Study On The Evaluation Of Differentiated Water Flooding And Measures For Injection-production Adjustment Of ChunHua Low Permeability Reservoir

Low permeability reservoirs are an important part of China's oil and gas resources.After years of development,the underground situation is further complicated,the difficulty of improving oil recovery is increasing year by year.The Chun Hua oil field is a typical multi-layer low permeability reservoir with the characteristics of complex lithology and serious heterogeneity,and it is resulting in significant flow difference between vertical layers,reserves producing nonuniformity problems.Therefore,studying the flooding law between the layers in the vertical direction,the distribution of remaining oil and the corresponding transformation measures are the key points of current enhanced oil recovery work.Based on the current development of Chun Hua oil field,this dissertation extracts the feature data from the most representative block to establish a conceptual mechanism model that reflects the characteristics of oilfield development.Exploring the relationship between vertical flooding law and permeability difference,layer combination and water flooding degree under the different development stages and different water conditions to find typical flooding patterns and characteristics.Exploring the influence of layer combination method on water flooding effect and finding the best combination of vertical water injection system by comparing technical indicators and economic indicators.Comparing the development effect between continuous water injection and cyclic water injection by designing an orthogonal test protocol with multi-factor and multi-level to get the boundary standard of injection-production coupling mode.The results show that the heterogeneity of layer permeability is the main reason for the difference between the flooding conditions and the remaining oil distribution.The vertical flooding condition has a relationship with reservoir permeability contrast.The smaller the difference in permeability,the smaller the difference in flooding between layers.After the permeability contrast is more than 4 times,the difference of longitudinal flooding increases rapidly;When the reservoir is in a low water-bearing stage,the difference in flooding between layers is small,the permissible permeability contrast is 10;As the water content rises,the difference of interlayer flooding is affected by permeability contrast,the difference in interlayer flooding will increase affected by the permeability difference,the permissible permeability contrast will decrease.Interlayer permeability difference should be controlled within 3 times to keep the longitudinal flooding uniform when the water cut of the reservoir exceeds 80%.Therefore,it is necessary to reduce water flooding difference by dividing the layer system combination.According to the vertical flooding difference and the influence on ultimate recovery,9 layered water injection schemes with different layer combination have been selected,the layered water injection scheme“C1,C2-C3,C4-C5 with two levels and three stages” is selected as the final plan by comparing technical indicators and economic indicators.An orthogonal test protocol with four factors and four levels is designed to find out the best cyclic water injection scheme with the recovery ratio as screening indicator,and the sensitivity of influencing factors is analyzed range method.After comparsion,the best cyclic water injection scheme is “start when the water cut is 82%,with the relative fluctuation range of water injection is 0.8,and the period is increasing water injection for 60 days,decrase water injection for another 60 days,the production wells and the injection wells share the alternating cycle working system”.The recovery ratio is 35.71%,increase by 1.14%,compared with continuous water injection scheme.