Effect of synthetic drilling fluid base oils on asphaltene stability and wetting in sandstone cores

Tests of imbibition rates in Berea sandstone cores have been used to examine the wettability effects of displacement of crude oils with a number of synthetic base oils. In all cases examined to date, the products that flocculated asphaltenes from crude oils also caused water-wet sandstone cores to become markedly less water-wet or even oil-wet. Relatively minor effects on wetting were observed with base oils that did not destabilize asphaltenes. A simple diagnostic test of asphaltene stability can be used to identify specific crude oil/base oil pairs that precipitate asphaltenes.