Microwave remediation of oil-contaminated drill cuttings – A review

Abstract

In the oil drilling process, drill cuttings are loaded to the surface by the drilling fluid. When using synthetic-based drilling fluids, drill cuttings should be subjected to a separation process for later disposal of cuttings and reuse of drilling fluid. Several techniques have been used to adapt the drilling waste disposal to the environmental legislation, including microwave thermal desorption technology. This review presents the main studies on the microwave drying remediation of drill cuttings contaminated with synthetic-based drilling fluids, with emphasis on the advantages and disadvantages of the technologies used, making a comparative analysis of the methods. Although batch remediation prototypes allow reaching low residual oil levels, it presents low processing rates and high specific energies. Alternative batch decontamination processes can be used to increase the efficiency of oil removal, such as changing the thickness and the mechanical stirring of the bed, injection of carrier gas, reduction of heating rate, etc. These prototypes are also capable of remediation of reservoir cuttings, but with higher energy costs. Continuous industrial scale prototypes also achieve low oil residual levels (<0.1%), with relatively high flow rates (100–750 kg/h) and lower energy costs, and are effective to treat both the conventional and pre-salt drill cuttings. However, despite their great commercialization potential, some adjustments are required for operation with diluted slurry and a more effective temperature control to prevent the chemical changes in the organic phase of the drilling fluids.