(1) Unocal Corporation, Sugar Land, TX
ABSTRACT: Facies-Controlled Hydrothermal Dolomite in Devonian Reservoirs, Western Alberta Basin, Canada
Hydrothermal dolomites are important hydrocarbon reservoirs in the Devonian of the western Alberta Basin, Canada. In many cases, hydrothermal waters have followed depositional facies resulting in a facies-controlled hydrothermal dolomite rather than a structurally controlled dolomite. Three examples of facies-controlled hydrothermal dolomite are the Swan Hills shelf, Wabamun over Leduc buildups in the deep basin, and Wabamun on the Peace River Arch. In the Swan Hills shelf, grainstones were preferentially dolomitized. The dolomitized grainstones were deposited along the shelf margin and along embayments into the shelf. Micrite-rich shelf interior and slope facies were not dolomitized. In the Wabamun in the deep basin, burrowed lagoonal mudstones were preferentially dolomitized, but adjacent grainstones remained limestone. In the Wabamun of the Peace River Arch, depositional mud mounds were preferentially dolomitized; whereas more open-marine wackestones, packstones and grainstones were not. In some cases, hydrothermal dolomite apparently followed and overprinted an early facies-controlled dolomite. In other cases, certain limestone facies preserved porosity and permeability until hydrothermal brines flowed through.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.