Simultaneous core sample measurements of elastic properties and resistivity at reservoir conditions employing a modified triaxial cell – a feasibility study

Abstract

ABSTRACTAdaptations of existing triaxial cells for ultrasonic P‐ and S‐wave measurements are well documented. This paper proposes further modification of such a cell so that also resistivity measurements can be carried out simultaneously at reservoir conditions. By employing the top cap and the pedestal of the cell as electrodes, axial resistivity measurements are now feasible. In order to minimize the polarization effect of this two‐electrode arrangement, careful analyses have been carried out to optimize the choice of electrode coating and measurement frequency band. Radial resistivity measurements are also included in the system by introducing a strap‐electrode system.In a reservoir under production changes in both saturations, temperature (if steam injection) and stresses can take place. Therefore the modified triaxial system should be able to measure the integrated effects on the acoustic parameters and electric responses caused by variations in each of these parameters. The feasibility of the system to obtain such reliable information is demonstrated, employing a small selection of core samples. In the future such combined measurements on reservoir core samples can be used to link both seismic and electromagnetic observations to the actual earth model and constrain both modelling and inversion.