Xn. Xie et Nr. Morrow, WETTING OF QUARTZ BY OLEIC AQUEOUS LIQUIDS AND ADSORPTION FROM CRUDE-OIL/, Colloids and surfaces. A, Physicochemical and engineering aspects, 138(1), 1998, pp. 97-108
Contact angles for crude oil and brine on smooth quartz are sometimes
used to assess the wettability of sandstone reservoirs. In this paper,
the dynamic Wilhelmy plate technique is applied to the study of wetti
ng of quartz by oil and brine. Changes in wetting of the quartz plate
from a completely water-wet state were induced by adsorption from crud
e oil or de-asphalted crude oil (maltenes). Other variables included b
rine composition, pH, aging temperature and time, the solvent used to
remove excess crude oil from the plate, and the temperature of measure
ment. The effect of plate speed and allowing an equilibration time dur
ing the course of measurement were also investigated. Force-distance r
elationships for a quartz plate passing through an oil-brine interface
were used to obtain water-receding and water-advancing contact angles
under dynamic conditions. Wetting states ranged from completely water
-wet through hybrid-wet (very large contact angle hysteresis) to very
strongly oil-wet. Contact angle hysteresis was often observed. Water-r
eceding force-distance curves sometimes exhibited small-scale fluctuat
ions for receding contact angles in the range of about 62-100 degrees.
These were ascribed to heterogeneity of wetting. Two modes of contact
angle transition, pinning and slippage, were observed. Experimental r
esults were compared with predicted force-distance relationships given
by interface pinning during transitions from receding to advancing co
ntact angles. Slippage during contact angle transitions was usually ob
served for receding angles in the range of 30 degrees to about 60 degr
ees with associated advancing angles in the range of 65-165 degrees, S
lippage was eliminated by allowing an equilibration time of about 30-6
0 min prior to reversing the direction of movement of the plate; exper
imental results were then in close agreement with theory. (C) 1998 Els
evier Science B.V.