ABSTRACT: Multistage Diagenesis of the Upper Devonian Rimbey-Meadowbrook Reef Trend in Central Alberta, Canada: Possible Implications for Large-Scale Fluid Flow

NING QIANG and HANS G. MACHEL, University of Alberta, Edmonton, Canada

The Upper Devonian (Leduc-age) Rimbey-Meadowbrook reef trend in the subsurface of central Alberta is being reexamined in order to determine whether it acted as a high-permeability fluid conduit system for dolomitization and petroleum migration. As a part of this study, a detailed petrographic investigation has been carried out of several reefs of the central part of the reef trend (Leduc, Glen Park, Wizard Lake, and Bonnie Glen).

Most Leduc reefs are located on top of the margin of the Cooking Lake platform. Generally, both the platform margin and the overlying reefs are pervasively dolomitized, and both have fairly high porosities and permeabilities. However, dolomitization was irregular, and fairly large parts of the Cooking Lake platform margin consist of limestones with very low porosity and/or permeability. Furthermore, diagenetic features are complex and include dolomites of variable crystal sizes and zonation and irregularly distributed anhydrite, calcite, silica, and metal sulfides.

The unexpectedly large amounts of tight limestones cast doubt on the hypothesis of the Cooking Lake platform margin being a fluid conduit. The variable distribution of several diagenetic phases suggests that formation water composition evolved through time. Further petrographic and geochemical investigations are being carried out in order to better define the properties of the reef trend.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)