Contact Angle And Interfacial Tension Studies of Some Hydrocarbon-Water-Solid Systems
Authors: McCaffery Frank G. , Mungan Necmettin 
Published: March 2010

An apparatus was built to measure interfacial tensions and contact angles of hydrocarbon-water-solid s:rstems at variable temperatures and atmospheric pressure. Interfacial tensions were measured for benzene, n-dodecane, Klearol and nitrogen against water over a temperature range of 25 to 90 °C. For the n-dodecane-water system, a water-soluble cationic surfactant, a water-soluble nonionic surfactant and an oil-soluble carboxylic acid were added. Relationships among interfacial tension, temperature, surfactant concentration and interface age were determined.

Contact angle measurements were made primarily for the n-dodecane-water system on flat quartz and calcite crystal surfaces. An oil-soluble amine, a carboxylic acid, and water-soluble anionic, cationic and nonionic surfactants were used as additives. Without the surfactants, the carefully cleaned solids were completely water-wet. Finite contact angles resulted from contamination or the addition of certain of the surface-active compounds, and were generally accompanied by hysteresis. The magnitude of the contact angles indicates the orientation and degree of packing of surface-active molecules at solid-liquid interfaces, and points out the role of surface charge and polarity in adsorption.

Introduction

IN CANADA AND THE UNITED STATES, approximately 90 per cent of all the oil produced through the application of enhanced recovery processes is obtained bywaterflooding. The rising cost of exploring for new oil, coupled with the higher cost of applying alternate recovery schemes, creates an incentive for waterfloods to be conducted under conditions favouring most efficient oil recovery. This requires that research be carried out into factors which might significantly improve the immiscible displacement mechanisms.

Mungan(1) has shown that interfacial effects in the immiscible displacement of oil from porous media can significantly influence the recovery, and Melrose(2) has recently discussed the role which interfacial phenomena or capillary forces play in determining the extent to which a fluid can be displaced from a porous solid by another immiscible fluid. A general discussion of capillarity was given recently by Schwartz(3). Three factors affect capillary forces in porous media:the interfacial tension between the two fluids,the contact angle between the fluids and the solid surface, andthe pore size and pore size distribution of the porous media.

Because of the small pore sizes and the large interfacial areas existing between oil, water and the reservoir rock, the interfacial forces become appreciable and can dominate in the displacement. Moore and Blum(4) estimated that to mobilize residual oil structures, assumed to be several grain sizes in length, through average reservoir rock openings would require a pressure gradient of something like 500 psi/ft - an impossible value to attain in operations. An alternative is to reduce the interfacial tension to low values, say 0.01 dyne/cm, which reduces the pressure requirement to move these same residuals to only 0.33 psi/ft.

Chatenever, et al.(5), using microscopic examination of fluid movement in all-glass and all-lucite cells, showed that the residual oil formation and structures we.re significantly different under water-wet and oil-wet situations.