Exploring hydraulic fracture behavior in glutenite formation with strong heterogeneity and variable lithology based on DEM simulation

Abstract

Glutenite is an important unconventional tight oil and gas reservoir. Due to the glutenite formation with strong heterogeneity and variable lithology which contains a large number of gravels with different sizes, shapes and mineral compositions, the mechanical characteristics of glutenite are more complicated, resulting in more complex fracture morphology. In this paper, a mathematical method for the generation of irregular polygonal gravels is proposed, and the hydraulic fracturing model of glutenite with different gravel characteristics is established based on 2D particle discrete element method. The internal mechanical mechanism of interaction between hydraulic fractures and gravels is first revealed, and the results show that the interaction is mainly affected by the non-uniformly distributed stress field caused by the coordination of deformation of glutenite. The influence of geologic and engineering factors on hydraulic fracture propagation in glutenite is studied. The results show that fracture morpgology in glutenite is mainly affected by injection rate, fracturing fluid viscosity, gravel strength and gravel spatial distribution. High gravel size, low gravel strength, high stress difference, high injection rate and high fracturing fluid viscosity are conducive to the occurrence of gravel penetration. The micro-mechanism of interaction between hydraulic fractures and gravels is mainly affected by the non-uniformly distributed stress field caused by the coordination of deformation of glutenite. This study can provide key technical support and theoretical guidance for oil and gas development in tight glutenite reservoir.