Date of Award
Marco J. Castaldi
Heavy oil, viscosity, reduction
World's energy challenges would be greatly improved upon if half of the world's heavy oil and extra heavy oil could be made to ow in pipelines. Viscosity reduction of heavy oils is the key to solving this problem. In this study, aside from injecting pure nitrogen and pure carbon dioxide separately into the oil, two different compositions of the mixture of the two gases were also injected. In the first mixture, varied quantities of the two gases were used; 62:5%, 82:2% and 86:4% of the mixture was nitrogen while 37:5%, 17:8% and 13:6% was carbon dioxide at total test pressures of 100, 300 and 500 psi. The second mixture was composed of equal composition of the two gases at the three different pressures listed above.
Against the expectation that the mixed gas effect on the heavy oil should be additive of the constituent gases and further reduce the oil viscosity, it was discovered that the viscosity of the oil increased compared to having pure carbon dioxide as the only injected gas. Using carbon dioxide at 40oC reduced the oil viscosity from 10.248 Pa.s to an average value of 2.2718 Pa.s, while the mixture of CO2 and N2 at the same temperature only reduced the viscosity to an average value of 2.4435 Pa.s. Nitrogen, being classified as a non-condensable gas, has a negligible solubility in the heavy oil as shown in the data, and when it is mixed with carbon dioxide, it caused a decrease in the carbon dioxide solubility in the oil. The main reason that is believed to contribute to the reduction of carbon dioxide solubility in the oil is the decrease in the carbon dioxide partial pressure due to the presence of nitrogen . Thus, the higher the nitrogen content in the mixture, the lower is the carbon dioxide partial pressure and its solubility and, hence, an increase would be observed in the viscosity of the heavy oil.
Ajumobi, Abdurahman, "A Study on the Heavy Crude Oil Viscosity Reduction with the Dissolution of Nitrogen and Carbon Dioxide" (2015). CUNY Academic Works.