Abstract

The interactions of bitumen with clays are known to cause asphaltene deposition. However, the role of clay type on this interaction remains uncertain. We study this interaction for two clay types at steam temperature. Two Steam Assisted Gravity Drainage (SAGD) experiments at identical experimental conditions are conducted. The reservoir rock for the first experiment (SAGD1) is prepared with sand (85 wt%) and kaolinite (15 wt%) mixture and the second experiment (SAGD2) with sand (85 wt%), kaolinite (13.5 wt%), and illite (1.5 wt%). The effectiveness of the steam chamber growth does not change with the clay type, however, 15 wt% less oil is recovered with SAGD2. The possible reasons are investigated through the contact angle, particle size, zeta potential, and interfacial tension measurements on produced oil, produced water, and spent rock. The spent rock samples are analyzed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses. The contact angle measurements on the spent rock sample display the higher oil-wetness for SAGD2 than SAGD1. However, the water-wetness of illite is known to be higher than kaolinite. This unexpected result is explained by the interaction of illite and the asphaltenes from SAGD2. The asphaltenes both from produced oil and residual oil separated and qualitative analyses are conducted with Fourier Transform InfraRed (FTIR). FTIR results confirm the presence of clay in the produced oil asphaltenes of SAGD2. The particle size measurements along with SEM images on postmortem samples reveal that illite containing clay exhibits cementation behavior at steam temperature, hence, reduces the permeability of the system. According to the experimental results, we developed hypotheses to understand the bitumen-illite and bitumen-kaolinite interactions for SAGD. Due to the high water-wetness of illite, illite particles first interact with steam. This interaction results in cementation and forms illite lumps with sand. And then, illite lumps continue to interact more vigorously with the polar molecules (water, asphaltenes, and resins). Clay migration and production occur in both clay types, however, while kaolinite is produced in the water phase, illite containing clay due to its interaction with asphaltenes produced in the oil phase.

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