AOSTRA Underground Test Facility--Concept and Geological Setting

B. A. Rottenfusser, N. K. Alwast, J. E. Palfreyman

The Underground Test Facility in northern Alberta is being developed by the Alberta Oil Sands Technology and Research Authority (AOSTRA) as a research facility to test novel concepts for recovery of bitumen from the giant Athabasca oil sands at depths too great for surface mining and too shallow for most in-situ processes. Access to the reservoir is by wells drilled upward into Lower Cretaceous oil sands from tunnels 5 m wide at a depth of 178-182 m in the underlying Devonian carbonates. The wells level off to subhorizontal in the oil sands and can expose much more of the reservoir to thermal stimulation than conventional vertical wells. Three injection/production pairs of horizontal wells on 24-m centers and 28 vertical observation wells are currently in place to measure the response of the formation to steam stimulation and for development of a gravity drainage process.

The richest reservoir is in stacked cross-bedded channel sands up to 20 m thick, which directly overlie the pre-Cretaceous unconformity at 163 m. A few thin shales and shale breccias are present in the main reservoir. The reservoir grades up into interbedded oil sand and bioturbated shale with shale beds increasing upward and is capped by marine shales. The entire sequence represents progressively more marine environments as the area was covered by the southward transgressing Clearwater sea during Albian time.

The extreme density of logging and coring at the Phase A site provides a new level of capability in the interpretation of the highly heterogeneous oil sands.

AAPG Search and Discovery Article #91033©1988 AAPG Rocky Mountain Section, Bismarck, North Dakota, 21-24 August 1988