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Lesson 13 |
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The search for oil |
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What do oilmen want to achieve as soon as they strike oil? |
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The deepest holes of all are made for oil, and they go down to as much as 25,000 feet. |
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But we do not need to send man down to get the oil out, as we must with other mineral deposits. |
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The holes are only borings, less than a foot in diameter. |
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My particular experience is largely in oil, and the search for oil has done more to improve deep drilling than any other mining activity. |
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When it has been decided where we are going to drill, |
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we put up at the surface an oil derrick. |
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It has to be tall because it is like a giant block and tackle and we have to lower into the ground |
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and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top |
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and are fitted with a cutting bit at the bottom. |
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The geologist needs to know what rocks the drill has reached, |
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so every so often a sample is obtained with a coring bit. |
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It cuts a clean cylinder of rock, from which can be seen the strata the drill has been cutting through. |
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Once we get down to the oil, it usually flows to the surface because great pressure either from gas or water, is pushing it. |
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This pressure must be under control, and we control it by means of the mud which we circulate down the drill pipe. |
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We endeavour to avoid the old, romantic idea of a gusher, which wastes oil and gas. |
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We want it to stay down the hole until we can lead it off in a controlled manner. |