For the purposes of this study, we have examined the demands that will be made on the environment of the Bituminous Sands Area by the production of 1.3 million barrels per day of bitumen by in situ methods of extraction, in situ extraction implying the recovery of bitumen from the pores without disturbing the reservoir rock. This process usually involves the drilling of many injection and production wells into the reservoir in a closely spaced pattern and the collection and delivery of the bitumen to a field plant for upgrading to a synthetic oil.
Most of the in situ methods require the application of differential pressure to the reservoir, and for this reason it is generally conceded that for safe and effective operations with today's technology, the overburden should not be less than 500 feet. The study area is therefore confined to that portion of the Athabasca deposit buried to depths of more than 500 feet in the Bituminous Sands Area. This in situ area comprises about 3700 square miles and is about 64 percent of the Athabasca deposit within the Bituminous Sands Area. Some 2000 square miles of the Athabasca deposit, all of it buried deeper than 500 feet, lies outside the Bituminous Sands Area and is not considered in this report. In addition, that portion of the Athabasca deposit covered by 200 to 500 feet of overburden has not been included, although it may conceivably be developed by in situ methods at some future time.
Existing patents on in situ technology and extensive literature on secondary recovery of petroleum have been reviewed. It is clear that much of this technology cannot be transferred to the Athabasca deposit without considerable modification.
Our predictions, at this time, of the environmental effects of large scale in situ production are subject to some significant limitations. Firstly, there is no commercial production from in situ operations in the Bituminous Sands Area, and although some experimental work has been carried out by two oil companies with two of the most promising methods, factual data is scarce. Secondly, the area has until very recently been largely inaccessible and little factual data exists on the meteorology, hydrology, soils, vegetation and wildlife of the area. Current evaluations of the economic values of the renewable resources of the area were not available during the preparation of this report.
Within this context, we have proceeded to examine in a theoretical way those actions which we believe will have a significant effect on the environment in the Bituminous Sands Area should commercial in situ production begin.
Shell Canada Limited and Muskeg Oil Company applied to the Energy Resources Conservation Board for permission to go into commercial or semi-commercial production, but both applications were subsequently withdrawn. The Shell Canada limited submission was based on a steam injection system for extraction and included data on upgrading the bitumen to a synthetic oil in two stages. The first stage processing was to take place at the production site and the final upgrading in Edmonton. The Muskeg oil company submission was concerned only with the production of the raw bitumen by a modified underground combustion method and did not include details of the bitumen upgrading phase; thus it is considered to be a semi-commercial venture. Because of these differences, it is difficult to make meaningful comparisons between the two systems. For example, in the Muskeg Oil Company application, details of the field gases are given because, in the absence of a processing plant, they will have to be flared or vented. In the Shell application, no field gas analyses are given because they enter the processing plant along with the steam and bitumen emulsion. Similarly, saline water produced along with the bitumen emulsion in the Muskeg Oil Company method has to be concentrated and disposed of before the bitumen is delivered to a distant processing plant, whereas in the Shell Canada Limited system, the saline water in the emulsion is diluted by process waters and ultimately discharged into the surface drainage system.
From our examination of these two applications for commercial and semi-commercial production by in situ methods, we believe the following major environmental impacts can be anticipated.
1. Air quality
2. Land clearing
3. Water consumption
4. Groundwater contamination
5. Liquid effluents
Carrigy, M.A. and McLaws, I.J. (1973): Athabasca tar sands study, the environmental impact of in situ technology; Alberta Research Council, ARC/AGS Open File Report 1973-23, 88 p.