中国部分煤储层解吸特性及甲烷采收率

根据常压下的解吸实验和煤层气参数井实测数据分析，我国煤的解吸特笥变化较大，解吸率主要受煤层埋深及煤级的影响。最侍解吸深度一般在４００～６００ｍ之间，镜质体反射率小于３％时，随煤级的升高而增大；大于３％时，则相反。我国煤储层的吸附时间长短琚煤级没有特定关系，但在某些地区工层的含气量高低有关，甲烷含量低则吸附时间长，尤其是小于８ｍ＾３／ｔ时急剧增长。从现有资料看，我国煤储层的吸附时间一般不超达９ｄ。煤

DESORPTION PROPERTIES OF SOME COAL RESERVOIRS AND METHANE RECOVERY RECOVERY RATE IN CHINA

Based on desorption experiments under normal pressure and the data obtained from coalbed methane(CBM) well tests,it is suggested that the desorption properties of coal reservoirs in China are very different from each other and the desorption rates are controlled primarily by buried depths and coal ranks The optimum desorption depth ranges from 400 to 600m However,it increases with coal rank if the vitrinite reflectance(R o,max )is less than 3%,and decreases with coal rank if R o,max larger than 3% In China there is no apparent correlation between adsorption time and coal ranks,however,in some places of China the adsorption time is related to gas content If the gas content is low,the adsorption time must be long,especially when the gas content is less than 8m 3/t The existing data show that the adsorption time of coal reservoirs in China is generally less than 9 d.The coalbed gas recovery rate is not only controlled by gas content,adsorption and desorption properties of coal,and by in place pressure system,but also by drilling techniques and mining technology According to experiences in the U S and measurement in China,the average theoretical recovery rate of CBM in China is estimated as 27%