Audrey Leon takes a look at recent exploration and production activities occurring offshore Tunisia.
Top: The Ashtart platform offshore Tunisia. Bottom: The Maamoura platform operated by Eni Tunisia. Photos from ETAP.
The US Energy Information Administration (EIA) lists Tunisia as a ‘relatively small hydrocarbon producer.’ Oil production in the country declined to 67,000b/d in 2012, from its peak of 120,000b/d in the 1980s. EIA says Tunisia’s proved natural gas reserves are 2.3Tcf.
Tunisia is currently listed an oil importer due to its limited refining capacity, not because of its reserves. The North African country has only a single oil refinery. Plans for a second are in the works, according to EIA.
Despite Tunisia’s decreasing production, foreign explorers are still attracted to the country and are sizing up new prospects off the North African coastline and into the southern Mediterranean.
In January 2014, Norway’s DNO International farmed into the Sfax offshore exploration permit and the Ras El Besh concession off Tunisia, which left DNO as operator with 87.5% interest. The Sfax and Ras El Besh permit areas are in the Gulf of Gabes, covering 3296sq km, in shallow waters.
DNO says the work program for the two permit areas includes a large 3D seismic acquisition campaign to confirm prospects identified on 2D seismic. The company plans to drill the Jawhara-3 exploration well to test additional upside potential, about 4km north of the Jawhara-1 discovery well that flowed 1500bo/d. The program is expected to begin 3Q 2014.
The Norwegian company also holds 30% participating interest in the Hammamet offshore permit. DNO says geologic and geophysical studies are ongoing to define the best prospect to be drilled in early 2015. The permit was operated by Canada’s Chinook Energy until it sold all of its Tunisian assets to Indonesia’s PT Medco Energi in August 2014 for US$13.7 million.
The acquisition is MedcoEnergi’s re-entrance into Tunisia’s oil and gas industry and gives the company working interest in eight fields in four exploration areas. While five fields are onshore, three are offshore. MedcoEnergi will serve as operator for three areas — Cosmos, Hammamet and Yasmin — in the Pelagian basin off the northeast coast of Tunisia. MedcoEnergi says the Cosmos and Yasmin developments are scheduled for completion in 2018.
The Cosmos concession, according to L’Entreprise Tunisienne d’Activités Pétrolières (ETAP), Tunisia’s state-owned oil and gas company (20% interest), contains recoverable resources of 9.45MMbo at Cosmos South blocks A and B. ETAP says that Cosmos, which is in the Gulf of Hammamet in 120m of water, will be developed with a central platform connected back to an FPSO. Development plans could include both gas lift and water injection to maintain pressure.
In August, Australia’s ADX Energy Ltd. won a two-year extension of the exploration period for its Kerkouane permit offshore Tunisia, extending the exploration period until 21 February 2016.
ADX operates the Kerkouane permit with 100% interest. The area contains both the Dougga gas condensate field and the Lambouka gas discovery. Kerkouane and ADX’s Pantelleria license off Italy are in the Terravecchia Foredeep in front of the Tunisian Atlas thrust front, a geological subprovince of the extensive Italian foredeep and foreland area.
|Image from ETAP.|
The Dougga gas field sits in 328m of water, about 45km east of Cap Bon in the Gulf of Hammamet, and 22km south-southeast of the Lambouka discovery. ADX estimates that Dougga has an assessed mean resource of 74MMboe (196Bcf and 42MMbbls). The field was originally discovered by Shell in 1981.
The Lambouka discovery is located 70km northeast of Cap Bon in the Sicily Channel. Drilling began on the Lambouka-1 well in July 2010. ADX conducted comprehensive logging while drilling analysis and susequent wireline logging runs. However, the company says further well tests were not possible due to instability of the borehole. Based on the well results and the 3D seismic interpretation, ADX estimates the mean recoverable gas resource at 309Bcf.
Prior to drilling its next well in the Kerkouane permit area, ADX is seeking to divest part of its interest.
Another company investing in Tunisia’s offshore is Ireland’s Circle Oil plc, which spudded the El Mediouni-1 (EMD-1) well in the Mahdia permit in June. Circle Oil used the PetroSaudi Discoverer drillship for the campaign. The company plans to test the potential of the El Mediouni prospect, including the primary Birsa Sands target and the secondary fractured carbonates of the Ketatna formation.
Awarded in 2009, the Mahdia permit covers a 3780sq km area near the Nabeul permit to the north and Lampedusa Island to the east. It is adjacent to commercial oilfields such as Tazerka, Birsa, Oudna, Halk El Menzel and Isis. Both 2D and 3D seismic surveys have been conducted on the permit area in 2009 and 2013, respectively. Circle Oil says that there are several classic tilted fault block structures that could provide traps for both sand or carbonate reservoirs, one of which is a target for the EMD-1 well.
As of 31 July, Circle Oil had drilled the EMD-1 well to 753m measured depth. The company ran 20-in. casing and successfully cemented the well. However, after it ran the blowout preventer and riser, mechanical problems resulted in damage to the permanent guide base that was irreparable.
A replacement guide base has been installed, and drilling is expected to continue on to the well’s primary and secondary targets at 1260m and 1460m depth.
Circle Oil also holds 23% working interest in the Ras Marmour permit in southeast Tunisia, which includes both onshore and offshore prospects covering Djerba Island and a portion of the Gulf of Gabes. Its partner in the permit is Tunisia’s Exxoil Ltd. (77% WI).The permit is near the offshore
El Biban oil and gas field that was discovered by Marathon Oil in 1982 (Marathon later sold all its Tunisian interests in 1996). Circle Oil says the main reservoir in the El Biban field is composed of fractured limestones from the Bireno formation of Middle to Early Turonian age.
Cooper Energy is another explorer offshore Tunisia, holding interest in the Bargou, Hammamet and Nabeul permits with 30%, 35%, and 85% interest, respectively.
|This map depicts the Mahdia permit area near the Tunisia-Italy maritime border. Image from Circle Oil.|
The old guard
One of Tunisia’s oldest offshore developments is the Ashtart field, discovered in 1971 and developed by the Elf-Aquitaine Oil Co. Ashtart is located in the Gulf of Gabes, 80km southeast of the port city of Sfax.
Currently, Serept (Society of Research and Exploitation of Petroleum in Tunisia) – a joint venture between 50:50 partners ETAP and Austria’s OMV – operates the field development.
The Ashtart field is the second-largest field in Tunisia, and celebrated its 40th year in production this May. According to Serept, Ashtart has a single, 70m-thick, porous limestone reservoir, El Gueria, that is heavily faulted.
The downhole temperature is 140ºC and the pressure ranges between 200-250bar. Serept says most wells have a depth of approximately 3000m. ETAP lists recoverable reserves at 12.5MMbbl.
The project underwent revitalization efforts from 2009 to 2013 to increase recovery using artificial gas lift, as well as increasing power generation capacity to meet ESP pump needs, and also modernizing management and control systems.
Eni, through its Tunisian subsidiary Eni Tunisia BV, operates the Maamoura field with 49% interest along with partner ETAP (51%). The Maamoura field, which began production in 2009, is located 19km off the Gulf of Hammamet in 50km of water. ETAP lists the field’s recoverable resources at 6.4MMcu m of oil and 985MMcu m of gas.
Tunisia is no stranger to border disputes, like most countries in the Mediterranean and elsewhere. However, the country has enjoyed stable relations with its European neighbor Italy, with which it shares the aforementioned Sicily Channel. Tunisia and Italy signed the Italy–Tunisia Delimitation Agreement 43 years ago on 20 August 1971, and it was later ratified in 1978.
The treaty states that the boundary terminates just short of an equidistant line between Malta and the Italian Pelagie Islands. It further created a 13nm semi-enclave around the Italian island of Pantelleria. Another semi-exclave was created comprising overlapping 13nm arcs around the Italian islands of Linosa and Lampedusa that also intersect a 12nm zone around Lampione. The boundary’s westernmost point forms a maritime tripoint with Algeria.