As offshore oilfields mature, PW volumes are expected to rise, increasing concerns about their environmental impact, especially in the North Sea, where production began in the late 1970s. Despite advances in extraction technology, direct discharge of PW into the sea remains the best available practice. Additionally, other discharges, such as drilling cuttings, also contribute to the cumulative environmental impact.
Current regulations mandate continuous monitoring of oil-in-water content prior to discharge, yet no other pollutant is measured with similar rigor. This focus extends to environmental reporting, where PW composition is used to run dispersion models and calculate risk. However, this approach overlooks less abundant but toxic pollutants like potentially toxic elements (PTEs). Despite the significant concerns surrounding their persistence and bioaccumulation potential, research into the occurrence of PTEs in PW remains limited.
This study employs advanced analytical techniques—Sector Field Inductively Coupled Plasma Mass Spectrometry (ICP-SFMS), Cold Vapor Atomic Fluorescence Spectroscopy (CV-AFS), and optimized sample pre-treatment—to comprehensively characterize environmental risks related to PTEs from offshore production. Results show significant variability in PW composition, influenced by reservoir characteristics, additives, and offshore operations. Thirty-five elements were analyzed, with mercury (Hg) and arsenic (As) identified as key contaminants in PW and flatfish tissue.
Geochemical anomalies in sediments near discharge sites indicate that offshore discharges affect the mobility and accumulation of elements like barium (Ba), zinc (Zn), and As in marine sediments. Ecotoxicological tests on marine copepods and oyster embryos reveal acute and sub-lethal effects of PW exposure, with suspended particulate matter (SPM) and dissolved compounds, including PTEs, contributing significantly to toxicity.
This project aims to improve analytical methods for PW analysis, broaden ecotoxicological evaluations, and strengthen regulations to better manage environmental risks associated with PW and other offshore discharges.
Examiners are Tina Puntervold, Professor, University of Stavanger, Niels Hemmingsen Schovsbo, Senior Researcher, GEUS, and Frédéric Amour, Researcher, DTU Offshore.
