| Irish Sea |
Article Index for Irish |
Website Links For Irish |
Information AboutIrish Sea |
|
The Irish Sea ( and Great Britain . It is connected to the Atlantic Ocean by St George's Channel between the Republic Of Ireland and Wales and Cornwall to the south and by the North Channel between Northern Ireland and Scotland to the north-east. The Isle Of Man lies in the middle of the Irish Sea. The sea is of high economic importance to regional trade, shipping and transport, fishing and power generation in the form of wind power and nuclear plants. There has been long discussion of building an 80 km (50 mile) rail tunnel to link Britain and Ireland; annual traffic between the two islands amounts to over 12 million passengers and 17 Megatonnes of trade. SHIPPING Ireland has no tunnel or bridge connection to a continent. Thus the vast majority of heavy goods trade is done by sea. Northern Irish ports handle 10 megatonnes of goods trade with Britain annually, while ports in the south handle 7.6 Mt, representing 50% and 40% respectively of total trade by weight. port handles most of the passenger traffic from Dublin and Dún Laoghaire port, as well as 3.3 million tonnes of freight.UK Port Traffic Highlights: 2002, (pdf) , UK Maritime Statistics, Dept of Transport Ports in the Republic handle 3,600,000 travellers crossing the Irish sea each year, amounting to 92% of all sea travel. Direct Passenger Movement by Sea from and to Ireland (Republic), (link) , Central Statistics Office of Ireland This has been steadily dropping for a number of years (20% since 1999), probably as a result of low cost airlines. Ferry connections between Britain to Ireland via the Irish Sea include the routes from Swansea to Cork , Fishguard and Pembroke to Rosslare , Holyhead to Dún Laoghaire, Stranraer to Belfast and Larne , and Cairnryan to Larne . There is also a connection between Liverpool and Belfast via the Isle Of Man or direct from Birkenhead ( Liverpool ). The world's largest car ferry, '' Ulysses '', is operated by Irish Ferries on the Dublin–Holyhead route. "Irish Sea" is also the name of one of the BBC 's Shipping Forecast areas. ORIGIN The Irish Sea has undergone a series of dramatic changes over the last 20,000 years as the last Ice Age ended and was replaced by warmer conditions. At the height of the ice age the central part of the modern sea was probably a long freshwater lake. As the ice retreated 10,000 years ago the lake reconnected to the sea, becoming brackish and then fully saline once again. ENVIRONMENT Radioactive pollution The Irish Sea has been described as the most radioactively contaminated sea in the world with some “eight million litres of nuclear waste” discharged into it each day from Sellafield reprocessing plants, contaminating seawater, sediments and marine life.Sellafield nuclear reprocessing facility, (Link) , Greenpeace Low level radioactive waste has been discharged into the Irish Sea as part of normal operations at – Chapter 4 Chemistry, p64 AnalysisLeon et al, 2000, (Link) , The environmental impact of the Sellafield discharges – sections 3-4McMahon et al, 2005, (Link) , Transfer of conservative and non-conservative radionuclides from the Sellafield Nuclear Fuel Reprocessing plant to the coastal waters of Ireland of the distribution of radioactive contamination after discharge reveals that mean sea currents result in much of the more soluble elements such as – Chapter 4 Chemistry, p66 The highest concentration is found in the eastern Irish Sea in sediment banks lying parallel to the Cumbrian coast. This area acts as a significant source of wider contamination as Radionuclides are dissolved once again. Studies have revealed that 80% of current sea water contamination by Caesium is sourced from sediment banks, whilst Plutonium levels in the western sediment banks between the Isle Of Man and the Irish coast are being maintained by contamination redistributed from the eastern sediment banks. The consumption of seafood harvested from the Irish Sea is the main pathway for exposure of humans to radioactivity.Radioactive Monitoring of the Irish Environment 2003-2005, (Link) , – Ionising Radiation Exposure of the UK Population: 2005 Review U-BOAT ALLEY During World War I the Irish Sea became known as “ U-boat Alley”. After the United States entered the war in 1917, the U-boats moved their emphasis from the Atlantic to the Irish Sea.''U-Boat Alley'' by Roy Stokes, published by Compuwreck, ISBN 0-9549186-0-6The War in Maps: The Irish Sea, (Link) , UBoat.net OIL AND GAS EXPLORATION East Irish Sea Basin With 7.5 trillion cubic feet (210 km³) of gas and 176 million barrels (28,000,000 m³) of oil estimated by the field operators as initially recoverable reserves from eight producing fields (DTI, 2001), the East Irish Sea Basin is at a mature exploration phase. Early Namurian basinal mudstones are the source rocks for these hydrocarbons. Production from all fields is from fault-bounded traps of the Lower Triassic Formation , principally aeolian Sherwood Sandstone reservoir, top-sealed by younger Triassic continental mudstones and evaporites. Future exploration will initially concentrate on extending this play, but there remains largely untested potential also for gas and oil within widespread Carboniferous fluvial sandstone reservoirs. This play requires intraformational mudstone seal units to be present, as there is no top-seal for reservoirs subcropping the regional base Permian unconformity in the east of the basin, and Carboniferous Strata crop out at the sea bed in the west. Caernarfon Bay Basin The Caernarfon Bay Basin contains up to 7 km of Permian and Triassic syn-rift sediments in an asymmetrical Graben that is bounded to the north and south by Lower Paleozoic massifs. Only two Exploration Well s have been drilled so far, and there remain numerous undrilled targets in tilted fault block plays. As in the East Irish Sea Basin, the principal target reservoir is the Lower Triassic, Sherwood Sandstone, top-sealed by younger Triassic mudstones and Evaporites . Wells in the Irish Sector to the west have demonstrated that pre-rift, Westphalian Coal Measure s are excellent hydrocarbon source rocks, and are at peak maturity for gas generation (Maddox et al., 1995). Seismic Profiles clearly image these strata continuing beneath a basal Permian unconformity into at least the western part of the Caernarfon Bay Basin. The timing of gas generation presents the greatest exploration risk. Maximum burial of, and primary gas migration from, the source rocks could have terminated as early as the Jurassic , whereas many of the tilted fault blocks were reactivated or created during Paleogene inversion of the basin. However, it is also possible that a secondary gas charge occurred during regional heating associated with intrusion of Paleogene dykes, such as those that crop out nearby on the coastline of north Wales. (Floodpage et al., 1999) have invoked this second phase of Paleogene hydrocarbon generation as an important factor in the charging of the East Irish Sea Basin’s oil and gas fields. It is not clear as yet whether aeromagnetic anomalies in the south-east of Caernarfon Bay are imaging a continuation of the dyke swarm into this area too, or whether they are instead associated with deeply buried Permian syn-rift volcanics. Alternatively, the fault block traps could have been recharged by Exsolution of Methane from formation Brine s as a direct result of the Tertiary uplift (cf. Doré and Jensen, 1996). The Cardigan Bay Basin The Cardigan Bay Basin forms a continuation into UK waters of Ireland’s North Celtic Sea Basin, which has two producing gas fields. The basin comprises a south-easterly deepening half-graben near the Welsh coastline, although its internal structure becomes increasingly complex towards the south-west. Permian to Triassic, syn-rift sediments within the basin are less than 3 km thick and are overlain by up to 4 km of Jurassic strata, and locally also by up to 2 km of Paleogene fluvio-deltaic sediments. The basin has a proven petroleum system, with potentially producible gas reserves at the Dragon discovery near the UK/Ireland median line, and oil shows in a further three wells. The Cardigan Bay Basin contains multiple reservoir targets, which include the Lower Triassic (Sherwood Sandstone), Middle Jurassic shallow marine sandstones and limestone (Great Oolite ), and Upper Jurassic fluvial sandstone, the reservoir for the Dragon discovery. The most likely hydrocarbon source rocks are early Jurassic marine mudstones (Lias Group). These are fully mature for oil generation in the west of the UK sector, and are mature for gas generation nearby in the Irish sector. Gas-prone, Westphalian pre-rift coal measures may also be present at depth locally. The Cardigan Bay Basin was subjected to two Tertiary phases of compressive uplift, whereas maximum burial that terminated primary hydrocarbon generation was probably around the end of the Cretaceous , or earlier if Cretaceous strata, now missing, were never deposited in the basin. Despite the Tertiary structuration, the Dragon discovery has proved that potentially commercial volumes of hydrocarbons were retained at least locally in Cardigan Bay. In addition to undrilled structural traps, the basin contains untested potential for stratigraphic entrapment of hydrocarbons near synsedimentary faults, especially in the Middle Jurassic section."Petroleum prospectivity of the principal sedimentary basins on the United Kingdom Continental Shelf" (pdf) , Dept Trade and Industry, 2003Liverpool Bay, UK, (Link) , BHP Oil Ltd The Liverpool Bay Development is BHP Billiton Petroleum 's largest operated asset. It comprises the integrated development of five offshore oil and gas fields in the Irish Sea:
Oil is produced from the Lennox and Douglas fields. It is then treated at the Douglas Complex and piped 17 kilometres to an oil storage barge ready for export by tankers. Gas is produced from the Hamilton, Hamilton North and Hamilton East reservoirs. After initial processing at the Douglas Complex the gas is piped by subsea pipeline to the Point Of Ayr gas terminal for further processing. The gas is then sent by onshore pipeline to PowerGen's combined cycle gas turbine power station at Connah's Quay . PowerGen is the sole purchaser of gas from the Liverpool Bay development. First production
Facility details The Liverpool Bay development comprises: Four offshore platforms. Offshore storage and loading facilities. The onshore gas processing terminal at Point of Ayr. PROPOSED TUNNEL PROJECTS Discussions of linking Britain to Ireland began in 1895,"TUNNEL UNDER THE SEA", The Washington Post, May 2, 1897 (Archive link) with an application £15,000 towards the cost of carrying out borings and soundings in the - Volume 597 - 15 February, 2005 Several potential Irish Sea tunnel projects have been proposed, most recently the "Tusker Tunnel" between the ports of news, Thursday, 23 December, 2004 A different proposed route is between Dublin and Holyhead , proposed in 1997 by a leading British engineering firm, Symonds, for a rail tunnel from Dublin to Holyhead. Either tunnel, at 80 km, would be by far the longest in the world, and would cost an estimated €20 billion. There could be an economic case for such a link. The Irish sea is one of the busiest shipping regions in the world and has the world's largest car , Mon, Dec 29, 97 With the addition of High-speed Rail , such a tunnel could cut journey times from the northern English cities of Liverpool and Manchester to Dublin to under an hour. The combined population of the three metropolitan areas is over 5 million. The line would probably be built to standard gauge, which is narrower than the Irish broad gauge, meaning that onward trains would have to use Variable Gauge Axles , or some Irish lines would have to be regauged to standard gauge or Dual Gauge to overcome the resultant Break Of Gauge . The Channel Tunnel has failed to generate adequate passenger numbers (partially due to low cost airlines). The construction of the Channel Tunnel also illustrated a funding problem, that since it is an all-or-nothing project, the tunnel cannot be built and funded in stages. Therefore cost over-runs (experienced on the Channel Tunnel) cannot be absorbed. Construction would also take a long time to complete. The project therefore would therefore be an expensive long-term high risk investment and various Irish government studies have therefore concluded that an Irish Sea tunnel is, as yet, economically unfeasible. WIND POWER One of the world's largest wind farms is being developed on Arklow BankArklow Bank Wind Park (Link) Airtricity , Arklow Bank Wind Park , about 10 km off the coast of County Wicklow in the south Irish Sea. The site currently has seven GE 3.6 MW turbines, each with 104 m rotor diameters, the world's first commercial application of offshore wind turbines over three megawatts in size. The operating company, Airtricity , has indefinite plans for nearly 100 further turbines on the site. Further wind turbine sites include:
REFERENCES |
|
|