低渗油藏径向水力射流压裂裂缝延伸规律

Research on fracturing extension by radial hydraulic jet in low permeability reservoirs

基于扩展有限元法基本理论,建立水力径向射流压裂裂缝延伸三维有限元模型,结合岩石的抗拉破坏准则,研究径向钻孔参数包括钻孔孔径、钻孔方位角及钻孔深度对地层破裂压力的影响。结果表明:随着孔眼直径的增加,起裂压力呈明显的线性降低趋势;地层破裂压力随着射孔方位角的增加而增大,40°为获得地层低破裂压力所允许的临界射孔方位角,优化钻孔与最大水平地应力的最佳夹角不超过40°;不同射孔角度下压裂裂缝扩展规律亦不同。

Based on the extended finite element method and combining with the criterion of tensile resistance failure, a three-dimensional finite element model of radical hydraulic jet fracturing fracture was built to study the influences of drilling pore diameter, drilling pore azimuth and depth on formation fracturing pressure. The results show that, with the increase of drill-ing pore diameter, the initiation fracture pressure has a significant linearly decreasing tendency. The formation fracturing pressure increases with the increase of perforation azimuth. 40° is the allowed critical perforation azimuth to obtain the low formation fracturing pressure. A angle less than 40° between the optimizing bore and the maximum horizontal stress is better. The propagation law of fracturing fracture varies under different perforation angles.