Mining at Athabasca - A New Approach to Oil Production

Abstract

Abstract The first large-scale commercial extraction plant in the Athabasca tar sands region of Canada begins operating in late 1967. The start of this plant hails the beginning of the use of mining technology in the production of crude oil on this continent. This article reports on two basically different mining approaches that could be used in a commercial tar sands, plant, and details economics and types of equipment to be used. Introduction Geological studies, including results from approximately 2,000 test holes, outlined the deposit and established the reserves in the Athabasca region.' The total in-place reserve of bitumen is calculated to be approximately 625 billion bbl. Of this amount, it is estimated that about 45 percent can be recovered by known techniques and transformed into a marketable synthetic crude oil. Hence, proved reserves in the tar sands total about 285 billion bbl of recoverable synthetic crude oil. Compare these reserves with two other major sources of oil in North America: conventional oil and potentially producible Colorado oil shales. Proved reserves of conventional oil are currently placed at 49 billion bbl. Total in-place reserves of shale oil are estimated at over 2 trillion bbl; but, on the basis of current technology, only 80 billion reserves of tar sand oil are more than twice the combined total of conventional oil and shale oil proved reserves. Description of Ore Body Though extremely variable in nature, good quality ore body in the Athabasca tar sands covers about 10,000 sq miles. The average thickness is 150 ft and the ore body reaches a maximum thickness of about 400 ft. The deposit is covered by overburden that varies in depth from a few feet to as much as 2,000 ft. Oil saturation varies from trace amounts to as much as 18 percent by weight. In a so-called good, average, potentially commercial area, the average saturation ranges from 10 to 15 weight percent. On this basis, at an average thickness of 150 ft, 1 sq mile of tar sand contains over 100 million bbl of bitumen in place - the equivalent of a major oil field. The extent of the overburden thickness determines how the bitumen might be recovered from the ore body. As a result, the main Athabasca oil deposit (Fig. 1) is generally divided into two principal areas: one where oil is recoverable by mining methods and the other where oil is considered recoverable only by in situ methods. Proved reserves of recoverable synthetic crude oil in these two areas are estimated at approximately 85 billion and 200 billion bbl, respectively. Division of the two areas has been roughly determined by the amount of overburden as related to the thickness of corresponding tar sand beds. However, this relationship is continually changing to allow for greater recoveries in the mineable area as operational techniques are improved. JPT P. 1337ˆ