Water saturation calculation using fractional flow and production logging data in a Caspian region sandstone petroleum reservoir

Abstract

Water saturation in porous media plays a significant role in static, dynamic reservoir modeling and petroleum reserves calculations. In this paper, a Pliocene conglomerate type of sandstone Caspian reservoir was studied. The objective of this paper is to apply water saturation calculation method using fractional flow and PLT (Production Logging Tool) and to compare the results with other methods. In this study, 6 petrophysical rock typing were defined by two methods at log level using the porosity, water saturation logs and RQI(Reservoir Quality Index). Core porosity and permeability correlations were calculated for each rock type where k-phi transforms were generated, respectively. Relative Permeability data of the reservoir was classified based on the rock types. Oil-Water relative permeability ratios versus water saturation data were correlated exponentially. A solution for water saturation was derived at log level using fractional flow, relative permeability, core porosity, permeability and production data. Leverett-J function and Archie saturations were calculated to compare to the proposed fractional flow approach. The comparison of the saturation logs with J-function and Archie saturation showed good match. This approach can be considered as a tool to validate the saturation-J function. This methodology helps to estimate pre-production water cut performance of the wells in reservoir models considering that not all the wells will start flowing at 100% dry oil. The employed methods regarding the petrophysical rock typing and water saturation calculations will facilitate reservoir characterization for future field development activities.