Coupled activation technology for low-efficiency productivity zones of high-rank coalbed methane in Zhengzhuang block,Shanxi,China

The prevalence of low-yield and low-efficiency areas in high-rank coalbed methane wells has become one of the main bottlenecks restricting the development of coalbed methane industry in China. In Zhengzhuang block of Qin-shui Basin,two-thirds of wells are low efficiency wells,the economic benefit of the block is poor,therefore,the influence factors causing the low-efficiency development of high-rank CBM wells of Zhengzhuang block were analyzed to study the technical measures of activating the low-efficiency blocks. Through the research of the well pattern type,res-ervoir reconstruction adaptability,and high efficiency drainage and production control mode,a series of technologies, including development well type and well pattern optimization technology and vertical well activating technology with horizontal well coupling depressurization based on the dynamic analysis and numerical simulation,high-rank coal res-ervoir reconstruction technology based on the analysis of the coal reservoir characteristics and the CBM development mechanism and high efficiency drainage and production control technology based on gas-water occurrence mechanism of coal reservoir and micro-fracture gas-water flow mechanism,suitable for the wells of high-rank coal reservoir stimu-lation had been developed. On this basis,the idea of coupling and activating technology for low-yield and low-efficien-cy area was put forward to take effective use of resources by adjusting the pattern and well type,applying reservoir re-construction technology and high efficiency drainage and production control technology. Then an activation model of low efficiency block was established to achieve the effect of overall activation of the block with the pressure declining synergistically,the new wells efficient development and the gas production steady improvement of old wells. Three years field experiments in Zhengzhuang block have achieved significant development results,such as,the average daily gas production of 44 wells is 2 400 m3 ,which is 3. 6 times that of the peak daily gas production of the surrounding old wells,the daily gas production of 22 experiment horizontal wells is 4. 2 times that of the pre-adjustment horizontal wells,and the gas production rate increases from 1. 8% to 7. 6% ,which have greatly improved the degree of producing reserves recovery and the gas production rate,as a result,the economic benefit of the block has been turned from loss to profit. The successful research and development of the technologies provide good references for activating other low-efficiency blocks with similar geological characteristics.