Abstract:

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 NaHCO3 to CaCl2. 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.

Key words: Shanshan oilfield, formation water, oilwater contact, hydrodynamic pressure system, influence factor