Supercritical CO2-EOR in an asphaltenic tight sandstone formation and the changes of rock petrophysical properties induced by asphaltene precipitation

摘要

This work targeted an asphaltenic tight formation and thoroughly investigated the effectiveness of supercritical CO2 (scCO(2)) injection in enhancing oil recovery. Particular attention was placed on the changes of rock petrophysical properties induced by asphaltene precipitation in porous media. Low-field Nuclear magnetic resonance (LF-NMR) spectrometer and SEM-EDS were employed to characterize the changes. The results indicated that high injection pressure was favorable for enhanced oil recovery (EOR) but accelerated asphaltene precipitation in formation. The precipitated asphaltenes notably reduced rock permeability and porosity, in which the large pores were more likely to be damaged. The wettability of rock surface was hardly altered with an exception of the inlet face. The results of this study supplement earlier observations and can provide insights into tight reservoirs EOR especially in the presence of asphaltenes.