Research on coalbed methane reservoir characteristics and the methods of improving surface extraction effect

Compared to conventional gas reservoirs, the coalbed methane (CBM) reservoirs are essential different from the former in its occurrence state, accumulation process, gas reservoir boundary and production law. According to the practice and exploration of CBM development in China in recent years, the idea of wells distribution in accordance with “the potential” was proposed, which means using “gravity potential energy” of water in coalbed as well location principle. Based on the distribution characteristics of coalbed gravitational field, in-situ stress field and pressure field, reasonable well type and well network were selected to improve ground CBM drainage effect. For CBM multi-branch horizontal wells, high coalbed drilling rates may not be able to bring high coalbed gas production. So the actual drilling of borehole trajectory control should follow the principle of smooth wellbore and overall angled up, to avoid "wavy" well eye. Analysis figures out that by increasing the temperature to rise CBM reservoir gas production, as well as to carry out drilling technology research for tectonic coal are main research direction of CBM development for future.