Treatment of Hydrocarbon-Based Drilling Waste Using Supercritical Carbon Dioxide

Abstract

Summary Nonaqueous drilling fluids are essential in challenging drill operations. Their use, however, requires special treatment and disposal because of their potential for environmental damage. In light of increasing costs for common treatment technologies and ever-tightening environmental legislation, alternative treatment technologies are being sought by the drilling industry. Supercritical fluid extraction is one such technology that employs a substance higher than its critical pressure and temperature as a solvent. In this paper, the results are presented of a study using super-critical carbon dioxide to treat synthetic based drilling waste. Unlike typical supercritical fluid extraction studies in which the process is optimized using changes in pressure and temperature, this study was undertaken to improve the extraction of hydrocarbons from drilling waste by increasing the supercritical fluid solvent to waste ratio. Efforts focused on improving supercritical fluid/drilling waste contact, eliminating system clogging with waste solids and minimizing solids carryover. Alterations to the waste using additives and alterations to the vessel both led to an increased amount of waste being treated effectively using the same amount of solvent. Optimization of the process yielded efficiencies as high as 97%. Also, it has been determined that the extracted hydrocarbons are unchanged by the supercritical fluid extraction process. This result suggests that the collected hydrocarbons may be reused in the drilling process, resulting in significant cost savings to the industry.