Estimating Saturation in Carbonate Rocks: Combining Fluid Contacts, Saturation Height Functions, Wireline Logs and Capillary Pressure

Summary Capillary pressure (Pc) data is utilized to calculate saturations through saturation height (SHF) modelling in a carbonate field, calibrated to an empirical model. Hydrocarbon saturation is the fraction of pore volume filled with gas, and this is crucial for reserve estimations. Water saturation (Sw) can be estimated via core analysis of Dean-Stark extractions, empirical models using logs data and SHF modelling. Archie’s equation calculates Sw from well logs, while Leverett’s equation calculates Sw-SHF. The latter is a reliable predictor of Sw, independent of the electrical properties in heterogenous carbonate environment. This method reduces the uncertainties linked to formation salinity and proved to be highly accurate. Fluid contacts are defined by integrating data from repeat formation tester (RFT), drill stem test (DST), production logging tool (PLT), pressure volume temperature (PVT) sample analysis, and petrophysical well logs. Alternatively, the SHF modelling also verified the contacts. This SHF approach achieves excellent saturation matches at the wells level and used for field-wide implementations.