地下水侵入对三间房组油藏油水界面的影响

INFLUNCE OF GROUDWATER ENCROACHMENT ON OIL-WATER CONTACT IN SANJIANFANG RESERVOIR

鄯善油田经过10多年开发,地层水的分布状况变得比较复杂。近期新钻加密井发现三间房组油藏油水界面分布特征与开发初期所认为的情况有明显差别,整体呈北高南低、西高东低特点。对油水界面变化情况及地层水矿化度、化学成分、水型等资料分析表明:自北向南地层水矿化度逐渐升高,水型也由NaHCO3型逐渐过渡到CaCl2型。通过对地层水中不同类型离子的组合特征及含量变化分析,结合邻区地层水分布特征,认为造成目前油水界面分布状态的主要原因是地下存在一个水动力系统,自西北部侵入鄯善油田,使西区、北区油水界面严重抬升,地层水矿化度及化学成分也发生了相应变化。为油田确定今后新钻加密井的井深及提高水淹层解释的符合率提供了有力的依据;同时也为分析油水界面变化的影响因素提供了一个新思路。

After ten years′ development, the distribution of formation water in Shanshan oilfield becomes complicated. In recent years, it can be found that there is an obvious difference between the present oil-water contact and the past one by the drilling of new infilling wells in Sanjianfang reservoir; and in the whole, the oil-water contact takes on a new situation that is high in the north and low in the south, high in the west and low in the east. The research on distribution of oil-water contact, salinity, chemical composition and aqueous phase of the formation water indicates that from north to south the salinity becomes higher, the aqueous phase changes from NaHCO3 to CaCl2. Through the analysis of combination and content change of the different ions in formation water, combining with groundwater distribution characteristics of adjacent area, it can be concluded that a underground hydrodynamic pressure system results in the present oil-water contact distribution. It encroaches from the north-west and raises the oil-water contact in the west and the north area, also results in the change of salinity and chemical composition in formation water. This research sets up a solid foundation for the deployment of the new infilling wells and the study of water invasion for the reservoir in the future, at the same time, it provides a new idea for the explanation to the change of oil-water contact.