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Chad R. Harris1, Murray K. Gingras1, Michael J. Ranger2, S. George Pemberton1
(1) University of Alberta, Edmonton, AB
(2) M.J. Ranger Consulting Ltd, Chestermere, AB

Abstract: Detailed mapping and analysis of a frozen paleo oil-water contact, Athabasca Oil Sands; implications regarding reserve calculation and reservoir management

The McMurray Formation is an upper Aptian to lower Albian deposit located in northeast Alberta. The largest known hydrocarbon resource, it contains almost one-trillion barrels of original bitumen in place. The sediments are indicative of fluvial and estuarine deposition. At present, the McMurray Formation sits near the surface and is exposed along cutbanks of local rivers. Microbial degradation has frozen the oil in place, allowing three-dimensional inspection of the paleo oil-water contact.

The oil-water contact in the McMurray Formation is a mappable and complex feature of the deposit. Although it has been studied regionally, no explanation or model has been put forward to explain the contact’s patchy, undulating, and generally variable nature at the outcrop scale. Development of an explanation through detailed mapping of this contact helps elucidate these variations and may provide insight to other deposits. The variation in the contact can also influence reserve calculations and proposed drill hole locations or mine expansions.

Several outcrops along the Steepbank River were measured, correlated, and sampled to generate maps and cross-sections. Hand samples and thin sections were examined for grain size and bitumen content. A new method of measuring a contact at the outcrop scale, using a fluid level connected to a hydrostatic-pressure sensing device, obtained reliable vertical centimeter accuracy data on the contact’s behaviour.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana