Characterization of Burrow-Mottled Reservoirs Influenced by dolomitization

Greg M. Baniak
University of Alberta, Department of Earth and Atmospheric Sciences Edmonton, Alberta, Canada
[email protected]

This project is an integration of core, spot-permeametry, microtomography (micro-CT), thin-section, ion-microprobe, and scanning electron microscopy (SEM) data to examine the influence trace fossils have on dolomite precipitation within carbonate reservoirs. Samples used for this study come from the Devonian Wabamun Group located in the Pine Creek gas field of western Canada.

An abundance of dolomitization occurring within and adjacent to the burrow fabrics suggests that the burrows are a controlling factor on initial dolomitization within the Wabamun Group. Spot permeametry and micro-CT work have shown that the burrows preferentially control permeability enhancement and porosity distribution within the reservoir. This suggests that movement of natural gas is initially concentrated through the burrow fabric during production.

To better understand the controls on dolomitization within the burrow fabrics, SEM and ion-microprobe analysis has been conducted. Initial examination of SEM data shows the preferential formation of sucrosic dolomite within the burrows. Subsequent ion-microprobe work has been used to obtain carbon and oxygen isotopes from the dolomite and calcite within the burrows and matrix. Ultimately, it is anticipated that the results obtained from these isotopes will help decipher the mechanism(s) causing preferential dolomitization to occur within the burrows relative to the limestone matrix.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects