Abstract
AbstractA novel level set‐based approach is presented to calculate in situ contact angle distribution, θ, from pore‐scale immiscible fluids and rock configuration directly imaged with micro‐computed tomography (micro‐CT) techniques. We first identify interfaces of the fluid‐fluid and fluid‐solid by their zero level set functions. This is accomplished by reinitializing the level set functions with a signed distance function. Then the three‐phase contact line is determined at the crossover of the two zero level set functions that represent the two interfaces. The normal vectors of both surfaces are calculated directly using the two level set functions, and the contact angle is found from the dot product of these vectors where they meet at the contact line. We first validated our newly proposed method for the semianalytically calculated fluid configurations in a 2‐D tube and then tested the algorithm on a synthetic spherical oil droplet residing on a tilted flat solid surface where the contact angle is analytically defined. It was then used to measure the in situ contact angle of droplets directly imaged by micro‐CT, and the results are compared with the manually and other available automatically measured results. Compared with other available automatic approaches, our approach is mathematically well defined, and it does not require any other complicated tuning procedures for surface smoothing. This proposed approach allow us to accurately characterize local in situ pore‐scale wettability, which is essential to model multiphase flow in porous media and eventually help us to design and assess optimal processes, such as hydrocarbon recovery and carbon dioxide storage.
Highlights
A novel level set‐based approach is presented to calculate in situ contact angle distribution, θ, from pore‐scale immiscible fluids and rock configuration directly imaged with micro‐computed tomography techniques
Wettability is a key property that defines the tendency of a fluid to spread on a solid surface in presence of two or more immiscible fluids, which plays a critical role in multiphase flow in porous media as it controls pore‐scale fluid configurations and displacement scenarios (Frette & Helland, 2010; Ma et al, 1996; Zhou et al, 2014), which in turn influences the macroscopic flow function, such as capillary pressure and relative permeability curves (Anderson, 1987; Jettestuen et al, 2013; Zhou et al, 2012, 2014)
We apply our algorithm on two sets of high‐resolution microtomography data sets of a ganglion in water‐wet and altered wettability systems
Summary
Wettability is a key property that defines the tendency of a fluid to spread on a solid surface in presence of two or more immiscible fluids, which plays a critical role in multiphase flow in porous media as it controls pore‐scale fluid configurations and displacement scenarios (Frette & Helland, 2010; Ma et al, 1996; Zhou et al, 2014), which in turn influences the macroscopic flow function, such as capillary pressure and relative permeability curves (Anderson, 1987; Jettestuen et al, 2013; Zhou et al, 2012, 2014). Besides conventional lab‐measured contact angle, quite a few numerical simulation approaches, for example, molecular dynamic simulations (Derksen, 2015; Stukan et al, 2010; Tian & Wang, 2017; Yong et al, 2019), disjoining pressure modeling using Frumkin–Derjaguin equation (Zhou et al, 2017) have proposed to simulate the contact angle under different contexts. These measurements and numerical approaches fail to capture the pore surface roughness and mineral heterogeneities at the pore space. In order to overcome the limitation of this manual in situ
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