Model for the origin of carboxylic acids in basinal brines

Carboxylic acids are ubiquitous in basinal brines from petroleum-producing sedimentary basins. Although the absolute concentrations of individual short-chain acids vary systematically over many orders of magnitude, relative abundances are characterized by approximately constant ratios. Laboratory experiments have demonstrated that oxidation of aqueous n-alkanes proceeds through a sequence of reactions involving alkene, alcohol, ketone, and carboxylic acid reaction intermediaries. The highly specific nature of these reactions allows the relative distribution of carboxylic acids produced during oxidation of n-alkanes to be predicted quantitatively as a function of petroleum composition. A model based on the results of laboratory experiments was developed to account for the thermogenic production of aqueous carboxylic acids in sedimentary basins.