The Impact of Pore Water Chemistry on Carbonate Surface Charge and Oil Wettability

Hiorth, A.; Cathles, L. M.; Madland, Merete Vadla

doi:10.1007/s11242-010-9543-6

Cited by 401 publications

(249 citation statements)

References 31 publications

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“…The d-plane charge density (i.e., that in the diffuse layer) is set by Poisson-Boltzmann (Verwey and Overbeek 1948;Berg 2010), as outlined in Appendix C: Hiorth et al (2010) and Heberling et al (2011).…”

Section: Methodsmentioning

confidence: 99%

Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

et al. 2017

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SummaryLow-salinity waterflooding (LSW) is ineffective when reservoir rock is strongly water-wet or when crude oil is not asphaltenic. Success of LSW relies heavily on the ability of injected brine to alter surface chemistry of reservoir crude-oil brine/rock (COBR) interfaces. Implementation of LSW in carbonate reservoirs is especially challenging because of high reservoir-brine salinity and, more importantly, because of high reactivity of the rock minerals. Both features complicate understanding of the COBR surface chemistries pertinent to successful LSW. Here, we tackle the complex physicochemical processes in chemically active carbonates flooded with diluted brine that is saturated with atmospheric carbon dioxide (CO 2 ) and possibly supplemented with additional ionic species, such as sulfates or phosphates.When waterflooding carbonate reservoirs, rock equilibrates with the injected brine over short distances. Injected-brine ion speciation is shifted substantially in the presence of reactive carbonate rock. Our new calculations demonstrate that rock-equilibrated aqueous pH is slightly alkaline quite independent of injected-brine pH. We establish, for the first time, that CO 2 content of a carbonate reservoir, originating from CO 2 -rich crude oil and gas, plays a dominant role in setting aqueous pH and rock-surface speciation.A simple ion-complexing model predicts the calcite-surface charge as a function of composition of reservoir brine. The surface charge of calcite may be positive or negative, depending on speciation of reservoir brine in contact with the calcite. There is no single point of zero charge; all dissolved aqueous species are charge determining. Rock-equilibrated aqueous composition controls the calcitesurface ion-exchange behavior, not the injected-brine composition. At high ionic strength, the electrical double layer collapses and is no longer diffuse. All surface charges are located directly in the inner and outer Helmholtz planes.Our evaluation of calcite bulk and surface equilibria draws several important inferences about the proposed LSW oil-recovery mechanisms. Diffuse double-layer expansion (DLE) is impossible for brine ionic strength greater than 0.1 molar. Because of rapid rock/brine equilibration, the dissolution mechanism for releasing adhered oil is eliminated. Also, fines mobilization and concomitant oil release cannot occur because there are few loose fines and clays in a majority of carbonates. LSW cannot be a low-interfacial-tension alkaline flood because carbonate dissolution exhausts all injected base near the wellbore and lowers pH to that set by the rock and by formation CO 2 . In spite of diffuse double-layer collapse in carbonate reservoirs, surface ion-exchange oil release remains feasible, but unproved.Introduction LSW refers to improved oil recovery achieved by waterflooding a reservoir with brine of lower salinity than that of the field brine. The process is alluring because of simplicity, favorable economics, and large potential. In some applications, seawater is inj...

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Section: Methodsmentioning

confidence: 99%

Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

et al. 2017

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“…The surface chemistry of most of the carbonate rocks significantly influences surfactant adsorption. Complex dissolution behavior is observed in certain minerals in carbonate rocks such as dolomite (CaMg (CO 3 ) 2 ), calcite (CaCO 3 ) and magnesite (MgCO 3 ) (Hiorth et al 2010). Interestingly, the isoelectric point of calcite is known to be dependent on the pH and sources of materials, equilibrium time and ionic strength in aqueous solutions .…”

Section: Overcoming Challenges In Eor: Future Perspectivesmentioning

confidence: 99%

Review of surfactant-assisted chemical enhanced oil recovery for carbonate reservoirs: challenges and future perspectives

et al. 2017

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“…The non-stoichiometry at 92 • C indicates that, e.g., CO 2− 3 ions are produced. The observed discrepancy between the estimated mass loss (from IC data) and the mass loss measured on the scale strengthens the need for complete geochemical models such as those presented in [18]. More detailed geo-chemical investigations of the rocks, before and after experiments, are required to determine whether or not the production of non-carbonates, such as silicate bearing clays, can be at play.…”

Section: Discussionmentioning

confidence: 99%

“…The same mass loss discrepancy has been reported and discussed earlier by Nermoen et al [17] for MgCl 2 flow through Liège chalk. Equilibrium calculations indicate that the silicate minerals that are present in some of these chalks will dissolve when using MgCl 2 brines at these pressure and temperature conditions [18,19]. Thus, dissolution of silicates (clays, quartz etc.)…”

Section: How Chemical Interactions Changes Rock Propertiesmentioning

confidence: 99%

“…For example adsorption processes occur at short time-intervals since it may occur within 1-2 pore volumes injected, while dissolution/precipitation is time-dependent occurring during injection for hundreds of pore volumes [17]. Rock-fluid interactions estimated from equilibrium calculations become increasingly important with temperatures above 100 • C, reported in e.g., [18][19][20]. At these conditions they showed that when seawater is injected into chalk reservoirs it becomes supersaturated with respect to magnesium bearing minerals, e.g., dolomite, magnesite, huntite, and brucite.…”

Section: Introductionmentioning

confidence: 99%

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How Stress and Temperature Conditions Affect Rock-Fluid Chemistry and Mechanical Deformation

et al. 2016

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We report the results from a series of chalk flow-through-compaction experiments performed at three effective stresses (0.5, 3.5, and 12.3 MPa) and two temperatures (92 and 130 • C). The results show that both stress and temperature are important to both chemical alteration and mechanical deformation. The experiments were conducted on cores drilled from the same block of outcrop chalks from the Obourg quarry within the Saint Vast formation (Mons, Belgium). The pore pressure was kept at 0.7 MPa for all experiments with a continuous flow of 0.219 M MgCl 2 brine at a constant flow rate; 1 original pore volume (PV) per day. The experiments have been performed in tri-axial cells with independent control of the external stress (hydraulic pressure in the confining oil), pore pressure, temperature, and the injected flow rate. Each experiment consists of two phases; a loading phase where stress-strain dependencies are investigated (approximately 2 days), and a creep phase that lasts for 150-160 days. During creep, the axial deformation was logged, and the effluent samples were collected for ion chromatography analyses. Any difference between the injected and produced water chemistry gives insight into the rock-fluid interactions that occur during flow through the core. The observed effluent concentration shows a reduction in Mg 2+ , while the Ca 2+ concentration is increased. This, together with SEM-EDS analysis, indicates that magnesium-bearing mineral phases are precipitated leading to dissolution of calcite. This is in-line with other flow-through experiments reported earlier. The observed dissolution and precipitation are sensitive to the effective stress and test temperature. Higher stress and temperature lead to increased Mg 2+ and Ca 2+ concentration changes. The observed strain can be partitioned additively into a mechanical and chemical driven component.

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The Impact of Pore Water Chemistry on Carbonate Surface Charge and Oil Wettability

Cited by 401 publications

References 31 publications

Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

Review of surfactant-assisted chemical enhanced oil recovery for carbonate reservoirs: challenges and future perspectives

How Stress and Temperature Conditions Affect Rock-Fluid Chemistry and Mechanical Deformation

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