Buschkuehle, Beate E.¹, Karsten Michael¹, Kristine Haug¹, Stefan Bachu¹
(1) Alberta Energy and Utilities Board - Alberta Geological Survey, Edmonton, AB

ABSTRACT: Acid Gas Injection into Upper Devonian Carbonates in West-Central Alberta, Canada - Analogues for Geological Sequestration of Carbon Dioxide

Oil and gas producers in western Canada have been faced with a growing challenge to reduce atmospheric emissions of hydrogen sulphide (H₂S) produced from sour hydrocarbon pools due to environmental regulations. Many operators are turning to acid gas disposal by injecting into deep geological formations. In addition to providing a cost-effective alternative to sulphur recovery, the deep injection of acid gas - a mixture of H₂S and CO₂ - reduces emissions of noxious substances into the atmosphere. Acid Gas Injection therefore constitutes a commercial-scale analogue for the reduction of CO₂ emissions through geological sequestration.
The Upper Devonian Nisku Formation and Wabamun Group in west-central Alberta host 4 of 39 acid-gas injection operations currently active in western Canada. Injection targets in the Nisku are depleted hydrocarbon reservoirs, whereas the Wabamun is a regional aquifer. Approximately 40 million m³, or 60 kt acid gas have been injected into the four Devonian sites since 1994.
The Nisku Formation consists of isolated reefal carbonate build-ups, which are sealed by surrounding shales. The Wabamun Group is a thick sequence of shallow marine, massive platform carbonates. Both carbonate units contain laterally continuous, dolomitized intervals, which form the major injection units. The subsurface depths of the injection intervals range from less than 2200 m to 3400 m, and their thickness varies between 15 and 90 m.
The relatively long record of acid gas injection in Alberta (Western Canada Sedimentary Basin) indicates that the large-scale CO₂ storage in on-shore continental sedimentary basins is feasible.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.