Accumulation conditions and key technologies for exploration and development of Qinshui coalbed methane field

Abstract

The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration & development of coalbed methane (CBM), it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world. Although the high-rank coal field is characterized by low pressure, low permeability, low saturation and strong heterogeneity, the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior. As main productive intervals, No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system. The coal seam has large thickness, and is mostly composed of humic coal and mainly contains vitrinite. Affected by tectonic thermal events in the Yanshanian period, the coal rank is high, the adsorption capacity is strong, and the gas content is large. Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation, gas phase transformation and sealing of hydrodynamics and roof and floor. In view of the characteristics of the Qinshui Basin topography and the high rank coal, a series of key technologies for exploration and development are developed, including mountainous region seismic acquisition, processing and interpretation technology, drilling and completion technology of multiple wells, drilling and completion technology of multiple horizontal wells dominated by compound V type, deplugging secondary fracturing stimulation technology, control technology of high rank CBM drainage, and CBM gathering and transportation technology, which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.