# Experimental Study on High-Energy Gas Fracturing Artificial Coal
###### Abstract  
The low permeability of coal seams has always been the main bottleneck restricting coabled 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. simulation coal; high-energy gas fracturing stress wave propagation and attenuation law; pressure in the borehole wall; experimental study +
Footnote †: journal: Applied Sciences  
and hydraulic cuttings consume large amounts of water, and the chemical additives in the fracturing fluid can pollute groundwater resources. In addition, a large amount of fracturing fluid will occupy the channels for gas flow, resulting in lower gas production. Deep hole pre-splitting blasting technology is prone to accidents; mining protective seams are suitable for gas extraction from coal seam groups, but the effect is not ideal for a single thick coal seam. Plasma pulse technology is difficult to guarantee the duration of the coal seam transformation effect, and the cost is too high. High-energy gas fracturing technology was proposed in the United States in the 1860s [12]. Its essence is to generate a large amount of gas in a non-explosive way; the gas causes the brittle coal rock body to produce longer fractures to communicate more natural fractures, thus forming a complex network of fractures to achieve the purpose of fracturing effect [13; 14; 15; 16]. [PERSON] et al. [17] used fracture mechanics to preliminarily reveal the mechanism of fracture under the action of high-energy gases. [PERSON] et al. [18] conducted field tests in the Enhong Basin and proved that the application of high-energy gas fracturing technology to extract coalbed methane is feasible. [PERSON] et al. [19] established a computational model for high-energy gas fracturing loads using dynamic destruction simulation tests and theoretical studies of rocks under different loading conditions. [PERSON]. [PERSON] et al. [20] quantified the enhanced gas extraction effect of high-pressure air blasting based on numerical simulation, and the results showed that the destruction caused by high-pressure gas blasting could effectively improve the gas extraction effect. [PERSON] et al. [21], using numerical simulation and theoretical analysis, explored the mechanism of fracture extension in composite coal seams under the action of high-energy gases. Using chemical fracturing agents to generate high-energy gas is one of the high-energy gas fracturing technologies, which has the following advantages: it does not require large construction equipment, the operation process is similar to that of traditional explosives blasting, the gas production volume and gas production rate can be adjusted by controlling the fracturing agent equivalent and composition.