Study on hydraulic fracture propagation of strong heterogeneous shale based on stress-seepage damage coupling model

Abstract

The developed laminar structure of shale makes it have obvious anisotropic characteristics, and the anisotropic characteristics are one of the important factors leading to the strong and weak heterogeneous properties of shale, and there is a common phenomenon that the propagation of hydraulic fracture heights is limited in the hydraulic fracturing process of strong heterogeneous shale reservoirs. In order to clarify the reasons for the limited height propagation of hydraulic fractures in strongly heterogeneous shale reservoirs, numerical simulation methods were used to study the propagation patterns of hydraulic fractures in shale reservoirs under different anisotropy, flow rate, viscosity, and stress differences. The results show that as the anisotropy value increases and the heterogeneity becomes stronger, the more difficult it is for hydraulic fractures to expand along the fracture height direction, and the larger the fracture width is at the fracture opening. For the strong heterogeneous shale reservoir, the hydraulic fracture height can be increased within a certain range by increasing the flow rate, increasing the viscosity and increasing the stress difference. When the upper limit value is exceeded, the hydraulic fracture height of the strong heterogeneous shale reservoir gradually becomes stable, and the increasing trend is no longer obvious. The strong or weak heterogeneity caused by the inherent anisotropic characteristics of shale reservoirs will affect the development and transformation effectiveness of shale reservoirs. The research in this article will provide some reference and guidance for the efficient development of shale reservoirs.