Simulation of burial diagenesis in the Eocene Wilcox Group of the Gulf of Mexico basin

Abstract

Diagenesis may be evaluated quantitatively by using petrographic observations and results of paleohydrologic reconstructions in combination with geochemical reaction path model calculations. The authors have applied a reaction path method by simulating diagenesis in the Eocene Wilcox sandstones in the Gulf of Mexico basin to evaluate the effects of variable Pco 2, fluid composition, amount of rock reaction and burial history. The results show that increases in Pco 2 cause the amount of carbonate phases to increase, instead of creating secondary porosity, and closed system reactions with a chemically evolved pore fluid cause a reduction in the amount of carbonate phases, thereby preserving primary porosity. Diagenesis resulting from increased rock reaction per pore volume is characterized by a dominance of Fe-free mineral phases, and albite forms in simulations at temperatures above 100°C with neutral pH evolved fluids. The results approximate petrographic observations of previous workers on the Wilcox with only a few exceptions. Continued simulations using different fluid compositions and organic acid anions may increase the capability to reproduce observed paragenetic sequences.