Research has been dedicated to the development of laboratory-scale simulation devices for studying mechanisms of gas migration. Cement-hydration analyzers (CHAs) are commercially available to assist industry in the design of gas-tight slurries. Although cement slurries under controlled conditions in the laboratory can be gas-tight, the in-situ performance of cement slurries is highly variable and difficult to predict. Therefore, a new approach has been designed to evaluate gas-migration potential under a range of representative borehole conditions. A laboratory-scale wellbore-simulation chamber (WSC) has been developed to replicate hydrostatic-pressure reduction in the cemented annulus and evaluate the potential for gas invasion under a range of borehole conditions. A discussion is presented on the development of the WSC that includes the details of the design and monitoring systems as well as the performance characteristics. Calibration-test results are examined to evaluate the performance of the WSC and the ability of the WSC to simulate in-situ wellbore conditions. Analysis of the results verifies the capability of the WSC in successfully recording the necessary parameters.