Nonmonotonic Effects of Salinity on Wettability Alteration and Two‐Phase Flow Dynamics in PDMS Micromodels

Abstract

The interaction between fluid‐fluid and solid‐fluid interfacial forces and surface roughness controls the wettability. The ionic strength is the most important factor that controls electrostatic forces. Thus, a modification of the ionic strength can potentially lead to a change of the wettability, as shown in recent experimental works related to low‐salinity waterflooding, which is an enhanced oil recovery technology. Despite the significant research published on this topic, for the first time, we present how a change of the ionic strength alters the wettability in a pore network micromodel made of silanized polydimethylsiloxane (PDMS). We visualized the invasion of brine in an elongated hydrophobic PDMS micromodel, initially saturated with Fluorinert. Under different injection rates and ionic strengths and using image processing, we quantified the contact angle distribution in the flow network, the recovery curve with time, the brine breakthrough time, and the temporal change of resident saturation. The results imply that there is an optimal range of salinity at which saturation change accelerates and the breakthrough saturation maximizes, which highlights the concept of optimal salinity in wettability alteration. Also, we observed a shift of the contact angle distribution toward a more water‐wet state. Given the nonmonotonic trend of the breakthrough saturation with brine salinity, as well as recovery time versus the ionic strength, we conclude that the induced surface roughness is not the primary drive behind the accelerated saturation change. Therefore, the recovery time difference can be primarily attributed to the local alterations of the wetting properties of the porous medium due to the change of the ionic strength.

Impacts of Mixed‐Wettability on Brine Drainage and Supercritical CO2 Storage Efficiency in a 2.5‐D Heterogeneous Micromodel

“…This brine was then injected from the back‐pressure pump to displace and dissolve the gaseous CO 2 through E → D → C → B → F → H. During these steps, the micromodel system was kept at atmospheric pressure. Similar low salinity brine was also used by Hu et al (2017b), with an aim to minimize any wettability changes induced by salinity and ionic composition (Fathi et al, 2010; Karadimitriou et al, 2019).…”

Unravelling Effects of the Pore‐Size Correlation Length on the Two‐Phase Flow and Solute Transport Properties: GPU‐based Pore‐Network Modeling

“…The quasi-static, two-phase drainage algorithm (controlled by the entry capillary pressure) was used to determine the saturation topology under controlled pressure conditions, resembling water flooding in an oil-wet system (e.g., low salinity waterflooding Aziz et al, 2019;Karadimitriou et al, 2019;Morrow & Buckley, 2011), as well as surfactant transport in NAPL-contaminated soils (hydrophobic soil surface) (Powers et al, 1996). Assuming Hagen-Poiseuille flow in pore throats and mass balance in pore bodies, the pressure field and velocity distributions were computed within the water-filled pores similar to Joekar-Niasar et al ( 2008) and Hasan et al (2019).…”

A brief review of the correlation between electrical properties and wetting behaviour in porous media

“…During the water flow, the role of electrical double layer is important for the interaction of solid-fluid interface. Karadimitriou et al (2019) presented a micromodel experimental study to show that the flow rate and ionic strength also play an important role in the wettability alteration by validating the two-phase model with the experimental two-phase flow on the salinized polydimethylsiloxane (PDMS) micromodel. As shown in Fig.…”