G. Alan Petzet
Exploration Editor
Tunisia is renewing its efforts to attract oil and gas companies to explore its territory.
About 400 exploratory wells have been drilled and about 100,000 line km of seismic data recorded in the North African country.
Four of the five concession or seismic option agreements signed since Jan. 1, 1989, have covered areas near Ashtart oil field in the Gulf of Gabes.
The 1985 petroleum law, as amended in 1987, remains in effect. New legislation being considered is intended to promote deep drilling, gas development, and extension of existing exploration commitments.
It isn't known to what extent, if any, the deep drilling and gas legislation might apply to existing permit holders.
Meanwhile, Schlumberger Ltd. and the national oil company, Entreprise Tunisienne d'Activites Petrolieres (ETAP), are performing a technical review of seven plays in Tunisia and plan to present the results in November 1990 followed by a 2 day field trip.
Of 23 Tunisian permit areas in force, 17 are scheduled to expire in 1990 or 1991. Four were to have expired in July 1990.
The last three agreements signed have been with independents Conquest Exploration Co., Houston, and Coho Resources Inc. and Maxus Energy Corp., both of Dallas.
Several acreage applications are pending.
Most of the country's oil and gas fields are small, but several large areas are unexplored or lightly explored.
ETAP has published Petroleum Geology of Tunisia, a 194 page review of the country's geology and oil and gas prospects.
Authors Ali Ben Ferjani, Pierre F. Burollet, and Fathia Mejri write that recent discoveries and important oil shows have proved the existence of hydrocarbons in newly identified depocenters.
EXPLORATION HISTORY
Exploration in Tunisia consisted of drilling about one well/year during 1909-42. First production came in 1948, when gas was produced from Lower Cretaceous in the Abderrahman structure on Cap-Bon peninsula.
The first commercial oil production appeared in 1964 from Middle Triassic sandstone on the large El Borma structure along the Algerian border. Oil was also discovered in Lower Cretaceous Aptian carbonates at Douleb in west central Tunisia.
The country's deepest test, to 17,525 ft, was drilled in the mid-1960s on the Abderrahman structure. Exploration then slowed.
Ashtart, Tunisia's second major oil field after El Borma, was discovered off Sfax in Lower Eocene El Gueria limestone in 1971, and Sidi El Itayem field was discovered in the plain of Sfax in southern Tunisia the same year in the same formation.
In 1975 Miskar gas field was discovered in Upper Cretaceous carbonates in the Gulf of Gabes. British Gas Tunisie (BGT) plans to decide this fall whether to develop the field, which it estimates contains about 1 tcf of gas reserves (OGJ, June 11, Newsletter).
Also in the 1970s, Birsa, Tazerka, and Yasmin oil fields were found in Middle Miocene sands in the Gulf of Hammamet; and oil, gas, and condensate were discovered in Ordovician quartzite in the Chott area.
Tunisian exploration peaked in 1981, when 32 wells were drilled. Activity later slowed markedly, especially after oil prices collapsed in 1986.
OPEC News Agency says Tunisia's oil production, which declined by about 1,000 b/d/year since the mid-1980s, is expected to average 90,000 b/d this year.
Oil output may at least level off for several years, owing to a number of onshore discoveries by BGT.
BGT said earlier this year that production from its Kerkennah concession near Sfax will rise to at least 10,000 b/d in 1991 from the current 3,200 b/d. BGT also plans to drill two wildcats, one soon and another in early 1991.
CHALLENGES
Many questions about Tunisian petroleum geology remain unanswered.
The book lists the following as problems:
- Structure and evolution of the grabens.
- Geochemical evaluation out of the classical source rocks. There is a lack of systematic analysis.
- Role of the paleoclimatology in regard to organic matter maturation, ecology, and sedimentology; e.g., the consequences of Upper Cretaceous ultrathermal events.
- Thermal effects of the Cretaceous volcanisms.
- Subsurface evolution of the salt structures and exploration of the traps along their flanks.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.