Effect Of Gaseous Additives On Steam Processes For Lindbergh Field, Alberta

Performance Of steam stimulation or steam flooding processes can be improved by the use of an appropriate gaseous additive such as carbon dioxide or methane. Several beneficial effects are postulated such as improving steam injectivity, increasing the size of the heated areas and providing additional drive energy which is likely to increase production rate. The over-all effect of these mechanisms on performance is difficult to predict. A laboratory program for the Lindbergh Field (Cummings Formation) was conducted to investigate the effect of carbon dioxide and methane on the performance of steam processes and investigate the differences in performance between simultaneous injection of steam and a gaseous additive and injection of a gas slug prior to steam injection. A total of eight coreflood tests were carried out, employing core and fluids from the Cummings zone of the Lindbergh Field. In addition, a validated numerical model was used to evaluate the impact of adding non-condensible gases to steam under various conditions. Results indicate that the presence of a non-condensible gas improved steam injectivity. Injectivity improvement was most pronounced when a gas slug was injected prior to steam injection, but the presence of a non-condensible gas with steam did not improve recovery and resulted in much higher residual oil saturation compared to steam injection alone. Results from numerical simulation work supported these observations. Introduction PanCanadian Petroleum Limited has a significant land position in the Lindbergh Field located near the town of Elk Point in northeastern Alberta. Formations of the Upper Mannville Group in this field are generally unconsolidated sands and contain heavy oil of 12 to 14 °C API. The Cummings formation, at a depth of about 600 m. contains the majority of the Upper Mannville oil in place and is considered to have good potential under primary and thermal recovery. Its thickness varies up to 20 m. The main purpose of the work reported in this paper was to evaluate the effect of gaseous additives on the performance of steam stimulation and steamflooding processes for the Cummings Formation. It should be noted that the over-all effect of gaseous additives on these processes is difficult to predict. Several potentially beneficial mechanisms could be assumed such as improving injectivity, increasing the heated volume, reducing interfacial tension between oil and water, providing additional reservoir energy by solution gas mechanisms, etc. But, gaseous additives could also have detrimental effects due to the presence of a free gas saturation and the associated effect of reducing relative permeability to oil. Limited field tests have been reported to date on the effect of gaseous additives on steam processes. Moreover, the published laboratory and simulation studies have led to some conflicting results. Additional investigation was necessary for the Cummings formation. Literature Review Meldau(1) reported the results of air-steam stimulation field tests in Paris Valley, California. The addition of air to steam nearly doubled oil production. He attributed this to several mechanisms including displacement of residual oil by trapped gas, gas drive and increased reservoir pressure.