煤岩裂缝宽度可视化模拟及影响因素分析

The visual simulation of hydraulic crack width in coal rock and the analysis of influencing factors

为了观察和研究煤岩水力压裂过程中裂缝的形态,采用真三轴压裂模拟系统,对煤岩岩样进行了室内物理模拟实验,实验后对采集的数据用MATLAB软件进行模拟,得到了裂缝的三维图像。观察三维图像发现:裂缝的宽度近似符合PKN模型。针对裂缝不闭合的情况,通过建立新的数值模型,修正了原有的宽度方程。然后采用样条插值法对相关数据进行拟合,结果发现:拟合值与利用新方程得到的理论值十分接近。最后分析了影响水力压裂裂缝宽度的影响因素(渗透率、天然裂隙宽度、吸附变形及温度),同时对水力裂缝相关的宽度方程进行了相应的推导,得到了裂缝宽度与每个影响因素的关系式。关系式表明:裂缝宽度分别随着渗透率、天然裂隙宽度、吸附变形的增大而减小,会表现出闭合的趋势。

To observe and study the geometry of hydraulic fractures directly in coal rock,a hydraulic fracturing simulation experiment was done using the large-scale triaxial fracturing test system in a laboratory.And the MATLAB software was used to simulate the geometry of fractures to obtain the images of cracks.The images of cracks indicate that the width of cracks is suitable for the PKN model.When the cracks are open,a new model was built to get a new equation of the width.Then a Spline Interpolation method was employed to get a fitted value.The comparison show that the fitted value is close to the theoretical value that we get from the new equation.Finally,the relationships between the width of cracks and the factors（permeability,the width of natural fissure,adsorption deformation,temperature）were analyzed and deducted,which indicates the width of hydraulic cracks will decrease with the increasing value of permeability,the width of natural fissure and adsorption deformation respectively.