In many cases, the primary waste management challenge facing operators is drilled cuttings generated using oil- or synthetic-based fluids (OBF, SBF). Low temperature thermal desorption units (TDUs) are commonly used treatment systems for removing oil from cuttings. The oil recovered from the thermal desorption process is often reused to make oil-based fluids. However, base oils change during the thermal desorption process, and these changes can have a detrimental impact on the performance of the base oil. In some cases the base oil can break down.

Typically the base oil used to formulate an OBF or SBF is selected for economical, drilling and logistical reasons and rarely, if ever, the thermal properties of the base oil. The thermal treatment company is left to determine how best to recover the oil so that the thermal degradation is minimal and the oil is suitable for reuse. To lower energy consumption and preserve the performance of the base oil, it is important to identify a base oil that has either a lower temperature for desorption or higher resistance to thermal degradation during the thermal desorption process. Ideally, a base oil would be chosen that incorporated both properties. The results of this study show that by correctly evaluating and selecting the base oil, the operator can benefit from using a fluid that may be much more suitable for reuse and will require much less energy to thermally treat.

This paper describes how to achieve both of these goals using Thermal Gravimetric Analysis, Gas Chromatography / Mass Spec and a low-temperature retort. Determining the optimal desorption temperature is also an important factor. The oils recovered using these methods contain no oxygenated products and exhibit little thermal degradation. Residual oil from on cuttings is less than 1% (w/w). A practical methodology for base oil selection also is included in this discussion.

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