Environmental Sustainability

Indicators, trends and commentary

Atmospheric conditions

2004 data shows total emissions of CO2 to be 22,902,430 tonnes, which is a reduction of 536,000 tonnes from 2003. NOx and SO2 show a slight but not significant increase. Methane emissions increased by 9% whilst non methane VOCs decreased by approximately 20%. These figures paint a relatively static picture of emissions.

All operators have been verifying emissions in order to participate in the EU Emissions Trading Scheme. The consolidated industry data do not reflect all the changes to historical data made during this verifi cation process and, at this stage, must be treated as indicative only. UKOOA and its advisers are currently assessing the best way of ensuring that the industry data accurately summarise individual operator data.

Figure 24: UKCS Atmospheric Emissions of a variety of gases 2000-2004

Figure 25: UKCS Atmospheric Emissions of Carbon Dioxide 2000-2004

Flaring and venting

The quantity of gas flared during 2004 (both onshore and offshore) rose by 71,400 tonnes to 1,594,640 tonnes hydrocarbons. However, the associated CO2 emissions have been more than compensated by reductions elsewhere. Data analysis to further understand this is underway.

Figure 26: UKCS Flaring and Venting Levels, 2000-2004

Energy usage

A substantial number of installations on the UKCS are in, or are approaching, late field life with production in decline. During this period, as reservoir pressures fall, production may need sustaining through an increase in:

• Water/gas injection for aquifer support
• Gas compression
• Dependency on other lift techniques e.g. gas lift / submersible pumps

All these techniques require considerable energy input, so energy consumption relative to net production can be expected to increase later in field life for a given facility/installation. This trend may be compounded by the need to respond to and comply with other environmental legislation e.g. mitigation of oil-inproduced-water risks may require energy-intensive solutions, such as produced water re-injection.

Reinforced by the advent of C02 emissions trading schemes, which place a financial value directly onto fuel use, significant industry effort is now being applied to gain a better understanding of energy efficiency drivers. UKOOA is in the early stages of developing a measure to monitor energy efficiency. The PSI study has provided some insight. One approach could be energy intensity, the amount of energy consumed per unit of production.

Marine hydrocarbon discharges and spills

During 2004 the 70 installations discharging oil-inproduced-water reported a total of 258 million tonnes of water containing 5227 tonnes of oil being discharged to sea. The average concentration of oil-in-producedwater for all installations was 20.3 parts per million, ppm, significantly below the current OSPAR requirement of 40 ppm and the industry voluntary target of 30 ppm. This shows a levelling off over the last few years, which could be an indication that current treatment technology is reaching its limits.

Figure 27: UKCS Average Oil Content of Discharged Produced Water, 2000-2004

Although there is no evidence to suggest that the oil content of produced water has a significant impact on the marine environment and recent survey data show that amounts of hydrocarbon in seabed sediments are declining rapidly, OSPAR is pursuing an initiative to discharge 15% less oil-in-produced-water than in 2000. The industry is working collaboratively to achieve this national target through a combination of engineering projects and a trading mechanism.

Figure 28: UKCS Total Discharge of Hydrocarbons, all sources 2000-2004

Oil reaching the sea as a result of spillage remains relatively constant year-on-year. During 2004 a total of 66 tonnes of oil were reported spilled as a result of 399 incidents. 95% of the spillages were less than 1 tonne and the largest was 16 tonnes. UKOOA intends to work with the DTI to examine the root causes of spillages to identify ways to reduce the number of incidents.

Marine chemical discharges

Since 1999, overall chemical usage is down by 8% to 333,940 tonnes and discharge is down by 15% to 109,260 tonnes. As in previous years, the discharge of chemicals presenting risk to the marine environment has been reduced significantly. For example, the discharge of the highest risk category has been reduced by 99% since 1999.

Figure 29: UKCS Chemicals Discharged, by type, 2000-2004

The discharge of production chemicals rose steadily to 2003 when 43,600 tonnes were discharged. In 2004 this trend has been reversed with 41,490 tonnes discharged. This resulted from a decline in production, a marginal reduction in produced water discharge and better chemical management.

The downward trend in drilling discharges continues with a significant reduction during 2004 to 66,930 tonnes. This reflects a combination of reduced drilling activity, changes in drilling practices and the reuse/ recycling of drilling chemicals.

Pipeline chemical discharges have increased to 830 tonnes as new infrastructure is added and, for the fi rst time, the data record the discharge of chemicals associated with decommissioning activities at 3 tonnes.

Marine acoustic discharges, noise

The issue of marine noise has been addressed in the past both through UKOOA sponsored work and through OGP activities. The conclusion of this work was that the acoustic energy emitted during exploration and production operations does not signifi cantly affect marine mammals, fish or fisheries. However, recognising that the NGO community believe that the evidence base for these conclusions is insufficient, UKOOA is to participate in a major OGP study on noise in the marine environment.

In trying to develop a measure which can be used as an indicator of offshore oil and gas acoustic energy, we have focused on the volume seismic surveys (although this does not include infrastructure noise). All such surveys, which involve acoustic energy, now require an environmental impact assessment. The plot shows that the number of these surveys has been considerably reduced in recent years.

Figure 30: UKCS Seismic Surveys 1970-2004

Waste disposal

The quantity of general and special wastes returned to 2000-2004 shore continues the downward trend from a peak in 2002, with 74,710 tonnes requiring disposal. Despite the downturn in drilling activity the quantity of cuttings returned to shore remains relatively constant at 52,370 tonnes for 2004. This is partly due to an increase in the use of organic phase drilling fluids which cannot be 100 discharged to sea and are returned to shore for recycling.

Changes to waste legislation and the subsequent increase in disposal costs, particularly for landfi ll, are beginning to affect disposal options. The quantity of waste sent to landfill continues to fall with 63,780 tonnes being disposed of in 2004. Waste recycled remains relatively constant; with efforts to increase this e.g. by treating cuttings to remove oil based fluids so they could be used for other purposes like making concrete, falling outside the legislation and having to be disposed of in landfill. Waste to energy is increasing and incineration remains low at 205 tonnes for 2004. Work is in hand to improve the reporting of waste disposal, particularly to better define the 'other' categories in the type of waste and the disposal routes.

Figure 31: UKCS Waste Disposal, by Type 2000-2004

Figure 32: UKCS Waste Disposal, by Route

Decommissioning

At the conclusion of exploration drilling, if nothing has been found, the well is decommissioned (using agreed UKOOA standards) to a clean seabed. The site is both inspected by cameras and, under an arrangement between UKOOA and the fishing federations, SFF and NFFO, over-trawled by fishermen. If there are hydrocarbons found then, sometimes, the option is taken of suspending the well for future use in any subsequent development.

In 1999 a review of the seabed showed 360 suspended wellheads in open water, which pose a potential hazard to fishermen trawling in the area. These are rigorously tracked, recorded on DEAL and regularly communicated to all fishing vessels via a range of different media. The industry has also committed itself to a programme of decommissioning those wellheads that are now unlikely to be used in any development, to reduce the stock to below 100 by end 2006. This figure shows progress.

Figure 33: UKCS Number of Open-water Suspended Wells, 1998-2006

Removal is regulated by the DTI, in conjunction with other government agencies and departments, in accordance with international agreements. The UK is a member of OSPAR and the IMO. The OSPAR 98/3 decision makes a clean seabed presumption but allows derogation from this for cases which can demonstrate practical reasons why this cannot be achieved. During 2004/5 two large structures, N.W. Hutton (steel) and Frigg MCP01 (concrete) have undergone both informal and statutory consultations of decommissioning programmes which include such derogations. In this same period there have also been other such consultations, for the Brent anchor blocks and flare and the five small platforms in Indefatigable, all of which proposed a clean seabed.

Industry continues to extend the economic life of much of the UKCS infrastructure through success in attracting incremental and new field developments. The figure below shows the projected timing for the decommissioning of facilities over the next few decades, based on existing plans. Total decommissioning costs are in the range £15-19 billion based on DTI estimates.

The first platform to be decommissioned in the UKCS was in the southern North Sea basin in 1978. Since then a further 30 structures have been decommissioned (2 subsea, 19 platforms and 9 others), all to a clean seabed.

Figure 34: UKCS Structures Decommissioning