ORGANIC-ACIDS IN RESERVOIR WATERS - RELATIONSHIP WITH INORGANIC-ION COMPOSITION AND INTERACTIONS WITH OIL AND ROCK

Though the existence of organic acid anions in reservoir waters is well documented, their influence on the multiphase water-rock-oil interactions is not well understood. An overview of several projects directed at some of these aspects is presented. The ionic composition of formation waters from the Norwegian Continental Shelf is analysed by multivariate data analysis to discover correlations between organic acid anion cencentrations, inorganic ion composition and reservoir conditions. The effects of realistic levels of aqueous acids are investigated experimentally for migration relevant systems. The partitioning of organic acids between oil and water phases is determined, an their influence on end-point relative permeabilities and breakthrough and irreducible saturations of oil in reservoir type rocks is measured. The effects of organic acid anion levels on mineral dissolution is investigated for two types of sandstone cores, showing significant effects for a mixed sandstone.