Keywords: Single-well test; residual CO_2 saturation; geologic carbon sequestration Residual trapping is one of the four trapping mechanisms that have been identified for geological CO_2 storage, a means to reduce atmospheric emissions and the related impacts as a result of continued use of fossil fuels. The objective of this research is to design a single-well injection with drawal test to estimate residual CO_2 trapping (S_(gr)) in brine aquifers. Due to the high cost associated with drilling to depths of potential CO_2 storage site, single-well test can cost-effectively provide data sets to assess reservoir properties and reduce uncertainties in the appraisal phase for finding commercial scale storage sites. The main challenges in the design are the following: (1) It is difficult to quantify the amount that is trapped using a mass balance approach; (2) correlations among various parameters leads to a highly uncertain or non-unique S_(gr) estimate; and (3) the S_(gr) estimate could be biased due to heterogeneity of the geological medium. We have proposed our design to address each of these challenges by (1) use a detailed reservoir model to simulate the relevant physical processes in the tests; (2) perform a test sequence that yields multiple types of complementary data to constrain the estimate of S_(gr); (3) remove or reduce the bias caused by the heterogeneity of the storage formation by repeating the same test under different saturation conditions. The design will be applied to a practical field test that will be carried out as part of the CO_2CRC Otway Project, at Victoria Australia.
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