Enhanced Oil Recovery: Retrospect And Prospect

Abstract

Introduction Outside of the ‘oil patch’, few people are aware that an oil reservoir normally will yield only a fraction of the oil held underground. However, much time and effort has been devoted to projects designed to recover a higher proportion of oil-in-place, to what in industry jargon is called enhanced recovery techniques. At present, enhanced recovery schemes1 account for about one-third of Alberta's conventional recoverable crude oil reserves. And as in the fullness of timeexploration prospects suffer from depletion, the ability to obtain more from what has already been found becomes of progressively greater importance as a source of additional oil supply. This paper looks at various aspects of enhanced recovery over the last decade or so, focussing on experience in Alberta where some 85 per cent of Canada's current conventional oil reserves is located. Trends in the nature and volume of reserves, costs, pricing provisions and economic incentives are examined. Finally, comments are made on the future outlook. Enhanced Recovery Reserve Trends Table 1 shows data for selected years on key features of Alberta oil reserves over the past decade. Over the 1973 to 1983 period, the TABLE 1. Recent trends in Alberta oil reserves. Available in Full Paper. average recovery factor for Alberta crude oil reserves fell by four percentage points [Column (2), Table 1], a reflection of a shift in the mix of reserves toward those with lower primary recovery factors especially heavy oil deposits such as Suffield and Provost. The relatively static volume of enhanced recovery reserves [Column (3) has somewhat reduced the share of such reserves in the over-all total [Column (4)] 2. The decline of late in the enhanced reserves recovery factor [Column (5) J is caused by the downward revision of many light and medium oil waterflood schemes. Examples here include Judy Creek BHL and Pembina Belly River. In short, the story of the last decade is that enhanced recovery reserves have shown no distinctive trends: they account ow for much the same proportion of provincial reserves as they did in 1973;similarly, the average recovery factor for enhanced recovery schemes has remained virtually constant. These trends seem disappointing in that although oil prices have been subjected to government controls nevertheless average wellhead prices rose over the decade by some $164/m3 ($26/bbl), an increase very considerably in excess of the rate of inflation. In other words, prices rose markedly in real terms. Ostensibly, suchan environment should and/or would ake the inception of new enhanced recovery schemes-especially those economically dubious at lower price levels more attractive and lead one to expect a strong growth in enhanced recovery reserves3. What, then, has happened to thwart the inception of more enhanced recovery schemes? The answer must lie in the interaction of the key elements of costs, ‘net back’ prices and technological scope. We look at each of these in turn.