Research On Macroscopic And Microscopic Damage Behavior And Laws Of Rock Mass Fractured By High Voltage Pulse Water Pressure

China's unconventional natural gas(shale gas,coalbed methane,etc.)has huge reserves and broad development prospects.However,because the pore cracks of most unconventional natural gas reservoirs in China are not developed,the permeability is extremely low,which is more difficult to develop than conventional natural gas reservoirs.Using the controllable and repeatable shock characteristics of pulsed discharge shock waves in water,high-voltage electric pulsed hydraulic fracturing is an important means to enhance the extraction of unconventional natural gas.However,there is still a lack of in-depth research on the precise evaluation of macroscopic and meso-damage behavior and fracturing effect of hydropneumatic pulsed fractured reservoirs.This is very detrimental to the application of high-voltage electric pulse hydraulic fracturing technology in the field of anti-conventional natural gas reservoir permeability enhancement.Therefore,further research is required to find the evaluation of reservoir fracture-induced permeability enhancement damage behavior and crack expansion,evolution,and distribution laws.In this paper,by studying crack damage initiation,fracture criterion and stress-strain equivalence principle,the macro and meso damage damage variables of rock mass under different loading conditions of high pressure electric pulse water pressure fractured rock mass are derived,and the fluid-electric coupling damage constitutive is established.The model and loss constitutive equation,combined with the hydraulic piezoelectric pulse physical test and numerical analysis,reveal the crack propagation law of the rock piezoelectric pulse.The main achievements are as follows:(1)Summarize and summarize the existing widely used hydraulic fracturing rock technology at home and abroad,and compare and analyze the feasibility and superiority of the high-voltage electric pulse hydraulic fracturing technology independently developed by the research group in the practical application of the project(2)Theoretical derivation of the damage constitutive equation and damage variable expression of the rock sample in the hydroelectric coupling state,and nesting it into the numerical simulation process,the damage variable results obtained by the numerical simulation and the experimental results The data obtained are in good agreement,which verifies the correctness of the constitutive equations and the expression of damage variables.At the same time,the numerical simulation and test results can accurately and quantitatively represent the development of the internal cracks in the rock sample;(3)high-pressure electric pulse water pressure fracture In the process of rock mass,the closer the rock mass is to the borehole,the greater the disturbance,the larger the rock mass damage variable,and the more obvious the crack width expansion.The farther the distance,the smaller the rock mass damage variable and the narrower the crack width.Due to the volatility of the water shock wave,with the increase of the electric pulse load,the crack width of the rock mass in the detection area shows an uneven fluctuation change;(4)keep 3MPa static Pressure,respectively applied on rock 7kV,9kV,11 kV,13kV discharge voltage,the peak shock suffered rock stress,effective stress,damage variable parameters increases as the discharge voltage increases,and the rate of increase significantly.Keeping the loading voltage at 11 kV unchanged,changing the loading of the system hydrostatic pressure,the damage variables and other parameters are also positively related to the loaded hydrostatic pressure,but the damage variable has a limited change range,and the rock mass damage does not change significantly,indicating that the high-voltage electric pulse in the water The damage and impact of the body is better.The effect of high-voltage pulsed hydraulic fracturing rock mass is far superior to the traditional hydraulic fracturing technology.