Technical advances in well types and drilling & completion for high-efficient development of coalbed methane in China

Compared with the United States, Australia, Canada, and other countries, China's coalbed methane reservoir has the characteristics of low formation pressure, low permeability, low gas saturation and strong heterogeneity, which increases the difficulty in the reservoir stimulation and restricts the single well production and recovery efficiency of coalbed methane(CBM).Focusing on the engineering technology issues faced by the efficient development of CBM in China, the research and application progress in horizontal drilling and completion technology of CBM at domestic and abroad are reviewed to provide references and theoretical supports for horizontal well engineering technology progress of CBM in China. A series of horizontal drilling and completion technologies, e.g., well type design, well structure optimization, well trajectory control, wellbore stability, well completion optimization, reservoir protection and so on, are discussed. The advanced technologies and their adaptability including screen pipe completion and stimulation with dual-layer tubular strings, radial horizontal well screen pipe completion and magnetic steering drilling are covered. A novel integrated engineering mode for efficient and green development of the deep CBM and coal through the underground 'well factory' is presented.