Advances and Reviews on Coalbed Methane Reservoir Formation in China

Abstract

Basic geological research of coalbed methane (CBM) in China, taking the reservoir formation as a key, has made significant progress in recent years. The researches such as the biogenic gas simulation of the lignite samples under the condition of coalbed-derived methanogen, catalytic CBM generation from mineral and element, origin of extremely abnormal heavy hydrocarbons in anthracite seam, and secondary biogenic CBM, deepened greatly the academic understanding of the diverse CBM origins in China. Macro-process and its geological controls of the CBM reservoir formation were discussed in the more basins and deeper level, which promoted the development of the classical CBM reservoir fromation theories. Based on the original ideas, the essence of the CBM reservoir fromation was studied in the light of the formation energy, some new academic viewpoints were suggested, and the particularity of the deep CBM reservoir formation was investigated. Geological conditions of CBM in China are complex and changeable and many basic geological problems need to be further resolved. It was suggested that the recent exploration should focus on four aspects including the geo-stress field, burial depth, coal-rank and granularity effects. The first two effects belong to the macro-dynamics of CBM rerservoir formation and the latter two to the micro-dynamics, which involves to the fields of the deep, tectonically deformed and low-rank coal reservoirs with a huge amount of CBM resources. Meanwhile, the basic geological problems related to the paragenetic reservoiring and co-mining of the unconventional natural gases in coal-bearing strata (coal-measures gas) will also be a focus of the CBM research in the future.