Eastern Section Meeting

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Petrophysical Characterization of a Niagaran-Salina Reef Complex Reservoir; Kalkaska 21 Field, Kalkaska Co., Northern Lower MI, USA


Multiple lines of evidence indicate the importance of diverse, overlying and adjacent facies relative to the well-known, Silurian, “dolomitized, boundstone reef core” in Niagaran-Salina reef complex reservoirs in the Michigan Basin. Study of a data-rich, reef complex reservoir (extensive core, modern log, and production data) was undertaken in the Kalkaska 21 field with emphasis on methodology modified from Lucia (1995) and Choquette and Pray (1970). This approach focuses on identification of a limited number of carbonate pore-types common in these reservoirs.

Identification of lithofacies was based off of the combined effect of primary (depositional) and secondary (digenetic) processes, and established the relationships of these lithofacies to petrophysical properties. Diverse lithofacies with similar petrophysical properties result from coincident pore types. Lithofacies and petrophysical properties were established through core, petrographic and mercury injection capillary pressure analysis in order to establish flow units and predict the spatial distribution of fluid flow properties. A depositional and diagenetic framework, developed for several Niagaran-Salina reef complex reservoirs in Michigan, facilitates spatial prediction of lithofacies in inter-well areas.

Fifteen distinct lithofacies are defined, each with comparable pore geometry, and preliminary results indicate that the individual facies have good correlation coefficient (R2) for porosity-permeability cross-plots. The spatial distribution of lithofacies in terms of pore type should allow for more reliable static geological models and enhanced flow simulation compared to historical production data. Effective static and flow simulation models are intended to optimize gas storage reservoir operations and CO2 enhanced oil recovery elsewhere in the Michigan Niagaran Reef trend.