煤岩拟三轴水力压裂实验研究

Experimental research on the quasi three-axis hydraulic fracturing of coal

为了更深入地研究煤岩水压致裂机理,首先对MTS815.02电液伺服岩石力学实验系统进行改造;利用煤粉、水泥和石膏不同的配比制作相似材料,对型煤试件和原煤试件进行了拟三轴水压致裂实验,并与现场压裂数据进行了比较分析。结果表明:合理的材料配比为煤∶水泥∶石膏=1.5∶1∶1;裂缝总是沿地应力最大的方向扩展,且裂缝表面特征对缝内压裂液的流动具有重要影响;泵注流量越大,起裂压力也越大。

In order to study the hydraulic fracturing of coal mechanism thoroughly,a modification of MTS815.02 electro-hydraulic servo rock mechanical testing system was carried firstly.Analogous materials consisting of powder coal,cement and gypsum with different material proportions were used.The quasi tree-axis hydraulic fracturing tests were carried out on the coal specimens and the raw coal specimens.The comparison of the test results with the scene compression fracture date was also conducted.The result indicate that reasonable material proportions can be described as∶Coal∶Cement∶Gypsum =1.5∶1∶1.The crack always propagates along the in-situ stress＇s biggest direction and the character of crack surface has the important influence on the fracturing fluid flowing in the seam.It also indicate that bigger pump jet quantity leads to bigger breakdown pressure.