Research on Horizontal Fracturing Crack Direction Change Mechanism of Shallow Layer Reservoir

Abstract

Yanchang Oil Field C6 Reservoir is a shallow-buried reservoir (500-600m) with natural fractures. During hydraulic fracturing, horizontal fractures are easy to form and direction turns frequently occur among hydraulic fractures. Thus, development of this shallow-buried reservoir is under great restriction. According to damage-fracture mechanics theory and based on continuous damage mechanics method, this thesis applied ABAQUS software cohesive unit to establish simulation model for the horizontal fracture propagation of C6 Reservoir. It simulated the propagation form of C6 Reservoir horizontal fracture and analyzed the induced stress field and mechanics diversion of horizontal fracture propagation. The findings of this numerical simulation include: when vertical stress was greater than the minimum horizontal principal stress. “Tâ€-profile fractures will appear; otherwise, the fractures will mainly be horizontal fractures. The greatest induced stress was from the hydraulic fractures in the middle of the reservoir. With the increase in hydraulic fracture distance, induced stress would firstly increase and then decrease. The influence caused by the induced stress from fractures was within 10m.