Research on CO/sub 2/ injection continued. The following tasks are reported on: (1) Work completed on the improved viscosity correlation, mechanistic modeling of high pressure gas/foam flow, and the effect of free gas on the development of miscibility; and (2) Recent work in three major subareas of the Task II research. The first of these subareas is concerned with rock and reservoir heterogeneity. The emphasis is to consider the effects of non-uniformity on displacement efficiency--both in the reservoir and in laboratory experiments. This work consists both of numerical experiments, in which the effects of large-scale reservoir heterogeneities on production and on tracer diagnostics are calculated, and of the analysis of unique 3-D miscible displacement experiments for the examination of smaller-scale features. Research in the second subarea is concerned with the development of direct thickeners--chemicals that will be soluble in CO/sub 2/ or other dense gases and produce polymeric solutions of high viscosity. The work reported here has been concerned with the synthesis of several new types of Method I hydrocarbon polymers. Their principal use in the research is as starting materials for further processing, to synthesize Method II ionomers. In the third subarea, recent developments of interest for the reservoir use of CO/sub 2/-foam are presented. It has become apparent that field use of this mobility-control additive can be considered at this time. Not only has our research been able to delineate the mobility decreases that can be expected, and the ranges of surfactant concentration and CO/sub 2/ fraction to be used, but it has been possible to define an additional advantage from the use of foam. We report a new measurement that defines the range of permeability over which this effect has been observed in our experiments, and over which it can be expected to be useful in the field. 11 refs., 60 figs., 9 tabs.