Niger Delta Basin (geology)

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The Niger Delta Basin is located in the Gulf of Guinea on the west coast of Africa.
Geologic map of the Niger Delta Basin and the Benue trough, and the oil fields in the region.

The Niger Delta Basin, also referred to as the Niger Delta province, is an extensional rift basin located in the

Cameroon Volcanic Line and the transform passive continental margin.[2]

Basin formation

The Niger Delta Basin was formed by a failed rift

thrust faults. Also at this time syn-rift sands and then shales were deposited in the late Cretaceous. This indicates that the shoreline regressed during this time. Concurrently, the basin had been undergoing extension resulting in high angle normal faults and fault block rotation. At the beginning of the Paleocene there was a significant shoreline transgression.[2] During the Paleocene, the Akata Formation was deposited, followed by the Agbada Formation during the Eocene. This loading caused the underlying shale Akata Formation to be squeezed into shale diapirs. Then in the Oligocene the Benin formation was deposited, which is still being deposited today. The overall basin is divided into a few different zones due to its tectonic structure.[1]
There is an extensional zone, which lies on the continental shelf, caused by the thickened crust. Moving basinward is a transition zone, and a contraction zone, which lies in the deep sea part of the basin.

Lithology

Sealevel highstand and lowstand mapped on a crossection of the basin

The sediment fill in the Niger Delta basin is characterized by three major depobelts. These three cycles show that the basin experienced an overall

Volcanic activity in the area may also result in thin deposits of ash (bentonite). The early Cretaceous sediments are thought to be from a tide-dominated system that were deposited on a concave shoreline, and throughout time the shoreline became convex and it is currently a wave
-dominated system.

Basement

The oceanic basement rock is the oldest rock in the basin and is

crops
out onshore.

Cretaceous

There is a section of rock in this basin from the middle to late Cretaceous which is poorly understood due to its significant burial depth. It is believed to be composed of sediments from a tide-dominated coastline,[1] and there are believed to be several layers of shales, although their distribution is unconstrained.

Akata Formation

The Akata Formation is

ductile shale formation which was squeezed into shale diapirs in the basin. The Akata Formation formed during lowstands in relative sea level and anoxic conditions. This formation is estimated to be up to 7,000 meters thick.[1]

Agbada Formation

The Agbada Formation dates back to Eocene in age. It is a marine facies defined by both freshwater and deep sea characteristics. This is the major oil and natural gas-bearing facies in the basin. The hydrocarbons in this layer formed when this layer of rock became subaerial and was covered in a marsh-type environment rich in organic content. It is estimated to be 3,700 meters thick.[1]

Benin Formation

The Benin Formation is Oligocene and younger in age. It is composed of continental flood plain sands and alluvial deposits. It is estimated to be up to 2,000 meters thick.[1]

Tectonic structures

The tectonic structures in the Niger Delta Basin are typical of an extensional rift system, but the added shale

diapirism due to loading makes this basin unique. The main method of deformation is gravitational collapse of the basin, although the older faulting and deformation in the basin are related to the continental breakup and rifting of the African plate and South American plates.[1]
The overall basin is divided into a few different zones due to its tectonic structure. There is an extensional zone, which lies on the continental shelf, that is caused by the thickened crust. There is a transition zone, and then there is a contraction zone, which lies in the deep sea part of the basin.

Basin inversion

Basin inversion is caused by uplift and/or compression in this basin. The compression is caused by the toe detachment of the shale diapirs. Basin inversion forms anticline structures, which serve as a great oil trap. Clay smears in the sediments seal the formations so oil does not escape out.[1]

Basinward dipping reflectors

Basinward dipping reflectors are a common feature of extensional type rift basins. As fault blocks extend they rotate to dip towards the center of the basin. At the top of these fault blocks sub basins can form.

Shale diapirs

The shale diapirs are from the Akata Formation. This structure is formed due to the improper dehydration of the formation and the over pressuring by the overlying and denser Agbada Formation.[1]

High-angle normal faulting

High-angle

normal faulting is a feature of the extensional portion of the rifting in this basin. It is considered a growth fault and the feature lies closer towards the basins edge and transitions to the toe detachment faulting as you continue down the basin.[3]

Oil and Gas

Minimum and maximum petroleum system

The Niger Delta is the twelfth largest province in the world by known oil and gas resources.[4] The Niger Delta Basin produces around 2 million barrels of oil per day. The entire system is predicted to contain 34.5 billion barrels of oil and 94 trillion feet3 of natural gas. This area is still very heavily explored by oil companies today. It is one of the largest oil producers in the world.[1]

Oil Pollution

farming are the main sources of livelihoods for majority of her residents.[10]

This incredibly well-endowed ecosystem contains one of the highest concentrations of biodiversity on the planet, in addition to supporting abundant flora and fauna, arable terrain that can sustain a wide variety of crops, lumber or agricultural trees, and more species of freshwater fish than any ecosystem in West Africa.[11]

The advent of

NNPC, long before popular unrest surfaced:[19]

We witnessed the slow poisoning of the waters of this country and the destruction of vegetation and agricultural land and good water source by oil spills which occur during petroleum operations. But since the inception of the oil industry in Nigeria, more than fifty years ago, there has been no concerned and effective effort on the part of the government, let alone the oil operators, to control environmental problems associated with the industry.[20]
The resultant
flaring, dredging of larger rivers, oil spillage and reclamation of land due to oil and gas extraction across the Niger Delta region costs about US$758 million every year.[21] Regrettably, 75% of the cost is borne by the local communities through polluted water, infertile farmland and lost biodiversity.[22] The region could experience a loss of 40% of its habitable terrain in the next thirty years as a result of extensive dam
construction in the region.

In July 1979, an incident on the coastal zone of the Forcado tank 6 terminal spilled 570 thousand barrels of oil into the Forcados estuary, affecting the sea species and surrounding swamp forest.[4] In January 1980, the Funiwa No.5 Well in Funiwa Field spilled 421 thousand barrels of oil into the ocean, damaging 836 acres of mangrove forest.[4] In 1983, 5 000 barrels were spilled causing high mortality in crabs, fish and shrimps.[4] Until 1999, an average of 240 thousand barrels of crude oil was spilled in the zone every year.[4]

See also

References

  1. ^ a b c d e f g h i j k Tuttle, Michele; Charpentier, Ronald; Brownfield, Michael. "The Niger Delta Petroleum System: Niger Delta Province, Nigeria, Cameroon, and Equatorial Guinea, Africa". United States Geologic Survey. United States Geologic Survey. Retrieved 6 March 2015.
  2. ^ a b c fatoke, oluwaseyi adedamola (2010). sequence stratigraphy of the pliocene-pleistocene strata and shelf-margin deltas of the eastern niger delta, nigeria (ph.d.). university of houston.
  3. .
  4. ^ a b c d e Tuttle, Michele L. W.; Brownfield, Michael E.; Charpentier, Ronald R. "Niger Delta (Akata-Agbada) Petroleum System OF99-50H, Chapter A". pubs.usgs.gov. Retrieved 12 August 2021.
  5. ^ "Oil and the environment - U.S. Energy Information Administration (EIA)". www.eia.gov. Retrieved 2022-05-31.
  6. .
  7. ^ "'This place used to be green': the brutal impact of oil in the Niger Delta". the Guardian. 2019-12-06. Retrieved 2022-03-20.
  8. ^ P.C. Nwilo & O. T. Badejo: Impacts of Oil spills along the Nigerian coast The Association for Environmental Health and Sciences, 2001
  9. ^ "Conserving and restoring wetlands in Nigeria's Niger River Delta". Wetlands International. Archived from the original on 2022-02-26. Retrieved 2022-02-26.
  10. ^ Adebayo, Bukola (2019-03-27). "Major new inquiry into oil spills in Nigeria's Niger Delta launched". CNN. Retrieved 2022-03-12.
  11. ^ "oil spill in Nigeria". 6 January 2012.
  12. ^ Donatus, Peter (2016-10-15). "Shell's Nigeria ecocide is creating a refugee crisis". www.greenleft.org.au. Retrieved 2023-07-06.
  13. ^ "UNEP Ogoniland Oil Assessment Reveals Extent of Environmental Contamination and Threats to Human Health". UNEP. 2017-08-07. Retrieved 2023-07-06.
  14. ^ "'Ecocide' movement pushes for a new international crime: Environmental destruction". NBC News. 2021-04-07. Retrieved 2023-07-06.
  15. ^ "Fighting ecocide in Nigeria". theecologist.org. 5 February 2014. Retrieved 2023-07-06.
  16. ^ "UNPO: Ogoni: An Ecocide in the Making?". unpo.org. Retrieved 2023-07-06.
  17. ISSN 0261-3077
    . Retrieved 2023-07-06.
  18. ^ Albert,Amaratunga, Haigh (Nov 29,2017) "Evaluation of the Impacts of oil spill Disaster on communities and its influence on Restiveness in Niger Delta, Nigeria."
  19. ^ Osemwengie, Garrick (2010-03-05). "As Goodluck would have it:Theophilus Danjuma ! His $500 Million Booty & $100 million Donation to Charity". Sahara Reporters. Retrieved 2022-03-20.
  20. ^ Vidal, John (2010-05-30). "Nigeria's agony dwarfs the Gulf oil spill. The US and Europe ignore it". The Observer. Retrieved 27 July 2010. government's National Oil Spill Detection and Response Agency (Nosdra) says that between 1976 and 1996 alone, more than 2.4m barrels
  21. ^ Ayanlade, Proske (August 31, 2015)."Assessing wetland degradation and loss of ecosystem services in the Niger Delta, Nigeria."
  22. ^ Ayanalde,Proske (August 31, 2015). "Assessing wetland degradation and loss of ecosystem services in the Niger Delta, Nigeria."

External links