Print this pageInteraction of Polar Compounds between Oil, Water and Rock: Towards a New Generation of Reservoir Geochemical Tools
LARTER, STEPHEN R., BARRY BENNETT, MEI CHEN, BERNI F. J. BOWLER, JASON D. DALE and ANDREW C. APLIN
Basic studies of polar compounds in petroleum systems provide a large amount of data on the nature and rate of interactions between petroleum, water and rock minerals in petroleum reservoirs. This allows the development of new geochemical tools relevant to the determination of field charging directions, wettability, oil leg proximity and the abundance of toxic compounds in produced waters. We describe two geochemical systems that have utility in various reservoir geochemical applications. The partition of alkylphenols and aromatic hydrocarbons such as benzene and toluene from oil into oilfield waters occurs on millimeter scales within minutes; partition coefficients are controlled principally by water salinity, oil composition and temperature, with pressure having little influence. Field data indicate that partition equilibrium is common between oils and oilfield waters and allow us to assess the levels of dissolved organics in production waters and to potentially use organic so lutes in waters as quantitative oil proximity indicators.
The sorption of benzocarbazoles onto solid surfaces takes many months in the laboratory, with field data suggesting that the real rates of sorption might occur on a 10{5}-10{6} year timescale. Selective sorption of benzo[a]carbazole over benzo[c]carbazole from migrating oil provides a chemical mileometer for practical assessment of oil migration range and aids in assessing field charging direction. These innovations in geochemical technology are described and illustrated with field examples.