Research On The Mechanism And Application Of Periodic Water Injection In Ultra-low Permeability Reservoirs

As the increasing demand for petroleum energy,the reserves of conventional oil reservoirs continue to decrease.The efficient development of ultra-low permeability oil reservoirs has become a new problem.Ultra-low permeability oil reservoirs are rich in China.Due to the characteristics of difficult reservoir development,periodic water injection is an effective method to improve the recovery of ultra-low permeability reservoirs.Periodic water injection can change the pressure of the formation during the water injection cycle,forming large pressure fluctuations and increasing the sweeping volume.Therefore,it is of great significance to conduct theoretical research and parameter design for ultra-low permeability reservoirs.By studying the pressure changes between injection and production wells,the displacement effect and sweep volume of the formation in the two stages of periodic water injection are analyzed.The analysis considers that the ultra-low permeability reservoir is an overall homogeneous and partially heterogeneous formation,which is generally circular during water injection In some areas,the intrusion will occur,so the pressurized injection in the first half of the injection cycle can increase the displacement area,and the pressure drop in the second half of the cycle can increase the longitudinal sweep volume.Analyze the analysis of the pressure distribution between wells in the pressurization and depressurization phases in the first cycle and the two different situations after multiple cycles,the analysis of the distribution of formation streamlines and the effective displacement pressure drop,and consider the periodic water injection scheme that best fits the ultra-low permeability reservoir parameter.Establish an ideal model for ultra-low permeability formations.Through numerical simulation,periodic water injection was carried out in different water injection stages,the influencing factors of water injection in different periods were analyzed,and the parameters of water injection were optimized.The laboratory experiment of periodic water injection is carried out.The actual situation of ultra-low permeability reservoir is simulated by using the field core.The experimental design is carried out on the basis of the theory,the influence of the injection timing,the injection intensity and the injection period on the whole process of the two stages of periodic water injection,and a better scheme to improve the production efficiency is given.Finally,the actual model of the stratum is established according to the actual parameters of the LPY stratum,the period parameters are optimized for this area,and the production effect is predicted to analyze the parameters of the injection well injection pressure and water injection period during actual production,and then given The optimal periodic water injection scheme for ultra-low permeability formations.The optimal scheme for this development area is to increase injection for 20 days,reduce pressure for60 days,increase injection pressure of 14 MPa,and reduce pressure of 2 MPa.