TERTIARY RECOVERY OF ACIDIC CRUDE OILS FROM OILSANDS: MECHANISMS AND MODELLING (CAUSTIC, TALL-OIL PITCH).

摘要

The decline of domestic reserves of petroleum has been well documented. Due to capillary trapping forces, reservoir heterogeneities, and the economics of oil production, abandoned reservoirs may contain up to two-thirds of the original oil in place. The recovery of this oil has been the target of a multitude of enhanced recovery processes. One of these processes is alkaline waterflooding. Due to the low cost of alkaline agents, such as sodium hydroxide and sodium orthosilicate, there is considerable economic impetus for the application of alkaline waterflooding.;The aim of this work was to understand the governing principles, and to apply this knowledge to optimize tertiary oil recovery via the alkaline waterflooding process. Only one crude oil was used in this study; an acidic crude from well C-331 in the Ranger Zone of the Wilmington Field. Since the Wilmington Field is the largest reservoir in California, there is a large potential benefit associated with the application of a successful alkaline flood. Due to reservoir stratification and a unfavorable water-oil mobility ratio, the waterflood performance has been poor, and significant amounts of oil remain trapped in the Ranger Zone.;The problem was approached from both experimental and theoretical standpoints.;Experimental tests were devised to screen the large possible number of alkaline formulations. Promising alkaline formulations were tested in a series of linear, tertiary, coreflooding experiments in unconsolidated sandpacks. An equilibrium model for linear alkaline waterflooding is presented here. This model is used in conjunction with the experimental results to refine the flood design. (Abstract shortened with permission of author.);Alkaline waterflooding is a complicated process, and many displacement mechanisms have been proposed. Despite wide divergence of opinion on the governing principles, one theme unifies present understanding. The crude oil must contain acidic components. Some of these acidic species react with hydroxide ions at the oil/water boundary to produce surfactants. It is not the alkali per se that enhances oil recovery, but rather than surfactant products of the reaction. These surfactants reduce the oil/water interfacial tension, thereby allowing the mobilization of trapped oil globules.