Discussion on methods for selected areas evaluation of coalbed methane:A case study of southern Junggar Basin

Selected areas evaluation of coalbed methane has always been an important link in the process of coalbed methane (CBM) exploration,in which the evaluation method is the key to favorable area. The methods gradually de- veloped from the qualitative evaluation to quantitative evaluation in recent years. This paper uses southern Junggar Ba- sin as an appraisal area. Firstly,five typical kinds of evaluation methods are discussed,in which the merits and demer- its are systematically expounded. It is founded that qualitative evaluations are still practical,although quantitative eval- uations have improved the veracity of evaluation,subjectivism and empirical judgments are still existed in the process of quantitative evaluations to some extent. Based on the differences and similarities of the five evaluation methods,prin- cipal component analysis (PCA) has been proposed for the purpose that avoids the subjectivism and empirical judg- ments. The Sigonghe to Dahuangshan area has been selected as a favorable area by PCA method,the same result is generated by the five evaluation methods,which proves that the PCA method is feasible in selecting the favorable CBM areas,and its greatest advantage is to avoid the subjectivism. The authors advocate that the thought of “first qualitative judgment,second quantitative analysis,and final qualitative verification” should be used to select favorable CBM are- as.