Flow Field Characterization And Regulation Methods For Waterflooding Reservoir

At present,many old oil fields in China have entered the stage of ultra-high water cut.The injection-production streamline has been fixed for a long time,the injected water is inefficient,and the remaining oil is highly dispersed and locally concentrated,which aggravates the imbalance of underground oil production.In the current waterflooding reservoir flow field evaluation,the evaluation indexes are not unified,and the evaluation methods have great uncertainty.In addition,the optimization results of injection-production optimization problems are still limited by the evaluation methods of the reservoir development effect and optimization algorithms.How to reduce the running times of reservoir numerical simulator and what efficient optimization algorithm to adopt are the problems that need to be solved at present.Therefore,based on the streamline numerical simulation method,this paper studies flow field characterization and regulation methods for waterflooding reservoir.Firstly,according to the basic principle of streamline numerical simulation,the fluid attribute data distributed along the streamline trajectory in the flow field was extracted,and the flow field characterization index reflecting the water drive capacity of each streamline was constructed,and the flow field characterization method based on streamline characteristic parameters was formed,and the reliability of the method was verified.On this basis,the flow field evaluation index system was constructed,and the DPCA algorithm was used to cluster the streamlines according to the spatial location and fluid properties,and the clustering effect was evaluated by the SC method,forming the flow field evaluation method based on streamline clustering in waterflooding reservoir.The flow field evaluation method carried out a fine description of flow field,and summarizing and proposing corresponding flow field adjustment countermeasures.Thirdly,with the goal of maximizing the potential coefficient of the instantaneous flow field and the constraints of production process as constraints,a mathematical model of injection and production optimization efficient regulation was established.Considering the characteristics of optimization problem and optimization algorithm,the BADS optimization algorithm was constructed by coupling Gaussian process and MADS algorithm,and the treatment method of constraint conditions was selected and determined.A set of injection and production optimization efficient regulation methods is formed.The performance of the common algorithm and BADS algorithm is compared and analyzed by using the EGG model.On this basis,the differences between the established injection-production optimization method and the traditional method in optimization results and solution efficiency are analyzed.Finally,the above methods were applied to a real large-scale reservoir,and the flow field evaluation and injection-production optimization control scheme were studied.The reasons and mechanism of waterflooding effect improvement before and after optimization were analyzed in depth.The results show that the instantaneous flow field potential coefficient can quickly reflect the long-term development effect of waterflooding reservoir and provide a performance index for injection and production optimization regulation.In the study of flow field evaluation method,the streamline clustering method is used to effectively identify the low-efficiency water injection cycle area and development potential area in the reservoir,which can better describe the evolution process of flow field,and put forward the corresponding flow field adjustment countermeasures,and further provide scientific decision-making for injection and production optimization regulation.In the study of injection-production optimization regulation,the established injection-production optimization method only needs to call the streamline simulator to simulate one time step at each iteration,and it does not need to simulate to the end of development.In other words,on the basis of satisfying the solution precision,the calculation time is greatly reduced,which can provide a feasible way for injection and production optimization of large-scale actual water drive oilfield.