13 The Search for Oil

名称：13 The Search for Oil
内容简介：
新概念英语第四册（英音）
[al:新概念英语（四）]
[ar:MP3 同步字幕版（英音）]
[ti:The Search for Oil]

[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.