所有钻孔中最深的是为开采石油而钻的，其深度可达25,000英尺之多。
The deepest holes of all are made for oil, and they go down to as much as 25,000 feet.
但是，我们不需要像开采其他矿藏那样派人下去把油取出来。
But we do not need to send man down to get the oil out, as we must with other mineral deposits.
这些钻孔不过是些孔径，直径不足一英尺。
The holes are only borings, less than a foot in diameter.
我的专业经验主要集中在石油领域，而石油勘探对深层钻探技术的推动，超过了任何其他采矿活动。
My particular experience is largely in oil, and the search for oil has done more to improve deep drilling than any other mining activity.
一旦确定了钻探地点，我们就会在地面上竖起一座石油钻井架。
When it has been decided where we are going to drill, we put up at the surface an oil derrick.
它必须足够高，因为它就像一个巨型滑轮组，我们必须将大量钻杆放入地下，再从地下吊出，这些钻杆顶部由发动机带动旋转，底部则安装有切削钻头。
It has to be tall because it is like a giant block and tackle and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.
地质学家需要了解钻头钻到了什么岩层，因此每隔一段时间就要用取芯钻头取得一个岩石样本。
The geologist needs to know what rocks the drill has reached, so every so often a sample is obtained with a coring bit.
它（取芯钻头）切割出一个整洁的圆柱形岩芯，从这个岩芯上可以看到钻头一路钻穿的各个地层。
It cuts a clean cylinder of rock, from which can be seen the strata the drill has been cutting through.
一旦我们钻到石油，它通常会自行流到地面，因为来自气体或水的巨大压力在推动它向上涌出。
Once we get down to the oil, it usually flows to the surface because great pressure either from gas or water, is pushing it.
这种压力必须处于受控状态，我们通过向钻杆内循环注入泥浆来控制它。
This pressure must be under control, and we control it by means of the mud which we circulate down the drill pipe.
我们力图避免那种关于井喷的陈旧而浪漫化的想象，因为井喷会浪费石油和天然气。
We endeavour to avoid the old, romantic idea of a gusher, which wastes oil and gas.
我们希望石油留在井下，直到我们能够以受控的方式将其引导出来。
We want it to stay down the hole until we can lead it off in a controlled manner.