Numerical Simulation And Flow Field Evaluation Considering Physical Properties Time Variation For Waterflooding Reservoir

After years of development,many old oil fields have entered ultra-high watercut stage,the distribution of remaining oil is highly dispersed,and subsequent development is difficult.Due to reservoir heterogeneity,displacement,both in plane and longitudinal direction,is not uniform,the difference caused by displacement will result in heterogeneity of the flow field distribution.After long-term waterflooding,physical properties of reservoir at ultra-high watercut stage have changed a lot,and reservoir heterogeneity becomes more and more serious,which furtherly exacerbate the spatial differences of flow field,resulting in increasingly prominent development contradictions.As the injection and production well net doesn't change,streamline stay the same for a long time,resulting in a large number of inefficient displacement,even inefficient water cycle.Therefore,on the basis of accurately predicting the distribution of residual oil,by optimizing liquid production structure,formating new flow order is the necessary measure to tap the remaining oil.By means of mine statistics and laboratory experimental study,we clarified the law of reservoir properties time variation after waterflooding,and summarized the variation mechanism.By analyszing problems of the existing methods in characterizing physical properties time variation,a new method was put forward to characterize physical time-varying properties based on surface flux,which realized the quantify,continuity,directivity and stability on physical properties time variation describtion.By means of traditional black oil model transformation and software programming,new mathematical model and numerical model were established,and corresponding numerical simulation technology was realized as well,which can solve the problem that commercial numerical simulation software can not consider reservoir property time variation.Then reliability of the software was verified by using conceptual model and actual mine mode.Effect of permeability and relative permeability variation on development was analysized by using the software.After applying the software on actual model,the historical fitting effect was improved obviously.By analysizing shortcomings of existing flow field evaluation method,it was proposed to use surface flux to characterize flow field.Then we defined flow field strength with normalized surface flux through membership function,and classified it through Fuzzy C homogeneous cluster analysis,which could eliminate the randomness and experience dependence of conventional aclassification methods,thus a complete flow field evaluation system was established.Development of physical property time variation numerical simulation software and flow field evaluation system provide the direction for liquid production optimization and remaining oil tapping.Results of the study were verified by A oil field,and the remaining oil distribution was obtained after historical fitting.According to the surface flux,flow field was evaluated,and then adjustment strategy of liquid production structure was made,which tapped the remaining oil effectively.