--> Abstract: The Hidden World of Dolomites: Self-Organization of Porosity and Permeability at the Decameter Scale During Dolomitization, by David Budd and Matthew J. Pranter; #90039 (2005)

Datapages, Inc.Print this page

The Hidden World of Dolomites: Self-Organization of Porosity and Permeability at the Decameter Scale During Dolomitization

David Budd and Matthew J. Pranter
University of Colorado, Boulder, CO

Dolomites are typically characterized by representative but spatially uncorrelated sampling. This strategy can define the general petrophysical character of a dolostone, but is there a hidden world of information that has been missed? We sampled, at a 1-ft spacing, two ~490 ft lateral transects through two dolostone beds of the Mississippian Madison Formation. Porosity, permeability, trace-element concentrations, and abundance of pore types were determined. Each attribute shows periodic oscillations in abundance across both transects. Based on variogram analyses, these features occur at periodicities of ~30 ft for porosity and log permeability, ~45 ft for Fe, ~60 ft for % moldic porosity, and ~100 ft for Sr and Na. The fact that all attributes exhibit these oscillations indicates that the pattern is neither a depositional characteristic nor a function of pore type. Rather, we suggest the oscillatory patterns are the product of self-organization during dolomitization. That is, feedbacks during dissolution, transport, and precipitation produce the periodic structures from an initial non-patterned state without any inherited template. If the reaction front is planar, the product might be a series of wave fronts. More likely is that the reaction front fingers and meanders, which in turn leads to reaction-induced flow diversion, the re-focusing of the flow past the reacted mass, and formation of a 3D spot pattern in attributes. In either case, a single lateral transect will yield the oscillatory structures observed. The patterns in porosity and permeability will affect recovery efficiencies and break-through times of water floods.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005