Xiong Jian, Liu Junjie, Lei Wei, Liu Xiangjun, Liang Lixi, Ding Yi
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, 74602Southwest Petroleum University, Chengdu, China.
Engineering Technology Research Institute of Southwest Oil & Gas Company, SINOPEC, Deyang, China.
Sci Prog. 2022 Jan-Mar;105(1):368504211070396. doi: 10.1177/00368504211070396.
Taking the fractured tight reservoir of the Fengcheng Formation in Mahu Depression as the research object, the RFPA software, a numerical simulation platform of real fracture process, was used to study the fracture propagation laws in fractured tight reservoirs during the fracturing process. On this basis, the influences of different factors on the fracture propagation laws in the fractured tight reservoirs were investigated, the influences of various factors on fracture propagation were quantitatively analyzed by the gray correlation method, and then the fractability calculation model for evaluating the fracturing effects was obtained by the analytic hierarchy process method. The results show that when the fracture angle is less than 70°, the natural fracture controls the hydraulic fracture propagation direction, whereas when the fracture angle is greater than 70°, the maximum horizontal principal stress controls the hydraulic fracture propagation direction. With the increase of the fracture angle, the hydraulic fracturing area firstly decreases and then increases, whereas with the increase of the fracture density, the hydraulic fracturing area gradually increases. The hydraulic fracturing area increases as the fracture compressive strength, tensile strength and elastic modulus reduction factor increase, whereas the hydraulic fracturing area decreases as the fracture Poisson's ratio reduction factor increases. Based on the gray correlation method, the ranking of the fracturing effect is clarified as fracture density > horizontal stress difference > fracture angle > elastic modulus > compressive strength > tensile strength > Poisson's ratio. Using the analytic hierarchy process, a model for calculating the reservoir fractability index is established, and has a good positive correlation with the dimensionless fracturing area.
以玛湖凹陷风城组裂缝性致密油藏为研究对象，采用真实裂缝过程数值模拟平台RFPA软件，研究了致密油藏压裂过程中裂缝扩展规律。在此基础上，研究了不同因素对致密油藏裂缝扩展规律的影响，采用灰色关联度方法定量分析了各因素对裂缝扩展的影响，进而通过层次分析法得到了评价压裂效果的可压裂性计算模型。结果表明，当裂缝角度小于70°时，天然裂缝控制水力裂缝扩展方向；当裂缝角度大于70°时，最大水平主应力控制水力裂缝扩展方向。随着裂缝角度的增大，水力压裂面积先减小后增大；随着裂缝密度的增大，水力压裂面积逐渐增大。水力压裂面积随着裂缝抗压强度、抗拉强度和弹性模量降低系数的增大而增大，随着裂缝泊松比降低系数的增大而减小。基于灰色关联度方法，明确了压裂效果排序为裂缝密度＞水平应力差＞裂缝角度＞弹性模量＞抗压强度＞抗拉强度＞泊松比。利用层次分析法建立了储层可压裂性指数计算模型，与无量纲压裂面积具有良好的正相关性。
