An integral method for calculation of capillary pressure based on centrifuge data of tight sandstone

Abstract

The traditional Hassler-Brunner (HB) interpretation method of centrifuge capillary pressure is widely used in materials, soil, biotechnology, and especially in the petroleum industry. However, the assumptions of the traditional method cannot be simultaneously satisfied, the traditional method has been known to lead significant errors in some cases. In this paper, a new double integral method is proposed to evaluate the centrifuge capillary pressure of long tight sandstone samples. Both the changes of capillary length and interface of wetting phase and non-wetting phase fluids are considered by the new integral method, thus the average pressure and saturation derived from the proposed double integral method is more sufficient in theoretic foundation and clearer on physical meaning. By comparing with the measured capillary pressure of long tight sandstone core samples from porous plate, the capillary pressure calculated from traditional HB method is obviously smaller than the measured value, and the discrepancy increases with the decreasing core porosity. However, the average capillary pressure obtained by the proposed double integral method is remarkably consistent with the measured value. The findings of this study can help for better understanding of distribution of wetting phase fluid and average centrifuge capillary pressure in the core during centrifugal process.