Planned discharges and emissions from host platform

The wells will be drilled utilising the most appropriate slots on SA-WHPN. The production and injection flowlines will be installed within the existing allocated future flowline space envelope and utilise existing future slot con-trol provisions on SA-WHPN and in the well head concon-trol panel. Production fluids will be metered by a new dedicated multiphase flow meter (MPFM). Post metering, the Solsort produced fluids will be routed to the existing production header and comingled with native South Arne production at SA-WHPN and then trans-ported onto South Arne main platform via the existing multiphase subsea production pipeline via SA-WHPE.

The West Lobe produced water will be reinjected as part of the South Arne produced water reinjection into the South Arne field and the Solsort West Lobe. Production before and after tie-in of the Solsort wells are shown in section 6.1.

A new produced water filter package for water injection pump D, filtering to 180 microns, will be installed on South Arne intermediate deck adjacent to the existing filter package for water injection pump B.

Injection water and gas lift gas will also be supplied from the South Arne facilities. The maximum oil production rate is expected to be 14000 BOPD.

New wax inhibition injection pumps will be provided on SA-WHPE to inject continuously into the SA-WHPE Production Header to mitigate against potential wax formation in the crude oil coolers, storage and export systems.

According to the SA EIA (2007) it was expected to discharge up to 50-60 tonnes oil per year with the produced water based on the assumption of oil in discharged produced water was 20-25 mg/l and produced water reinjection of 50%.

Discharge of oil with the produced water after tie-in of the Solsort wells will be below 9 tonnes based on the assumption that oil in discharged produced water will be around 10 mg/l and produced water reinjection in the area of 80-90% and by that below the described discharges in the SA EIA (2007).

11.2.2 Discharge of chemicals

The impact from discharge of chemicals during production is not impacted by the tie-in of the Solsort West Lobe wells.

However, occasionally (with intervals from at least 6 months up to several years), there will be a need for well service maintenance of which some types of jobs (e.g., acid jobs (8 jobs over the lifetime of the field) and wireline jobs (3 jobs over the lifetime of the field) will result in short-terms discharges of yellow chemicals. The discharges from the well service jobs will typically take place within just 2-4 hours/job (Table 11-2).

Table 11-2 Overview of results of dispersal modelling comparing PEC with PNEC for well service chemicals planned to be used at Solsort West Lobe wells.

Well service activity Type of chemical Max. distance (m) from discharge point

Corrosion inhibitor 4700 (2800) 2 hours Iron stabilizer 700 (<100) 2 hours Wireline jobs Brine lubricant 400 (<100) 2 hours

* Figures in parentheses are calculated based on PNEC values for short-term effects

As appears from the table, the discharges from the well service jobs imply a risk of acute effects on marine organisms at distances up to 4700 metres from the platform, based on use of long-term PNEC values. How-ever, as the discharges will take place within a very short period and only with intervals of more than one year, it is considered more appropriate to base the risk considerations on PNEC values for short-term effects, which results in a distance up to 2800 metres from the platform. The results of this assessment are shown in paren-theses and give much shorter maximum effect distances than the modelling based on long-term PNECs. The dilution calculations are based on the conservative assumption that 20% of the well service chemicals used will be discharged to the sea.

11.2.2.1 Cumulative effects – Whole effluent test

Chemical analysis and bioassays (test of acute ecotoxicity of produced water on bacteria, algae and crusta-cea) have been conducted for produced water samples from South Arne in 2010. The results of the study were concentrations of a large number of contaminants and acute toxicity data as shown in Table 11-3.

Table 11-3 Some of the results from the whole effluent test – DTI July 2010 – Whole Effluent Assessment (WEA) for discharge from the offshore industry within Danish waters – Conducted for Hess.

The results show among others that the acute toxicity (EC/LC50) is above 10 mg/l and that the concentration of mercury is below the detection limit of 3 μg/l and benzo(a+e) pyrene/Perylene is below the detection limit of 0,2 μg/l.

11.2.3 Air emissions

Tie-in of the Solsort West Lobe wells are covered by the results in additional production on the host platform, South Arne, since the multiphase is transported to South Arne, where the processing of the oil and gas takes place. The emissions to air during the operation phase will subsequently be at the host platform and be related to combustion of fuel gas and diesel, tanker loading of export oil and flaring.

It is assumed that the emissions to air are proportional to the production volume for diesel and fuel gas con-sumption and tanker loading. However, the flaring is independent of the production and thus are likely to be unchanged after Solsort West Lobe production has been tied in.

In comparison with the overall national emissions of CO2 from the oil and gas industry, the production of oil originated from Solsort West Lobe wells will equal 5.7% of the CO2 emissions of 2013 (Danmarks olie- og gasproduction, 2013).

The emissions to air related to production and maintenance of the two Solsort West Lobe wells are covered within the emissions to air from planned production and maintenance for the South Arne field as the well are utilising the most appropriate slots on the SA-WHPN platform already covered by the South Arne EIA.

Emissions may be higher during start-up and commissioning of the production from the Solsort West Lobe wells, due to non-scheduled closures and increased flaring from unstable production.

11.2.4 Risk assessment - Planned discharges and emissions from host platform

Based on the above and using the criteria described in chapter 9, it is assessed that the environmental risk of presence of planned discharges and emissions from host platform (South Arne) will be negligible (Table 11-4).

Table 11-4 Environmental severity and risk of discharge and emissions related production and well service related to the Solsort West Lobe wells.

Impact Extension of impact

Duration of impact

Magnitude of impact

Severity of impact

Probability of impact

Environmental Risk

Impacts of discharge of produced wa-ter

Local Long term Small Insignificant

impact

Low Negligible

Impacts of air emissions (VOC)

Local Long term Small Insignificant

impact

Low Negligible

Impacts of air emissions (NOX, SOX)

Regional Long term Medium Insignificant impact

Low Negligible

Impacts of air emissions (CO₂-eq)

Regional Long term Medium Insignificant impact

Low Negligible