致密油体积压裂复杂缝网形成规律数值模拟研究

Numerical Simulation on Formation Law of Complex Fracture Network by Volume Fracturing in Tight Oil Reservoir

水力压裂作为一种油田增产改造措施,已经广泛地应用于非常规油气藏开发之中。为准确反映实际压裂结果,须要进一步提高水力压裂数值模拟技术的水平。为此,结合压裂施工现场数据分析,通过建立复杂缝网数值模型进行模拟研究,以寻找其背后的根本机理。研究结果表明:水力压裂过程中,裂缝易沿倾角较大的天然裂缝方向转移;地应力差越大,裂缝越倾向于沿一个方向快速扩展,形成单一直缝,地应力差越小,裂缝缓慢扩展,在周边形成较为复杂的缝网结构;天然裂缝面摩擦因数在0.5以下时,水力裂缝会沿天然裂缝方向转移,形成较为复杂的缝网结构;天然裂缝面摩擦因数为0.4时,形成的缝网复杂度最高。所得结论可为压裂施工设计及优化提供有益指导。

Hydraulic fracturing,as a technology of oilfield stimulation,has been widely used in the development of unconventional oil and gas reservoirs.In order to accurately reflect the fracturing results,it is necessary to further improve the numerical simulation technology of hydraulic fracturing.Through field data analysis and numerical simulations of complex fracture network,a numerical model was established to simulate and investigate the formation mechanism of complex fracture network.The results show that,during hydraulic fracturing,fractures are prone to divert along the direction of natural fractures with large dip angles.As the difference of in-situ stress increases,fractures tend to propagate rapidly in one direction,forming single straight fractures.As the difference of in-situ stress decreases,fractures propagate slowly,forming complex fracture network.When the friction coefficient of natural fracture surface is below 0.5,hydraulic fractures divert along the direction of natural fractures,forming complex fracture network.When the friction coefficient of natural fracture surface is 0.4,the fracture network complexity is the highest.The conclusions provide a guidance for the design and optimization of fracturing operations.