瓦斯在煤体水压致裂过程中的作用试验研究

摘要

为分析瓦斯对煤体水压致裂过程的影响,利用自制的含瓦斯煤水压致裂实验系统,开展了恒定流量下含瓦斯煤水压致裂实验,得到了煤体压裂形态及电阻率响应特征,并分析了瓦斯在压裂过程中的作用.结果表明,无瓦斯条件下煤体压裂形成的裂隙少而宽,随着瓦斯压力的增大,新生裂隙数目逐渐减少,而原生裂隙则逐渐被激活;瓦斯压力的增大提高了煤体的起裂压力;含瓦斯条件下电阻率曲线呈现两种形态,即新生裂隙较多时呈现增大型曲线,原生裂隙被大量激活时呈现减小型曲线.基于试验结果分析,瓦斯在水压致裂过程中的作用有两个,一是瓦斯压力增大了水压致裂阻力,提高了起裂压力;二是高压水驱气作用诱导高压水进入、激活了原生裂隙.%The experiments under different gas pressures and constant injection rate were carried on,with the self-developed coal hydraulic fracture experimental system,to obtain the resistivity response curves and fracture morphology of coal samples.Based on the test results,the influence of gas on hydraulic fracture process was analyzed.The results showed that the fracture morphology of coal samples tends to be complicated.Number of fracture is much less and wider for coal samples without gas compared with that in the gas-borne coal.Meanwhile,the generated new fractures become less with the increase of gas pressure and the raw fractures are motivated gradually.Gas pressure makes the initial pressure increase.And the resistivity curves show two shapes.Resistivity curve tends to increase if the gas pressure is low and tends to decrease if the gas pressure is high.Based on the test results,the gas may has two actions in the process of hydraulic fracture of coal.First of all,the gas pressure increases the fracture resistivity and thus the initial pressure of coal.And the second one is that the gas induces the water flow into the raw cracks and thus motivates the raw fracture.