Integrating Plug to Well-Scale Petrophysics with Detailed Sedimentology to Quantify Fracture, Vug, and Matrix Properties in Carbonate Reservoirs
Kansas Geological Survey
Open-file Report 99-47
Arbuckle reservoirs in Kansas have produced over 1.6 billion barrels of oil and represent an enormous resource of post-waterflood trapped oil; before these can be successfully CO2 flooded it is necessary to fully understand the distribution of porosity, permeability, and saturation
Historically, Arbuckle production is often attributed to karst-related vuggy porosity and fracturing but integration of lithofacies with petrophysical properties indicates that only certain lithofacies are reservoir rocks and that some lithofacies do not exhibit reservoir properties even when they have extensive vuggy porosity
Correlation of petrophysical properties and lithofacies indicates that matrix-scale permeability is principally a function of grain size and that all lithologies can be characterized as lying on the same general porosity-permeability trend
Reservoir rock lithofacies, exhibiting porosities from 10-25% and permeabilities from 10 to 1,500 millidarcies, include laminated grainy algal boundstones and moldic packstone and grainstone
Non-reservoir rock lithofacies include mudstone, peloidal wackestone and packstone, muddy algal boundstone, and chert. These facies are unlikely to exhibit reservoir properties at the inter-well scale even when they contain vuggy porosity
Permeability at the whole-core scale correlates well with detailed geometric mean permeability values tied to lithofacies, however, in some core vugs locally enhance whole-core permeabilities < 10 times; for non-reservoir lithologies these high permeaiblities are unlikely to represent larger scale permeabilities
In unfractured strata, differences between core and DST permeabilities may be explained by differences in flow-model assumptions and data averaging methods. Geometric mean permeabilities do not appear to accurately represent the layered flow system. Arithmetic mean permeabilities are more consistent with the conceptual flow model for this system and provide better correlation with DST-calculated permeabilities
Modeled permeabilities based on upscaled core and log data indicate that small-scale laterally persistent stratal packages exert significant control on flow properties of the entire Arbuckle section
Integration of lithologic, stratigraphic and petrophysical data at the plug, whole-core, and drill-stem test scales allows separation of the relative contributions of fractures, vugs, and matrix properties to reservoir flow
This integrated approach has applicability to the study of other Arbuckle-equivalent reservoirs elsewhere as well as unconformity related carbonate reservoirs of all ages.
Carr, J.E., McGovern, H.E., Gogel, T., And Doveton, J.H., 1986, Geohydrology of and potential for fluid disposal in the Arbuckle aquifer in Kansas, U.S.G.S. Open File Report 86-491, 101 p.
Warren, J.E., And Price, H.S., 1961, Flow in heterogeneous porous media, Soc. Petroleum Eng. J., V. 1, number 3, p. 153-170.
We gratefully acknowledge Paul Gerlach for all things database, Saibal Bhattacharya
for fruitful discussions, Dana Adkins-Heljeson for assistance with all things
network, and Tim Carr for support of this research effort.
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Last updated November 2002