The Lure and Challenge of the Oilsands - a look beyond SAGD
Subodh C. Gupta
With the anticipated decline in the supply of conventional oil and the rising global energy demand, world’s focus has turned to the vast potential of heavy oil and bitumen resources such as oilsands of Alberta. While there are environmental incentives to harness renewable energy sources such as wind, hydro, wave and solar power etc., the state of current technology in these areas and associated economics do not allow for a large-scale application.
Bitumen contained in the oilsands is a highly viscous, solid-like substance at the reservoir conditions. For its recovery, especially from deeper reservoirs where surface mining is not economic, it needs to be heated. This heating traditionally has been accomplished using steam. Cyclic Steam Stimulation (CSS) and Steam Assisted Gravity Drainage (SAGD) are two prominent methods of recovery used in Albertan oilsands which use steam to ‘thaw’ the bitumen and make it sufficiently mobile to facilitate its flow to the surface. Although applied on a large scale in Clearwater formation, use of CSS has not caught on for other reservoirs, mainly on account of superior promise of SAGD. In SAGD, two horizontal wells, an injector and a producer are made use of. Steam is injected in the upper injector well, and condensed water and mobilized oil are collected from the bottom producer. The process results in a growing vapor chamber in the reservoir governed by the mechanisms that include thermal diffusion and gravity flow.
SAGD is the current technology of choice for majority of the existing and upcoming in situ projects in Albertan oilsands. While SAGD is a commercial technology, in its current form it is an energy intensive process. To make bitumen recovery environmentally and economically sustainable in the long term, the oilsands industry is exploring not only to improve SAGD but also a use of novel approaches.
In this presentation the author will review current challenges faced by the industry and discuss some of these novel approaches mentioned above and technological routes being taken, for example the use of solvents, air, alternate geometries and other possible future trends in the scheme of reservoir exploitation.
AAPG Search and Discovery Article #90075©2008 AAPG Hedberg Conference, Banff, Alberta, Canada