Low Temperature Thermal Desorption (LTTD) of Oil-Based Drill Cuttings (OBDCs): Influence of Treatment Temperature and Duration on the Fate of Organic Constituents
Authors:   , Idemudia Destiny Osaivbie 
Published: April 2024

Drilling waste management is one of the problems facing the oil and gas industry. This has often confronted the industry with various challenges ranging from innovative advancement to a more sustainable environment. Oil and Gas well drilling processes produce extensive volume of wastes (spent drilling muds, drill cuttings) and drill cuttings is one of the largest drilling wastes generated. Due to the use of oil-based muds (OBMs) during drilling process, large amount of oil-based drill cuttings (OBDCs) is generated; this waste contains relatively high content of petroleum hydrocarbons (PHCs) and other contaminants, which have the potential to affect the environment as well as human health (for example, carcinogenesis and mutagenesis). The effective removal of PHCs from OBDCs has attracted attention prompting the development and employment of a variety of treatment and disposal methods/techniques (Thermal desorption, Incineration, Bioremediation, Re-injection, Burial/Landfill, Incineration Recycle/Re-use). In this study, a replicated bench-scale thermal desorption unit was set up in the laboratory to treat OBDCs from the North Sea to determine the feasibility and potential of low temperature thermal desorption (LTTD) to achieve relatively complete PHCs removal and OBDCs remediation. Each sample was thermally treated and subjected to Fourier-transform infrared spectroscopy (FTIR) analysis using Jasco FT/IR-6100 analyser and TPH analysis using Infracal 2 TRANS-SP analyser. Two treatment approaches were adopted for the remediation of OBDCs. The first approach involved treatment at various temperatures (100oC, 110oC, 120oC, 130oC, 140oC, 150oC, 160oC, 170oC, 180oC, 190oC, 200oC, and 250oC) for 60 minutes. And the second involved treatment at various temperature (100oC, 110oC, 120oC, 130oC, 140oC, 150oC, 160oC, 170oC, 180oC, 190oC, 200oC, and 250oC) for 30 minutes. These approaches were adopted to determine the optimal treatment conditions and enhance phase separation of the OBDCs into their oil, water, and solid components by LTTD. Both approaches showed an exponential increase in desorption until levelling from 190oC – 200oC thereby justifying the adoption of 60 minutes treatment approach in this research. Untreated and treated drill cuttings were successfully analysed with FTIR. The spectra of the untreated and treated drill cuttings show various functional groups and various peak levels. When compared it shows disappearance of some functional groups and a decrease of the various peak level across the various treatment temperatures. As the temperature rises the peak level reduces which indicate the reduction in concentrations of material in the media. This establishes the degradation of compounds in oil-based drill cuttings across the various treatment temperature. The TPH concentrations of OBDCs treated at 250oC for 60 minutes resulted in an efficiency of 70% removal which is equivalent to a residual TPH content of 0.97%., which meets SEPA’s TPH limit of 1% for OBDCs disposal to landfill, thereby conforming and complying with SEPA standards. The application of LTTD in the treatment of OBDCs appears to be amenable to effective recovery of reusable oil that can be re-introduced into the drilling mud circulation system and into other uses, thereby making this research a viable approach for sustainable environmental management in oil and gas industry by promoting resource efficiency, waste minimisation, energy conservation, and environmental compliance, particularly in the context of Scotland’s North Sea region.