Comparative analysis of hydrocarbon potential in shaly sand Reservoirs using archie and simandoux models: A case study of “x” field, Niger Delta, Nigeria

Abstract

The comparative analyses of four wells in “X” Field within the Niger Delta were carried out with the aim of determining the hydrocarbon potential of the shaly-sand reservoirs using the Archie and Simandoux Models. The plots of effective porosity against volume of shale were used to determine the clay distribution. Composite logs comprising gamma ray, resistivity and porosity logs (density and neutron) were utilized to generate petrophysical properties in four (4) wells using Simandoux and Archie Models. Also, statistical analysis of water saturation values for both models were analysed and compared. The results of the plots of effective porosity against shale volume reveal decrease in effective porosity against increase in shale volume. The trends of the plots indicate laminated shale distribution mainly while only one hydrocarbon zone in well 3 denotes dispersed shale. Both models show very good to excellent porosity values (21-36%), and favourable hydrocarbon movability index (0.09-0.43). The statistical analyses show lower standard deviation and mean values of water saturation for Simandoux (0.008-0.2) and (0.03-0.2) when compared with that of Archie Model (0.08-0.24) and (0.15-0.5) which is indicative of higher hydrocarbon saturation than the Archie Model. At 5% error level, statistical test of difference between mean and standard deviation for both Models computed reveal t- statistics range of -20.6 to 1.8 for mean and f- statistics range of 0.005 to 11.5 for standard deviation. Their respective P (probability) - values are less than 0.05, indicating statistically significant difference between mean and standard deviation of the two models. The study reveals that the Simandoux Model has favourable petrophysical parameters indicating higher hydrocarbon potential than the Archie Model. This model could be a valuable tool in a shaly sand environment.

 Keywords: Hydrocarbon Reservoir, Simandoux and Archie Models, Petrophysical Evaluation