A New Approach to 3D Saturation Height Modeling by Coupling a Capillary Pressure Model with Pore Throat Size Distribution

Propagation and upscaling of water saturation in a geological model are crucial in reservoir evaluation and volumetric calculations. Upscaling of saturation in heterogeneous carbonate reservoirs poses significant problems due to extensive lateral variations in reservoir properties. In this study, a new approach was developed for 3D saturation height modeling based on the relationship of pore throat size distribution (PTSD) with porosity and permeability via the Winland equation. An existing capillary pressure model developed based on fractal theory was implemented to model the capillary pressure measurements in various carbonate core plug samples. The saturations predicted by the proposed model were cross-checked against the saturations derived from petrophysical logs. The results were also compared with some of the most widely applied saturation height models, including the J-Function, Equivalent Radius, Brooks-Corey, and Thomeer's approach. The predicted saturations from the PTSD method agreed well with the log data, providing superior and more reasonable results compared to other methodologies. The PTSD model was able to capture successfully the reservoir dynamics and it correlated reasonably the saturation trends with height in all the drilled wells and over the entire reservoir.

Automated summary

The study presents a new approach for 3D saturation height modeling based on pore throat size distribution, with validations through capillary pressure modeling and comparison with well logs data. The predicted saturations from the PTSD method show superior results compared to other methodologies, successfully capturing reservoir dynamics and correlating saturation trends with height.