Impact of injection pressure and polyaxial stress on hydraulic fracture propagation and permeability evolution in graywacke:Insights from discrete element models of a laboratory test  

作　　者：Haimeng Shen Jeoung Seok Yoon Arno Zang Hannes Hofmann Xiaying Li Qi Li 

机构地区：[1]State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,430071,China [2]University of Chinese Academy of Sciences,Beijing,100049,China [3]DynaFrax UG(Limited Liability Company),Potsdam,14467,Germany [4]Helmholtz Centre Potsdam,GFZ German Research Centre for Geosciences,Telegrafenberg,Potsdam,14473,Germany [5]Technische Universität Berlin,Straße des 17.Juni 135,Berlin,10623,Germany

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2025年第4期2344-2359,共16页岩石力学与岩土工程学报(英文)

基　　金：supported by the Knowledge Innovation Program of Wuhan-Basic Research (Grant No.2022010801010159);support from the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES (Contract number VH-NG-1516);supported by the Swedish Radiation Safety Authority (Project SSM2020-2758).

摘　　要：Understanding the hydromechanical behavior and permeability stress sensitivity of hydraulic fractures is fundamental for geotechnical applications associated with fluid injection.This paper presents a three-dimensional(3D)benchmark model of a laboratory experiment on graywacke to examine the dynamic hydraulic fracturing process under a polyaxial stress state.In the numerical model,injection pressures after breakdown(postbreakdown)are varied to study the impact on fracture growth.The fluid pressure front and crack front are identified in the numerical model to analyze the dynamic relationship between fluid diffusion and fracture propagation.Following the hydraulic fracturing test,the polyaxial stresses are rotated to investigate the influence of the stress field rotation on the fracture slip behavior and permeability.The results show that fracture propagation guides fluid diffusion under a high postbreakdown injection pressure.The crack front runs ahead of the fluid pressure front.Under a low postbreakdown injection pressure,the fluid pressure front gradually reaches the crack front,and fluid diffusion is the main driving factor of fracture propagation.Under polyaxial stress conditions,fluid injection not only opens tensile fractures but also induces hydroshearing.When the polyaxial stress is rotated,the fracture slip direction of a fully extended fracture is consistent with the shear stress direction.The fracture slip direction of a partly extended fracture is influenced by the increase in shear stress.Normal stress affects the permeability evolution by changing the average mechanical aperture.Shear stress can induce shearing and sliding on the fracture plane,thereby increasing permeability.

关 键 词：Hydraulic fracture Discrete element model(DEM) Polyaxial stress Permeability evolution Crack front Fluid pressure front 

分 类 号：TU45[建筑科学—岩土工程]