Petrophysical Characterization of shaly sandstone reservoirs in Jake-South oil field Muglad basin, Sudan

Abstract

Water saturation estimation by interpretation of Archie’s model in clean formations has successfully been used over the years. However, due to shale or clay effects in shaly sand formation this model results in inaccurate water saturation values. Many shaly sand interpretation models have been developed, unfortunately there is no unique model that appears to fit all shaly sand reservoirs. A comparison study of water saturations on wells Jake-south (28, 34, 37and S2) was carried out using three different saturation models (Archie, Indonesian, Simandoux). The entire interpretation was done using the Interactive Petro physics Software. Formation permeability was estimated using porosity – permeability relationship derived from core measurement. The results from the study have shown that the average water saturation values from Archie model ranges from (16% - 28%) were higher than that of simandoux models. The result from the Simandoux model is (8% - 20%). The Indonesian model yields average water saturation value is (18% - 32%) which is close to that given by Archie model and higher than the value of the Simandoux model. Indonesian model is the most optimistic for the study after the correlation of all models with the core data given. Sub zones bearing commercial hydrocarbon were identified by determining their porosity, permeability, oil saturation and the hydrocarbon mobility index.