Mineral reactions in quartzose rocks during thermal recovery of heavy oil, Lloydminster, Saskatchewan, Canada

Abstract

X-ray diffraction analysis, thin section analysis and scanning electron microscopy were used to compare the mineralogy of pre- and post-recovery cores from the Lower Cretaceous Sparky interval in Aberfeldy steamflood and fireflood pilot projects. Lloydminster area, Saskatchewan, Canada. The objectives were to document the potential changes in mineralogy that may occur during recovery of heavy oil and to evaluate the risk of formation damage from mineral reactions. These unconsolidated sediments are very quartzose (90%) and they also contain feldspars, clays (mainly kaolinite) and carbonate cements (siderite and ankerite). The formation of new minerals in the burned zone and the plugging of pores by coke in the zones below the burned zones is likely to cause small reductions in porosity and permeability. Illite formation is observed in the steamflood pilot but is not extensive enough to cause formation damage. Carbonate scale is observed at the producing wells. During steamflooding illite and chlorite are formed; the smectite which is observed is due to mud invasion. During fireflooding, illite forms in the coked zones, whereas K-feldspar and hematite form in the burned zones. Thermodynamic calculations of the stability of mineral-forming reactions are in agreement with physical conditions during steaming. The decomposition of kaolinite in the burned zones indicates combustion temperatures greater than 510–540°C. It may be concluded that in a period of a few years only minor detrimental effects related to mineralogy occurred during thermal recovery in the Aberfeldy pilot projects.