The Thermal Stability of Organic Acids in Sedimentary Basins

CROSSEY, LAURA J., University of New Mexico, Albuquerque, NM

Water-soluble organic compounds in subsurface brines directly affect the evolution of porosity and permeability during sedimentary diagenesis. Recent examination of the aqueous thermal degradation of oxalic acid (a naturally occurring dicarboxylic acid) and its anions has implications for the thermal stability of dicarboxylic acids under sedimentary basin conditions. Because the thermal stability of these compounds is pH-dependent, consideration of the dissociation behavior of carboxylic acids as a function of temperature is essential for estimating the longevity of difunctional carboxylic acids. Results of burial history models suggest that dicarboxylic acid species may be long-lived in formation waters. Comparison with other experimental studies of carboxylic acids and their anions ndicates that acetate stability is greater than formate stability, which is greater than oxalate stability, which is greater than gallate and malonate stability. In addition to the implications for natural systems, the aqueous degradation behavior is critical in evaluating other types of experimental results; notably mineral dissolution studies performed at elevated temperatures in the presence of organic materials and hydrous pyrolysis experiments involving kerogens.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)