Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding

Jackson was funded by the TOTAL Chairs Programme at Imperial College London, and Vinogradov through the TOTAL Laboratory for Reservoir Physics at Imperial College London.Peer reviewedPublisher PD

Zeta potential of artificial and natural calcite in aqueous solution

TOTAL are thanked for partially funding Jackson under the TOTAL Chairs programme at Imperial College London, and for supporting Vinogradov through the TOTAL Laboratory for Reservoir Physics where the experiments reported were undertaken. Petroleum Development Oman are thanked for supporting Al Mahrouqi.Peer reviewedPostprin

Thermodynamic parameters of bonds in glassy materials from viscosity-temperature relationships

Doremus's model of viscosity assumes that viscous flow in amorphous materials is mediated by broken bonds (configurons). The resulting equation contains four coefficients, which are directly related to the entropies and enthalpies of formation and motion of the configurons. Thus by fitting this viscosity equation to experimental viscosity data these enthalpy and entropy terms can be obtained. The non-linear nature of the equation obtained means that the fitting process is non-trivial. A genetic algorithm based approach has been developed to fit the equation to experimental viscosity data for a number of glassy materials, including SiO2, GeO2, B2O3, anorthite, diopside, xNa2O–(1-x)SiO2, xPbO–(1-x)SiO2, soda-lime-silica glasses, salol, and α-phenyl-o-cresol. Excellent fits of the equation to the viscosity data were obtained over the entire temperature range. The fitting parameters were used to quantitatively determine the enthalpies and entropies of formation and motion of configurons in the analysed systems and the activation energies for flow at high and low temperatures as well as fragility ratios using the Doremus criterion for fragility. A direct anti-correlation between fragility ratio and configuron percolation threshold, which determines the glass transition temperature in the analysed materials, was found

Electrostatic Origins of CO2-Increased Hydrophilicity in Carbonate Reservoirs

Injecting CO2 into oil reservoirs appears to be cost-effective and environmentally friendly due to decreasing the use of chemicals and cutting back on the greenhouse gas emission released. However, there is a pressing need for new algorithms to characterize oil/brine/rock system wettability, thus better predict and manage CO2 geological storage and enhanced oil recovery in oil reservoirs. We coupled surface complexation/CO2 and calcite dissolution model, and accurately predicted measured oil-on-calcite contact angles in NaCl and CaCl2 solutions with and without CO2. Contact angles decreased in carbonated water indicating increased hydrophilicity under carbonation. Lowered salinity increased hydrophilicity as did Ca2+. Hydrophilicity correlates with independently calculated oil-calcite electrostatic bridging. The link between the two may be used to better implement CO2 EOR in fields

Temperature-dependence of the zeta potential in intact natural carbonates

The zeta potential is a measure of the electrical charge on mineral surfaces and is an important control on subsurface geophysical monitoring, adsorption of polar species in aquifers, and rock wettability. We report the first measurements of zeta potential in intact, water-saturated, natural carbonate samples at temperatures up to 120°C. The zeta potential is negative and decreases in magnitude with increasing temperature at low ionic strength (0.01 M NaCl, comparable to potable water) but is independent of temperature at high ionic strength (0.5 M NaCl, comparable to seawater). The equilibrium calcium concentration resulting from carbonate dissolution also increases with increasing temperature at low ionic strength but is independent of temperature at high ionic strength. The temperature dependence of the zeta potential is correlated with the temperature dependence of the equilibrium calcium concentration and shows a Nernstian linear relationship. Our findings are applicable to many subsurface carbonate rocks at elevated temperature

Falls and falls-related injuries in individuals with chronic ankle symptoms: a cross-sectional study

Abstract Background Falls are a major public health concern globally. While falls are associated with osteoarthritis and persistent pain at the hip and knee, falls have not been investigated in people with chronic ankle symptoms. This study aimed to compare self-reported history of falls between adults with and without chronic ankle symptoms. Secondary aims were to compare concern about falling and balance confidence between groups, and to identify factors associated with falling. Methods A total of 226 participants (134 with chronic ankle pain and/or stiffness and 92 controls) participated in this cross-sectional case–control study. Participants completed an online questionnaire about falls in the past 12 months, injuries associated with falling, concern about falling, balance confidence, function, pain and multimorbidity. Results Eighty-six (64%) participants with chronic ankle symptoms and 24 (26%) controls reported at least one fall in the last 12 months (p  0.002). There was a small effect for lower balance confidence and higher concern about falling in symptomatic participants (standardised mean difference: 0.39–0.49; p > 0.017). Logistic regression analysis identified that falling was associated with the presence of ankle symptoms (3.08 (1.20, 7.92); p = 0.02) and concern about falling (odds ratio (95% confidence intervals): 1.13 (1.05, 1.23); p = 0.002). Conclusions Falls and falls-related injuries are a problem in individuals with chronic ankle symptoms. The high falls occurrence and concern about falling in individuals with chronic ankle symptoms suggest the need for clinicians to assess these factors in this population