Date of Award


Degree Type



F.J. Longstaffe


The Cold Lake oil sands occur in the Lower Cretaceous Mannville Group and cover an area of approximately 9065kmJ in northeastern Alberta, Canada. Because of the viscous nature of the bitumen in these oil sands, and their depth of burial, in situ thermal recovery methods are necessary to produce hydrocarbons. These methods include injection of steam. Unfortunately, the steam or its condensate can react with the original mineralogy of the sands, causing a loss of permeability and a reduction in the quantity of hydrocarbons that can be produced. Therefore, it is important to characterize the original mineralogy of the reservoir, especially clays, so that deleterious reactions with steam can be predicted.

The Clearwater Formation oil sands are feldspathic litharenites and litharenites, and are composed of abundant rock fragments (mostly chert and volcanic rock fragments), and lesser amounts of quartz and feldspars. Major systematic variations in the bulk mineralogy of sands from core 2-10-65-4 W4, which represents this particular Cold Lake reservoir, were not observed. However, sedimentary clasts, which are abundant within these sands, commonly contain much higher abundances of siderite and detrital clays. Bitumen saturation vanes from approximately 4% - 15% for non-clast bearing oil sands and from 2% -12% for the clasts themselves.

Diagenetic minerals are abundant in these sands, including clay minerals (berthierine, kaolinite, illite, chlorite, mixed-layer smectitic clays and glauconite), pyrite, K-feldspar, zeolites and carbonates (siderite and calcite). Although the clay mineralogy is variable throughout the core, it is dominated mostly by 0.7nm (berthierine and kaolinite) and 1 .Onm clays (illite) with lesser amounts of 1,4nm (chlorite) and 1,7nm clays (smectitic clays). Interaction of these clay minerals with hot injected fluids (mostly steam or steam condensate) may result in neogenesis (growth of new minerals in pore spaces) or physical fines migration. Both processes have strong potential to reduce the permeability of the reservoir. For example, dissolution of diagenetic berthierine, accompanied by neoformation of analcime or smectite, might be particularly important, given that berthierine can comprise up to 88% of the <2pm size-fraction. Swelling of mixed-layer smectitic clays, and the associated effects on permeability, also must be considered as both smectite/illite and smectite/chlorite are present throughout the core. Reaction of kaolinite plus carbonates to form smectite also may cause similar problems. In addition, all clays formed or modified within the pore space have the potential to contribute to the migration of fines during in situ recovery. Such behaviour can cause a substantial loss of permeability, especially close to the production well-bore.



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