Wireless Acquisition for Resistivity Index in Centrifuge – WiRI: A Comparative Study of Three P_c-RI Methods

Technological improvements and innovations are made to offer solutions with superior efficiency in terms of cost, quality, speed, or all of them. In the special core analysis (SCAL) field, the conventional resistivity index measurement (the porous plate technique) is a cost-effective method that provides good-quality results but is very time consuming. For this purpose, several methods were developed to reduce the time taken to acquire resistivity measurements. In 2017, we proposed the ultra-fast capillary pressure and resistivity index measurements (UFPCRI) combining centrifugation, nuclear magnetic resonance (NMR) imaging, and resistivity profiling. Since 2021, the wireless resistivity index (WiRI) method allows the acquisition of capillary pressure and resistivity index in a matter of days. This method is based on a new in-house system to acquire wirelessly resistivity indexes along a rock sample during centrifugation. The determination of the resistivity vs. saturation curve and the n exponent of Archie’s law is done thanks to an optimization algorithm. In this paper, we present the results obtained from multiple simulations and experiments for WiRI, UFPCRI, and porous plate to discuss the advantages and drawbacks of each method in terms of reliability and experimental duration. Six rock samples are studied. A comparison of the three methods regarding Archie’s n exponent, resistivity indexes, and capillary pressure curves is performed.