Automated contact angle estimation for three-dimensional X-ray microtomography data

Abstract

Multiphase flow in capillary regimes is a fundamental process in a number of geoscience applications. The ability to accurately define wetting characteristics of porous media can have a large impact on numerical models. In this paper, a newly developed automated three-dimensional contact angle algorithm is described and applied to high-resolution X-ray microtomography data from multiphase bead pack experiments with varying wettability characteristics. The algorithm calculates the contact angle by finding the angle between planes fit to each solid/fluid and fluid/fluid interface in the region surrounding each solid/fluid/fluid contact point. Results show that the algorithm is able to reliably compute contact angles using the experimental data. The in situ contact angles are typically larger than flat surface laboratory measurements using the same material. Wetting characteristics in mixed-wet systems also change significantly after displacement cycles.

Direct Measurement of Static and Dynamic Contact Angles Using a Random Micromodel Considering Geological CO2 Sequestration

“…Figure 7 shows the average and standard deviation of all contact angles (RCA, ACA, and SCA) measured in this study. These results show that SCA, RCA, and ACA have high discrepancies at each pore throat size, consistent with previous studies [38,40,47]. Contact angles measured using micro-CT with rock cores and beads packs also have a wide range of values due to hysteresis of contact angle, exposure time, complex geometry, and physical and chemical heterogeneity of the surface [38,40,47].…”

“…Shojai Kaveh et al [59] have reported that smaller bubbles have higher contact angles in comparison with larger ones as a result of buoyancy force. Previous studies have also shown that contact angles on a flat surface of rocks are smaller than those measured inside rock pores using X-ray tomography method due to gravity and buoyancy [40,47]. These results indicate the important conclusion that glass (or rock) in pore-scale are as water-wet as already recognized by conventional macro-scale measurement.…”

“…Thus, static contact angles have been measured with rocks, sand packs, and glass bids, showing a wide range of contact angles at pore level. The wide range of static contact angles are due to the following: (1) pore topology, hysteresis, surface chemical and physical heterogeneity, and injection patterns (i.e., drainage and imbibition) [9,30,33,[38][39][40]; (2) relaxation of contact angle [30]; and (3) low resolution of images. Thus, Scanziani et al [9] have proposed an "effective contact angle" measurement using fluid-fluid interface curvature instead of "true contact angle" at the contact line of fluids and rock surface.…”

Spatial Correlation of Contact Angle and Curvature in Pore‐Space Images

“…This study will analyze in situ contact angle and fluid/fluid interface curvature measurements in the pore space of millimeter-sized rock samples after waterflooding experiment to provide (a) the spatial correlation in wettability and (b) correlations between fluid/fluid interface curvature (local capillary pressure) and wettability. The advent of micron-resolution imaging tools has made it possible to measure fluid/fluid interface curvature (Andrew et al, 2014b;Armstrong et al, 2012;Singh et al, 2016) and contact angle (Andrew et al, 2014b;Klise et al, 2016;Scanziani et al, 2017) between immiscible fluids at the pore scale. Also, recent studies have employed some of these methods for the in situ characterization of wettability and pore-scale multiphase displacements in natural porous media (Garing et al, 2017;Khishvand et al, 2017Khishvand et al, , 2016Lv et al, 2016Lv et al, , 2017Tudek et al, 2017).…”

Validation of model predictions of pore-scale fluid distributions during two-phase flow

“…In most previous work, advancing contact angles were randomly distributed within certain ranges that are assumed to be plausible, and simulations were then mainly used for sensitivity assessment [41][42][43]. A approach which carries the potential of being more predictive is to measure contact angles on an image of the rock with the wetting and nonwetting fluids present [44][45][46][47]. Here we assign the advancing contact angles in the pore network model randomly in the range between 15…”