Thermal recovery of heavy oil has been a tantalizing prospect for Saskatchewan's heavy oil reservoirs. Over the past 30 years, many thermal methods have been tested in Lloydminster area, ranging from electrical heating and cyclic steam stimulation (CSS) in the early sixties, to tailor-made steam injectionprocesses. Along the way, many in situ combustion tests were also carried out, with limited success. The question is: will thermal methods ever work in the thin, relatively deep formations of Saskatchewan, many now riddled with horizontal wells? The answer is yes, if one is willing to approach each specific field situation on its own merits, and design a thermal process to suit the conditions. Selected thermal recovery projects, specifically steam injection, in Saskatchewan are reviewed to determine what worked and what did not. For example, CSS did not have a chance in the thin formations, but it did work in thicker sands; in situ combustion was unsuccessful in many field tests, but it has been a qualified success in one or two cases; steamflooding as such has been unsuccessful, but it can be made to work under some apparently unfavourable conditions. The extensive laboratory work done supporting thermal processes is also mentioned. The paper does not give another screening guide. Rather, an attempt is made to identify the conditions for the application of steam in typical Saskatchewan heavy oil reservoirs. The conclusion is that there is definitely a place for thermal methods in Saskatchewan. Extensive horizontal well drilling has not made the task any easier, and good laboratory work is the key to success, as shown by current experience.
Steam injection is the most successful heavy oil recovery method. At present, the total oil production by steam in North America is 530,000 BID1 (84,200 m3/day), of which approximately 110,000 BID is in Canada. Most of this production is by steam. In situ combustion accounts for 2,520 BID in the U.S. and 5,200 BID in Canada. (The largest steam injection project is in Indonesia, producing 250,000 BID; in Venezuela production is 277,000 BID). But the application of steam injection technology is far from uniform in the different areas. In some cases, such as Peace River and Tangleflags, great ingenuity is used to make steam workable under adverse conditions. In other case, such as Cold Lake, the steam injection technology has been dictated by the reservoir response, and has evolved accordingly.
This paper addresses the question of whether steam injection is likely to be viable in the thin formations of Lloydminster area, and if so, what forms it might take. In 1960's, cyclic steam stimulation (CSS) was tested in a number of thin sands in Saskatchewan. In most cases, the first cycle was relatively good, with an oilsteam ratio of over 0.5, but subsequent cycles produced very little oil, because solution gas, which provided the drive, was depleted.
Steam is a unique fluid: it is the best heat carrier (with the exception of certain exotic substances), with a mix of sensible and latent heats.