Study On Flow Field Evaluation And Adjustment Method Of High Water Cut Reservoir

After decades of development,most domestic water drive oilfields have been in the stage of high recovery and high water cut.After long-term water injection development,the distribution form of reservoir flow field is fixed and increasingly complex.Because the flow field controls the distribution of remaining oil,it leads to low efficiency circulation of injected water and restricts the excavating remaining oil and the improvement of oil recovery.Due to the lack of research on flow field evaluation by domestic scholars and abroad,a complete flow field evaluation system has not been formed.Therefore,establish a complete flow field evaluation system suitable for high water cut reservoir,implement appropriate flow field adjustment measures and predicate upon the evaluation system play an important guiding role in excavating remaining oil and improving the reservoir development effect.By analyzing the influencing factors of reservoir flow field,this paper puts forward that the flow field parameters can be divided into control parameter field and displacement parameter field.The evaluation indexes of different parameter fields are selected by factor analysis.The membership function is used to normalize the evaluation index values,and the analytic hierarchy process is used to determine the weight of each evaluation index,so as to realize the characterization of the flow field parameter field.The Mahalanobis distance function is used to calculate the oil phase matching degree and water phase matching degree between the parameter fields,so as to establish the flow field evaluation system of high water content reservoir.Based on the results of flow field evaluation and taking Chengdong reservoir as the research object,it is proposed that injection production optimization and well pattern adjustment are effective methods to improve the flow field distribution and the degree of remaining oil production.In the process of injection production optimization,the injection volume and liquid production are taken as variables,and the maximum cumulative oil production is taken as the objective function.The mathematical model of injection production optimization is constructed.The improved ant colony algorithm is used to solve the model,and the optimal injection production scheme is obtained.Well pattern thinning and well pattern type adjustment carried out in well pattern thinning.In the well pattern adjustment,the well pattern thinning and well pattern type adjusted.In the well pattern thinning,the development effects of the original injection production well pattern and six different thinning schemes are compared.In the well pattern type,the development effects of the original irregular well pattern and five point well pattern,nine point well pattern and straight line well pattern under the optimal thinning scheme are mainly compared.Finally,the development effect is affected by the change of reservoir matching degree before and after optimization.The results were verified.The results show that the proposed flow field evaluation system of high water cut reservoir can quickly and accurately calculate the matching degree of each layer,so as to screen out the sub layers that need to be adjusted,which provides a fast and accurate method for reservoir flow field characterization and evaluation.Injection production optimization and well pattern adjustment measures can effectively improve the reservoir development effect and flow field distribution of each sub layer.The cumulative oil production corresponding to the optimal injection production optimization scheme is 2.0906×10~7 m~3,which is increased by 17376 m~3and water cut reduced by 0.0287%compared with the original development scheme.The existing well pattern is diluted by 10%with the well pattern type changed to five points method is the optimal well pattern adjustment scheme.Cumulative oil production is 2.0939×10~7 m~3.Compared with the existing well pattern development scheme,the cumulative oil production is increased by 50356 m~3 and the water cut is reduced by 0.337%.At the same time,the flow field evaluation system is used to verify the development effect,which proves that injection production optimization and well pattern adjustment can improve the distribution of reservoir flow field,improve the utilization degree of remaining oil,fully tap the potential of remaining oil and improve the reservoir recovery.