Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings: field-sample evaluation and process performance.

Drilling operations generate large volumes of drill cuttings contaminated with hydrocarbons, salts, and trace metals, creating significant environmental and regulatory challenges for offshore disposal. Most regulatory frameworks prohibit the discharge of drill cuttings containing more than 1 wt.% oil-on-cuttings, necessitating effective on-site treatment technologies. This study evaluates a novel continuous hybrid microwave-infrared thermal desorption process, the Advanced Thermal Processor (ATP), which, unlike conventional batch thermal desorption systems, simultaneously applies microwave volumetric heating and infrared surface heating within a rotating drum under continuous feed operation. Six samples of offshore water-based drill cuttings contaminated with sour crude oil were collected from Middle Eastern drilling operations and processed in two batches using a pilot-scale ATP unit under inert, low-oxygen conditions. The treatment was carried out at a solid discharge temperature of 60-100 °C and a residence time of approximately 15-30 min. The process achieved oil removal efficiencies of 95.0-97.8%, consistently reducing oil-on-cuttings to below 1 wt.%. Total Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) were reduced by more than 96% across all samples. Thermogravimetric analysis confirmed that most volatile contaminants were removed at temperatures below 110 °C, suggesting a substantially lower thermal demand than conventional incineration or friction-based thermal desorption, which typically operate above 300-500 °C. The results demonstrate that hybrid microwave/infrared thermal processing is an effective and energy-efficient approach for the treatment of offshore drill cuttings, enabling regulatory compliance while minimising secondary emissions and operational disruption.