Dispersion and fate of produced formation water constituents in an Australian Northwest Shelf shallow water ecosystem

This was a study of produced formation water (PFW) discharged into a shallo w tropical marine ecosystem on the Northwest Shelf of Australia. A combinat ion of oceanographic techniques, geochemical tracer studies, chemical and b iological assessment methods, and dispersion modelling was used to describe the distribution and fate of petroleum hydrocarbons and added nutrients di scharged from an offshore production platform. Using fine scale volatile hy drocarbon data, the horizontal and vertical diffusion parameters for a thre e dimensional dispersion model were calibrated under local conditions. Trac e hydrocarbon chemistry studies and integration of the data into a mass bal ance model, facilitated a comprehensive description of dispersion and degra dation pathways and rates, Bio-accumulation into bivalves and water column microbial growth inhibition studies confirmed the chemistry and model predi ctions that the area of potential biological impact extended to 0.5 nautica l miles (similar to 900 m) from the discharge with additional skewing in th e direction of the predominant tidal flows, Impact would be expected to be concentrated in transient surface slicks and near surface seawater, Dispers ion and degradation processes were fast enough to prevent any long-term bui ld-up of contamination within the system. Trace levels of oil in the near f ield sandy sediments were directly related to the magnitude of the daily di scharge. The study is a benchmark to help predict the effects of further oi l industry expansion in this pristine coastal region, (C) 1999 Elsevier Sci ence Ltd. All rights reserved.