Experimental Study on High-Energy Gas Fracturing Artificial Coal

Abstract

The low permeability of coal seams has always been the main bottleneck restricting coalbed gas drainage. To improve the permeability of a coal seam, a high-energy gas fracturing technology is proposed. Firstly, based on the high-energy gas fracturing mechanism and gas production principle of fracturing agent, a fracturing agent applicable to coal reservoirs was developed, and its performance and sensitivity were tested. Then, a high-energy gas-fracturing simulated coal sample test was conducted, and the drilling wall pressure and strain of the simulated coal sample were tested. The results show that high-energy gas fracturing technology is a safe and efficient technical means for improving the permeability of coal reservoirs. The pressure–time curve of the borehole wall under the action of high-energy gas can be divided into three stages, namely, the rapid pressure-rising stage, steady pressure stage, and falling stage; the maximum pressure in the borehole is about several hundred MPa, and the pressure distribution in the borehole is not uniform. Compared with explosives blasting, the stress wave intensity in coal caused by the action of high-energy gases is low, the duration is short, and the peak stress attenuates slowly with increasing distance. Under the action of high-energy gas, no crush zone is generated near the borehole; the number of radial cracks produced is small but long. The extent of the fracture zone depends mainly on the quasi-static splitting wedge effect of the high-energy gas.

Keywords

• simulation coal
• high-energy gas fracturing
• stress wave propagation and attenuation law
• pressure in the borehole wall
• experimental study