Utilização da radiação ultravioleta (UV-C) visando a atenuação da ecotoxicidade em fluidos de teste hidrostático e hibernação de dutos na indústria de petróleo e gás

Abstract

The flow of oil and gas production through terrestrial (on-shore) and submarine (off-shore) pipelines is an economic, efficient and secure way to transport these goods from production facilities (upstream) to terminals and refineries (downstream). After the pipelines assembling and positioning, they are filled with fluids to prevent collapse due to external pressure and must be submitted to a hydrostatic test to investigate the occurrence of leakages. These fluids usually are sea water or industrial water added with chemicals to prevent and inhibit oxygen promoted or microbiologically induced corrosion processes, during the retention time, which can last for several months (hibernation period). Previously to the pipelines start up, the hydrostatic test fluid is generally discharged at sea, and the Brazilian Environmental Agency (IBAMA) demands ecotoxicity evaluation studies and dispersion modeling to estimate the potential environmental impact of the fluid over the biota. The fluid’s ecotoxicity persistency allied to the extension of the dispersion, with chronic ecotoxicity indicatives in the ocean, are critical factors that might make its discharge in situ unfeasible. Aiming to reduce the hydrostatic fluids’ ecotoxicity, the use of lesser biocides concentrations was attempted with the application of ultraviolet radiation (UV) as a seawater pre-treatment technique. The formulations were tested in different temperature conditions, UV applying or not as well as the adding of oxygen scavenger or not. Microbiological and ecotoxicity parameters were evaluated. It was observed that a 50% reduction in the biocide concentration does not reduce the microbiological control efficiency when the seawater is previously UV treated. That improvement not only represents a cost reduction but also represents a substantial reduction in the environmental impact caused by the fluids’ discharge.