练习材料：
[Day 1735 2019-06-26]
Lesson 13-2 The search for oil
The geologist needs to know what rocks the drill has reached, so every so often a sample is obtained with a coring bit. It cuts a clean cylinder of rock, from which can be seen the strata the drill has been cutting through. Once we get down to the oil, it usually flows to the surface because great pressure, either from gas or water, is pushing it. This pressure must be under control, and we control it by means of the mud which we circulate down the drill pipe. We endeavour to avoid the old, romantic idea of a gusher, which wastes oil and gas. We want it to stay down the hole until we can lead it off in a controlled manner.
朗读时间：46s/45s
任务配置： L0+L4
知识笔记：
cutting bit 钻头 /
练习感悟：
有点绕嘴 读的太少很仓促 之前都是边遛狗边听边跟读 这样能读好几遍 现在天气热了 干啥都没心情 热热热
