Ex. 10 Translate the sentences into Russian, using the active vocabulary from the previous exercises.

1. All oil and gas deposits are found in structural or stratigraphic traps in

sandstones and coarse-grained limestones.

2. A piece of sandstone or limestone is very much like a hard sponge, full of holes, but not compressible. These holes, or pores, can contain water or oil or gas, and the rock will be saturated with one of the three. The holes are much tinier than sponge holes, but they are still holes, and they are called porosity.

3. It is important to study the formation and the decay of oil and gas deposits as it allows targeted prospecting and exploration as well as the improved quest for oil.

4. Tectonic movements may lead to the loss of traps as a result of their inclination or fault, thus oil and gas will migrate to another trap or to the surface.

5. It is not unusual to have layers in the earth’s crust made up mostly of shale that are 4 miles thick, deposited in quiet ocean waters over millions of years time.

6. At first, the oil and gas only exist between the shale particles as extremely tiny blobs, left over from the decay of the tiny animals. Then, the intense pressure of the earth squeezes the oil and gas out of the shale, and the oil and gas fluids gather together in a porous layer and move sideways many miles. On their way, they may meet up with other traveling oil or gas fluids.

7. The trap may be a simple dome (or big bump), just a “crease” in the rocks, or it may be a more complex fault trap. All pore spaces in the rocks are filled with fluid, either water, gas, or oil. Gas, being the lightest, moves to the top. Oil locates right beneath the gas, and water stays lower.

8. Once the oil and gas reach an impenetrable layer, a layer that is very dense or non-permeable, the movement stops. The impenetrable layer is called a “ cap rock ”.

9. Stratigraphic traps are depositional in nature. This means they are formed in place, often by a body of porous sandstone or limestone becoming enclosed in shale. The shale keeps the oil and gas from escaping the trap, as it is generally very difficult for fluids (either oil or gas) to migrate through shales. In essence, this kind of stratigraphic trap is surrounded by “ cap rock ”.

10. The anticline is a structural type of trap, as is the fault trap and the salt dome trap. The stratigraphic trap was formed when rock layers at the bottom were tilted, then eroded flat. Then more layers were formed horizontally on top of

the tilted ones. The oil moved up through the tilted porous rock and was trapped underneath the horizontal, nonporous (cap) rocks.

 

Ex. 11 Translate Text 2 into English.

Text 3

Oil and gas exploration

Earth scientists in the petroleum industry – including geologists, geophysicists, geochemists and paleontologists – study what has happened to rocks that may be buried thousands of meters below surface, how those rocks were formed and affected by events stretching back millions of years, and how to identify traps where oil and gas accumulated within rock formations.

An explorer may have a well-developed theory or intuition why an area should contain oil and gas.

A first-hand look at outcrop geology and surface features sometimes helps to confirm the basic requirements – that there may be sedimentary rocks, potential reservoirs and hydrocarbon-bearing source rocks in a sedimentary basin.

Within a basin, the explorer’s first step is to examine all the information already known about the area. This might include academic papers, surface geology observations, any wells drilled, data from relevant agencies or departments and previous exploration results from nearby or similar areas. Geophysicists can identify the structure, configuration, thickness and depth of new sedimentary basins by measuring slight variations in the Earth’s gravitational and magnetic fields and by measuring the time taken for seismic energy waves to pass through and be reflected from sedimentary layers.

In a typical trap, gas accumulates on the top of the reservoir as a “gas cap” over the oil, which in turn overlies the water-saturated zone in the reservoir. This occurs because natural gas is lighter than oil which is lighter than water. However, all three fluids are often intermingled in parts of the reservoir. Porosity is the ability of rock to hold oil and gas like water in a sponge. A trap requires three elements:

• A porous reservoir rock to accumulate the oil and gas, typically sandstones, limestones and dolomites

• An overlaying impermeable rock to prevent oil and gas from escaping

• A source for the oil and gas, typically black waxy shales.

There are 6 common oil and gas traps: 1) thrust fault; 2) normal fault; 3) stratigraphic pinch-out; 4) reef; 5) anticlines; 6) salt dome.

If it is impossible to obtain the geophysical data from regulatory bodies, the seismic survey is required. In a seismic survey it is necessary to lay out a line or several lines of sensitive receivers, called geophones or jugs, on the ground. Then explosions or mechanical vibrations are created on the surface. The geophones record the energy reflected back as seismic waves from rock layers at various depths. Geophysicists and geologists examine the seismic data for the presence of suitable traps and for similarities with other petroleum-producing areas. If the results seem promising, they use the seismic data to pinpoint where to drill a well.

 

Exercises