Otimização do processo em batelada de descontaminação de cascalho de perfuração via aquecimento por micro-ondas.

Abstract

In the drilling of oil and gas wells, synthetic fluids can be used to remove rock fragments generated during the operation. However, the use of these fluids creates a solid-liquid mixture that must be separated in order to reduce the operational costs by the recovery of the fluid adhered to the solids and also to guarantee compliance with environmental legislation regarding drilling waste disposal. Nowadays, environmental agencies establish that the organic mass content of synthetic fluids adhered to drill cuttings discharged in offshore platforms cannot exceed 6.9%. However, it is expected a reduction of this limit to a zero-discharge rule in the near future, which has created a need to optimize processes responsible for the decontamination. The microwave drying technique has been identified as a promising alternative to promote this solid-liquid separation, in which the components of the material are heated individually and instantaneously, resulting in a selective heating. The general objective of this study was to obtain a greater knowledge about the process of decontamination of drill cuttings by microwave heating. For this purpose, the influence of some process variables on the removal of the organic phase adhered to the cuttings was evaluated, such as heating time, cavity pressure, applied power, bed temperature and mass of material. Furthermore, numerical simulations were executed for a better understanding of the microwave heating and drying process. Experimental conditions relative to the heating time, bed temperature and mass of samples contaminated with synthetic drilling fluid were optimized by means of central composite design (CCD) and a canonical analysis, reaching organic residual contents lower than 1% (mass). Analyses using the gas chromatography technique were performed in order to evaluate possible composition changes in the recovered liquid samples during the condensation operation, which showed themselves to be sensitive to heating at higher temperatures. Based on the results obtained by this work and also by previous works, a new prototype of microwave drying was designed for the development and the usage of this technology on an industrial scale.