Summarization of geological study on low rank coalbed methane in China

According to the status that no commercial exploration of the low rank coalbed methane in a level of a exploration block or a basin in China,in order to d eepen the understanding the geological conditions of the low rank coalbed methane exploration with a "mineability" as a core,from the origin of the low rank coalbed me thane,the low rank coal reservoir features,the low rank coalbed methane formation mode and other aspects,the paper systematically summarized the update progress 0 n the basic geological feature study of the low rank coalbed methane in China and pointed out the existed problems in the study process and the future development te ndency.The results showed that the low rank coalbed methane would have three type origins and multi source supplement features.The macro crack open degree and t he connection of the coal reservoir were good and the matrix porosity was high.The low rank coalbed methane would have the features of a short adsorption time,a high desorption efficiency,a low diffusion volume,a high diffusion coefficient and a high diffusion rate and a low permeability. The gas recharge and storage condition were the key to control the gas content of the low rank coal.At present,the exploration and development of the low rank coalbed methane would have four geological problems to be solved.The first would be the available technique and technical level applied to define the gas content coefficient low limit of the industrial gas flow formed from the | ow rank coalbed methane.The second would be the reservoir sensitivity evaluation and the main controlled geological factors to study and realize the prediction of the r eservoir reconstructability.The third would be the three-phase time and space distribution and the each phase geological control factor would be the key problems to ex plore the low rank coalbed methane enrichment law and the favorable geological conditions.The forth would be the establishment of the low rank coalbed methane mine able geological mode and the geological selected block evaluation system based on the " mineability" as the core.