North sea basin

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Table of Contents

  1. Introduction
  2. History
  3. Geologic Setting
  4. The North Sea Today
  5. Further Reading

1: The North Sea

The North Sea basin is a hydrocarbon-rich Northern European basin that is bordered by nine European countries. The countries bordering the basin are Britain, Iceland, Norway, Sweden, Denmark, Germany, Netherlands, Belgium and France. Over the years, the North Sea basin has had many companies invest in this location due to its lucrative reservoirs. The North Sea's resources are a mixture of liquid petroleum and natural gas. The British and Norwegian areas of the basin contain the largest oil reserves compared to the remaining sectors[1]. As of this date, the North Sea has been greatly explored and millions of barrels extracted from its reservoirs. In previous years, the North Sea and its resources were largely responsible for many thriving European economies. As of early 2015, the North Sea was one of the most active drilling regions in the world for oil and natural gas[2].

File:North Sea image provided by USGS.png
Satellite image of the North Sea (Public Domain image provided by USGS)


2: North Sea History

Picture of the Sea Gem, first rig to find oil in the North Sea. image by http://www.oilrig-photos.com

The first company to find oil in the North Sea was BP on their Sea Gem rig in the West Sole Field in 1965[3]. Shortly after their discovery, many other companies began discovering oil and gas in different areas of the basin leading to the numerous fields that are present to this day. In the 1970's BP discovered the Forties Oil Field which was the largest developed oil field in the North Sea, measuring an estimated 23,000 acres. The Forties Formation is composed of a shale unit below and a sandstone unit above which was deposited in a submarine fan environment. The initial development of the reservoir included a complete replacement water injection system. BP used five fixed platforms around the field which work in conjunction with a pipeline to transport recovered oil.

Location of Forties Oil Field in the North Sea, image by http://vestnikkavkaza.net

The Forties oil field has produced over 1.9 billion barrels of oil before being sold to Apache. Apache has since extended the life of this field by an additional 20 years with the discovery of an additional 800 million barrels of oil [4]. Similar to the discovery and production of the Forties field, other oil fields in the basin have been under production for decades. The UK has estimated that approximately 75% of its reserves have been extracted at the end of 2010. Similar to the UK, the Norwegian sector estimates that 60% of its reserves have been extracted by 2007 and production has gradually decreased as new sources of energy are explored and developed.

Mapped Seismic image of the Forties formation in the North Sea, image by http://nhm2.uio.no/norges/litho/forties.php
File:Oil production Norwegian North Sea.PNG
Graph of production in the Norwegian sector showing an overall decline in production in recent years. (Public Domain Image provided by SEGWIKI)

3: Geologic Setting this area


The North Sea Basin began as the Appalachian - Caledonian Geosyncline in the Cambrian - Devonian. The geosyncline was part of a large mountain belt which extended from Greenland and Norway over to the southeast of North America. This orogeny resulted in the combination of western Europe and North America. Later, this area subsided and eroded into a horst and graben structure which resulted in the red sandstones that make up many of the reservoirs in the basin. Later, rifting occurred in this region which created two inter-cratonic basins which vary in the age of their formation. The northern basin formed during the late Devonian and the southern basin was formed during the Carboniferous.[5]</nowiki></ref> During the Cretaceous, rifting and subsidence continued along with the deposition of limestones, siliciclastics and clay dominated sediments. This influx of clay sediments, once lithified, became the Kimmeridge formation which became a major source rock for many oil and gas fields in the North Sea[6]. During the Jurassic, the North and South basin were both dominated by widespread marine transgression until the Cretaceous. At this time in the Cretaceous, both the North and South basin continued with a thermal subsidence and deposition of new sediments with only minor deformation. During the Miocene, tectonic movement surrounded the basin by land masses with the deepest areas being located in the center of the basin. This new positioning of the basins resulted in changes in the formations encountered, alternating between the clay deposits and siliciclastics[7]. Shortly after the area was affected by the Quaternary ice age, an influx of sediment was deposited into the basin as the sea level had dropped. As the ice age ended and sea level rose, the new sediments buried previous formations deep enough to produce hydrocarbons[8].


File:Kimmeridge Bay, cliff - geograph.org.uk - 1411669.jpg
Kimmeridge clay, major soruce rock for the North Sea, Image by  geograph.org.uk

4: The North Sea Today

The North Sea still today remains a very active region for oil and gas exploration. Although several of the older fields in this region are coming to the end of their lifespan, companies continue to make new discoveries and extend their durations. The North Sea is still the leading region for the most amount of offshore rigs.[9] Several energy companies have plans to invest more money into this region as they see future potential due to the rising price of oil.[10]

5: Learn more about the North Sea

Geology of the North Sea

Forties Oil Field

References

  1. Norwegian "Facts 2007" official report, available freely here, [1], page 82
  2. Swartz, Kenneth I. (16 April 2015). "Setting the Standard". Vertical Magazine. Archived from the original on 18 April 2015. Retrieved 18 April 2015.
  3. Pratt, J. A. (1983). The History of the British Petroleum Company: The Developing Years, 1901–1932 (Volume I). By R. W. Ferrier. (London: Cambridge University Press, 1982. xxx 801 pp. $64.50. Business History Review, 57(04), 606-609. doi:10.2307/3114838
  4. "Forties Field bigger than perceived". December 2005. Archived from the original on 21 January 2008.
  5. <ref name=Allen>Allen, P. A., & Mange-Rajetzky, M. A. (1992). Devonian-Carboniferous sedimentary evolution of the Clair area, offshore north-western UK: Impact of changing provenance. Marine and Petroleum Geology, 9(1), 29-52. doi:10.1016/0264-8172(92)90003-w<nowiki>
  6. Graversen, Ole. (2006). The Jurassic-Cretaceous North Sea Rift Dome and Associated Basin Evolution. AAPG Convention, Search and Discovery Article #30040
  7. Dybkjær, K., King, C., & Sheldon, E. (2012). Identification and characterization of the Oligocene–Miocene boundary (base Neogene) in the eastern North Sea Basin — based on dinocyst stratigraphy, micropalaeontology and δ13C-isotope data. Palaeogeography, Palaeoclimatology, Palaeoecology, 363-364,  11-22
  8. King, E. L., Sejrup, H. P., Haflidason, H., Elverhøi, A., & Aarseth, I. (1996). Quaternary seismic stratigraphy of the North Sea Fan: glacially-fed gravity flow aprons,  hemipelagic sediments, and large submarine slides. Marine Geology, 130(3-4), 293-315.
  9. https://www.statista.com/statistics/279100/number-of-offshore-rigs-worldwide-by-region/
  10. https://www.ft.com/content/39ee4fa0-2b64-11e8-a34a-7e7563b0b0f4