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Duration and Climate Effects on Meteoric Diagenesis: Non-Karstic Control on Distribution of Porosity and Permeability

Robert H. Goldstein, Zhaoqi Li, and Evan K. Franseen
University of Kansas, Department of Geology, Lawrence, KS, USA

As porosity and permeability in carbonate reservoir systems are the products of both depositional history and diagenetic alteration, predictive models typically require an understanding of deposition and diagenesis. Improved understanding of carbonate depositional systems and sequence stratigraphy has led to models for prediction of depositional facies in the subsurface. Prediction of diagenetic effects on porosity and permeability, however, has been more challenging because of the complexity of geochemical and hydrologic processes, the relative inaccessibility of such systems for study, and the immense amount of geologic time involved. Fundamentally, part of the diagenetic history of a carbonate reservoir system can be predictable from its depositional and stratigraphic framework.

This work, which is part of the ExxonMobil-sponsored Fundamental Controls on Flow in Carbonates academic alliance, presents results from a series of studies of Miocene carbonate strata from southeast Spain. The site is chosen because of its well-constrained sequence stratigraphic framework and preserved paleotopography, which allows evaluation of the diagenetic effects that are related to meteoric diagenesis associated with subaerial exposure along sequence boundaries. Furthermore, as these young strata have never been buried, the porosity and permeability result from deposition and early diagenesis alone, without the ambiguity of a later history of burial diagenesis. As both paleotopography and sequence boundaries can be either identified or reconstructed in the subsurface, this study adds to the understanding of how these parameters can be used as predictors of diagenetic alteration of porosity and permeability in carbonate reservoirs.

The results show that even with seven surfaces of subaerial exposure, each with associated meteoric diagenesis, significant diagenetic alteration was only associated with the uppermost one.

AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012