Abstract
Foam is a possible mobility control agent for effective oil displacement from reservoirs. Micromodel studies and prior gas-phase tracer experiments show that a significant fraction of the gas in a foam exists as trapped bubbles which, therefore, have a major impact on the flow resistance. To obtain quantitative measurements of trapped gas saturations, we have developed a unique experimental apparatus employing dual gas tracers. During steady foam flow in a porous medium, dilute sulfur hexafluoride (SF{sub 6}) and methane (CH{sub 4}) tracers in a nitrogen carrier are injected, and the effluent concentration is monitored by gas chromatography. The measured tracer histories are fit to a simple mass transfer model which describes any partitioning between the mobil and trapped foam phases. Tracer effluent concentrations predicted by the model are strongly influenced by the solubility of each tracer in the liquid phase. Hence, multiple gas tracers provide a discriminating assessment of trapped gas saturation during foam flow through porous media. New trapped gas saturations are reported for an aqueous C{sub 14-16} {alpha}-olefin sulfonate foamer solution and nitrogen flowing through a 2.3-{mu}m{sup 2} fired Berea sandstone at 10{sup 5} Pa (1 atm) back pressure and at room temperature. 26 refs., 7 figs., 1 tab.
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