页岩储层水平井分段压裂裂缝间距设计及影响因素分析

水平井分段压裂技术在页岩储层中广泛应用。多级裂缝间的相互作用对裂缝周围的应力转向有很大的影响,如何优化裂缝间距是一个亟待解决的关键问题。以KGD水力裂缝模型为基础,建立了水力裂缝周围诱导应力场的计算模型和分段压裂裂缝周围复合应力场的计算模型。以水平最大主应力的偏转角、分段压裂段数极限、压裂井段总长度为判断依据,形成了水平井分段压裂裂缝间距设计方法。实例计算表明：裂缝间距与裂缝半长、原水平主应力差、裂缝内压有一定关系；在顺序分段压裂中,后压裂的裂缝间距应大于之前的裂缝间距。

An Approach to Design Fracture Spacing in Horizontal-Well Multi-Stage Fracturing and Factors Analysis in Shale Reservoir

Horizontal-well multi-stage fracturing is commonly used in shale reservoir. The complex interactions between multiple hydraulic fractures have a strong impact on stress reorientation around the fractures. How to optimize the fracture spacing is a key issue needed to be solved. Based on KGD fracture geometry, a simple mathematical model used for calculating fracture induced stress field is proposed and a compound stress field around fractures in horizontal-well multi-stage fracturing is derived. Treating the reorientation angle of the maximum horizontal stress, limited staged number and fracture-segment length as the judgments, an approach to design the fracture spacing in horizontal-well multi-stage fracturing is proposed. Numerical calculation shows that fracture half length, horizontal in-situ stress contrast, liquid pressure inside the fracture all have some relationships with fracture spacing. In sequential fracturing, the previous fracture spacing should be smaller than the sequent fracture spacing.