Sirte Basin

Source: Wikipedia, the free encyclopedia.
Map of Libya

The Sirte Basin is a late

bathymetric contour.[1] It borders in the north on the Gulf of Sidra and extends south into northern Chad
.

Characteristics

The Sirte Basin ranks 13th among the world's

NGL
), an amount that constitutes 1.7% of the world’s known oil reserves. The basin consists of one dominant total petroleum system, known as the Sirte-Zelten.

The Late Cretaceous Sirte Shale is the primary hydrocarbon source bed.[2] Reservoirs range in rock type and age from fractured Precambrian basement, clastic reservoirs in the Cambrian-Ordovician Gargaf Sandstone, and Lower Cretaceous Nubian Sandstone to Paleocene Zelten Formation and Eocene carbonates usually in the form of bioherms.

Hydrocarbon generation commenced about 50 million years ago (Ma) in the deeper basins, about 40 Ma in many other areas, and may continue to the present day. Geothermal gradients generally range from 1 °F/100 ft to 1.8 °F/100 ft; horsts and grabens generally have roughly equivalent thermal regimes relative to the primary source rock. Along the southwest and west margins of the province are extrusive igneous deposits that tend to diminish the hydrocarbon potential of these areas. The Gialo High is a relatively small horst block in the eastern Sirte Basin. It is most important and primarily known for the stacked oil fields in rocks ranging from the Early Cretaceous to Oligocene age. There are several billion barrels of oil reserves associated with the structure both over the crest of the horst as well as flanking the high in the adjacent graben.[3]

Characteristics

Statistic Amount
Formation Late Mesozoic-Cenozoic
Land area ≈230,000 km2
Source rock Sirte Shale
Dominant trap style Structural
Rift Type Triple junction
System Tethyan Rift System

Notes:
1. USGS 2002.

Land area

Topography of Libya

The land area in the Sirte basin is characterized by desert steppes and includes

Sahara Desert. In a relatively narrow, northern coastal strip, some land areas are as much as 47 m below sea level. The basin is floored by a northwest-southeast-trending mosaic of narrow horsts and grabens, an important structural characteristic that distinguishes it from the adjacent intracratonic Kufra, Murzuk, and Ghadames basins.[4]

The area of the Sirte Basin occupies about 230,000 km2, with a

wildcat drilling
density of one new field wildcat per 145 km2. Overall drilling density of the basin is 3.3 wells per 100 km2, with an average field depth of 2,100 m. Recent indications of hydrocarbons within grabens suggest that these areas have potential as well as clastic reservoirs beneath the carbonate reservoirs in the Central Sirte Basin. The offshore area beyond 200 m depths is largely unexplored.

Geologic setting

The Sirte Basin province is considered to be a

tectonic plate margin, which characteristically has an axis at an angle to that margin.[7]

The area's structural weakness is exemplified by alternating periods of

strike-slip faulting. To the south, the Nubian Swell is the stable continental basement for this rifted basin.[8]

Trap style

In geology, "trap" refers to the stratigraphic or tectonic structural feature that ensures the juxtaposition of reservoir and seal such that hydrocarbons remain trapped in the subsurface, rather than escaping (due to their natural

stratigraphic traps such as at Sarir or Messla field are superimposed on structures.[9]

Petroleum history

The first reported petroleum occurrence in the Sirte Basin was observed in a coastal water well drilled by Italian colonists during the

Amerada Hess), and ETAP of Tunisia.[10]
In 2020, operations were transferred by Wintershall Aktiengesellschaft to Sarir Oil Operations.[11] In August 2021, state-owned company NOC announced plans for resuming operations in the basin.[12]

Petroleum occurrence

In 2007, the Energy Information Administration estimated that the Sirte Basin Province contains approximately 80% of Libya's total proven oil reserves (41.5 billion barrels (6.60×109 m3) as of January 2007) and accounted for roughly 90% of the country's total oil output, which was 1.80 Mbbl/d (286,000 m3/d) in 2006.[13] Over twenty-three large oil fields and sixteen giant oil fields occur in the province.[14] Libya's onshore oil has historically been discovered mainly within the confines of three major geological trends occurring in the Sirte Basin:

  1. Western fairway
  2. North-central Libya
  3. Easterly trend

Basin petroleum data: selected fields

Field Geological Trend Annual Production Reserves Discovery Operator(s)
Samah Field Western NA Gof NA Libya WOC
Beida Field Western NA Gof NA Libya NOC
Dahra-Hofra Field Western NA Gof NA Libya WOC
Raguba Field Western NA Gof 1961 Libya SOC
Bahi Field Western NA NA 1958 Libya NOC
Waha Field Northcentral 350,000 bbl/d (56,000 m3/d) Gof 1961 United States ConocoPhillips
Nasser Field Northcentral NA 2.5 Bbbl 1956 Libya SOC
Hateiba gas field Northcentral NA NA 1960 Libya SOC
Sarir Field Eastern NA 12.0 Bbbl 1961 Libya Agoco
Messla Field Eastern NA Gof 1971 Libya Agoco
Gialo Field Eastern NA Gof NA Libya WOC
Bu Attifel Field Eastern 80,000 bbl/d (13,000 m3/d) Gof 1968 Italy Agip
Intisar Field Eastern NA Gof 1967 Libya ZOC
Nafoora-Augila Field Eastern 100,000 bbl/d (16,000 m3/d) Gof 1965 Libya Agoco
Amal Field Eastern Gof 1959 Libya Harouge
En-Naga Field Western 24,000 bbl/d (3,800 m3/d)[15] Gof 1998 Libya Harouge

Notes:
1. USGS 2002 (Bbbl = "billion barrels of oil"). 2. LOF = large oil fields (>100 million

barrels of oil equivalent
): GOF = giant oil fields (>500 million barrels of oil equivalent).

The Amal Field produces from the Cambro-

fluvial Sarir sandstone 27 m thick at a depth of 2682 m.[18] The Intisar 'D' Oil Field produces from an upper Paleocene pinnacle reef 385 m thick, 5 km in diameter, and at a depth of about 2700 m[19]

Due to the debts of companies in the sector, oil production dropped by 300,000 barrels per day in Libya, falling to less than 1 million b/d in April 2021 from 1.3 million the month before.[20]

References

  1. ^ "NPA Group - Oil and Mineral Study: Libya". Archived from the original on 2007-07-14. Retrieved 2007-09-12.
  2. ^ USGS Bulletin 2202–F
  3. ^ G. Abdulghader (1996)
  4. ^ C. Lewis (1990)
  5. ^ Futyan (1996)
  6. ^ A. Bally and S. Snelson (1980) p.9
  7. ^ A. Clifford (1986) p.336
  8. ^ T. Ahlbrandt (2002) p.9
  9. ^ T. Ahlbrandt (2002) p.21
  10. ^ P. Mobbs (2004) p. 19.1
  11. ^ "Libya: Operations onshore Sirte Basin transferred to new company | The North Africa Post". northafricapost.com. Retrieved 15 September 2021.
  12. ^ "LIBYA : How the NOC is trying to resurrect the ill-fated Mourzouq and Ghadames oil basins - 30/08/2021". Africa Intelligence. 30 August 2021. Retrieved 15 September 2021.
  13. ^ EIA 2005 p.2
  14. ^ H. Belazi (1989) p. 353
  15. ^ Major Discoveries 2001
  16. ^ Roberts, J.M., 1970, Amal Field, Libya, in Geology of Giant Petroleum Fields, AAPG Memoir 14, Halbouty, M.T., editor, Tulsa, American Association of Petroleum Geologists, p. 438.
  17. ^ Sanford, R.M., Sarir Oil Field, Libya-Desert Surprise, in Geology of Giant Petroleum Fields, AAPG Memoir 14, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, p. 449
  18. ISBN 0891813063
    , p. 507
  19. ISBN 0891813063
    , p. 543
  20. ^ Dubessy, Frédéric. "Libya to study the establishment of several oil refineries". Econostrum | Economic News in the Mediterranean. Retrieved 15 September 2021.

Bibliography

Retrieved from "https://en.wikipedia.org/w/index.php?title=Sirte_Basin&oldid=1216295649"