Research On Optimization Of Reservoir Engineering Parameters In Deep-buried Low-permeability Reservoirs By CO₂ Flooding

The Y21-22 fault block in Dagang Oilfield has a complex fault structure with an average buried depth of 3800 meters and an average permeability of 1 md.It is a typical low-permeability fault block reservoir.Due to the complex formation faults and poor physical properties of the reservoir,the Y21 fault block has been produced by water injection for 8 years and its recovery rate is only 4%.At present,there are problems of severe reservoir water sensitivity and excessive injection pressure.Gas flooding is an effective method to improve the development effect of low permeability reservoirs.Co MPared with traditional flooding methods,gas flooding has strong injection ability,high flooding efficiency,and no water sensitivity.Therefore,this paper takes the Y21-22fault block as the research object,and uses numerical simulation as a means to research on CO₂ flooding development parameters and effect evaluation.First,by analyzing the geological and fluid characteristics of the target block,it is clear that the target block is suitable for CO₂ flooding.Secondly,a CO₂ minimum miscible pressure neural network prediction model for Y21-22 fault block was established,which provided a convenient tool for future development to grasp the degree of miscibility in time.After that,a hydraulic fracturing-CO₂ flooding mechanism model was established,and the influence of the main factors on the ultimate recovery factor was studied.The Latin hypercube sampling experiment was used to design and study the main control factors at different times during development,providing theoretical guidance for future development adjustments.Finally,the geological model and numerical model of the Ye 21-22 fault block are established,and multiple development schemes are designed for the Ye 21 fault block and the Ye 22 fault block,respectively.The development parameters of the optimal solution are optimized,and the development effect of the optimal solution is predicted.The results show that the production wells use highly deviated wells,and hydraulic fracturing in the early stage to compensate for the initial production development method can not only obtain the optimal final recovery rate,but also achieve stable production in the early development stage.The average recovery efficiency of the block reached 23.9percentage points.