The environmental effects of Produced Formation Water (PFW) discharged from offshore oil production platforms into the marine environment is of growing concern among environmental regulators and industry. Analyses of PFW discharges have found various concentrations of hydrocarbons, which are potentially toxic to marine organisms. Environmental agencies require petroleum companies to carry out predictive dispersion modelling to determine the likely distribution and concentration of PFW after discharge from a platform and its toxicity to surrounding marine ecosystems.
Asia-Pacific ASA (APASA) were commissioned by Apache Energy to forecast the dispersal of PFW from the "Stag" oil production platform on the Northwest Shelf, Australia. To simulate the PFW release under environmental conditions, APASA applied numerical models to describe two important processes. Firstly, the hydrodynamics of the receiving waters was simulated by Mr Scott Langtry of GEMS (WA) using the three-dimensional circulation model, GCOM3D. Secondly, the mixing and dispersion process was simulated using the subsurface plume model, MUDMAP. MUDMAP was used to assist in understanding the dilution, mixing and ultimate fate of PFW when discharged from "Stag". Included were estimates of the excursion of the plume until concentrations weremixed to levels well below those of likely environmental concern.
The information was used by John Nielsen and Shane Chaplin, scientists from International Risk Consultants (IRC), to select appropriate sampling sites for testing seawater concentrations of hydrocarbons arising from discharged PFW. The results provided by APASA assisted the IRC scientists in locating and sampling within the plume at different times during the day and during different stages of tidal water movement. IRC's field observations confirmed the MUDMAP predictions of plume dynamics under average prevailing conditions experienced in the region during autumn.
Finally, peak concentration levels attained from both the simulations and the laboratory analysis from the field sampling, were used by the Apache Energy environmental managers to demonstrate that the total oil concentrations are well below the Statutory Release Concentration for platform PFW discharge in Western Australia.
For more information please contact
