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Drilled cuttings generated using invert emulsion drilling fluids represent the primary waste disposal challenge facing offshore drilling operators. If this waste cannot be appropriately disposed of on-site, it is typically shipped to shore for treatment and subsequent disposal or reuse. Although several types of cleaning processes are utilised, low-temperature thermal desorption systems (TDS) are the most predominant. The recovery of base fluids from these processes has assumed increasing importance in recent years, primarily in terms of fluid economics and waste reduction. Both synthetic and mineral oil base fluids have been reclaimed for further use. However, recovery has typically emphasised the separation of solids, water and emulsifiers from the base oil, with little published information on any changes to the overall composition of the fluid through the recovery processes. The primary objective of this paper is to describe the application of improved methods to identify and quantify potential contaminants and by-products that may be introduced into the base fluids by thermal recovery and handling processes. Contaminant and by-product identity and concentration have been determined primarily by headspace and liquid injection gas chromatography-mass spectrometry (GC-MS) techniques. To the authors' knowledge, this approach has not been documented previously, but offers significant improvements over existing analytical techniques. Particular benefits include the identification of most volatile and non-volatile contaminants that may be present in the reclaimed fluids. A variety of contaminants and possible by-products in a small number of reclaimed base fluid samples have been identified over a wide range of concentrations. Low levels of contaminants can have important implications for the reuse of base fluids, such as flash point, marine toxicity and occupational hygiene. This, in turn, will determine the fate of the reclaimed fluid. A recommendation is made for further work to assess those factors that may affect the quality of the recovered fluid. |
