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

Abstract

A B S T R A C TAdaptations 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.

Effect of brine-CO2 fracture flow on velocity and electrical resistivity of naturally fractured tight sandstones

“…To quantify the radial resistivity and to account for variations due to anisotropy and tortuosity, a correction factor was used to obtain the true radial resistivity. Following the procedure introduced by Wang et al (2009) andChoi et al (2017), numerical simulation and iteration were performed to find the correction factor.…”

“…Epsilon measures the difference in normal stiffness between vertical and horizontal directions (Sarout and Guéguen, 2008). The electrical resistivity anisotropy is defined as the ratio of radial (horizontal) to axial (vertical) measurements (Wang et al, 2009) and is presented in Figure 9f.…”

“…Although it is assumed that the electrical resistivity perpendicular to the bedding (vertical resistivity) is higher than the one parallel to bedding (Wang et al, 2009), it is the radial measurements that span the whole range of the scatter (Fig. 10).…”

Electric and elastic properties of rock samples: a unified measurement approach

“…In order to make the simultaneous acquisition of velocity and resistivity feasible, a modified triaxial cell has been used (Wang et al 2009). The original cell has been described in more detail earlier by Berre (1981) and Chryssanthakis et al (1999).…”

“…temperature, stress and saturation and avoid velocity-stress hysteresis) if tests are run sequentially. In this paper we analyse data from a modified triaxial cell (Wang et al 2009), where the electrical conductivity and P-and S-wave velocities can be measured simultaneously. This provides the feasibility of investigating both the electrical and elastic properties of the rock samples at the same conditions.…”