Accidental spills of oil and chemicals

can arise during operation. In 2012 totally 122 small incidents were reported with a total oil discharge of 16 m3. Acute spills of chemicals have been stable at 100–150 incidents per year on the Epigenetic inhibitor cost NCS over the past decade (Norwegian Oil and Gas, 2013). Large chemical spills in 2007, 2009 and 2010 came from leakages from injection wells. No leakage has occurred after that due to technical improvements (Norwegian Oil and Gas, 2013). Until the mid 1990s the discharge of cuttings with oil based drilling mud (OBM cuttings) was the main source of oil hydrocarbons entering the marine environment from the offshore petroleum industry in the NS. The average annual discharge of oil on cuttings to the NCS for the period 1981–1986 was 1940 tons (Reiersen et al., 1989). This source was gradually eliminated by regulation, in 1993 in Norway and in 1996 and 2000 within the OSPAR region (OSPAR Commission, 2000). Concurrently oil discharged with PW on the NCS has increased and amounted to 1535 tons in 2012 (Norwegian Oil and Gas, 2013) i.e. almost at level with the former peak discharges of oil on cuttings. This is primarily due to an increase in overall PW volumes due to well ageing and rising number of producing fields.

One of the main objectives of environmental monitoring is to assess if discharge regulations are sufficiently protective. The history of sediment monitoring on the NCS has demonstrated that detection of unexpected ecological effects alone has led to stricter discharge legislation. The most conspicuous Obeticholic Acid ic50 example is the identification in the early 1990′s of much larger areas with fauna

effects from OBM cuttings discharges than previously known (Gray et al., 1990), leading to the prohibition of such discharges by OSPAR in 1996 (Gray et al., 1999). Extensive experimental and field studies have later been made to assess the ecological effects of the discharges. This review summarizes the findings Niclosamide of a large, Norwegian research program1 which combines experimental research and in situ monitoring on the NCS to address the likelihood of population and ecosystem effects from operational discharges of PW and drill cuttings. The concern and focus of the program is very much on PW since the potential environmental effects are less clearly understood than for drilling waste. PW is water from the formation produced along with oil or gas. It may sometimes also contain injection water and condensation water. The composition and characteristics of naturally-occurring chemical substances in PW are closely coupled to the geological characteristics of each reservoir. The composition of PW is complex and can comprise several thousand compounds that vary in concentration between wells and over the lifetime of a well.