| After long time water injection,at present the contradiction of oilfield development that high produced fluid and water cut and low reservoir developed degree is exposed in Unit 1-9oil layer,Sa II Group,western area of Array I-II,Bei I Block of Sazhong Development Zone and Gaotai Reservoir as well.Based on abundant static and dynamic data under infill well pattern,with the techniques of fine reservoir description,high precision dynamic monitoring as well as stimulation modeling,sound development adjustment method is designed according to two target layers with different reservoir characteristics to further produce the remaining oil.On the basis of fine study on plane sedimentary facies of different units in the target layer and summarizing sand body with various distribution characteristics,reservoir produce degree,type of remaining oil and its distribution,it is found that the developed degree in Unit1-9 oil layer,Sa II Group is 40.9%.Its remaining oil can be divided into three types---out of well pattern control,incomplete water driving and producing and the top of thick oil layer,which is mainly distributed in narrow,small channel sand,lump-shaped sheet sand,edge part of large,wide channel sand and top of thick channel sand;As for Gaotaizi Reservoir,whose produced degree is only 30%,its remaining oil can be divided into three types as well---out of well pattern control,incomplete water driving and producing and narrow,small channel sand,which is mainly distributed in narrow and lump-shaped underwater distributary channel,lump-shaped sheet sand and untabulated sheet sand.Three sets of development adjustment methods are designed respectively on the basis of fine geologic study and stimulation modeling as well as the development experience of neighboring block with similar reservoir characteristics.The most reasonable and economic adjustment method is selected based on study on adjustment target and method,oil layer combination,development sequence and well pattern adaptability.That is,in terms of Class II reservoirs in Unit 1-9 oil layer,Sa II Group,whose reservoir development is relatively good,re-perforation upwards is carried out to the original polymer injection wells in the oil layer 10Sa II-Sa III,while five-spot polymer injection well pattern is adopted,with producer-injector spacing of 175m;As for Gaotaizi Reservoir with poor reservoir development,five-spot infill well pattern is used to improve development degree,with producer-injector spacing of 175m.In this paper,study on reasonable parameter matching while polymer injection is conducted in Unit 1-9,Sa II Group,including type and molecular weight of polymer,injection concentration and injection rate and so on.Also it's the first time to explore the development result by using oily water to prepare salt-resistant polymer,in this way to solve the problem of too much oily water produced from the development.By optimizing on the development adjustment and stimulation modeling,it is predicted that the EOR of Class II Reservoir in Unit 1-9,Sa II Group by tertiary recovery and that of Gaotaizi Reservoir by infill wells can be13.8 and 3%,with increased recoverable reserve of 170.74×10~4t and 23.8×10~4t,respectively.Evaluation on the economic benefit of the target layer is conducted and remarkable economic benefit is expected. |
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