高煤阶煤层气储层产气能力定量评价

Quantitative evaluation of production capacity of high rank coalbed methane reservoir

煤层气高产区有效预测对提高煤层气单井产量和开发效益具有重要意义,为了实现煤层气储层产气能力的定量评价,基于沁水盆地南部煤层气开发数据,通过理论和统计分析,定义了储层含气性指数、煤层甲烷解吸效率指数、气水产出效率指数和产气能力指数4个参数对煤层气储层产气能力进行评价。结果表明:煤层气井日产气量随储层含气性指数、煤层甲烷解吸效率指数、气水产出效率指数的增加而增加,但相关性相对较差;当储层含气性指数大于100 m·m3/t时,或煤层甲烷解吸效率指数大于0.04(MPa·d)^-1时,或气水产出效率指数大于1 mD·MPa时,单井日产气量能够达到800 m3/d以上。产气能力指数为储层含气性指数、煤层甲烷解吸效率指数和气水产出效率指数的乘积,能够有效表征储层产气能力强弱,产气能力指数越大,煤层气井产量越高。当产气能力指数大于0.3和10 mD·m·m^3(/t·d)时,对应的单井日产气量分别大于800和1 500 m^3/d。

The effective prediction of the high production zone of the coalbed methane(CBM)is important to improve the single well production and the development benefits. In order to quantitatively evaluate the production capacity of the CBM reservoir,the gas-bearing index,desorption efficiency index of CBM,gas-water production efficiency index and production capacity index were defined through theoretical and statistical analysis of the CBM development data in southern Qinshui Basin. Results show that the daily gas production rate increases with the increase of gas-bearing index,desorption efficiency index of CBM and gas-water production efficiency index,however the correlations is not obvious. The daily gas production rate can be higher than 800 m^3/d when the gas-bearing index is higher than 100 m·m^3/t,the desorption efficiency index of CBM is higher than 0.04(MPa·d)^- 1,or the gas-water production efficiency index is higher than 1 mD·MPa. The gas-production capacity index is the product of the gas-bearing index,desorption efficiency index of CBM and the gas-water production efficiency index,and it can effectively characterize the production capacity of CBM reservoir. A higher gasproduction capacity index results in a higher daily gas production rate. When the gas-production capacity indexes are higher than 0.3 and 10 mD·m·m^3(/ t·d),the daily gas production rates are higher than 800 and 1 500 m^3/d,respectively.