The layers of organic material were com-pressed ........

3) The source rock within the earth has got...........

4) Underground traps of oil and gas are called...........

5) Reservoirs can hold...........

6) Fluids in a reservoir are separated.......

7) New technologies allow to identity and access .............

8) Future discoveries will take place......

В

a) large amounts of fluids in their pore spaces.

b) in remote areas of the earth.

c) according to their density.

d) the remains of prehistoric plants and animals.

e) reservoirs.

f) tiny pore spaces that contain oil and natural gas.

g) under the weight of the sediments

h) thinner bands of reservoir rock.

 

5. Choose the only correct variant to fill in the gaps:

 

1) Rocks and silt settled layer upon layer over................

a) tiny pore spaces b) the remains of plants and animals

c) the source rock d) permeable rock

2) The source rock contains oil and natural gas in...............

a) underground lakes b) a sponge

c) tiny pore spaces d) geological shifts

3) Below the surface the petroleum hydrocarbons............. by nonporous rocks.

a) are produced b) are allowed c) are penetrated d) are trapped

4) .......... reservoirs have been discovered at 9 kilometers depth.

a) a lot of b) some c) many d) plenty of

5) Fluids are separated in the reservoir because of..............

a) gravity b) water c) pressure d) temperature

6) In a reservoir........is usually on top, then......, then........

a) water, gas, oil b) oil, water, gas

c) gas, water, oil d) gas, oil, water

7) 3D seismic allows production engineer to identify and access ..............

a) the sea floor b) thinner bands of reservoir rocks

c) remote areas of the earth d) mature production areas

 

6. Give the summary of the text about oil and natural gas reservoirs using the following word-combinations:

 

Remains of prehistoric plants and animals, be compressed under the weight of sediments, source rock, be trapped by nonporous rocks, to form a reservoir, of different depth, gravity, to separate according to density, to locate subsurface traps, to develop new technologies, to identify and access thinner bands of reservoir rock, remote areas of the earth.