Text 11 Exploratory Wells
The best way to gain a full understanding of subsurface geology and the potential for natural gas deposits to exist in a given area is to drill an exploratory well. This consists of actually digging into the earth's crust to allow geologists to study the composition of the underground rock layers in detail. In addition to looking for natural gas and petroleum deposits by drilling an exploratory well, geologists also examine the drill cuttings and fluids to gain a better understanding of the geologic features of the area. Drilling an exploratory well is an expensive, time consuming effort. Therefore, exploratory wells are only drilled in areas where other data has indicated a high probability of petroleum formations.
Even with modern geology and geophysical techniques, drilling remains risky. An exploratory or "wildcat" well in an area that has not been drilled before faces high odds against success: perhaps one of 7 or even 10 exploratory wells finds commercial accumulations of oil or gas. To be commercially viable, a well must be able to produce enough oil or gas to justify the costs of drilling and placing it on production. In wildcat areas the first exploratory wells are often drilled as tests; they are not expected to yield oil or gas. Such wells, however, produce valuable information about the nature of the rocks and their oil and gas potential through the analysis of core samples, rock cuttings and data gathered from down-hole surveys.
If exploratory wells establish the presence of producible quantities of oil or gas, "development" wells are drilled to define the size and extent of the field. In development drilling the odds for success are higher: perhaps 6 or 7 successful wells for every 10 drilled. But the element of risk is still present: there may not be enough oil or gas to be commercially attractive; or the technology required to produce oil or gas may be too expensive.
Figure 3.
Ex.1 What sentence in the text does Figure 3 refer to?
Ex2. Translate from Russian into English.
Бурение разведочной скважины является лучшим способом получить представление о возможности залежей нефти или газа.
Это помогает геологам подробно изучить структуру подземных слоев пород.
Бурение разведочной скважины – дорогой и длительный процесс, поэтому их пробуривают лишь в районах с высокой вероятностью нефтегазовых формаций.
Лишь одна из семи или десяти разведочных скважин содержит залежь нефти или газа, имеющую промышленное значение.
Скважина промышленного масштаба должна произвести достаточно нефти или газа, чтобы оправдать расходы на бурение и производство.
Бурение разработочных скважин имеет больше шансов на успех.
Text 12 Logging
Ex.1. Translate the following word combinations and make up your own sentences with them:
to monitor the progress, subsurface formations, to illuminate the true composition, different layers of rock, drill cuttings, to examine fluid content, to measure the electric resistance, to provide readings
Logging is another tool used in developed as well as exploratory wells. Logging refers to performing tests during or after the drilling process to allow geologists and drill operators to monitor the progress of the well drilling and to gain a clearer picture of subsurface formations. There are many different types of logging, in fact; over 100 different logging tests can be performed, but essentially they consist of a variety of tests that illuminate the true composition and characteristics of the different layers of rock that the well passes through.
Various types of tests include standard, electric, acoustic, radioactivity, density, induction, caliper, directional and nuclear logging, to name but a few. Two of the most prolific and often performed tests include standard logging and electric logging.
Standard logging consists of examining and recording the physical aspects of a well. For example, the drill cuttings (rock that is displaced by the drilling of the well) are all examined and recorded, allowing geologists to physically examine the subsurface rock. Also, core samples are taken, which consists of lifting a sample of underground rock intact to the surface, allowing the various layers of rock, and their thickness, to be examined. These cuttings and cores are often examined using powerful microscopes, which can magnify the rock up to 2000 times. This allows the geologist to examine the porosity and fluid content of the subsurface rock, and to gain a better understanding of the earth in which the well is being drilled.
Electric logging consists of lowering a device used to measure the electric resistance of the rock layers in the 'down hole' portion of the well. This is done by running an electric current through the rock formation and measuring the resistance that it encounters along its way. This gives geologists an idea of the fluid content and characteristics. A newer version of electric logging, called induction electric logging, provides much the same types of readings but is more easily performed and provides data that is more easily interpreted.
Ex.2 Express the main idea of each paragraph in a single sentence in English.
Ex.3 Write a précis of the text. It shouldn’t exceed one third of the text.
Ex.4 Render the précis in English.