Abu Dhabi - The Offshore Fields - Abu Dhabi Marine Operating Co.

ADMA-OPCO is the third biggest oil producer next to ADCO and ZADCO. Its area has one of the world's biggest reserves of natural gas. ADMA-OPCO is owned 60% by ADNOC, 14.67% by BP, 13.33% by Total and 12% by JODCO (Japan Oil Development Co. - now a unit of Inpex). JODCO acquired its equity from BP in 1973. A few years later JODCO acquired 12% in the Upper Zakum field, a very complex super-giant which ADMA's foreign partners did not want to develop. Upper Zakum was developed by ADNOC in co-operation with Total, and the company investing in it was named ZADCO (see below). By then, ADMA had discovered most of Abu Dhabi's offshore fields, which were relinquished to ADNOC and some of them were taken up by Japanese companies.

Of ADMA-OPCO's fields, two are giants: Umm Shaif and Lower Zakum. Both have been expanded and together can produce at a peak of 600,000 b/d but only for a short period. They have a sustainable capacity of 480,000 b/d, producing from more than 300 wells. Crude oils from Umm Shaif, Lower Zakum and smaller fields are exported from the nearby Das Island terminal. ADMA-OPCO's export grades are: Zakum, 40.1[degrees] API with 1.1% sulphur; and Umm Shaif, 37.4[degrees] API with 1.5% sulphur.

Umm Shaif, the first offshore field found in March 1958 by Abu Dhabi Marine Areas (ADMA), is one of the biggest in the Middle East - 20x15 km. It went on stream in 1962 as the first oil producing and exporting field in Abu Dhabi.

Umm Shaif is a complex field with fractured reservoirs. Its pay zones are: Lower Cretaceous (Thamama I & II), Upper Jurassic (Arab A-C & D carbonates) and Middle Jurassic (Upper Araej, Uwainat & Lower Araej limestones). It needs advanced technology, mainly for pressure support and infill drilling. The crude's water cut is also a problem. The field has about 150 producing wells and 62 injection wells. About 40 of its wells are horizontal. Oils in place at Umm Shaif exceed 20 bn barrels.

In December 2006 Adma-Opco awarded Hyundai Heavy Industries (HHI) of South Korea the main contract for the Umm Shaif gas reinjection project. The $1,600m EPC contract will involve the supply and installation of three platforms, 16 subsea pipelines and tie-ins to three existing wellhead towers and the existing Umm Shaif super complex for gas reinjection. The scheme is to take 45 months to complete. HHI is expected to nominate subcontractors for the various construction packages. WorleyParsons of Australia has carried out the FEED optimisation study.

Umm Shaif, about 150 km north-west of Abu Dhabi city, has 268 oil wells producing 200,000 b/d. In an emergency they can yield up to 350,000 b/d but for a short time. Under the $1,600m contract, Umm Shaif's long-term sustainable capacity will be 300,000 b/d by 2010.

Like ADCO, ADMA-OPCO applies advanced techniques in 3D and horizontal drilling. Horizontal drilling, which costs much more than vertical drilling but yields four times as much oil, has involved 44 wells since the company introduced this in 1989 The field can produce 1,200 MCF/d of natural gas for export in LNG form by ADGAS, another JV not involving ADMA-OPCO.

The Permian Khuff reservoir of non-associated gas beneath Umm Shaif is a huge limestone structure discovered in 1979. It lies beneath the oil-bearing zones and a Thamama reservoir. But the gas has a high content of sulphur and other impurities. The first phase of its development, in a $350m ADNOC plan, was completed in September 1994. The gas output, 1,200 MCF/d, is piped to Das Island to feed a major LNG complex whose third train went on stream in late 1994. Bechtel was the main contractor for the gas development programme.

A further development of the Khuff reservoir at both Umm Shaif and the nearby offshore field of Abu al-Bukhoosh, a project delayed since 1998, was contracted in September 2000 to ABB Lummus Global in partnership with ADNOC affiliate NPCC for $260m. Completed in 2004, this has allowed production to rise from 300 MCF/d to more than 640 MCF/d as an initial phase. This has involved five new wells at Abu al-Bukhoosh, a platform for each of the two fields processing dry sour gas, marine pipelines to gather the gas and link the platforms, a pipeline from Abu al-Bukhoosh to Umm Shaif, a modification and upgrading of 13 gas platforms, a pipeline to Das island, and a two-train gas processing system. Later on this system should produce almost 1,000 MCF/d.

Associated gas has been produced at Umm Shaif since 1988 from two 150 MCF/d wellhead platforms and two producer/injector platforms all connected to the Umm Shaif Supercomplex. Gas is produced from the field's Uwainat reservoir, and from four gas cap wells repressurised in 1990 by installation of four wellhead towers for drilling deep into the Khuff (see Vol. 64, in gmt2AbuDfieldsJan10-05)

Lower Zakum is ADMA-OPCO's largest oilfield found in July 1963 and developed in 1966. It produces from Thamama IV and V reservoirs. Its capacity has been raised from 270,000 b/d in 1991 to 300,000 b/d. But now its sustainable capacity is limited to 280,000 b/d. To maintain pressure, 200 MCF/d of Khuff gas are re-injected into Lower Zakum's Thamama reservoir in a project completed in 2004. Another project will enable Lower Zakum and Umm Shaif together to raise oil production to 625,000 b/d by 2010. This will involve debottlenecking of crude processing facilities on Das island.

The Zakum Central Supercomplex, mothballed in 1986 as a result of output restrictions, was recommissioned in early 1994. In October 1990 the company recommissioned ADNOC's gas gathering plant (GG-II) on the Zakum West Supercomplex, mothballed in 1986, to allow the field's associated gas to be recovered rather than flared. The plant can collect and compress 250 MCF/d from both the Lower and Upper Zakum fields and pump it to the Das Island LNG complex through the Umm Shaif Supercomplex.

The Zakum system (Lower & Upper) is rated as the third biggest oil zone in the Middle East next to Ghawar (Saudi Arabia) and Greater Burgan (Kuwait), although geologists say Iraq's Great Rumaila Triangle could potentially prove to be bigger than Ghawar. Lower Zakum is 30 km long and 25 km wide, lying to the south-east of Umm Shaif. Oil in place at Lower Zakum has been estimated at 16 bn barrels. Oil in place at Upper Zakum, which belongs to ZADCO, has been estimated at 50 bn barrels.

ADMA-OPCO also has the capacity to produce 20,000 b/d (down from 70,000 b/d in late 2002) from smaller fields which are satellites to the Umm Shaif and Lower Zakum systems. Nasr, discovered by ADMA in 1971, is one of the ADMA-OPCO fields awaiting further development. It lies 20 km north-east of Umm Al Shaif and has Arab reservoirs with the oil of 30-35[degrees] API. Beneath them lie Permian Khuff gas carbonates proven in 1982. The field's development, initially planned to be on stream in 1993 with a first-phase capacity of 50,000 b/d, was deferred in 1992 and in the subsequent years because of OPEC quota limitations and the priority to Upper Zakum granted by ADNOC. Nasr should produce 100,000 b/d by 2010. Umm al-Lulu is another field to be developed for a 100,000 b/d capacity by 2010.

ADMA-OPCO has been spending $300m to replace about 260 km of ageing marine oil and water supply pipelines. After the restructuring of the hydrocarbon sector in the late 1980s, ADMA-OPCO managed to reduce costs across the board.