An Experimental Study on the Influence of Sub-Core Scale Heterogeneities on CO2 Distribution in Reservoir Rocks

Abstract

This article presents the results of CO 2 /brine two-phase flow experiments in rocks at reservoir conditions. X-ray CT scanning is used to determine CO 2 saturation at a fine scale with a resolution of a few pore volumes and provide 3D porosity and saturation maps that can be use to correlate CO 2 saturations and rock properties. The study highlights the strong influence of sub-core scale heterogeneities on the spatial distribution of CO 2 at steady state and provides useful relative permeability data on a sample originated from an actual storage site (CO2CRC-Otway project, Victoria, South-West Australia). Two different samples tested, although different in nature, present strong heterogeneities, but differ in the detail of the connectivity of high porosity layers. In both samples, the results of the investigations show that sub-core scale heterogeneities control the sweep efficiency and may cause channeling through the porous medium. In one of the samples, CO 2 saturation appears uncorrelated to porosity close to the outlet end of the core. This observation is understood as a result of the position and the orientation of high porosity layers with respect to the inlet face of the core. Finally, in the operating conditions of the two experiments, the saturation maps demonstrate that gravity does not play a major role since no detectable buoyancy driven flow is observed.

Lattice Boltzmann simulation of immiscible fluid displacement in porous media: Homogeneous versus heterogeneous pore network

“…The viscosity ratio is defined as the ratio of the advancing non-wetting fluid viscosity to the defending wetting fluid viscosity (η w ), i.e., M = η n /η w . In addition, recent laboratory studies [41][42][43][44] have shown the strong influence of subcore scale heterogeneities on steady-state migration patterns, spatial distributions, and fluid saturations. To gain a better understanding of pore-scale two-phase displacement mechanisms, a series of numerical simulations are conducted to study the effect of Ca and M on displacement stability and fluid saturation in a homogeneous and a heterogeneous pore networks, and the obtained results are compared to indicate the effect of media heterogeneity.…”

High-Resolution X-Ray Computed Tomography of Liquid CO<SUB>2</SUB> Permeation in Water-Saturated Sandstone

“…On the other hand, previous studies in which supercritical CO 2 was used indicate a thicker permeation front region with 3 to 13.4 PV injected before CO 2 saturation reached a steady distribution (14,15) . The influence of the sub-core scale heterogeneity was discussed by Perrin et al (14) and Shi et al (15) , and recent studies noted that permeability discontinuities cause saturation discontinuities (18,19) . In this study, a thin laminar structure in a large-diameter sandstone sample can be observed by employing microfocus X-ray CT.…”

“…The porosity and CO 2 saturation of the sandstone were measured by X-ray CT and mapped from several images or by varying the X-ray energy (12)(13)(14) . In this study, six images at constant X-ray energy were obtained for each of: the dry and water-saturated sample holder without the sandstone; the water and CO 2 saturated sandstone (the core was filled …”

“…One of the visualization techniques is X-ray computed tomography (CT). Several previous studies have used X-ray CT to observe CO 2 injection in rock samples (12)(13)(14)(15) . Fluoroscopic X-ray images were acquired by rotating the X-ray source and detector.…”

Moving across scales: a quantitative assessment of X-ray CT to measure the porosity of rocks

“…an uncertainty that is similar in strength to 120 spatial variations in the porosity of many reservoir rocks at the same scale [32,121 33, [17][18][19]. As explained in a previous publication [13], this uncertainty can be 122 assessed by subtracting two scans that have been taken at the same position and 123 it can be significantly reduced by proper combination of sufficient repeated mea-124 surements and image coarsening (see Section 3.2).…”