Fracture Expansion Pattern Of Sparse Sandstone Fractured By Coupled Seepage And Flow Stress

Due to the weak bonding force and low strength of loose sandstone,sand production is prone to occur during mining,which affects production.Fracturing and sand control technology is currently a commonly used method for increasing production and sand control in loose sandstone reservoirs.In the actual fracturing process,short and wide fractures must be formed to achieve the ideal sand control effect.In order to better solve this problem.This article explores the law of crack propagation in loose sandstone,providing a basis for fracturing construction process parameters.This article first introduces the physical properties strain equations of loose sandstone under different stress states,and selects the modified Cambridge model as the constitutive model to describe the mechanical behavior of loose sandstone;Secondly,the finite element method was used to numerically simulate the crack propagation of loose sandstone under the coupling effect of seepage stress.The seepage changes during the compaction and hardening process of the rock in the early stage of fracturing and the shear expansion process of the rock in the later stage of fracturing were discussed,respectively;Finally,the effects of factors such as fracturing fluid displacement,crustal stress difference,and fracturing fluid viscosity on the propagation pattern and morphology of fractures were analyzed.The research results indicate that:(1)there is a certain good correlation between the permeability and porosity of loose sandstone reservoirs and overburden pressure.(2)Under uniaxial conditions,the rock undergoes compaction hardening before the peak and shear expansion after the peak.When the confining pressure and historical consolidation stress are similar under triaxial conditions,plastic compaction occurs inside the rock core.(3)In the early stage of fracturing,the rock near the perforation section will undergo compaction and hardening,leading to a decrease in rock pore volume,an increase in volumetric strain,and a decrease in permeability.As the fracturing fluid is injected,the stress path of the rock near the perforation section moves to the upper left until the rock undergoes shear expansion.When the fluid pressure exceeds the compressive strength of loose sandstone,the rock around the crack undergoes shear expansion and expansion,leading to an increase in rock volume strain and permeability.(4)As the displacement of fracturing fluid and the degree of difference in ground stress increase,the degree of shear expansion of rocks near the fracture increases,the volume strain increases,and the permeability also increases.The length and width of the fracture will increase,but the extent of the increase will decrease;The increase in viscosity of the fracturing fluid leads to a decrease in fracture length and an increase in fracture width,resulting in a decrease in the shear expansion of rocks near the fracture and a decrease in permeability.(5)When the difference in ground stress is relatively high,high displacement and high viscosity fracturing fluids can be used to fracture loose sandstone reservoirs,forming short and wide fractures to achieve sand control effects.Exploring the propagation law of fractures in loose sandstone reservoirs provides data support for future fracturing construction and sand control treatment in loose sandstone reservoirs,which has important theoretical significance and engineering application value.