Acid-gas injection in the Alberta basin, Canada: a CO 2 -storage experience

Abstract

Abstract Over the past decade, oil and gas producers in the Alberta basin have been faced with a growing challenge to reduce atmospheric emissions of hydrogen sulphide (H 2 S) that is produced from ‘sour’ hydrocarbon pools. Since surface desulphurization is uneconomic, increasingly operators are turning to acid-gas disposal by injection into deep geological formations. Acid gas, a mixture of hydrogen sulphide and carbon dioxide (H 2 S and CO 2 ), is the by-product of ‘sweetening’ sour hydrocarbons. Although the purpose of the acid-gas injection operations is to dispose of H 2 S, significant quantities of CO 2 are also being injected because it is uneconomical to separate the two gases. The acid-gas injection operations in the Alberta basin represent an analogue to geological sequestration of CO 2 . Large-scale injection of CO 2 into depleted oil and gas reservoirs and into deep saline aquifers is one of the most promising methods of geological sequestration of CO 2 , and in this respect it is no different from acid-gas disposal operations. However, before implementation of greenhouse-gas geological sequestration, a series of questions need to be addressed; the most important ones relate to the short- and long-term fate of the injected CO 2 . Thus, the study of the acid-gas injection operations in Alberta provides the opportunity to learn about the safety of these operations and about the fate of the injected gases, and represents a unique opportunity to investigate the feasibility of CO 2 geological sequestration.