Asphaltene Deposition During CO2 Flooding

Abstract

Summary In this article we present results of dynamic and static precipitation tests to investigate the likelihood of asphaltene deposition problems in southeast 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 contaminants in CO2, and presence of formation brine was investigated for three different oil samples using static pressure/volume/temperature (PVT) tests. The extent of asphaltene deposition was also assessed through coreflood experiments and through an x-ray computer- aided tomograph (CAT)-scanning visualization experiment. Static tests indicated the most important factor on which the asphaltene precipitation depended was the CO2 concentration. For oils belonging to the same pool, the increase in asphaltene precipitation with solvent concentration was proportional to the initial asphaltene contents of the oil. Coreflood experiments showed a considerable increase in asphaltene deposition in the core matrix following CO2 injection. Pore topography of the core matrix played 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 ofthe core, with significant deposition suspected to be occurring near the inlet of the core.