EXPERIMENTAL STUDIES OF SILICATE-CARBONATE REACTIONS .2. APPLICATIONSTO STEAM FLOODING OF OIL SANDS

The reactions between silicates and carbonates were experimentally sim ulated at conditions similar to thermal recovery of oil from oil sands . Several important observations are: (1) in general, smectite forms f rom silicate-carbonate reactions in fresh water or in dilute Na-bearin g fluids. For this reaction silicate can be kaolinite, feldspar or vol canic glass whereas carbonate can be dolomite, calcite, ankerite or si derite; (2) analcime instead of smectite forms in fluids with higher [ Na+] or pH; (3) illite or mixed-layered illite-smectites form in the p resence of [K+] and NH4-zeolites and N-4-illite form in the presence o f NH4+; (4) Ca-mica(margarite) forms from calcite and kaolinite with h igh fluid/rock ratio (200:1); (5) talc forms from dolomite and silica in fresh water; (6) chlorite forms from kaolinite and dolomite in runs with low fluid/rock ratio; (7) the reaction temperature significantly increases with increasing CO2/H2O ratio in the fluid; and (8) the rea ction rate decreases as the P-CO2 in the system increases but increase s again to the initial reaction rate as CO2 is released from the react ion vessel. The simulations show that mineralogy, injection fluid comp osition and Bow rate (fluid/rock ratio) are key factors that control f ormation damage during steam flooding. The phase relationships and kin etic data suggest that formation damage during steam treatment may be prevented or retarded by maintaining high X(CO2) in the reservoir. The results are useful for improving the efficiency of thermal recovery.