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In many important hydrocarbon reservoirs, aluminosilicate framework grain dissolution constitutes an important part of the porosity (i.e., the Gulf Coast). Our experimental work has shown that difunctional carboxylic acids can increase aluminum solubility by three orders of magnitude. Oil field brines are observed to contain concentrations of monofunctional carboxylic acids up to 10,000 ppm, but only traces of difunctional acids. Oxidative degradation of kerogen is a commonly used technique in the study of kerogen structure, and results in extremely high concentrations of difunctional carboxylic acids (up to 40% of the carbon released from type 3 kerogen is in the form of oxalic acid).
The reduction of mineral oxidants and consequent oxidation of organic matter may be as effective in releasing peripheral difunctional carboxylic acid groups from kerogen as thermal degradation in the natural system. The coincidence in time, temperature, and space of smectite/illite ordering (release of Fe+3 from octahedral layers) and the peak concentrations of carboxylic acids suggests a possible mechanism for the generation of difunctional carboxylic acids. This mechanism would allow highly soluble difunctional carboxylic acids to be swept through adjacent sandstones just prior to hydrocarbon generation. Thus, an ideal mechanism is available for dissolving carbonates and/or aluminosilicates out of pores and pore throats, thereby enhancing porosity and permeability in hydr carbon reservoirs.
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