Intra-Reservoir Generation of Organic Acids and Late Stage Enhanced Porosity in Sandstones

Reinhard Gaupp and Robert Schoener
Earth Sciences, Friedrich Schiller University, Jena, Germany

The source of organic acids is commonly attributed to the early maturation of kerogen in source rocks. Organic acids are frequently interpreted as cause of burial related secondary porosity. Major deficiencies of this concept are insufficient oxygen in the associated kerogen and likely deactivation of the acids already within the source rocks or during migration. Experimental studies by Eglinton et al. (1987) and Seewald (2001, 2003) proved the generation of significant amounts of water-soluble organic acids (carboxylic acids) by oxidation of n-alkanes. This implies that oxidation of oil compounds and generation of organic acids is likely to occur not only in source rocks but even more effectively along migration paths and in reservoirs. We aim at supplementary experimental work, based on a wealth of field observations and lab data from Permian red bed reservoir sandstones in the Central European Basin. We want to evaluate the hypothesis, that liquid hydrocarbons in hematitic reservoirs can generate reactive organic acids and/or CO₂ during post-emplacement thermal evolution. The expected outcome could allow a better understanding of late stage (syn- and post-oil) porosity enhancement in deep basinal settings with methane source/reservoir potential (tight gas plays).

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas