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THE SEARCH FOR OIL

When men first began to seek petroleum, the easiest way to find it was to look for evidence of oil seeps on the earth’s surface. Generally, oil seeps are either up-dips or seepage along a fracture. Observation of seeps has led to the discovery of many of the world’s great oil fields in the U. S., the Middle East, Venezuela, and at other points on the globe.

Indeed, the search for oil begins with geologists and geophysicists using their knowledge of the earth to locate geographic areas that are likely to contain reservoir rock. Once such a “likely area” is found, then more specific tests and investigations are made and the information gained from these is used to construct “maps” of the earth’s substructure. By 1920 it was found that looking for domes, seeps and anticlines on the surface maps was not sufficient. Thus geophysical methods were devised that gave the searchers an idea of what lay beneath the surface.

The first method developed was the torsion balance, followed closely by the seismograph. With the seismograph, subsurface structures can be deduced by measuring the transit times of sound waves generated by an explosion. Other tools developed for use by geophysicists are gravity meters and magnetometers. Another space age technique is remote sensing.

But of course, the basic tool in any search for oil is a knowledge of the earth itself – how it was formed, its composition and its present configuration. It is not enough though, to merely become aware of the existence of an oil accumulation at a given location. Before investing what may be millions of dollars, the operator needs to know if the well will be commercially feasible, or simply stated, will he recover his investment and perhaps make a profit? Not every well drilled today is assured of a rich strike. There are still many dusters, but modern techniques lessen the risk. However, a great many steps must be taken between exploration and actual drilling.

18. Ответьте на следующие вопросы:

1. What was the easiest way to find oil? 2. What has observation of seeps led to? 3. What does the search for oil begin with? 4. How are maps of the earth’s substructure constructed? 5. When and why were geophysical methods of prospecting devised? 6. Can you name the main geophysical methods and tools? 7. What is the basic tool in any search for oil? 8. What is it necessary to know before investing millions of dollars into a well? 9. Why must one take a great many steps between exploration and actual drilling?

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