Inferring Capillary Pressure from Resistivity

Abstract

A model has been derived theoretically to correlate capillary pressure and resistivity index. The model is simple and predicts a power law relationship between capillary pressure and resistivity index. To verify the model, gas-water capillary pressure and resistivity were measured simultaneously at a room temperature in 14 core samples from two formations in an oil reservoir. The permeability of the core samples ranged from 0.028 to over 3000 md. The porosity ranged from less than 8% to over 30%. Capillary pressure curves were measured using a semi-permeable porous-plate technique. The model was tested against the experimental data obtained in this study. The results demonstrated that the model could match the experimental data satisfactorily. An existing model was also tested against the experimental data. The results showed that the existing model did not work in most of the cases studied. The new model developed in this study may be useful to evaluate capillary pressure function from resistivity data both in laboratories and reservoirs, especially in the case in which permeability is low.