Study On Development Rule And Adjustment Strategy Of Toothbrush Edge-water Reservoir

Toothbrush edge-water reservoir is defined as a toothbrush shaped edge-water reservoir with thin reservoir thickness and distributed along fault edges.Compared with conventional multilayer edge-water reservoirs,these reservoirs have a smaller trap size and thinner single layer thickness.During the development of this type of reservoir,the water cut increases rapidly,the production decreases rapidly,and the development law is quite different from that of conventional edge-water reservoirs.Therefore,it is urgent to clarify the influencing factors of recovery efficiency,development technology policy and remaining oil distribution mode of toothbrush edge-water reservoirs,so as to lay a foundation for development adjustment.In this paper,reservoir engineering method and reservoir numerical simulation method are used to study the development law and adjustment strategy of toothbrush edge-water reservoir.The understanding and conclusions are as follows:(1)The geological characteristics of toothbrush edgewater reservoir are analyzed and summarized,including the definition of toothbrush reservoir,structural characteristics,reservoir characteristics,reservoir heterogeneity characteristics and development characteristics.(2)Three typical mathematical models of water flooding are analyzed,the characteristics,adaptability and limitations of the three typical mathematical models are summarized and compared,and the key parameters of the three typical models are calculated in combination with specific numerical values.The numerical model of a typical toothbrush edge-water reservoir is established,and the factors affecting the development effect of the toothbrush edge-water reservoir are analyzed according to the actual block dynamics.Based on the single variable principle,seven factors affecting the recovery efficiency of toothbrush edgewater reservoir are analyzed.The first three factors are water multiple ratio,well location and oil-water viscosity ratio,followed by the number of bristles and the amount of constant liquid.However,the single oil layer thickness and formation Angle have relatively little influence on the recovery efficiency of toothbrush edgewater reservoir.(3)On the basis of clear geological characteristics and influencing factors of recovery efficiency,the development technology policy of toothbrush edgewater reservoir is demonstrated from the aspects of stratification,reasonable development mode,reasonable well pattern form,reasonable well spacing,reasonable working system,reasonable water injection strategy and reasonable development strategy.The results show that in the initial stage of reservoir development,the optimal development mode is to use layer by layer up-return,triangular well pattern with well spacing from 200 m to250m,daily fluid volume from 50m~3 to 100m~3,and injection-production ratio of 0.5.In the later stage of development,the reservoir recovery can be further improved by local oil and water well encryption,local well spacing to 150 m and injection-production ratio to 0.7.(4)The numerical model of toothbrush edgewater reservoir in typical blocks is established and historical fitting is carried out.The distribution law and distribution mode of remaining oil in toothbrush edgewater reservoir are analyzed,and four remaining oil distribution modes are proposed.Based on the conclusion of influencing factors of recovery efficiency,the results of development technology policy demonstration and the law of remaining oil distribution,the development adjustment scheme of typical blocks is prepared and predicted.The results show that the combination of local well pattern encryption,increasing injection-production ratio and layer-by-layer up-return development is the best development adjustment scheme.