Gafsa trough of central Tunisia: Basin evolution and maturation of hydrocarbons

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7271177

Schamel, S; Reed, J K ^[1]; Traut, M ^[2]; Hassine, B K ^[3]

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1. Univ. of South Carolina, Columbia (United States)
2. Occidental International, Bakersfield, CA (United States)
3. ETAP, Tunis (Tunisia)

The Gafsa trough of onshore central Tunisia is one of the more interesting and underexplored features of North Africa. It is a 5-12 km deep, east-west-trending depression along the inner edge of the Tunisian-Libyan shelf margin. The basin has had a long and virtually uninterrupted history of subsidence from the late Paleozoic into the early Cenozoic. Subsidence began in the late Carboniferous, soon after the close of the Hercynian orogeny, and resulted in deposition of a 3000+ m succession of Permo-Carboniferous carbonates and shale that pinches out southward onto the Saharan Flexure. The tectonic setting for this earliest phase of subsidence is not clear. The main episode of subsidence, which began in the Middle Triassic, continued through the Jurassic as left-lateral, transtensional rifting along the South Saharan and Maghrebian Shear zones. A set of organic maturation maps for onshore central Tunisia depicts the minimum time of entry into the oil and gas generative windows of the two potential source rocks in the region, the Lower Silurian Tannezufft Formation and Middle-Upper Jurassic basinal shales. Maturation modeling suggests that the Lower Silurian source rocks beneath the deeper portions of the Gafsa trough are overmature, even for generation of dry gas. Everywhere north of the Saharan Flexure potential Paleozoic source rocks are highly mature to overmature. The Middle-Upper Jurassic basinal shales in the deeper, central portions of the Gafsa trough entered the oil generative window as early as mid-cretaceous time and into the gas generative window in the Late Cretaceous - early Tertiary. These possible source rocks are mature to highly mature beneath nearly all of the basin. The Gafsa trough is a probable gas province, with occurrences of condensate possible.

• OSTI ID: 7271177
• Report Number(s): CONF-910403--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
AFRICA
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
JURASSIC PERIOD
MATURATION
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS DEPOSITS
PALEOZOIC ERA
PETROLEUM DEPOSITS
RESOURCES
SEDIMENTARY BASINS
SILURIAN PERIOD
SOURCE ROCKS
TUNISIA