Study on methodology of small scale coalbed methane exploitation target block evaluation

摘要

Coalbed methane (CBM) reservoir is usually divided into a number of small-scale blocks for development. It is important for the explorer to do a quantitative evaluation work on these blocks to find the optimal ones. Firstly, according to the principle of isofeature blocks, the block is divided into series of small units. Then factors including gas bearing, and coal reservoir physical features and exploitation background are used as evaluation index to form the evaluation index system. Secondly, expert investigation and analytic hierarchy process (AHP)method are combined to determine weight of every factor. Further more, "one factor rejection" and risk probability index and comprehensive sortation index is used to screening and ranking the units. Finally, throwing-dots and grouping are managed by using resource and insurance index, and then remark is given. The optimal units of the best group are regarded as target area of CBM exploitation. Evaluation work has been done for a CBM block in Qinshui Basin, the results showed that among 21 units, there are 3 favorable, 3 relatively favorable, 4 middle, 3 unfavorable, and 8 extremely unfavorable. The favorable section mainly locates in the west and northwest of the block. Based on the above, reasonable basis for CBM exploitation target can be provided.