Enrichment mechanism and exploration and development technologies of high coal rank coalbed methane in south Qinshui Basin, Shanxi Province

Abstract

Based on analysis of the basic geologic characteristics and enrichment controlling factors of the high coal rank coalbed methane (CBM) in south Qinshui Basin in China, its enrichment mode, and exploration and development technologies are studied. Practices on the CBM exploration and development proved that the CBM reservoirs in this study area have the following three major properties: (1) High coal rank, strong adsorption ability, and good resources condition; (2) Low porosity, bimodal porosity structure, and obvious “bottleneck” of flow condition; (3) low reservoir pressure gradient that can constrain production. Based on deep analysis of high coal rank coal properties, this study proposes a coexistence and complementarity concept of structure, sedimentary, thermal power and hydro-geological conditions, and establishes a CBM dissipation model, which can simplify CBM enrichment problem and directly guide the region selection of CBM development. Five major critical technical systems have been formed for the CBM exploration and development in south Qinshui Basin: (1) Comprehensive geophyisical exploration and evaluation technologies; (2) Well drilling and completion technologies for high coal rank coal reservoirs; (3) Major reservoir treatment technologies; (4) Intelligent drainage and production control technologies; (5) Digital technology of coalbed methane field. These have effectively provided technical support for an orderly productivity construction of new CBM blocks. Key words: Qinshui Basin, high coal rank coal, coalbed methane, enrichment characteristics, enrichment condition, exploration and development technologies