Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway

Abstract

The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250m from the drill site in the eastward downstream direction. Downstream dispersion of drill cuttings is evaluated by examining sediment grain size distribution and barium (Ba), heavy metal, total organic carbon and sulphur concentrations. Dispersion of drill cuttings was limited to <125m east from the drill site. Influence of drill cutting releases on the marine environment is assessed via microfaunal analysis of primarily calcareous benthic foraminifera. The findings suggest contemporaneous physical smothering at ≤30m from the drill site, with a natural fauna reestablishing after drilling cessation indicating no long-term effect of drill cutting releases.

Impact of drill cutting releases on benthic foraminifera at three exploration wells drilled between 1992 and 2012 in the SW Barents Sea, Norway

“…Rose Bengal adsorbs to protein in live and/or not yet decomposed cytoplasm. Due to practical reasons staining of the samples had to be done after sediment samples were frozen during the thawing process (following Aagaard-Sørensen et al, 2018). This is done with the assumption that the protein of cytoplasm stays preserved by freezing of the sediment samples.…”

“…Dead and live faunas were studied in the 100 µm to 1 mm fraction to enable comparison to previous studies from the area (Aagaard-Sørensen et al, 2018;Dijkstra et al, 2017a;Dijkstra et al, 2013;Dijkstra et al, 2015).…”

“…Opening of new areas for petroleum exploration drilling can result in enhanced environmental pressure on the marine environment, which might result into changes in sediment quality and ecosystem structure (e.g. Aagaard-Sørensen et al, 2018;Breuer et al, 2004;Davies et al, 1984;Jorissen et al, 2009;Junttila et al, 2018). Changes in ecosystem structure will affect the types of organisms dominating the marine environment, which in turn can affect the potential for marine bio-resources (e.g.…”

“…By studying living and fossilized foraminiferal assemblages in sediment cores, it is possible to go back in time and reconstruct past environmental conditions. This includes environmental impact of contaminants (Aagaard-Sørensen et al, 2018;Dijkstra et al, 2017b;Hess et al, 2013), reconstruction of environmental baselines in already impacted areas (Dijkstra et al, 2017a;Dolven et al, 2013), and monitoring of ecosystem recovery after environmental pressure has diminished (e.g. Aagaard-Sørensen et al, 2018;Berg, 2017;Polovodova Asteman et al, 2015).…”

“…Previous studies showed that the main effect of drill cuttings on foraminifera is smothering by drill cutting material, resulting in a rapid drop in foraminiferal density (e.g. Aagaard-Sørensen et al, in review;Aagaard-Sørensen et al, 2018;Berg, 2017;Hess et al, 2013). Elevated sediment heavy metal concentrations are another factor that might influence foraminiferal faunal composition (e.g.…”