DETERMINATION OF RELATIVE WETTABILITY OF POROUS SANDSTONES BY IMBIBITION STUDIES

The effective wettability of consolidated sandstone rocks has been det ermined using the Washburn equation by measuring the rate of imbibitio n of water, ethanol and their mixtures into cores and thin rectangular sections. The rocks behaved as low energy surfaces with a critical su rface energy of spreading, as defined by Zisman, of 28 mN m(-1). This behaviour is believed to be caused by clay particles or organic materi al present on the pore surfaces. A discussion of the validity and limi tations of the Washburn equation for obtaining effective wettabilities in consolidated porous media is presented. The general conclusion is that effective wettability depends on the preparation and general cond itions of the samples.