煤层气井钻井工艺技术探讨

DISCUSS ON DRILLING TECHNOLOGY FOR COALBED GAS WELL

我国煤层气资源十分丰富，但开发利用刚刚起步。煤层与一般油气层相比，机械强度低，孔隙度低，所以易坍塌、易污染。煤层气是吸附在煤层中的甲烷和少量的其它气体，煤层既是生气层，又是储气层，煤岩颗粒和微孔隙组成储集空间，天然裂缝是渗流通道。煤层孔隙压力低，所以开采时要先抽吸排水，压力降到解吸压力之下才能采气。采气时气水同产，地面再分离。文中主要介绍了煤层气井的井身结构、钻井参数、取心工具和工艺等。

China is very rich in coalbed gas resources, but the development and utilization of the resources is just in its initial stage. The coal bed has a low mechanical strength and porosity in comparison with the normal oil and gas formation, so it is easy to collapse and easy to be polluted. The coalbed gas includes the methane absorbed in coal bed and a little other gases. The coal bed is either gas source bed or gas-bearing reservoir, the reservoir space is made up of the coal rock particles and micropore and the percolation flow passage is made up of the natural fracture. The water must be drained first by swabbing during producing because of the low pore pressure of coal bed. When the pressure is under desorption pressure, the gas can be conducted. This paper mainly introduced the casing program of the coalbed gas well, drilling parameter, coring tool and technologies and so on.