深层页岩气藏水平井防压窜工艺效果与适配性研究OA

There exists the challenges of frequent frac-hits and varying frac-hit patterns caused by tight reservoir rocks and abnormally developed natural fracture zones,and the lack of targeted anti-frac-hit technologies during hydraulic fracturing of deep shale gas wells in the southern Sichuan Basin.To address these challenges and thus improve reservoir stimulation,a frac-hit fracture propagation model for horizontal wells in deep shale gas reservoirs was constructed using a method integrating numerical simulation and theoretical analysis.Based on three frac-hit patterns,the effectiveness of four anti-frac-hit technologies were investigated and compared under varying frac-hit degrees.The following results are obtained.(i)Three evaluation indices relating to the constructed model,namely stress front radius,fracture asymmetric growth coefficient(AGC),and pressure change integral(PCI)index,are conducive to the multi-dimensional quantitative characterization of frac-hit degree.Specifically,the stress front radius reflects the scope of in-situ stress disturbance,the fracture AGC quantifies the asymmetry in fracture propagation,and the PCI index characterizes the abnormality in the wellhead pressure field.The three indices jointly form a comprehensive frac-hit evaluation system.(ii)The W-shaped well placement technology shows strong pertinence,offering optimal prevention and control against two frac-hit patterns:natural fracture-mediated interference(Type Ⅱ)and direct hydraulic fracture-mediated interference(Type Ⅲ),by effectively blocking the formation and extension of frac-hit channels.(iii)Alternate well zipper fracturing and stepwise drainage rate increase technologies are widely applicable,and can significantly control frac-hits for both pore-elastic interference mediated by rock matrix(Type Ⅰ)and natural fracture-mediated interference(Type Ⅱ)by regulating the stress field and fracture propagation direction.(iv)The technology of diversion while pump shutdown combined with high-concentration proppant injection in pad stage is suitable for the Type Ⅰ and small-scale TypeⅡ,inhibiting interference impacts by optimizing fracture morphology.In conclusion,this study clarifies the application scenarios and regulation mechanisms of different anti-frac-hit technologies,and proposes the applicable schemes of the technologies,providing technical support for frac-hit prevention and control during pre-production fracturing operations of deep shale gas horizontal wells in the southern Sichuan Basin.