Study On The Numerical Simulation Mechanism Of CO₂ Injection For EOR In Dense Water Bearing Condensate Gas Reservoir

With the national energy structure adjustment and the decline in domestic oil reserves.Relying on its characteristics of being cleaner,cheaper,and richer in reserves than oil,natural gas has played a pivotal role in the country's implementation of clean energy development strategies.As a result,the exploration of the development methods and methods of natural gas has become more in-depth.As a special natural gas reservoir,condensate gas reservoirs have complex phase characteristics,which makes them more demanding than ordinary dry gas reservoirs.Complex mining methods.In the development of condensate gas reservoirs,the phase characteristics of the condensate gas system need to be taken as the primary consideration,but due to the complexity of the corresponding influencing factors,the phase characteristics of the condensate gas cannot be accurately predicted during the development process.Change,which makes it impossible to accurately formulate an efficient development plan.In this paper,a series of studies are conducted on special condensate gas reservoirs,such as tight water-containing condensate gas reservoirs,to summarize and summarize the effects of factors such as tight reservoirs and water vapor in the condensate gas system on the condensate gas phase characteristics.Therefore,the study of the phase change characteristics of multi-factor effects in condensate gas reservoirs will be realized,which will have far-reaching significance for optimizing the development of condensate gas reservoirs.In this paper,the CT microscopic observation experiment of the condensate gas system in porous media is used to realize the difference between the condensate gas phase changes in real porous media and the condensate gas phase changes in traditional PVT experiments that do not consider the effect of capillary forces in dense reservoirs.Show.However,because CT microscopic observation experiments cannot describe and quantitatively characterize the limitations of the phase characteristics of condensate gas in porous media,this paper uses a PR equation with improved capillary force to quantitatively characterize the gas phase characteristics of condensate in porous media.Firstly,the flash vapor phase simulation and PVT experimental simulation of condensate gas were carried out in a single hole,and the condensate gas phase characteristics and physical property changes considering the influence of capillary force were explored.Secondly,microstructures reflecting the connectivity of different pore throats were constructed.Phase characteristics of the condensate system were simulated in the pore model.The simulation results show that the stochastic fractal network model reflecting the characteristics of real reservoirs can better reflect the comprehensive influence of pore throats on the phase state of the condensate system than the simplified microscopic model.The dew point pressure and the amount of condensate oil calculated by the microscopic network model are higher.,Further explained the experimental phenomenon of CT microscopic observation experiment of condensate gas system in porous.Furthermore,the compression factor of the condensate gas containing water vapor and other parameters are modified to introduce the consideration of the water vapor content in the system based on the numerical phase characteristic model of the condensate gas.Using the modified model,the flash vapor phase simulation and PVT experimental simulation of water vapor in the condensate gas system were first performed to explore the gas phase characteristics and physical property changes of the condensate gas under the influence of water vapor;then combined with the previous reflection of the truth The random fractal network model of reservoir characteristics performs flash phase simulation and PVT experiment simulation under the influence of multiple factors to realize the simulation of phase characteristics of the condensate system under the influence of multiple factors.The mechanism of CO₂ flooding and the effect of CO₂ on the gas phase characteristics of condensate were also studied.Finally,the fractal characterization of porous media permeability,porosity,and phasepermeability curves was performed using the relevant parameters of the random typing network,and the calculation results were used to establish a model for numerical simulation of the reservoir.In addition,phase state fitting is performed based on the physical properties of the condensate gas system considering the influencing factors obtained by the numerical calculations in the foregoing to generate a pseudo-component model that meets the corresponding conditions.The above model is used for the numerical simulation calculation of single well depletion production,single well throughput with different CO₂ injection rates and single well throughput with different CO₂ injection volumes.The research results provide theoretical support for the phase characteristics and dynamic prediction of water-containing steam condensate gas reservoirs in tight reservoirs.