Exploration history is such that the largest fields in a given basin tend to be discovered early in the exploration cycle, but this has not been the case in Algeria's Ghadames basin.
Supergiant Hassi Messaoud field, discovered in 1956, is the basin's and the country's largest oil field, with estimated ultimate recovery (EUR) of 9 billion bbl of 43° gravity oil. It produces from a 900-ft oil column in a Cambrian sandstone reservoir at 11,000 ft in a 1,300 sq km productive area.
Ourhoud field, not found until 1994, is second largest, with EUR greater than 1 billion bbl of 40° gravity oil. Its reservoir is a 930-ft oil column in Triassic Argilo-Greseux Inferieur (TAGI) at 9,800 ft in a 180 sq km area.
"By 1959," said A. Balducchi and G. Pommier in AAPG Memoir 14 in 1968, "Algeria had become the 10th largest oil-producing country in the world, with an average daily production in 1967 of approximately 830,000 bbl of oil. Hassi Messaoud field contributes about 40% of this total."
Ourhoud field went on production in November 2002 and reached capacity of 230,000 b/d in May 2003.
Since the 1980s
The joint venture of which Anadarko Petroleum Corp., Houston, is a part has discovered 2 billion bbl of oil in place in 15 fields, invested more than $3 billion, and established 530,000 b/d of production capacity since the 1980s.
Production started in May 1998 from Hassi Berkine South field, Don MacLiver, managing director, Anadarko Algeria Co., said earlier this year. Cumulative production from Hassi Berkine South and Ourhoud is near 450 million bbl since then.
Production averages more than 500,000 b/d of oil, close to 40% of Algeria's daily output. Earlier in 2004 production averaged 530,000 b/d, or 300,000 b/d from Hassi Berkine South and 230,000 b/d from Ourhoud.
Anadarko has 361 million bbl of crude oil, condensate, and natural gas liquids proved reserves in Algeria. It is in partnership there with Maersk Olie Algeriet AS—a unit of Denmark's Mærsk Olie & Gas AS—and ENI SPA unit ENI Oil (Algeria) Ltd. in more than 4 million acres.
Operating efficiencies
In the 1980s, Anadarko promised Algeria's state-owned Sonatrach to conduct as much of the work as possible in Algeria, including subsurface management.
From that promise came Groupement Berkine, which has 600 employees seconded from Sonatrach and Anadarko. Management is based in Hassi Messaoud, with operational departments at Hassi Berkine.
Five years ago, MacLiver said, the organization was operating out of Portakabins, could only access email from time to time, and was working off generator power.
Today the reservoir modeling technology and software "rival what their Anadarko counterparts are doing in Houston," he said.
The first exploratory well, a dry hole, took 180 days to drill in 1991 and cost $15 million. Drilling cost and time averaged $9 million/well and 73 days/well in 1991-94, and that is cut to $4 million and 25 days in 2002-03.
The companies have cut production costs to just above $1/bbl today from $2.09/bbl in 1998, Anadarko said.
Anadarko was testing its first well on Block 406b in November. It drilled RFR-1, 15 miles west of the border with Tunisia, to TD 14,400 ft and set casing to test "a number of encouraging shows."
The company was processing 3D seismic data acquired on Block 403c/e northwest of Hassi Berkine and planned to drill its first well in early 2005.
The future
A further 100,000 b/d is to come on production in 2007 as the result of work under way to convert 120 million bbl of oil in El Merk field to proved developed reserves. El Merk is the first field to be developed on Block 208 of four discovered.
Anadarko has expanded its holdings in the greater Ghadames basin into southern Tunisia with acquisition of the larger Anaguid and Jenein Nord Permits. It is evaluating commerciality of the 2003 CEM-1 and SEA-1 Upper Ordovician discoveries on Anaguid. It operates both permits with 55% interest, and Pioneer Natural Resources Inc., Dallas, holds the rest. Pioneer is tending to discoveries on the Borj El Khadra block south of Anaguid.
Anadarko continues to explore in Algeria. It shares Blocks 404, 208, and 211 with Maersk and ENI-Lasmo. It farmed out a 40% working interest to Kuwait Foreign Petroleum Exploration Co. in 690,000-acre Block 406b. And it explores 400,000-acre Block 403c/e with Maersk.