Volume fracturing technology with high-energy electric detonation and engineering test of ground coalbed methane

The efficient development of coalbed methane has become the preferred and strategic development goal of clean energy and gas disaster prevention and control, and it is urgent to innovate the theory and technology of coal reservoir transformation. In order to solve a series of problems such as strong reservoir adsorption, low permeability, easy blockage of migration channels, water lock effect, and lack of water resources in the development process of surface coalbed methane. In this research, the theory of high-energy electric detonation (HEED) volume fracturing and permeability enhancement in surface coalbed methane wells were deeply analyzed. Based on the energy release characteristics of shock wave-stress wave-vibration wave propagation in electric detonation liquid phase discharge, A multi-point electric detonation-induced volumetric fracturing model of high-precision energy allocation roof, floor, and coal reservoir was established. The method of strengthening coalbed methane extraction by HEED volume fracturing in coal reservoirs is put forward, and the technology and process of HEED volume fracturing of surface coalbed methane are formed. Using the self-developed HEED volume fracturing and permeability increasing equipment with storage energy up to 604.92 kJ and adjustable, an engineering experimental study of roof, floor, and coal seam fracturing caused by different HEED energy cycles was carried out. During this period, the surface microseismic monitoring system was used to characterize the influence radius of the reservoir fracture network in real-time, and the reliability of HEED volume fracturing technology and equipment was investigated according to the volume fracturing effect and long-term coalbed methane production. The results show that the HEED cycle induces the development and expansion of cracks or micropores, and forms a volume fracturing effect with high crack density. The amplitude of the microseismic signal near the well was large and gradually decreased with the increase in distance. The plane distribution of microseismic events was ring-shaped and spread around. The increase of HEED energy and induction times leads to the increase and then decrease of the influence radius of the coal reservoir fracture network. The influence radius of the fracture network induced was as high as 200 m by HEED underwater excitation energy of 361.97 kJ. The average coalbed methane production during the re-extraction period was 0.80～1.53 times higher than that during the depletion period. It was verified that the proposed HEED volume fracturing technology could effectively improve the coal reservoir and promote the desorption, diffusion, and migration of coalbed methane. The research results have theoretical and engineering guiding significance for the fracture network transformation of low permeability soft coal reservoir to realize the efficient development of coalbed methane.