考虑应力干扰的页岩储层裂缝穿透准则

 根据页岩储层多裂缝应力干扰效应形成机理,建立了考虑水平有效地应力、裂缝尖端集中应力以及多缝干扰应力影响的页岩储层裂缝穿透准则。模型分析表明:考虑多缝应力干扰效应影响,压裂缝穿过天然裂缝的能力减弱,分段多簇压裂更有利于在页岩储藏中形成复杂缝网结构。裂缝越长,裂缝间距越小,天然裂缝分布位置越靠近中间裂缝,缝内净压力越大,导致裂缝间的干扰应力越大。随着压裂缝与天然缝间逼近角的减小,在一定应力比和裂缝内摩擦系数范围内,压裂缝穿过天然裂缝能力减弱,超过一定范围后,压裂缝穿透天然裂缝的能力增强。高应力比条件,裂缝穿透能力基本不受逼近角影响。

A crossing criterion of hydraulic fracture in shale gas reservoir with consideration of stress interference

Based on the formation mechanisms of stress interference of multi-fractures induced by network fracturing in shale gas reservoirs, this paper establishes a crossing criterion with consideration of remote stress, stress intensity near the tip of fracture and stress interference of multi-fractures. The results of model analysis illustrate that the ability of hydraulic fractures to cross natural fractures decreases under impact of stress interference of multi-fractures; Meanwhile, the net fracture pressure was higher when the fracture was longer, the distance between fractures was shorter, and the natural fracture was closer to the intermediate fracture, leading to larger interference stress between fractures. With decrease of the intersection angle between the hydraulic fractures and natural fractures, the ability of the former to cross the latter decreased within a certain range of stress ratio and friction coefficient, and increased when the stress ratio and friction coefficient were beyond this range. The crossing ability is not affected by the intersection angle under high stress ratios. These results may provide references for practical fracturing stimulation of shale gas reservoirs.