Capillary trapping in sandstones and carbonates: Dependence on pore structure

Abstract

[1] Residual non-wetting phase saturation and wetting-phase permeability were measured in three limestones and four sandstones ranging in porosity from 0.13 to 0.28 and in absolute permeability from 2 Â 10 À15 to 3 Â 10 À12 m 2 . This paper focuses on the residual state established by waterflooding at low capillary number from minimum water saturation achieved using the porous plate technique, which yields the maximum residual under strongly water-wet conditions. The pore coordination number and pore body-throat aspect ratio of each rock were estimated using pore networks extracted from X-ray microtomography images of the rocks. Residual saturation decreases with increasing porosity, with no apparent difference in magnitude between the limestones and sandstones at a given porosity. Thus intraparticle/intra-aggregate microporosity does not significantly alter the efficiency of capillary trapping in the rocks considered presently. Residual saturation broadly decreases as conditions become less favorable for snap-off, i.e., with decreasing pore aspect ratio and increasing coordination number. The measured residual saturations imply that capillary trapping may be an effective mechanism for storing carbon dioxide in both sandstones and carbonates provided that the systems are strongly water-wet.Citation: Tanino, Y., and M. J. Blunt (2012), Capillary trapping in sandstones and carbonates: Dependence on pore structure, Water Resour. Res., 48, W08525,

Enhanced gas recovery with CO2 sequestration: The effect of medium heterogeneity on the dispersion of supercritical CO2–CH4

“…In our previous work, large proportions of the pores in these sandstones were demonstrated to be over one micron (Honari et al, 2013) and the relatively small numbers of micro pores observed was attributed to the presence of claybound water (Jorand et al, 2011;Straley et al, 1997). The distributions of T 2 relaxation for the carbonate rocks consisted of two distinct peaks, which was consistent with the pore size distributions previously reported (Bijeljic et al, 2013a;Tanino and Blunt, 2012). Ketton that is attributed to intra-aggregate pores and intra-particle pores.…”

“…In contrast, since Ketton had the most well-connected pores at larger length scales (as evident in the XMT images) and also the smallest micro-pores indicated by the MICP measurements of pore size distribution (Bijeljic et al, 2013a;Tanino and Blunt, 2012) and by the NMR measurements in Section 4.2. Thus, we hypothesize that while bulk fluid flowed preferentially through Ketton's larger inter particle pores (very high permeable region), an appreciable number of CO 2 molecules travelled through to and from the intra-grain stagnant pores via extremely tortuous paths to reach the fast flow regions.…”

“…Estaillades and Ketton carbonate rock cores, each 1.5 inch diameter and with lengths of 100-105 mm were used -the 2D cross sections of 3D micro-CT images of these carbonate rocks have been provided elsewhere (Bijeljic et al, 2013a;Tanino and Blunt, 2012). Berea and Donnybrook sandstone cores were also considered for reference purposes.…”

Oil/water displacement in microfluidic packed beds under weakly water-wetting conditions: competition between precursor film flow and piston-like displacement

“…It can be readily seen that after t = O(10) , oil displacement ceased at all Ca and ⟨ s o ⟩ L reached its long-time, steady-state value. This transient time falls between t = O(1) typically reported under strongly water-wet conditions e.g., (Salathiel 1973;Mungan 1966;Tanino and Blunt 2012;Christensen and Tanino 2017a) and t = O(50 − 1000) reported under mixed-wet conditions (e.g., Salathiel 1973;Tanino and Blunt 2013;Christensen and Tanino 2017a), further corroborating the near-neutral wettability indicated by the measured s . In the discussion that follows, the remaining oil saturation at the end of the waterflood experiment, Ŝ or , was evaluated as the time-average of ⟨ s o ⟩ L after � t > 100.…”

Micro-computed tomography pore-scale study of flow in porous media: Effect of voxel resolution

“…The single-phase permeability was predicted using PN modelling by extracting pore and throat networks, and LB simulation on the macro-phase segmented sandstone and carbonate sample images. The average coordination number is also calculated for all the carbonate and sandstone samples at varying voxel resolution which represents the number of independent throats connected to a pore, and has a critical influence on the transport properties (Yuan, 1981, Jerauld & Salter 1990, Arns et al, 2004, Dong & Blunt 2009and Tanino & Blunt 2012. The experimental (total) porosity and single-phase permeability was measured on the each of the cylindrical sandstone and carbonate core samples.…”