Oxygen Fireflooding: Combustion Tube Tests With Light, Medium, and Heavy Crude Oils

Abstract

Summary Five light, medium, and heavy crude oils were evaluated in a combustion tube, primarily at 750 and 2,000 psig [5.2 and 13.8 MPa] and with O2 concentrations between 21 (air) and 95%. The overall characteristics of combustion with O2 appear to be superior to those with air. For light and medium crude oils, when the combustion conditions are marginal (e.g., at low temperatures at which the kinetics appears to control coke combustion), the apparent kinetics and the quality of the combustion were substantially improved when O2 enrichment was used. Three of the crude oils in this study did not burn in air; however, with the same flux of contained O2, high levels of O2 enrichment could sustain combustion. For two of the crude oils, as the O2 concentration was increased, the peak front temperatures actually decreased slightly while the O2 use efficiency increased significantly with no change in the coke loading. Further, for a heavy oil at 2,000 psig [13.8 MPa], it was found that O2 enrichment, which provided a higher partial pressure of combustion-derived CO2 and (perhaps) steam because of O2 removal, may have served to reduce the coke loading in comparison with air. An attempt was made to correlate the relative combustion performance of four of the crude oils. It was found that a high coke loading alone was not adequate to ensure satisfactory in-situ combustion. The relative reactivity of the coke with O2 also appeared to be critical.