Environmental Report 2000 Index

Emissions and Discharges In exploring for and developing offshore oil and gas reserves, some items must be consumed. In the process, some by-products are created and must be disposed of. Offshore operators record these items in the UKOOA database of discharges, emissions and wastes arising from offshore operations. This database provides information that meets the regulators' needs and is also used to assess Industry performance. The database contains information on: 01 Accidental oil spills 02 Produced water 03 Chemicals used and discharged 04 Production chemicals 05 Drilling chemicals 06 Pipeline chemicals 07 Drill cuttings 08 Atmospherics 09 Gas flaring 10 Waste returned to shore This section of our report presents the data held in the database for 1999, and includes information for earlier years to show the trends in emissions and discharges. Further information is available in the 1999 UKOOA Environment Report. 01.Oil spills Our member companies report every oil spill, whatever its size, and carry out an investigation into its cause. Measures are then put in place to prevent repetition. Oil spills are reported to the DTI, the Maritime and Coastguard Agency and the Joint Nature Conservancy Committee. In 1999, UKOOA member companies presented revised risk based oil spill contingency plans to regulators in order to meet the new regulations arising from the Oil Pollution Preparedness Response Convention, which the UK introduced in 1998. Unfortunately, the accidental spill information compiled by the Advisory Committee on Pollution of the Sea, which shows spills from all offshore sources, was not available in time to be included in this publication. However, so that we have some comparative figures, we have repeated the 1998 data we showed in our last report. Fig 1: Types and quantities of oil spilled during 1999. Type Number of Spills Quantity (Tonnes) Base Oil 6 8.82 Condensate 20 1.457 Crude Oil 172 30.803 Diesel/Fuel Oil 82 69.205 Graphite Grease 5 1.295 Hydraulic Oil 29 2.54 Lube Oil 17 0.32 Oil Based Mud 3 1.198 Unknown 38 3.593 Total 372 119.231 Fig 2: Three year trend in the number of spills reported and the quantities spilled. Year Number Quantity (Tonnes) 1997 349 866 1998 376 137 1999 372 119 Fig 3: Reported spills into the marine environment for 1998. Source Quantity (Tonnes) *Open Sea 175.9 Oil and Gas Operations 136.5 Vessel Casualties 114.9 Ports 72.6 Rivers & Estuaries 25.8 *Excludes oil and gas operations 02.Produced Water Many oil and gas reservoirs have a natural water layer that comes to the surface with the oil. The produced water is separated from the hydrocarbons and then further treated to remove as much of the remaining oil as possible. The produced water is then either discharged into the sea or injected back downhole. In 1999, the Industry-wide average oil in produced water was 21.67 parts per million (ppm), well below the legal requirement of 40ppm and, also, well below the Industry's target of 30ppm. This figure compares well with the1998 produced water figure of 22.45 parts per million recorded, showing the benefits of the further efforts the Industry is making, in line with the commitment made in our last report, to control produced water. Fig 4: The quantities of water discharged from oil producing offshore installations over the last three years, along with the amounts of oil discharged with the produced water. The progressive increase in produced water results from a combination of factors, including an increasing number of producing installations and increasingly ageing fields. The gradual decrease in the concentration of oil in water arises mainly from improvements in the technology used for separating small quantities of oil from water. Year Number of Installations (Millions of Tons) Water Quantity Oil Levels (PPM) Quantity (Tonnes) 1997 64 234 25 5,764 1998 67 253 22.45 5,690 1999 67 260 21.67 5,643 Fig 5: The quantities of water discharged from offshore gas producing installations over the last three years, along with the amounts of condensate discharged with the produced water. The rise in the amount of produced water is for the same reasons as above. Despite the large increase in water being produced, the total discharged produced has been held almost static because of reduced concentrations. Year Number of Installations Water (Tonnes) Total Produced Content (PPM) Average Condensate Discharged (Tonnes) Total Condensate 1997 24 328,394 65 21 1998 32 450,769 66 30 1999 33 1,005,393 32 32 03.Chemicals Chemicals are used for a number of different purposes in exploration for and production of oil and gas. They can be divided broadly into three categories: drilling, production and pipeline chemicals. The government controls the discharge of these chemicals by assessing their impacts and assigning a classification code (the Offshore Chemicals Classification Scheme, OCNS) that defines how much of each chemical can be discharged (the trigger level) before the regulators must be consulted and further risk assessment considered. The scale ranges from 'A' (hazardous) to 'E' (benign). The trigger levels for these chemicals are shown in Figure 6: Fig 6: Trigger levels for DTI notification on chemicals. Group Production Chemicals (Tonnes) Drilling Chemical (Tonnes) A 40 All proposed usage to be Notified B 70 3 C 150 15 D 375 350 E 1,000 4,750 04.Production Chemicals Chemicals are used in the production process to make the extraction of oil and gas more efficient and to maintain structural integrity of the installation. For example, corrosion inhibitors are used to protect process plant and pipework from corrosive attack by water and other materials contained in the reservoir fluids. Without these chemicals, corrosion damage could occur to plant and pipework resulting in hydrocarbon release. Fig 7: The quantities of production chemicals discharged to sea from 126 installations during 1999 (tonnes). Year Number of Installations E D C B A Unclassified 1997 106 10,377 2,987 1,210 183 433 1,646 1998 126 13,710 3,049 1,992 660 372 516 1999 135 17,067 2,619 2,264 1,827 387 72 05.Drilling Chemicals Figure 8 shows the discharge of chemicals used in the drilling process. These chemicals ensure that wells are drilled safely, and that oil does not come to the surface in an uncontrolled rush that would cause environmental and safety problems. Figure 8 includes the disposal of drilling muds which are authorised to be discharged into the sea. It also shows a reduction in the discharge of synthetic muds to the sea. At the end of 2000, these discharges will end, for all but the rarest situations, under an agreement between the Industry and government. Fig 8: Drilling/workover Chemicals - total amounts (tonnes) of such substances discharged to sea from a total of 299 Wells during 1999. This includes Water Based Muds. Year Number of Wells E D C B A Unclassified 1997 353 176,850 3,237 1,005 171 94 14,226 1998 318 160,217 3,644 577 153 12 14,186 1999 300 146,152 1,684 674 68 2 5,377 06.Pipeline Chemicals The number of pipelines requiring the use of chemicals more than doubled in 1999. Chemicals are used to ensure the pipelines are cleaned before being brought into use, and/or in testing the pipeline to ensure that it is leak-proof. Fig 9: Quantities of chemicals (tonnes) discharged from pipelines in each OCNS category. Year Number of Pipelines E D C B A Unclassified 1997 36 152 5 0 1 0 7 1998 25 24 3 2 0 12 0 1999 52 362 2 3 4 0 0 Fig 10: The total amounts of chemicals (tonnes) from all sources which were discharged over the last three years. Year E D C B A Unclassified 1997 187,379 6,229 2,215 355 5,274 15,879 1998 173,951 6,696 2,571 813 3,964 14,702 1999 163,583 4,305 2,941 1,899 389 5,449 07.Drill Cuttings Drill cuttings are the rock removed when a well is drilled. Drilling muds, a group of chemicals, are used to lubricate the drill bit and to maintain well safety. Some of these chemicals stick to the drill cuttings, and the disposal of the muddy cuttings is controlled through legislation and a voluntary agreement between Industry and the regulator. Figure 11 shows how drill cuttings were disposed of in 1999. Fig 11: Disposal routes and quantities of cuttings disposed of by UKOOA member companies in 1999. Base Fluid Number of Wells Quantity of Cuttings (Tonnes) Disposal Route Quantity of Oil/Fluid on Cuttings (Tonnes) Synthetic 23 10,123 Shore 931 Synthetic 107 48,518 Discharged to sea 4,591 Synthetic 2 763 Injected into the well 86 Oil 21 6,072 Shore 833 Oil 13 2,750 Injected into the well 268 08.Atmospherics Information on UKOOA members' total emissions for 1999, shown in Figure 12, covers five main emission streams. We had hoped to compare our Industry's emission figures with those for the whole of the UK in 1999. Unfortunately up-to-date UK-wide statistics are not yet available and, therefore, the data shown in Figure 16 are for 1998. We will include them in our next report. Within the Oil and Gas Industry, emissions generally arise from generating the energy needed to carry out operations offshore, from transporting the oil and gas, and from gases produced from the reservoir but which cannot be marketed for technical reasons. Fig 12: Offshore emissions by source. Gas Offshore Production Platforms (Tonnes) Offshore Mobile Drilling Rigs (Tonnes) Onshore E&P Facilities (Tonnes) Carbon dioxide 19,158,454 599,515 4,533,368 Carbon monoxide 28,585 2,823 5,696 NOx 48,371 7434 16,078 Sulphur dioxide 9,317 344 1,927 Methane 62,048 2,442 7,519 Volatile hydrocarbons 73,378 1,328 101,230 Fig 13: Total Industry emissions from 1997 - 1999. Year Carbon Dioxide Carbon Monoxide NOx Sulphur Dioxide Methane VOCs 1997 23,122,018 41,519 65,241 14,234 92,462 182,451 1998 24,770,465 43,381 73,941 12,198 87,151 184,474 1999 24,290,502 37,055 71,640 11,582 71,578 154,295 Fig 14: Sources of CO2 emissions. Source Percentage Fuel gas 66.10 Flare gas 20.55 Diesel 6.48 Venting 0.05 Well testing 0.87 Other 6.00 09.Gas Flaring Natural gas is a valuable commodity that UKOOA members produce and sell to industry, consumers and gas distributors. Not surprisingly, we try not to waste any by letting it escape to the atmosphere. Nevertheless, on most platforms small amounts of gas are deliberately burnt in the flare system. Flaring, which accounts for about a fifth of the Industry's atmospheric emissions, takes place for two reasons. On installations that produce both gas and oil (most fields produce at least some associated gas), a flare is kept lit at all times as a vital safety precaution. In addition, some fields do not produce gas in quantities that would justify the investment needed to transport it to shore. In these cases, gas may be re-injected into the reservoir to help maintain reservoir pressure, while some will be flared to maintain oil production rates. Gas flaring is controlled by the DTI through a 'Flare Consent', which puts a ceiling on the amount of gas each facility can flare each year. Because gas has economic or practical value, operators reduce the amount flared even further, if possible. Fig 15:Gas flared. Year Onshore Gas Flared (Tonnes) Offshore Total 1997 182,586 1,860,947 2,043,533 1998 169,177 1,886,572 2,055,749 1999 179,736 1,768,184 1,947,920 Fig 16: UKOOA members' gas emissions for 1998 as a percentage of total emissions in the UK in 1998. Gas UK Total Emissions 1998 (Tonnes) UKOOA Total Emissions 1998 (Tonnes) UKOOA Percentage of UK Total Emissions (%) CO2 573,000,000 24,770,465 4.3 Methane 2,640,000 87,151 3.3 NOx 1,930,000 73,941 3.8 SOx 1,620,000 12,198 0.8 VOCs 1,780,000 184,474 10.4 *Source: DETR National Air Emissions Database. We are unable to show 1999 data because the UK totals are not yet available. 10.Waste Returned to Shore As with any industrial process, waste is generated from, for example, the containers in which materials such as chemicals are delivered to the installation. These materials are returned to shore for re-use or disposal, and Figure 17 shows the tonnage involved and the disposal routes. Fig 17: Quantity of waste returned to shore for disposal during 1999. Type of Waste Tonnes General 36,085 Special 79,430 Other 28 Fig 18: Disposal routes. Disposal Route Tonnes Return to Vendor 92 Incineration 374 Landfill 22,046 Recycling/reuse 74,953 Other 18,079 In addition, 7,798 drums/containers were returned for treatment.