A Non-Resistivity Approach for Estimating Water Saturation A Case Study in Niger-Delta, Nigeria

Abstract

The notion of Water Saturation is of importance in determining the hydrocarbon saturation (1-Sw) in reservoirs, calculating hydrocarbon in place, hence a vital evidence of reliable formation evaluation. Preconceptions in reserves quantification and hydrocarbon in place estimations arise once the outcome of the water saturation value is erroneous. Several models in the literature have been used for estimating water saturation and oftentimes the variance in confidence level of their results lead to substantial variance in original hydrocarbon in place volumes. Obtaining a better resolution with deeper understanding of the gaps observed in the existing approaches for estimating water saturation (Sw) values have been a major challenge in accurate calculation of hydrocarbon in place. This paper presents a non-resistivity approach for estimating water saturation using Leverett J-function and Reservoir Quality Index with dependency on fluid and facies Values. The innovative approach involves the use of Saturation Height Modelling through Leverett J- function, build facies through Magnetic Resonance Graphical-Based clustering (MRGC) option, use of Regression method and making a simple scripting using logging language (LOGLAN) program in Geolog to achieve the purpose. This current approach has been applied to Niger-Delta alternate shale-sand formation in optimisation of somewhat low recovery of the hydrocarbon reserves due to probably erroneous over estimation of Water Saturation value from Resistivity-based approach. Reliable results from current non-resistivity approach were obtained with average Water Saturation value of 25% as compared to resistivity approach presented by Juhasz with average water saturation value of 32% and non-resistivity approach presented by Brooks-Corey with average water saturation value of 26% and Leverett J- function with average water saturation values of 27% respectively.