DISCUSS ON DRILLING TECHNOLOGY FOR COALBED GAS WELL

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.