Surface interaction of crude oil, maltenes, and asphaltenes with calcite: An atomic force microscopy perspective of incipient wettability change (original) (raw)
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Energy & Fuels, 2019
Low salinity water flooding appears to be a promising means to improve oil recovery in carbonate reservoirs due to a wettability alteration process. Contact angle measurement is a direct approach to reveal the wettability alteration in oil-brine-carbonate system. However, questions have been raised about using contact angle measurement to justify the wettability alteration. This is because contact angle may be significantly affected by surface roughness variation in the presence of low salinity water due to calcite dissolution during the contact angle measurement. To clarify the cause and effect of wettability alteration during low salinity water flooding, we measured contact angle on two calcite substrates with similar surface roughness
Energy & Fuels, 2017
Atomic force microscopy (AFM) is frequently used to elucidate complex interactions in emulsion systems. However, comparing results obtained with "model" planar surfaces to curved emulsion interfaces often proves unreliable, since droplet curvature can affect adsorption and arrangement of surface-active species, while droplet deformation affects the net interaction force. In the current study, AFM was utilized to study the interactions between a colloidal probe and water droplet. Force magnitude and water droplet deformation were measured in asphaltene and bitumen solutions of different concentrations at various droplet aging times. Interfacial stiffening and an increase in particle-droplet adhesion force were observed upon droplet aging in bitumen solution. As reported in our previous study (Kuznicki, N. P.; Harbottle, D.; Masliyah, J.; Xu, Z. Dynamic Interactions between a Silica Sphere and Deformable Interfaces in Organic Solvents Studied by Atomic Force Microscopy. Langmuir 2016, 32 (38), 9797−9806), a viscoelasticity parameter should be included in the high force Stokes-Reynolds-Young-Laplace (SRYL) equations to account for the interfacial stiffening and non-Laplacian response of the water droplet at longer aging times. However, following the addition of a biodegradable demulsifier, ethyl cellulose (EC), an immediate reduction in both the particle-droplet adhesion force and the rigidity of the water droplet occurred. Following EC addition, the interface reverted back to a Laplacian response and droplet deformation was once again accurately predicted by the classical SRYL model. These changes in both droplet deformation and particle-droplet adhesion, tracked by AFM, imply a rapid asphaltene/bitumen film displacement by EC molecules. The colloidal probe technique provides a convenient way to quantify forces at deformable oil/water interfaces and characterize the in-situ effectiveness of competing surface active species.
Journal of Colloid and Interface Science, 2008
Effect of Mg 2+ and SO 2− 4 on wettability alteration of modified calcite surface to oil-wet by stearic acid (SA) is addressed both in macroscopic and nanoscale using contact angle and atomic force microscopy technique (AFM), respectively. No apparent difference is shown by AFM images, compared to a clear trend that is obtained form contact angle measurements, where Mg 2+ ions have shown to alter the modified calcite surface to more water-wet than that in presence of SO 2− 4 ions. The adhesion forces, due to the presence of SA, are shown to be less pronounced in presence of Mg 2+ ion than that in case of SO 2− 4 . This confirms the macroscale measurements of contact angle by nanoscale level. The phenomenon of the alteration to more water-wet calcite surface is related to the distribution coefficient of SA in n-decane/water system, which decreased in presence of Mg 2+ and SO 2− 4 ions, indicating less adsorption of SA on calcite surface.
Energy & Fuels
While it is generally known that aging protocols have an important impact on the interaction between crude oil (CRO), brines, and mineral surfaces, the microscopic consequences of the various steps of aging have hardly been described. In this study, we characterize the properties of fluids and carbonate mineral surfaces throughout a series of equilibration steps at 95°C and correlate these microscopic observations with macroscopic contact angle measurements. Chemical equilibration of CRO (eqCRO) and FW (eqFW) leads to transfer of organic molecules from the former to the latter, causing also a pH change in the eqFW. Confocal Raman microscopy, atomic force microscopy, and infrared spectroscopy are used to reveal how consecutive aging of calcite in eqFW and eqCRO induces: first, in eqFW, considerable surface reconstruction and precipitation of mineral particles with colocalized organic species, and second, upon exposure to eqCRO, the formation of a second adlayer primarily composed of polyaromatic hydrocarbon-rich particles. Our results show how these interconnected microscopic chemical and topographical surface modifications give rise to more "oil wetting" contact angles after the two-step aging procedure.
Impact of surface roughness on wettability of oil-brine-calcite system at sub-pore scale
Journal of Molecular Liquids, 2019
Wettability alternation appears to be an important physicochemical process in carbonate reservoirs during low salinity water flooding. Contact angle measurement is widely used as a simple and direct method to demonstrate wettability alteration by low salinity water. The effect of various parameters, e.g., brine salinity, oil composition, and rock mineralogy on contact angle have been well documented. However, uncertainty over effect of rock surface roughness on contact angle of oil-brine-calcite is a major impediment to upscaling laboratory results and predicting wettability at field scale, knowing oil-brine-rock interaction is governed by electrostatic forces. We thus measured contact angle of oil on calcite substrates with different surface roughness (17 nm, 366 nm, and 943 nm), in high and low salinity brines. Moreover, we compared our experimental results with contact angles predicted by Wenzel's equation. Contact angle results show that in high salinity brine, contact angles decreased from 170°to 134°(36°decrease) with increasing surface roughness from 17 to 943 nm, suggesting a less hydrophobic system. Similar correlation between contact angles and surface roughness was observed in low salinity brine. Nevertheless, contact angles only slightly decreased from 117°to 101°(16°decrease) in low salinity brine, suggesting the effect of surface roughness on contact angle is more subtle in low salinity condition. We also found that for oil-brine-calcite system, the correlation between contact angle and surface roughness contradicts the trend predicted by Wenzel's equation. This is largely because the surface forces that govern oil-brine-calcite interactions are not captured by Wenzel's equation. Therefore, we hypothesize that at pore-scale level, wettability alteration by low salinity brine will likely be more subtle than that shown by contact angles when performed on smooth substrates (at sub-pore scale). To predict contact angle at pore-scale, surface roughness and surface forces governing oilbrine-calcite interactions need to be considered. The findings of this research will provide further insight into water-assisted EOR in carbonate reservoirs.
Energies, 2019
While the effect of polar-oil component on oil-brine-carbonate system wettability has been extensively investigated, there has been little quantitative analysis of the effect of non-polar components on system wettability, in particular as a function of pH. In this context, we measured the contact angle of non-polar oil on calcite surface in the presence of 10,000 ppm NaCl at pH values of 6.5, 9.5 and 11. We also measured the adhesion of non-polar oil group (–CH3) and calcite using atomic force microscopy (AFM) under the same conditions of contact angle measurements. Furthermore, to gain a deeper understanding, we performed zeta potential measurements of the non-polar oil-brine and brine-calcite interfaces, and calculated the total disjoining pressure. Our results show that the contact angle decreases from 125° to 78° with an increase in pH from 6.5 to 11. AFM measurements show that the adhesion force decreases with increasing pH. Zeta potential results indicate that an increase in p...
Shale adhesion force measurements via atomic force microscopy
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles
Wettability of sedimentary rock surface is an essential parameter that defines oil recovery and production rates of a reservoir. The discovery of wettability alteration in reservoirs, as well as complications that occur in analysis of heterogeneous sample, such as shale, for instance, have prompted scientists to look for the methods of wettability assessment at nanoscale. At the same time, bulk techniques, which are commonly applied, such as USBM (United States Bureau of Mines) or Amott tests, are not sensitive enough in cases with mixed wettability of rocks as they provide average wettability values of a core plug. Atomic Force Microscopy (AFM) has been identified as one of the methods that allow for measurement of adhesion forces between cantilever and sample surface in an exact location at nanoscale. These adhesion forces can be used to estimate wettability locally. Current research, however, shows that the correlation is not trivial. Moreover, adhesion force measurement via AFM ...