[al:新概念英语（四）] [ar:MP3 同步字幕版（英音）] [ti:The Search for Oil] [by:更多学习内容，请到chazidian.com搜索“新概念”] [00:01.52]Lesson 13 [00:03.47]The search for oil [00:11.78]What do oilmen want to achieve as soon as they strike oil? [00:18.47]The deepest holes of all are made for oil, and they go down to as much as 25,000 feet. [00:26.54]But we do not need to send man down to get the oil out, as we must with other mineral deposits. [00:34.26]The holes are only borings, less than a foot in diameter. [00:39.32]My particular experience is largely in oil, and the search for oil has done more to improve deep drilling than any other mining activity. [00:49.86]When it has been decided where we are going to drill, [00:53.45]we put up at the surface an oil derrick. [00:57.67]It has to be tall because it is like a giant block and tackle and we have to lower into the ground [01:04.36]and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top [01:10.79]and are fitted with a cutting bit at the bottom. [01:14.86]The geologist needs to know what rocks the drill has reached, [01:19.45]so every so often a sample is obtained with a coring bit. [01:24.87]It cuts a clean cylinder of rock, from which can be seen the strata the drill has been cutting through. [01:32.45]Once we get down to the oil, it usually flows to the surface because great pressure either from gas or water, is pushing it. [01:42.48]This pressure must be under control, and we control it by means of the mud which we circulate down the drill pipe. [01:51.53]We endeavour to avoid the old, romantic idea of a gusher, which wastes oil and gas. [01:59.14]We want it to stay down the hole until we can lead it off in a controlled manner.