The Role of Moldic Porosity in Paleozoic Kansas Reservoirs and the Association of Original Depositional Facies and Early Diagenesis With Reservoir Properties

Kansas Geological Survey
Open-file Report 2003-32

Summary of Petrophysical Trends

Petrophysics of lithofacies at the core-plug scale, and for many lithologies at the whole-core scale, are dominantly controlled by grain size. Each lithology exhibits a generally unique range of petrophysical properties modified by the presence of fractures, vuggy porosity, and grain size variation within the lithologic class. Facies comprising multiple lithologies of differing grain size exhibit bulk properties that are scale-dependent and are a function of the architecture of the constituent facies.

Variance in permeability at any given porosity is approximately two orders of magnitude and may be primarily attributed to the influence of such lithologic variables as the ratio and distribution of matrix and fenestral/vuggy porosity, grain size variations, and subtle mixing or interlamination of lithologies. Fracturing enhances permeability but does not add significantly to porosity. Vuggy porosity is largely isolated in mudstones, even up to vuggy porosities as high as 8%, but is better connected in wackestones. Vuggy pores can be well connected where vuggy porosity is extensive near the unconformity surface.

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Last updated June 2003