• Methodological and Theory •

### Influence of orthogonal joint and stress ratio coefficients on hydraulic fracture propagation

ZHANG Bohu1(),ZHOU Changman1,ZHENG Yongxiang1,LIU Jianjun1,2

1. 1. School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China
2. Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China
• Received:2019-07-09 Online:2020-10-26 Published:2020-09-24

Abstract:

The joints in the stratum have a greater impact on the formation of complex fracture networks with hydraulic fractures. In order to study the propagation behavior of hydraulic fractures when they encounter orthogonal joints, the hydraulic fracturing of 3D orthogonal fractures is simulated based on the discrete element method, and the influence of the stress ratio coefficient k on the pressure and width of fractures is analyzed. The research results show that when the hydraulic fracture expands to the intersection of orthogonal joints, it will be hindered, so that the intersecting joint plane will slip and the fracture tip will be passivated, which will hinder the fracture expansion. Shear stress is the main factor that causes the obstruction. When the hydraulic fracture extends along the width direction, the shear stress changes and the hindrance decreases, so the crack can break through the hindrance and continues to extend. The extension direction is greatly affected by the value of k. When k is 0.8 and 1.0, vertical cracks extend through the horizontal joints and expand in the original direction. When k is 1.2, the vertical cracks will turn and expand along the horizontal joints. The maximum width of the hydraulic fracture and the pressure in the fracture are also greatly affected by the value of k. When k is 1.0, the maximum width of the fracture is stable, and the pressure in the fracture is unchanged. When k is 1.2, the hydraulic fracture expands along the horizontal joint after turning, the maximum width decreases, and the pressure in the fracture drops suddenly, and then gradually stabilizes. Whether the hydraulic fracture penetrates will affect the fracturing effect, a suitable stress ratio to control the direction of hydraulic fracture propagation can be chosen. Therefore, it can be a good guide for the determination of the shale hydraulic fracture propagation form and the formulation of the construction plan.

CLC Number:

• TE357.1