Geological characteristics and high efficiency development technology of coalbed methane in Duijiangnan coal mine, Guizhou Province

The development progress of coalbed methane in Duijiangnan mine field is slow. The main problems are low drilling efficiency, serious cementing leakage, long fracturing transformation period and low single well production in the block. Objectively evaluating the geological characteristics and development technology of coalbed methane is very im-portant for coalbed methane in the future. The coalbed thickness, coal body structure, reservoir pressure, gas content and permeability are systematically studied, combining with the past drilling, fracturing and drainage practices. It is proposed that directional wells are the main method of coalbed methane development in the coalfield. The coal seam M18 which has simple structure, good coal structure, high gas content, stable coal seam and thicker than 3 m is developed by horizontal wells. The seams M25 and M29, M78 and M79 which have simple structure, high gas content, stable coal seam and less than 5 m interval are developed by interlayer horizontal wells. The technology of air downhole hammer is adopted in the missing section. The technology of screw compound drilling is adopted in non-leakage well section. The variable density cement slurry and anhydrous calcium chloride are used in cementing. Multistage fracturing of composite bridge plug formation is used in vertical and directional wells. Tubing-driven hydraulic sand blasting perforation fracturing technology is used in horizontal wells. The technology of combined layer drainage and stratified pressure control should be adopted in the block. A set of coalbed methane development technology suitable for Duijiangnan minefield is formed,which provides a reference for coalbed methane development.