Adhesion of Oil to Kaolinite in Water

Abstract

Uniform coats of kaolinite particles on a flat glass substrate were prepared to be sufficiently smooth and thin to allow reliable measurement of contact angles of captive crude oil drops in a range of salt solutions, without any particle removal. The contact angle hysteresis was used to infer the extent of oil adhesion via rupture of the intervening water film and anchoring of charged groups to kaolinite. For sodium chloride solutions, adhesion decreases monotonically with pH and/or salinity, with strong adhesion only manifested under acidic conditions with salinity at most 0.1 M. Calcium chloride solutions at pH around 6 switch from strong adhesion in the range 0.001-0.01 M to weak adhesion at higher concentrations. For all mixtures of sodium and calcium chlorides investigated, a total ionic strength above 0.1 M guarantees a weak adhesion of oil to kaolinite. Results are qualitatively consistent with theoretical expectations of electrostatic interactions, with H(+) and Ca(2+) being potential-determining ions for both interfaces.

Consequences of shifted ion adsorption equilibria due to nonelectrostatic interaction potentials in electrical double layers

“…6 shows in ([NaCl], pH) space the experimental boundary between adhesion (below) and non-adhesion (above), calculated from camera image analysis (solid black line) or solution spectroscopy (dashed-dotted black line) of adhering oil. The two measures gave good agreement and the trends agreed with traditional adhesion testing of drops of other crude oils and silicate substrates [53,54,[57][58][59][60][61][62].…”

“…In the most common macroscopic test method [53,54,[57][58][59][60][61][62], a captive oil drop is contacted with the substrate for a short time and then retracted. The overall interaction is judged as adhesive or nonadhesive if oil remains in contact or is cleanly removed.…”

“…The overall interaction is judged as adhesive or nonadhesive if oil remains in contact or is cleanly removed. For a single 1:1 electrolyte, at concentrations ranging up to typical reservoir brine ionic strengths of around 1 M and at varying pH, adhesion exhibits an almost universal trend irrespective of the oil or the silicate substrate [54,57,[59][60][61][62]. Low concentration and low pH leads to oil adhesion, while high concentration and high pH gives nonadhesion.…”

Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations

“…The abundance of polar components in crude oils will probably reduce the effect of the contact angle variations compared with the idealized situation of a single fatty acid component, as reported by various authors. 23,24,48 On the other hand, the increased temperatures in the reservoirs, which tend to promote the adsorption of polar organics, might increase the effect on water wettability again. 49,50 In any case, according to reservoir simulations, a reduction in the water contact angles of a few degrees is still consistent with the recovery enhancements of several percent, as seen in many core flood experiments.…”

Functionalization of micromodels with kaolinite for investigation of low salinity oil-recovery processes

“…A clean, unaltered sandstone is strongly water wet. [3][4][5] Oil-wet systems generally result in lower recovery factors compared to mixed-wet or water-wet systems for economic amounts of water injection. 2,3 Naturally occurring sandstones that encompass petroleum reservoirs contain significant amounts of clay that are natively adhered to the surface of sand grains.…”