New Integrated Capillary Pressure and Initial Water Saturation Modeling

Abstract

Abstract This paper presents a new capillary pressure model, integrated and consistent capillary pressure modeling, and initial fluid saturation along wells and in reservoirs. The new capillary pressure model is obtained by fitting Pc curves, end Pc values at end saturations, and threshold entrance Pc values satisfactorily. Analytical Pc derivative is then obtained. A consistent Pc derivative value can be used to obtain irreducible water saturation and corresponding maximum capillary pressure. After Pc curve fitting for multiple cores, correlations can be developed for the parameters in the new Pc model with different reservoir rock types and reservoir properties. The new capillary pressure model is then used with free water level and reservoir fluid gravity to obtain the initial water saturation at any place in the reservoir. The initial water saturation vs. depth obtained dynamically from the new Pc model is integrated with that obtained statically from logs to achieve the integrated, reconciled, and consistent initial water saturation vs. depth. Real examples are presented to show the step by step workflow procedure to obtain the new capillary pressure model and the integrated initial water saturation vs. depth. These examples include SCAL Pc curve data from cores and log Swi data vs. depth from wells in two offshore reservoirs. This paper has three significant technical contributions. The new capillary pressure model is more versatile than those published and can handle Pc data while other existing Pc models cannot. The analytical Pc derivative from the new capillary pressure model can provide a consistent criterion for obtaining irreducible water saturation and maximum capillary pressure values for different rocks. The new capillary pressure model, when integrated with initial water saturation vs. depth from logs, can provide a consistent initial fluid saturation distribution in integrated static and dynamic reservoir modeling.