Geological evaluation system of potential coalbed methane exploration and development blocks with low and medium coal ranks

Geological constituency is the basic work of CBM exploration and development. The resource of low and medium rank CBM is rich in China, thus, it is very important to optimize the evaluation system for prioritizing CBM exploration and development areas. Based on comprehensive analysis on influencing factors of CBM exploitation potential, the authors identified the main influencing factors, and then, established the evaluation system for prioritizing exploration and development areas of low and medium rank CBM by using the multi-layered fuzzy judgment method. Results show that, the main influencing factors of low rank CBM blocks in early exploration period include gas potential and reservoir property of the coal seam, and the preservation conditions of CBM; whereas, the main influencing factors of medium rank CBM blocks in development period comprise resource conditions, occurrence conditions and development conditions of CBM. According to application examples, the exploration areas of low rank CBM of Binchang block can be divided into six types, and the first type, as the most favorable areas in this block, includes the areas of Tingnan mining area to Dafosi mining area and north of Yadian mining area, whereas the CBM exploration potential decreases toward to the surrounding areas. The development areas of medium rank CBM of Liulin block can be divided into five types, and the primary type contain the areas of CLY well group at southeast of this block and northeast of FL-EP1 well group, whereas the areas near the Jucaita fault are the least favorable areas for CBM development.