Zeta potential of intact natural limestone: Impact of potential-determining ions Ca, Mg and SO4

Abstract

We report measurements of the zeta potential on intact limestone samples obtained using the streaming potential method (SPM), supplemented by the more ubiquitous electrophoretic mobility method (EPM). The effect of the potential-determining ions (PDI) Ca, Mg and SO4, and the total ionic strength controlled by NaCl concentration, is investigated over the range typical of natural brines. We find that the zeta potential varies identically and linearly with calcium and magnesium concentration expressed as pCa or pMg. The zeta potential also varies linearly with pSO4. The sensitivity of the zeta potential to PDI concentration, and the IEP expressed as pCa or pMg, both decrease with increasing NaCl concentration. We report considerably lower values of IEP than most previous studies, and the first observed IEP expressed as pMg. The sensitivity of the zeta potential to PDI concentration is lower when measured using the SPM compared to the EPM, owing to the differing location of the shear 2 plane at which the zeta potential is defined. SPM measurements are more appropriate in natural porous samples because they reflect the mineral surfaces that predominantly interact with the adjacent fluids. We demonstrate that special cleaning procedures are required to return samples to a pristine zeta potential after exposure to PDIs. We apply our results to an engineering process: the use of modified injection brine composition to increase oil recovery from carbonate reservoirs. We find a correlation between an increasingly negative zeta potential and increased oil recovery.

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

“…The zeta potential of calcite depends on the concentration-dependent adsorption of the lattice ions Ca 2+ , Mg 2+ and CO 3 2− in the Stern layer (the inner part of the EDL)303132333435363738394041. At the high Ca 2+ and/or Mg 2+ concentration typical of formation brines, the zeta potential of the calcite surface is positive.…”

“…At the high Ca 2+ and/or Mg 2+ concentration typical of formation brines, the zeta potential of the calcite surface is positive. Reduction of Ca 2+ and/or Mg 2+ concentration, either selectively or by bulk dilution, can invert the polarity, yielding negative zeta potential404142434445. Addition of SO 4 2− can also yield more negative zeta potential8304046.…”

“…Reduction of Ca 2+ and/or Mg 2+ concentration, either selectively or by bulk dilution, can invert the polarity, yielding negative zeta potential404142434445. Addition of SO 4 2− can also yield more negative zeta potential8304046. Several studies have suggested a link between wettability and zeta potential in carbonates, although none have shown a direct correlation between changes in zeta potential, wettability and improved recovery during CSW21404347.…”

“…Addition of SO 4 2− can also yield more negative zeta potential8304046. Several studies have suggested a link between wettability and zeta potential in carbonates, although none have shown a direct correlation between changes in zeta potential, wettability and improved recovery during CSW21404347.…”

The impact of zeta potential changes on Ceratium hirundinella cell removal and the ability of cells to restore its natural surface charge during drinking water purification

“…A study conducted by Alroudhan et al 1 found that two cations (Ca and Mg) changed the ZP (decreasing the negative magnitude of ZP) of intact lime-stone solutions as a result of increasing concentrations. It is evident from previous studies 1,10,23 that natural ZP in aqueous solutions are inuenced by the addition of ions (anion and cations), which can support aggregation of particles suspended in water accomplished by destabilization. When coagulants are added to source water during treatment, positively charged coagulants react with suspended particles (colloidal and dissolved NOM) to aggregate and form ocs that are removed during separation processes such as sedimentation.…”