A Method to Determine the Layered Injection Allocation Rates for Water Injection Wells in High Water Cut Oilfield Based on Displacement Quantitative Characterization

After reservoirs with multi-layer commingled production enter the high water cut stage,the interlayer displacement disparity is increased and the effect of commonly used layered injection allocation method is deteriorated.Through the analysis of the characteristics of long-term water flooding in reservoirs,a quantitative characterization method using displacement flux to describe the displacement disparity among each layer was put forward.Aiming at balancing the displacement,a new method was established to determine the injection allocation rates for water injection wells based on the idea of displacement flux balance,which took into consideration the influence of reservoir thickness,porosity,water injection history and adjustment cycle.The fine reservoir numerical simulation technique was used to analyze the adaptability of thickness method,formation coefficient method,remaining oil method and the new method at different water cut stages.Numerical simulation results showed that the thickness method is to be recommended when the water cut is less than 50%.When the water cut is from 50% to 80%,the remaining oil method is recommended,and when the water cut is in the range of 80%-90%,the new method can be recommended.The new method was applied to the well group X1 in the Bohai SZ Oilfield as the pilot test and had significant effect,with the average water cut decreased by 4% and daily oil production increased by 117 m3.The research results indicated that the new layered injection allocation method with displacement quantitative characterization could be effective in guiding the optimization and adjustment of the allocations rates in reservoirs under high water cut stage.