An Innovative Approach to Evaluate Residual Oil Saturation in Insitu Condition

摘要

Residual oil Saturation plays a big role in simulation study for forecasting oil production. Generally it is determined through core flood experiments under reservoir conditions in small core plugs which do not capture the actual reservoir heterogeneity. More over it uses dead crude oil after matching the reservoir oil viscosity. Due to this, it is often difficult to generate representative ROS distribution throughout the field. There are other methods reported in the literature having some inherent limitations. Cased hole formation resistivity, a relatively new technology introduced in the industries to know the by passed oil in mature fields. It is mainly used for re-completion of old producing wells either through zone transfer or placement of horizontal wells. In this paper use of Cased hole formation resistivity in injectors having long injection history are conceptualized with the aim to get remaining oil saturation with respect to water injection in the formation. Due to prolong water injection / flushing it is expected that maximum water intake zone will show the oil saturation close to the residual oil saturation. The present paper discussed the results of two injectors where Cased hole formation resistivity along with injection profile were recoded. The oil saturation in the maximum water intake zone was compared with the residual oil saturation determined through laboratory established correlation based on core flood studies. The results indicate that the oil saturation is much lower than the core flood ROS in the reservoir area where maximum water has been injected. This adds a new dimension in determining the in-situ measurement of ROS. The interpretation issues like effect of injected water salinity etc are also illustrated in the paper.