Asphaltene deposition during CO2 flooding

In this article we present results of dynamic and static precipitation test s to investigate the likelihood of asphaltene deposition problems in southe ast Saskatchewan's Weyburn reservoir. Tests were conducted at the reservoir temperature and pressure conditions. The effect on asphaltene flocculation /precipitation of the operating pressure, CO2 concentration, gas contaminan ts in CO2, and presence of formation brine was investigated for three diffe rent oil samples using static pressure/volume/temperature (PVT) tests. The extent of asphaltene deposition was also assessed through coreflood experim ents and through an x-ray computer-aided tomograph (CAT)-scanning visualiza tion experiment. Static tests indicated the most important factor on which the asphaltene pr ecipitation depended was the CO2 concentration. For oils belonging to the s ame pool, the increase in asphaltene precipitation with solvent concentrati on was proportional to the initial asphaltene contents of the oil. Corefloo d experiments showed a considerable increase in asphaltene deposition in th e core matrix following CO2 injection. Pore topography of the core matrix p layed an important role in the extent of CO2-induced asphaltene deposition. X-ray CAT-scanning tests depicted localized areas of asphaltene deposition along the length of the core, with significant deposition suspected to be occurring near the inlet of the core.