Paper: Miscible Displacement By High Pressure Nitrogen Injection

Primary oil recovery frequently results in oil recoveries of only 10 to 20 percent of the original oil in place. Several hydrocarbon miscible methods have been tested and proven successful as a secondary or tertiary method of oil recovery under certain reservoir conditions."2"3 Wide application of these methods has been limited by economic factors. Hydrocarbon miscible displacement had its beginning with high-pressure natural-gas injection more than 25 years ago.4 Complete miscible displacement results in the displacement of one fluid by another with the lack of a phase boundary between the two fluids. Natural gas injection was followed by other miscible displacement methods using LPG slugs, enriched gas, and COz. With the increasing cost of these gases, it appeared desirable to study the feasibility of oil recovery by use of high pressure nitrogen injection.