水力裂缝与天然裂缝交错延伸规律

非常规与致密储层的缝网压裂或分段压裂改造技术使水力压裂裂缝与天然裂缝交错延伸的问题成为焦点。为了更好地控制水力裂缝的延伸方位，达到最优缝网状态，以位移不连续方法为基础，依据单元体的叠加原理，建立了二维裂缝延伸计算模型，对一条水力裂缝与一条天然裂缝在不同倾角、间距、应力等条件下的交错延伸规律进行了量化模拟。研究结果表明：裂缝间距、倾角能较大地影响裂缝延伸幅度，天然裂缝与压裂裂缝间距大于1 m、倾斜角小于70°时，压裂裂缝会诱使天然裂缝转弯延伸，直至相交；主应力比值对交错裂缝延伸幅度有一定程度的影响；储层泊松比与杨氏模量对交错裂缝延伸幅度却不明显。

Staggered extension laws of hydraulic fracture and natural fracture

The fracture-network fracturing or staged fracturing reformation technology for unconventional and tight reservoirs focuses on the scientific problem about the staggered extension of hydraulic fracture and natural fracture. To better control the extension azimuth of hydraulic fracture and achieve the optimal fracture network state, a two-dimensional fracture extension calculation model was built based on displacement discontinuity and element superposition principle, so as to conduct the quantitative simulation research on the staggered extension laws of a hydraulic fracture and a natural fracture under the conditions of different dip angles, intervals and stresses. The research results show that fracture intervals and dip angles can greatly affect the fracture extension amplitude. When the interval between natural fracture and fracturing fissure is greater than 1 m and the dip angle is less than 70°, the fracturing fissure will force the natural fracture to turn and extend until intersection. Principal stress ratio has an effect on the extension amplitude of staggered fracture to some extent. However, the Poisson's ratio and Young's modulus have insignificant influences on the extension amplitude of staggered fractures.