Study On The Adaptability And Evaluation Of Gas Injection Development In Tight Reservoir

The permeability of tight reservoir is very low,the pore throat is small,the microfracture is developed and the heterogeneity is strong.The recovery rate of conventional development method is low.After years of research,gas injection technology has become an important method to improve oil recovery.However,at present,most of the gas injection technology remains above 1×10^-3?m²,and there are few studies on the tight reservoir.The gas medium is mainly CO₂ and N₂.However,CO₂ is often insufficient in the actual oil field,while CH₄ is sufficient.Therefore,it is urgent to study gas injection in reservoirs with permeability less than 1×10^-3?m².In this paper,the effects of gas injection in tight core under indoor conditions are studied,which are mainly divided into pure gas flooding and mixed gas flooding experiments.And from the point of view of improving the physical properties of oil and water,the principle of mixture gas flooding is studied and analyzed.Finally,numerical simulation is carried out to evaluate the effects of gas injection development from different angles.Firstly,the gas flooding experiment of a single medium is carried out by using the tight core obtained from the field.Phase permeability curve and oil displacement efficiency of N₂,CO₂and CH₄ were studied respectively.And compared with waterflood displacement,the experiment proves that the injection of CO₂and CH₄into the tight reservoir can achieve high oil displacement efficiency.Then the mixed gas flooding experiments were carried out,including the mixed gas flooding experiments of CO₂ and N₂,CO₂ and CH₄.In addition,the reasons for the enhanced recovery of CO₂ and CH₄ hybrid flooding were studied from the perspectives of improving interfacial tension,density and viscosity.Finally,the numerical simulation software is used to build the model with the experimental data.The daily oil production,cumulative oil production,production degree and uplifted formation pressure are studied.Gas injection development was evaluated from different angles such as injection mode,mixture ratio and injection time.The research results of this paper have certain guiding significance for gas injection development in tight reservoir.