Effect of Fluid–Rock Interactions on In Situ Bacterial Alteration of Interfacial Properties and Wettability of CO₂–Brine–Mineral Systems for Geologic Carbon Storage

Abstract

This study explored the feasibility of biosurfactant amendment in modifying the interfacial characteristics of carbon dioxide (CO 2 ) with rock minerals under high-pressure conditions for GCS. In particular, while varying the CO 2 phase and the rock mineral, we quantitatively examined the production of biosurfactants by Bacillus subtilis and their effects on interfacial tension (IFT) and wettability in CO 2 −brine−mineral systems. The results demonstrated that surfactin produced by B. subtilis caused the reduction of CO 2 −brine IFT and modified the wettability of both quartz and calcite minerals to be more CO 2 -wet. The production yield of surfactin was substantially greater with the calcite mineral than with the quartz mineral. The calcite played the role of a pH buffer, consistently maintaining the brine pH above 6. By contrast, an acidic condition in CO 2 −brine−quartz systems caused the precipitation of surfactin, and hence surfactin lost its ability as a surface-active agent. Meanwhile, the CO 2 -driven mineral dissolution and precipitation in CO 2 −brine−calcite systems under a non-equilibrium system altered the solid substrates, produced surface roughness, and caused contact angle variations. These results provide unique experimental data on biosurfactant-mediated interfacial properties and wettability in GCS-relevant conditions, which support the exploitation of in situ biosurfactant production for biosurfactant-aided CO 2 injection.

Quartz–H2–Brine Bacterium Wettability under Realistic Geo-Conditions: Towards Geological Hydrogen Storage

“…16 The bacterial strain of Bacillus subtilis produced a biosurfactant that can reduce the CO 2 -brine interfacial tension and change the wettability of both quartz and calcite minerals, causing less water-wet conditions for the CO 2 geological storage. 30 However, the wettability of H 2 on the quartz's surface after the bacterium effect remained unanswered. It is not predicted how bacteria alter the wettability of rock, which results in adverse effects on withdrawing and injection efficiencies at the field scale.…”

“…38,39 Recent findings predict that wettability can alter due to the release of in situ biomolecules and organic acids from the bacteria for CO 2 geological storage. 30 No solid data is available on the H 2 −brine−rock wettability in the presence of microorganisms. In this paper, we sought to address this gap by evaluating the effect of wettability alteration on the quartz, i.e., sandstone forming unit in the presence of SRB.…”

“…Thus, a proper evaluation and regular monitoring of H 2 storage well will be required to maintain the well integrity to avoid corrosion and leakage problems . Besides the corrosion issues, the microorganisms can decrease the pH of the formation water, clog the pore network, and change the hydrogeochemistry and wettability of rock …”

Contact Angle on Rough Curved Surfaces and Its Implications in Porous Media

“…The discussion about the effect of surface microstructures on the equilibrium contact angle in porous media is available in the literature but seldomly the focus of the research. Although contact angle plays an important role in critical topics including multiphase flow, capillarity, fingering effect, and the pore-scale distribution of immiscible fluid in porous media. − Other effects on contact angle such as pressure, temperature, and salinity draw more attention. ,,,, Even the influences of surface chemistry and surface roughness of flat rock surfaces are investigated by a high-resolution camera, the discussion mostly used previous models. Micro-CT has been used to consider the pore topology in real porous media, , and the complex fluid topology and internal energy are considered, − but there was no theoretical explanation for the effect of surface roughness and pore geometry on contact angle.…”

“…33−36 Other effects on contact angle such as pressure, temperature, and salinity draw more attention. 1,2,5,6,37 rock surfaces are investigated by a high-resolution camera, the discussion mostly used previous models. Micro-CT has been used to consider the pore topology in real porous media, 8,38 and the complex fluid topology and internal energy are considered, 39−42 but there was no theoretical explanation for the effect of surface roughness and pore geometry on contact angle.…”