The Evolution of Reservoir Geochemistry
Published:December 01, 2006
R. Paul Philp, Michael Hsieh, 2006. "The Evolution of Reservoir Geochemistry", Reservoir Characterization: Integrating Technology and Business Practices, Roger M. Slatt, Norman c. Rosen, Michael Bowman, John Castagna, Timothy Good, Robert Loucks, Rebecca Latimer, Mark Scheihing, Hu Smith
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Reservoir geochemistry evolved during the late 1980s and early 1990s during one of the many downturns in exploration activity. A landmark paper in 1989 by William England of BP was one of the primary catalysts for the emergence of geochemistry as a tool for reservoir characterization. Among the many concepts appearing in that paper was the idea that compartments within a reservoir could be distinguished through the use of geochemical maturity parameters since oil in the different compartments had been generated at different levels of source rock maturity. At the same time, the geochemists at Chevron were utilizing high resolution gas chromatography of crude oils to demonstrate whether or not oils in different fault blocks or compartments were in communication. The increase in interest in applying geochemistry to reservoir characterization was manifested by numerous papers using many different techniques and concepts applied to a variety of reservoir problems. Many of these ideas quickly fell by the wayside but those that had real application were well received in the industry and are still in widespread use today.
Not all of these techniques are necessarily connected with communication between fault blocks but may cover topics such as wax accumulation; asphaltene precipitation; biodegradation; effects of water washing; and numerous other problems. It is also important to remember that geochemistry can be applied to characterization of gas reservoirs as well as oil reservoirs. In the same way as oil reservoirs, continuity and compartmentalization in gas reservoirs are two areas where geochemistry can play a key role. With gas samples, this is typically done through a combination of carbon and hydrogen stable isotopes. The development of the combined gas chromatograph–isotope ratio mass spectrometer now permits one to determine the isotopic composition of individual compounds, and as a result, it is a relatively facile process to determine the isotopic composition of the individual compounds in a natural gas sample. The purpose of this paper is to review the developments in reservoir geochemistry over the past two decades and to highlight this with examples of where geochemistry has been used successfully as one tool to address reservoir problems.