Wetting Behavior of Tight Rocks: From Core Scale to Pore Scale

Abstract

Previous measurements show mixed‐wet behavior of tight siltstone core plugs, initially saturated with air. However, the same plugs show water‐wet behavior when saturated with oil or water. This study aims at explaining these observations by investigating the effects of mineral heterogeneity and intermolecular forces acting on solid/liquid and liquid/liquid interfaces. First, we conduct pore‐scale visualizations to characterize the minerals surrounding the pores of the tight rock samples. Thin‐section and scanning electron microscopy/energy dispersive X‐ray spectroscopy analyses show the existence of multimineral pores, which can be responsible for the mixed‐wet behavior. Next, we apply the DLVO theory to investigate the intermolecular forces acting on solid/liquid and liquid/liquid interfaces. We use disjoining pressure‐distance profiles and contact angles calculated for different minerals to evaluate the stability of the thin film covering the rock grains and to explain the wettability of the core plugs during spontaneous imbibition tests. The disjoining pressure values calculated for the dry core plugs suggest similar wetting affinities toward oil and water. However, the contact angles calculated for the water‐saturated core plugs suggest the water‐wet behavior, which agrees with the countercurrent imbibition results. Finally, we measure the adhesion forces between the tip of a cantilever and (1) pure quartz slide, (2) pure calcite crystal, and (3) the rock thin section using an atomic force microscope. The values of adhesion forces measured for the thin section composed of multimineral pores are between those measured for pure quartz slide and pure calcite crystal.

Upscaling Water Flow in Composite Nanoporous Shale Matrix Using Lattice Boltzmann Method

“…Estimations by Yassin et al () show the contact angles for both the organic and inorganic matter vary enormously with different rock properties. In addition, measurement errors (Habibi & Dehghanpour, ) and confinement effects (Wang, Javadpour, & Feng, ) further increase uncertainty to evaluate contact angle in OM or clay. Therefore, we assume contact angle in OM is greater than 90° (hydrophobic) and in clay is less than 90° (hydrophilic).…”

“…The nanopores in shale are usually bounded by multimineral matrix, hence, exhibit heterogeneous wetting affinities. Therefore, we expect the heterogeneity in these pore surface minerals to cause heterogeneity of wetting properties of these pores (Habibi & Dehghanpour, 2018). In this work, we simply assume uniform hydrophobic and hydrophilic wettabilities of OM and clay pores, respectively.…”

Impact of the Water Adsorption Monolayer on Methane Ad-/Desorption Behavior in Gas Shale Nanopores

“…The stability of a water film–methane adsorption layer–shale surface system is indicated by the disjoining pressure. If the disjoining pressure is positive, the methane adsorption layer is stable, and the water film cannot replace the methane adsorption on the shale surface . Otherwise, the methane adsorption layer is unstable, and the water film is then adsorbed on the shale surface.…”

“…b is a dimensionless fitting constant obtained from the Overbeek expression, which is 5.32 eq . , where A 11 , A 22 , and A 33 are the Hamaker constants of the shale surface, water film, and methane, respectively.…”

Wastewater Fines Influence the Adsorption Behavior of Pollutants onto Microplastics

“…Organic particles such as coffee grounds have an insoluble cellulose structure that makes them potential pollution sorbents [18]. The inorganic fines such as quartz with a silica-oxygen layer that inducing negative charges are more prone to adsorb charged sorptive [19,20]. While adsorption processes between wastewater constituents and MPs surfaces in sewers depend on several factors, such as the nature of the interaction, mechanical variables, pollutant concentration, MPs shape, age, and density as well as the dynamics of adsorption at the interfaces [21][22][23].…”