Experimental investigation of trapped oil clusters in a water‐wet bead pack using X‐ray microtomography

Abstract

[1] Uncertainties in the quantification of transport properties associated with multiphase flow in porous systems often make the prediction of fluid residence and migration a difficult task. Movement and trapping of immiscible fluids in permeable formations depends upon a complex combination of fluid properties, rock properties, fluid-solid interactions, and forcing conditions. This work consists of using X-rays and visualization techniques to map the distribution of immiscible fluids, particularly trapped oil clusters, residing in a glass bead pack subject to different flow conditions. We analyze the effect of flowing conditions on the evolution of fluid microstructures using X-ray microtomography. Spherical glass beads (0.425-0.600 mm in diameter), a water-wet porous medium, were packed inside a specially designed core holder. High-resolution imaging provides detailed mapping of pore structures resulting from bead packing, and characterization of fluid microstructures formed during sequential water and oil injections. We present spatial distribution of trapped oil clusters for the entire bead pack, as well as mechanistic explanations leading to the fluid configurations observed. We also present simple statistical analyses of blob size, shape, and surface area at the end of different fluid injection cycles. Trapped oil clusters appear in sizes that range from 5.923 × 10 −5 mm 3 to 3.119 × 10 3 mm 3 , where 0.01-0.50 mm 3 clusters are most common. About 98% of the total trapped oil at the end of drainage and imbibition cycles corresponds to blobs that are smaller than 1 mm 3 . It is also shown that most blobs are larger than the mean pore size (0.03 mm 3 ). The mean oil blob size is about 5 times larger than the average pore. A typical blob extends through various interconnected pores, exhibiting elongated of ramified shapes that include multiple voids and constrictions at the same time. The mean aspect ratio of these clusters is less than 2, and the surface area to volume ratio is constant for those larger than 0.1 mm 3 . Experimental methods and findings presented in this paper are expected to lead to powerful calibration mechanisms for multiphase flow models.Citation: Karpyn, Z. T., M. Piri, and G. Singh (2010), Experimental investigation of trapped oil clusters in a water-wet bead pack using X-ray microtomography, Water Resour. Res., 46, W04510,

Experimental investigation of residual saturation in mixed-wet porous media using a pore-scale approach

“…A spatial distribution of the trapped oil clusters for the entire bead pack was presented to explain fluid distribution. Likewise, Landry et al (2011) presented quantitative evidence of immiscible fluid distribution in an oil-wet acrylic bead pack, thereby offering a direct comparison with the results presented by Karpyn et al (2010). Landry's experimental results showed how wettability and saturation history affect fluid distribution.…”

“…3 shows that most of the blobs fell in a size between 0.0001 and 0.001 mm 3 , making them 100 times smaller in size than those in the single-wettability glass and plastic bead packs reported by Karpyn et al (2010) and Landry et al (2011). This difference in sizes of the blobs is expected since the wetting fluid tends to be imbibed by the small pores in the uniformly wet system, causing the nonwetting fluid to be trapped in the larger pores Raeesi and Piri (2009), Kumar et al (2008), Zhao et al (2010) and Al-Futaisi and Patzek (2003).…”

“…The MCT system consists of an X-ray source, a detector, a translation system, and a computer system that controls motion and data acquisition Karpyn et al (2010). MCT imaging is a visualization technique used for examining internal structure of opaque three-dimensional objects by producing stacks of twodimensional images (slices) that reveal the interior of the objects in a nondestructive manner Denison et al (1997).…”

“…MCT is a non-invasive technique that reveals the internal structure of an object by capturing variations in density and atomic composition. Thus, MCT images give a representation of the pore geometry of a system Chaouki et al (1997) and Karpyn et al (2010). In dry granular samples, the strong contrast between the solid phase and the pore space provides information for studying the porosity distribution of the system Ketcham and Carlson (2001).…”

“…Previous investigations of trapped oil clusters in waterwet glass bead packs using X-ray microCT by Karpyn et al (2010) were performed at larger dimensions (approximately 25.4 mm in diameter and 90.53 mm long). The granular system used in this experiment consisted of spherical glass beads ranging from 0.40 to 0.60 mm in diameter.…”