Analysis of the steam injection at the Visalia Superfund Project with fully compositional nonisothermal finite...

By injecting steam, over 1.1 million pounds of creosote has been recovered at the Visalia, California Superfund Site from an aquifer 102ft underground. In the first 6 weeks of injection 320,000lb of creosote were recovered or destroyed versus <1lb per day in a pump and treat. The finite difference simulator STARS1, which is widely used in the oil industry to model thermal recovery, has been used to simulate simplified models of the project, to analyze recovery mechanisms, and to demonstrate how the operation of similar projects can be improved. The simulations indicate that vaporization of dense, nonaqueous, phase liquids (DNAPLs) is the most important recovery mechanism, that liquid production is enhanced because a gas phase is present, and that the project could have been completed more rapidly if an additional injector or producer had been added in the center of the site. In addition, the mineralization (conversion to carbon dioxide) of DNAPLs could result from reaction with water, injected air or, most likely, both. The mechanisms are likely to be similar to subcritical water oxidation. While this analysis suggests methods to improve operation of future steam projects, Visalia has been a very successful demonstration of the potential of steam injection to clean up recalcitrant hydrocarbons and will be an inspiration for future projects.