Practice and cognition of efficient CBM development under complex geological conditions: A case study of Zhengzhuang Block, Qinshui Basin

Abstract: The geological conditions of various CBM sites in China are complicated and features similarly. With the recent development of exploring CBM towards the medium-deep, ultra-low permeability and structurally complex areas, it is of great significance to develop a set of efficient exploring techniques in complex areas to revitalize a large number of domestic CBM resources. Taking an example of the successful development of Zhengzhuang Block with early low yield and relatively complex geology, it had faced a series of problems, including complex geological conditions with internal fracture, strong heterogeneity, low permeability, lack of corresponding developing technologies for the early stage development, production rate less than 30% in the early stage. The sweet area optimization and efficient development theory was developed through deepening the research on CBM geological enrichment law and the development and application of new technologies. With these proposed techniques on optimal rapid drilling, dredging capacity increasing revamp and quantitative dredging and drainage control in two-open full-diameter horizontal wells, the production of single well was greatly increased, and the project yield increased from 29.3% to 98.5%. The research results indicate: (1) Timely and appropriate adjustment on the development plan is essential for the successful development of complex and low-permeability high-rank coalbed methane, providing space and platform for the continuous improvement in CBM exploring techniques; (2) The rolling operation mode of cluster well group can significantly reduce production and construction risks, and increase the overall scheme productivity by more than 20%; (3) The continuous innovation of horizontal well geology and engineering integration technology is a key element to achieve the overall improvement of productivity.