Are rocks still water‐wet in the presence of dense CO₂ or H₂S?

Abstract

The various modes of acid gas storage in aquifers, namely structural, residual, and local capillary trapping, are effective only if the rock remains water‐wet. This paper reports an evaluation, by means of the captive‐bubble method, of the water‐wet character in presence of dense acid gases (CO2, H2S) of typical rock‐forming minerals such as mica, quartz, calcite, and of a carbonate‐rich rock sampled from the caprock of a CO2 storage reservoir in the South‐West of France. The method, which is improved from that previously implemented with similar systems by Chiquet et al. (Geofluids 2007; 7: 112), allows the advancing and receding contact angles, as well as the adhesion behavior of the acid gas on the mineral substrate, to be evaluated over a large range of temperatures (up to 140°C), pressures (up to 150 bar), and brine salinities (up to NaCl saturation) representative of various geological storage conditions. The water‐receding (or gas‐advancing) angle that controls structural and local capillary trapping is observed to be not significantly altered in the presence of dense CO2 or H2S. In contrast, some alteration of the water‐advancing (or gas‐receding) angle involved in residual trapping is observed, along with acid gas adhesion, particularly on mica. A spectacular wettability reversal is even observed with mica and liquid H2S. These results complement other recent observations on similar systems and present analogies with the wetting behavior of crude oil/brine/mineral systems, which has been thoroughly studied over the past decades. An insight is given into the interfacial forces that govern wettability in acid gas‐bearing aquifers, and the consequences for acid gas geological storage are discussed along with open questions for future work.

A molecular dynamics investigation into the adsorption behavior inside {001} kaolinite and {1014} calcite nano-scale channels: the case with confined hydrocarbon liquid, acid gases, and water

“…4C, c and D, d. The simulation findings on the tendency of hydrocarbon, acid gases, and water towards the calcite surface are also in agreement with published experimental reports (Broseta et al 2012;Karoussi and Hamouda 2008;Tabrizy et al 2011a, b).…”

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

“…Figure 2a. Results show that the advancing contact angle is considerably higher than the receding contact angle in the same pore throat, consistent with previous studies [18,22,[43][44][45]. The difference between ACA and RCA is attributed to the blemishes on non-ideal surfaces which results in pinning the interfaces to the solid surface [46].…”

“…Average contact angles on flat surface inside micromodel at pressure of one and eight megapascals are 62° ± 7° and 49° ± 21°, respectively, in agreement with Kim et al [58] observations showing a wide range of contact angles from 40° to 80° inside a uniform micromodel. Contact angles on a flat surface in this study are higher than those shown in previous sessile drop or captive bubble tests with large droplet of water or bubble of CO2 (i.e., 8° to 45° on silica or glass surface) [18,22,43,[50][51][52]. This could be due to the micro-scaled CO2 bubble size on a flat surface inside the micromodel of [18,22,43,[50][51][52].…”

“…Because of different level of relaxation of the interfaces, various mode of interfaces before stoppage (i.e., receding or advancing), and pinning effect originated from solid surface imperfection, SCA shows wide range of values for the two different tests and also for each test in any throat sizes. The range of SCA at each pore throat size is higher than that of equilibrium contact angle (ECA) measured with CO 2 or water droplet on flat surface (i.e., 8 • to 45 • on silica or glass surface) [18,22,43,[50][51][52]. Static contact angle during drainage and imbibition processes.…”

“…Values of in-situ contact angles and local capillary pressure are not distinguishable [9]. In a different approach, static and dynamic contact angles have been vastly measured on a flat surface representing a specific mineral surface (i.e., silica, mica, or natural rock) using various methods such as sessile drop, captive bubble, Wilhelmy plate, and dual-drop dual-crystal (DDDC) methods [18][19][20][21][22][23][24][25][26][27][28][29]. High discrepancies in contact angles measured in literature have been observed.…”