In certain reservoir situations, highly compressed carbon dioxide has a great advantage over more common fluids as a displacement agent to force crude oil from the porous rock in which it's found. The advantage is that a much higher microscopic efficiency can be attained in the displacement process - at least in the laboratory. This research aims to relieve a major difficulty that has so far prevented this high efficiency from being reached in field applications. The difficulty is that because CO/sub 2/ is much less viscous than oil or water, the injected fluid does not displace the oil uniformly. Instead, the CO/sub 2/ moves faster in some regions and directions than others, and viscous fingers are formed, through which most of the injected fluid flows. Some of these breakthrough into the production wells, lowering the effectivenesss of both the injected CO/sub 2/ and of the production pumping capacity. The aims of this project has been to develop ways to thicken the injected CO/sub 2/, so as to forestall the growth of these parasitic flow patterns and the premature breakthrough that results from them. Two ways of thickening CO/sub 2/ have been investigated. Substantial progress has been made in both developments and both are promising. The first of the methods studied considers the use of polymer dissolved in the dense CO/sub 2/ to increase its viscosity by the needed extent. The second method to thicken the injected CO/sub 2/ is to combine it with aqueous surfactant solution in a CO/sub 2/ foam. The second of these methods is much nearer to field use than the other, particularly in lower temperature reservoirs. Work in this project has covered many details of the development of these thickening methods and has also considered the means by which they might be applied in the oilfield.