Research On The Dynamic Evolution Of Stress And Hydraulic Fracture Propagation Of Xinjiang Glutenite Reservoirs

Glutenite Reservoirs in the northwest of the Junggar Basin in Xinjiang are widely distributed,with enormous development potential.However,the reservoirs have problems such as low porosity,low permeability,and lack of natural fractures.Hydraulic fracturing technology is indispensable for efficiently developing oil and gas resources.In recent years,with the advancement of technology and accumulation of experience,oil companies have experienced the process from initial large well spacing to infill small well spacing and from single well deployment to "well factory" deployment.During this period,the stress is not fixed but a dynamic process.Ground stress affects the geometry of hydraulic fractures and is a critical parameter that cannot be ignored in the study of fracture propagation.In the early stage of development,when the well spacing is large and the well interference is not apparent,the original in-suit stress controls the propagation of hydraulic fractures.As the development progresses,the production of parent wells leads to pressure depletion,which changes the stress and affects the fracture geometry of infill wells.In addition,fracturing causes dynamic evolution of the stress field,and under the "small well spacing + well factory" fracturing scheme,well interference gradually becomes a non-negligible factor affecting the fracture propagation of neighboring wells.Therefore,describing the distribution and dynamic changes of the ground stress in different development stages of gluenite reservoirs and predicting the fracture geometry under different stress conditions are vital challenges.This article systematically researches the dynamic evolution of the stress in gluenite reservoirs and the propagation of hydraulic fractures:(1)Construction of initial 3D in-situ stress model and the propagation of hydraulic fracturesBased on lab experiments and field test data,a standardized process and method for constructing a geomechanical model are proposed.A finely detailed 3D in-situ stress model is constructed to clarify the stress distribution.The hydraulic fracture propagation under the initial stress is revealed using true triaxial hydraulic fracturing experiments and a 3D FEM fracture propagation model.A comprehensive prediction model of reservoir fracture geometry is formed.(2)Dynamic evolution of stress under production and the propagation of hydraulic fracturesBased on the RANSC algorithm and linear regression algorithm,the fracture network of parent wells is reconstructed.A discontinuous discrete fracture model is established to investigate the dynamic evolution of stress under the influence of production,fluid injection,and stoker process in old wells and then analyze the fracture propagation of infill wells.A method to determine the injection volume of the parent well is established to reduce the negative impact of production interference between wells effectively.(3)Dynamic evolution of stress under fracturing and the propagation of hydraulic fracturesA multi-well fracture propagation model based on the XFEM and CZM was established to clarify the dynamic evolution of pore pressure and ground stress during fracturing.The effect of fracturing sequence and perforation location on the propagation and geometric shape of fractures of multiple horizontal well groups is explored.A comparative analysis of the reservoir stimulation effect of different fracturing schemes is conducted,and a multi-well fracturing scheme for obtaining optimal effects is proposed.