ABU DHABI - The Gas Sector & OGD Projects.

Total gas production capacities in Abu Dhabi rose from 1.8 BCF/day in 1992 to more than 4 BCF/day by August 1996. A major part of the production is associated gas, which will be fully utilised before end-2001 compared to 89% in 1992. Most of the onshore gas supplies go to GASCO which has a major gas liquids complex at Ruwais. Most of the offshore gas goes to the LNG export complex on Das Island.

The SPC, ruling over the petroleum sector, decided in 1991 to launch ADNOC's Onshore Gas Development (OGD) programme, with the cost then estimated at about $2 bn, based on developing Thamama gas at the Bab and Asab fields and ADCO's other structures close to the Habshan area. This was prompted by rising demand, both for domestic consumption and for export in liquid form.

Development of Bab gas, called OGD-1 or Project 545, has cost $1.35 bn. It was completed in August 1996. The main contracts were awarded in March 1993 and June 1994 to a consortium of Technip of France (40%), Bechtel of the US (30%) and Athens-based Consolidated Contractors Co. (30%). The project manager was Brown & Root of the US, with supervision done by a projects unit at ADNOC on ADCO's behalf. Completed in November 1996, OGD-1 raised output and processing at Habshan from 540 MCF/day to 1,865 MCF/day. It raised to 131,000 b/d the condensate recovery rate, from 5,000 b/d. Most of the condensates were exported until the condensate units at the Ruwais refinery came on stream (see DT).

OGD-1 involved the following: (1) non-associated gas developed from the Thamama C and F reservoirs, beneath the field's oil reservoirs, and associated gas from Thamama B; (2) two new trains at the Habshan gas treatment complex, each with a capacity of 350 MCF/day, to process associated and non-associated gas; (3) another new train at Habshan, with a capacity of 625 MCF/day, to process non-associated gas from Thamama F into NGLs and condensates; (4) a new gas compression station for Thamama B in an area 5 km from Habshan; (5) two new gas injection trains which raised capacity from 280 MCF/day to 1,100 MCF/day for the dry sour gas for injection into the F reservoir; (6) facilities for dry gas to be processed into LPG and for power plants; (7) condensate storage and transfer facilities, consisting of six 430,000-barrel tanks at Ruwais, 105 km from Bab, and two 195,000-barrel tanks at Habshan; (8) three sulphur recovery units of 600 t/day each.

In addition, the OGD-1 system has 245 km of pipelines with diameters ranging from 10 to 30 inches. About 830 MCF/day of the gas goes for domestic consumption.

The second phase, OGD-2, costing $1.4 bn, was in April 1998 won by Technip/ Bechtel, with CCC as one of the sub-contractors. Completed in late 2000, this has involved development of Thamama C North & South and Thamama D of the Bab and Habshan structure and the drilling of 52 wells to extract 1,100 MCF/day of gas. The gas is processed at Habshan to produce 55,000 b/d of condensate, about 500 t/y of NGL, and 2,100 t/d of sulphur. The front-end engineering and designs were done by Technip. Sub-contractors included Snamprogetti which installed OGD-2's gas gathering system involving 300 km of flowlines and a receiving terminal.

An important part of the gas goes for domestic consumption. A related $150m gas pipeline from Bab to Maqta and the new Taweelah-B power station, known as Project 1,204, has been completed. This involves a 42-inch, 125 km pipe from Bab to Maqta and a 36-inch, 57 km pipe from Maqta to Taweelah. To increase the sulphur handling capacity for its OGD system, called Project 1205 and costing $15m, ADNOC awarded the contract in 1994 for completion before end-1994. Pritchard Corp. did the front-end engineering design.

OGD-2 turned Habshan into one of the world's largest gas processing plants with total gas treatment capacity of almost 3 BCF/day.

The related Asab gas development project (AGD), costing about $700m, was awarded in July 1997 to Snamprogetti. Completed in 1999, this involved new wells to extract 856 MCF/day of wet associated gas from Thamama F and G formations under Asab's oil reservoirs, plus about 95,000 b/d of condensates stripped out. The remaining dry gas is reinjected into the reservoirs to maintain field pressure. The AGD system includes a gas gathering and injection pipeline and related facilities. Pritchard has done AGD's front-end engineering and design. Willbros Engineering did the designs for the pipeline under a sub-contract.

ADCO in May 1993 had contracted Babcock Engineering to install a system to inject gas into the North Shuaiba reservoir by end-1995, with management and front-end engineering design done by Bechtel. It also awarded a contract for a gas gathering network from Thamama C and F to link up with ADNOC's OGD in 1996. This project cost $150m, with Bechtel as consultant. Brown & Root provided the front-end engineering and design.