In 1990 a single well chemical tracer (SWCT) test was performed in Prudhoe Bay to measure the effective water flood and miscible gas flood residuals over a 12 ft reservoir interval. This is believed to be the first such use of this technology for a hydrocarbon miscible gas. This paper describes how the usual SWCT design was modified to accommodate the miscible gas, the results of the SWCT, which for the miscible gas part were significantly higher than miscible gas coreflood residuals, and the subsequent simulation of the test which has provided good agreement with the observed results. The paper explains, with simulation support, what caused the measured residuals to be higher than expected, and draws on the experiences of this test to make recommendations for the design of future SWCT tests measuring residuals to gas flooding.
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