Enhanced oil recovery by CO/sub 2/ foam flooding. Second annual report. [109 references]

The objective is to identify commercially available additives which are effective in reducing the mobility of carbon dioxide, CO/sub 2/, thereby improving its efficiency in the recovery of tertiary oil, and which are low enough in cost to be economically attractive. During 1980 significant progress has been accomplished on each major contract objective. The apparatus, design and construction phase of this project is essentially complete. Correlation work on dynamic foam stability, in two-phase flow experiments in a linear sandpack, has shown that the most active foaming agents, as identified in static tests, may not necessarily be the best choices for mobility control in the field. The Alipal CD128-Monamid 150AD system, the leading foam generator in the static test, is slightly inferior to an ethoxylated alcohol, Neodol 23-6.5, that produces only a modest amount of foam in the static test. In the dynamic test, Neodol 23-6.5 lowered gas mobility by about a factor of 2 greater than the Alipal system. Both systems are outstanding in their performance, and further comparative tests are scheduled. A third structure which looks promising based on the interpretation of the above test is a Pluronic surfactant whose hydrophobe consists of polypropylene oxide rather than a linearmore » alcohol as used in the Neodol surfactants. Additional tests on the hydrolysis rate of Alipal-type surfactants indicate that molecular breakdown may not be as rapid as at first suspected. Under neutral conditions the half-life of ethoxylated alcohol sulfates appears to be two to three years at a reservoir temperature of 120/sup 0/F. The Neodol and Pluronic structures should be even more stable.« less