Assessment of the discharges, spills and emissions from offshore installations on the Norwegian Continental Shelf 2016-2020
This report presents the discharge, spill and emission data from offshore oil and gas operations on Norwegian Continental Shelf (NCS) over the period 2016–2020 and the assessment of the data. The annual data is provided in Annex 1.
a. Level of Activity
The Norwegian Continental Shelf (NCS) is a mature petroleum region. Many of the fields in production are old, but some still have large remaining reserves. The resource base in these fields is also increasing as small discoveries in the vicinity are linked to existing infrastructure. There is still a high activity level, with 231 wells drilled in 2020.
New fields have come into production since 2016 and new discoveries have been made in the last few years. Production declined by 4 % between 2016 and 2019, but recovered in 2020. Production increased by approximately 2 % in 2020 compared to the production in 2016.
Discharges & spills
The annual total quantity of dispersed1oil (aliphatic oil) discharged to sea from produced water and displacement water decreased slightly during the 2016–2020 period.
Produced water is the main contributor to the oil discharges from the petroleum industry. Discharge of produced water reached a maximum of 160 million m3 in 2007. The volume of produced water discharged has slightly decreased between 2016 and 2020. Injection decreased from 2016 to 2018, but increased again in 2019 and 2020. The percentage produced water injected (26 %) is still small compared to the amount being discharged (74 %). Almost 60 % of the discharges of produced water comes from four large and mature fields. Discharge of displacement water remained stable over the assessment period.
The annual average dispersed oil content in produced and displacement water increased over the period. During the assessment period between three and eight installations on the NCS failed to meet the performance standard for oil content as an annual average. However, these installations typically had small discharge volumes as they reinjected most of their produced water. The total amount of oil discharged with water exceeding the performance standard was highest in 2016 and 2019 with 15,7 tonnes and 11,7 tonnes respectively, compared to 2-5 tonnes in the other years during the 2016-2020 period.
The number of oil spills to sea have varied from 36 oil spills in 2016 to 47 spills in 2020. There is typically no particular reason for the trend in the number of spills reported. The majority of oil spills are smaller than 1 tonne.
The use of chemicals was higher in 2020 compared to 2016, mainly due to higher drilling activity, resulting in an increased use of drilling chemicals (Figure 8).
The level of discharge seems to mainly coincide with the amount of water based mud used and discharged during drilling. Most of the chemicals used and discharged were non-substitution chemicals.
The total quantity of chemicals used offshore in 2020 was 432 601 tonnes, out of which 71 % (wt.) were on the PLONOR list and another 28 % (wt.) were other non-substitution chemicals, while 1 % of chemicals were substitution chemicals. There was no use of LCPA-substances during the assessment period.
Total quantity of chemicals discharged into the sea in 2020 was 94 904 tonnes on the NCS. Around 84 % (wt.) of these were listed on the PLONOR list and approximately 15 % (wt.) were other non-substitution chemicals. Less than 1 % were substitution chemicals.
It was a peak in the use of other substitution chemicals in 2018 and 2020. The peak in 2018 correlates with an increased use of chemicals at one field related to P&A operations (plug and abandon). The peak in 2020 correlates with in-situ production of sodium hypochlorite, and increased use of lubricating oil. It was a significant increase in reported discharge of other substitution chemicals from 2019 to 2020, due to reported in-situ produced sodium hypochlorite. Use and discharge of in-situ sodium hypochlorite was first reported in 2020, due to a new reporting requirement in Norway.
The number and quantity of chemical spills varies over the assessment period and no clear discernible trend is observed.
Emissions of CO2 decreased over the assessment period from 12,1 and 13,3 million tonnes (Figure 12). Variations are related to variations in the production levels, energy efficiency measures and hydropower from shore.
NOx emissions has varied between 41 and 45 thousand tonnes. Variations in NOx emissions are related to start up and shutdown of fields, rig activity, and production rate.
Reported emissions of methane were reduced by 21 % between 2016 and 2017. This is mainly due to new measurements and calculation methods for direct emissions. Emissions of methane have remained stable since 2017 (Figure 13). Emissions of nmVOCs have been quite stable during the assessment period from 2016 to 2020 (Figure 13). Emissions of SO2 have varied between the high of 584 tonnes in 2016 to the low of 516 tonnes in 2017 (Figure 12). The variation in SO2 is partly due to an incidient of flaring of gas due to H2S issues, more exact knowledge of the H2S content of the burned gas, and to the number of rig operations.
1 “Aliphatics” and “aromatics” are defined by the reference method set in OSPAR Agreement 2005-15 (Solvent extraction, Infra-Red measurement at 3 wavelengths). In that context, “aliphatics” and “dispersed oil” mean the same thing.