Development of unconventional gas and technologies adopted in China

This study analyses the geological characteristics and development progress of unconventional gas in China, summarizes the development theories and technologies, discusses the prospects and challenges of unconventional gas development, and puts forward the future trends of development technologies. Various technologies of unconventional gas development are available in China. Shale gas development technologies include comprehensive geological evaluation, volume fracturing of cluster horizontal wells under complex stress conditions, and factory-like operation of horizontal wells in complex mountainous area et al. Tight gas development technologies include fluid identification and quantitative prediction, optimization of well patterns, multi-layer fracturing in vertical well, staged fracturing in horizontal well, and drainage gas recovery. Coalbed methane (CBM) development technologies include the prediction of medium-high- and medium-low-rank CBM enrichment areas, rate-variable hydraulic fracturing, and quantitative drainage recovery with five stages, three pressures, and four controls. For economic and effective development of unconventional gas, further efforts should be made. First, intensified studies should be conducted on high-precision prediction and fine characterization technologies of high-quality shale reservoirs in deep marine, continental, and transitional facies. Second, key theories and technologies such as fast drilling and completion of wells with long laterals as well as large-scale volume fracturing should be developed to improve well productivity. Third, new technologies such as multiple well-type development, fluid injection, and nano-flooding should be developed to enhance the recovery. Fourth, effort should be made to identify the accumulation mechanism and large-scale effective development technologies for CBM. Fifth, the application of large amounts of data and artificial intelligence in the entire process of unconventional gas development should be considered to reduce the development cost. [Display omitted] •Advances in precise prediction and fine characterization of unconventional gas.•New generation of shale gas fracturing technologies is taking shape.•Big data and artificial intelligence are the future trends.