Primary Controlling Factors of Coalbed Methane Well Productivity and High Productive Well Patterns in Eastern Yunnan and Western Guizhou, China

Coalbed methane (CBM) resources are abundant in eastern Yunnan and western Guizhou of China. However, despite the vast reserves, large-scale commercial development of CBM in these areas has not yet been realized. In this study, a comprehensive analysis of the productivity of CBM wells is conducted, leveraging geological and production data from a dataset comprising 19 wells. The investigation encompasses both geological and engineering perspectives, aiming to identify and assess the various factors that significantly influence CBM well productivity. The analysis of the results reveals that the well productivity is positively correlated with the proportion of Type I coal (PTIC), the ratio of critical desorption pressure to reservoir pressure (RCRP), the gas saturation (GS), the initial permeability after reservoir stimulation (IPRS) and the permeability before gas production (PBGP). The well productivity is negatively correlated with the burial depth of the coal seam floor (BDCF) and has a complex relationship with the span of the co-production coal seam. Moreover, to achieve commercial development of CBM wells, the PTIC and GS in co-production coal seam should exceed 60%, the BDCF is less than 800 m, and RCRP, IPRS and PBGP are greater than 0.6, 2.4 mD (Millidarcy. 1 mD = 0.9869233 × 10−15 m2), and 0.3 mD, respectively. The quantitative evaluation of the sensitivity of these influencing factors on CBM well productivity in eastern Yunnan and western Guizhou is accomplished using the gray relational analysis method. The study identifies GS and PBGP as the primary controlling factors impacting the productivity of CBM wells. Building upon these findings, the research presents high productive patterns for CBM wells that emphasize coordinated control of geological and engineering aspects. This research has significant implications for the exploration and development of natural gas resources, offering potential advancements in the field.