Study On The Mechanism Of Hydraulic Fractures In Glutenite In The Presence Of Gravel

Hydraulic fracturing is an efficient technique often used in the reconstruction of glutenite reservoirs.In the process of hydraulic fracturing,hydraulic fractures are formed at the bottom of the well,and the fractures are continuously expanding,turning,bifurcating and gathering in the rock,and finally a fracture network with a complex geometry is formed.In glutenite fracturing,the interaction between hydraulic fractures and gravel affects the complexity of the fracture network.New research results have found that there is a thin transition zone between gravel and rock matrix,which can be regarded as Weak interface.Therefore,using the maximum tensile strain criterion and the Mohr-Coulomb criterion to study the interaction between hydraulic fractures and gravels is an effective research method.Based on linear elastic fracture mechanics,the stress field at the crack tip is calculated and the in-situ stress field is used as a non-singular term.The stress in the cracked micro-fracture area is analyzed.According to the connection structure of gravel in glutenite and the expansion characteristics of hydraulic fractures in glutenite,a model of hydraulic fractures and gravel expansion was established.The maximal tensile strain criterion and Mohr-Coulomb criterion are used to analyze the expansion of hydraulic fractures and gravel,and the judgment criteria for the interaction results of hydraulic fractures and gravels are established.Based on the virtual crack method,the gravel-wrapping behavior of hydraulic fractures is analyzed,a judgment criterion for the hydraulic cracks to propagate around the gravel is established.The influence of approach angle,minimum horizontal principal stress,stress difference,interface cohesion,Poisson's ratio,and gravel shape on the penetration or surrounding of hydraulic fractures is analyzed.Finally,the ABAQUS software combined with the extended finite element method was used to carry out numerical simulation research on the glutenite fracture propagation.The influence of each factor on the results of the interaction between hydraulic fractures and gravels is analyzed,and the influence of each influential factor on the propagation of hydraulic fractures in glutenite is analyzed.Starting from the micro-crack zone at the crack tip,this paper analyzes in detail the results and influencing factors of the interaction between hydraulic fractures and gravels,reveals the interaction rules between hydraulic fractures and gravels,and has important guiding significance for field construction and software writing.