--> ABSTRACT: Diagenesis and Reservoir Quality of Devonian Reservoir Rocks of Nevada, Blackburn, and Grant Canyon Fields, by S. R. Bereskin, T. M. Little, and G. D. Lord; #91022 (1989)

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Diagenesis and Reservoir Quality of Devonian Reservoir Rocks of Nevada, Blackburn, and Grant Canyon Fields

S. R. Bereskin, T. M. Little, G. D. Lord

Devonian carbonate rocks of the Basin and Range province are largely responsible for the current enthusiastic search for petroleum in Nevada. Severely dolomitized Givetian and Frasnian rocks, given various formational names, contain numerous marine intertidal to sublittoral facies that are cyclically interbedded. Exploration complications can arise from physical and chemical diagenesis; however, recent advancements in petrology and petrophysics allow evaluation and behavior predictability of fractured reservoirs from the Blackburn 16 and Grant Canyon 4 wells.

Complex diagenesis and deformation are common to the hydrocarbon-producing intervals and included numerous cementation, dissolution, and fracturing events. Abundant fractures are dominantly nonpenetrative, partially open types, and such closely spaced fractures resulted from two episodes represented by conjugate sets in each case. Dissolution porosity associated with leached Amphipora is also present. Silica, barite, and kaolinite are the most volumetrically important authigenic fracture-filling minerals. Fluorescence microscopy has revealed shallow burial diagenetic events that are masked by the more severe overprint of solution(?) brecciation of tectonically inspired diagenesis.

Further use of fluorescence microscopy and CAT scan documented the connectivity and abundance of fracture porosity. Quantitative studies demonstrated a strong correlation between CAT scan-derived porosity and porosity obtained from routine core analysis procedures. All petrologic findings must be applied to downhole conditions to insure accurate interpretation of electric log signatures.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.