SAUDI ARABIA - The Main Fields Producing Heavier Crudes.
There will be a further mothballing of field capacities producing heavy crudes as additional fields, including those in the Najd area south of Riyadh, come on stream.
Safaniyah: By far the largest offshore field in the world, Safaniyah was found in 1951 by Texaco (which in 1937 was the first to join SoCal - now Chevron - in Saudi Arabia as a 50% partner in Aramco). Texaco discovered and developed other offshore fields containing heavy oil. Safaniyah has about 19 bn barrels of proven oil reserves recoverable at relatively low cost. But the oil is heavy, 27 deg. API with 2.93-2.96% sulphur, and much of Safaniyah's 1.5m b/d capacity has been mothballed. Like most other offshore fields in the north-east, the oil is reservoired in Cretaceous sandstones and carbonates mainly at a depth of 5,100 feet. (Texaco, once a crude-long major now having become crude-short, sold 50% of its US East Coast system to Saudi Aramco in 1988. The resultant JV Star Enterprise made Texaco "crude-sufficient", at least in superstructural terms, as it gained a virtually permanent access to 630,000 b/d of Saudi crude oil). In 1996, Saudi Aramco brought some of the mothballed desalting units and other facilities at Safaniyah back into operation. They enabled the company to handle more Arab Medium crude from the offshore Zuluf field. Reservoir pressure at Safaniyah, however, is beginning to decline. Two rigs are working continuously there to prevent a fall in production.
Zuluf: Another offshore giant discovered by Texaco in 1968, Zuluf has 8 bn barrels of proven oil reserves in a Lower Cretaceous formation at a depth of 5,800 feet. Its capacity is over 500,000 b/d, with another 200,000 b/d and two GOSPs mothballed. Saudi Aramco has planned to raise the field's capacity to 1.2m b/d. Of this a further 500,000-700,000 b/d has been earmarked for closure. But related facilities to upgrade the field's production of heavy crudes to the Arabian Medium grade have been built.
Manifa: An offshore giant discovered in 1957, Manifa has 11 bn barrels of proven reserves. It was developed to produce 200,000 b/d of 28 deg. API oil with 2.97-3.66% sulphur. Oils come mainly from two reservoirs, a Lower Cretaceous containing very sour 26 deg. grade, and an Upper Jurassic having a 29 deg. grade with 2.97% sulphur. The wells are 7,950 feet deep.
Marjan: An offshore giant discovered in 1967 by Chevron, Marjan extends well into Iranian waters, where the field is known as Forouzan. Marjan forms an axis of fields off the Saudi coast, all in Cretaceous-to-Upper Jurassic carbonates, which include Hamur, Maharah, Lawhah, and Hasbah. Marjan, a producer of Arabian Medium, now has a working capacity of 270,000 b/d. About 300,000 b/d of its 570,000 b/d capacity installed by late 1993 has been mothballed. Khursaniya: An onshore field discovered in 1956, has 3.5 bn barrels of proven oil reserves in an Upper Jurassic formation at a depth of 6,560 feet. The field's installed capacity by 1994 reached 150,000 b/d of Arabian Medium (31 deg. with 2.63% S), compared with 75,000 b/d in 1991 and 50,000 b/d in the late 1980s. But about 50,000 b/d of the new capacity has been mothballed. Abu Saafa, discovered in 1963, straddles Saudi and Bahraini territorial waters. It has 6 bn barrels of proven oil reserves. The field, shared with Bahrain, was shut down by Saudi Aramco in April 1987. It was reopened in recent years and all its production was given to Bahrain.
Universal modular platforms at to be installed by late August 2000 at Safaniyah, Zuluf, Marjan and Abu Saafa by Dubai-based J. Ray McDermott Middle East under a contract signed in May 1999.
The Najd Fields: There are a number of producing fields in the Najd area south of Riyadh, all rich in light/sweet oil, sweet gas and condensates of 60-65 deg. API. Also called the Hawtah Trend, they include Al Hawtah and structures discovered from June 1989. They are producing 200,000 b/d of Arab Super Light (ASL), 50 deg. API with 0.06% sulphur.
The Najd reservoirs have lower pressure than first thought. Since 1994, production has been affected by the encroachment of sand into the wells. Underground pumps installed at the fields have clogged up with sand, with the blockage occurring roughly every three months. To prevent production from falling below 200,000 b/d, Saudi Aramco has been hooking up new fields discovered since 1994. The fields need gas reinjection facilities to maintain reservoir pressure. Most of the gas is being produced from the Nuayyim field, where the crude has the highest gas-to-oil ratio among the Najd structures. A 75,000 b/d GOSP at the field has been built, together with underground pumps, to raise gas supplies for a modified EOR system at the Hawtah centre. Recoverable reserves of oil and condensates in the Najd area are estimated at 10 bn barrels. Saudi Aramco experts still point to an earlier estimate that the Najd fields have up to 30 bn barrels of liquids and major reserves of natural gas. The liquids and gas are reservoired in Paleozoic formations older than the Khuff, at depths ranging from 7,900 to more than 9,000 feet. Some of the reservoirs are more than 150 feet thick. About 85-90% of the liquids and gas tested had no traces of hydrogen sulphide. Some of the crudes are free of sulphur and have been tested as a motor fuel.
The main producing Najd fields are: Al Hawtah, 190 km south of Riyadh, on stream since late 1994 with a capacity of 150,000 b/d, and its proven reserve of liquids is said to exceed 1.5 bn barrels; Nuayyim, 25 km east of Hawtah, which came on stream with a very limited capacity in January 1997, using facilities at Al Hawtah; Hazmiyah, south of Hawtah; and Ghinah, whose liquid reserves are almost 1 bn barrels. They and several other Najd field are linked to Petroline (the east-west pipeline) by a 325-km pipeline for export to Ras Tanura in the Gulf or Yanbu' on the Red Sea. At present, the ASL is exported through Ras Tanura. The pipeline link has been designed for other fields to be hooked up in the coming years.
Shaybah: A super-giant discovered in the early 1970s - with light/sweet oil in place estimated at about 14 bn of which 7 bn barrels are recoverable, plus 25 TCF of gas - Shaybah came on stream in mid-1998 for tests. Its capacity reached 500,000 b/d in early 1999 and it was inaugurated in March 1999. The field lies in the Rub' Al Khali (Empty Quarter) region on the border with Abu Dhabi. A final decision on developing it was taken in early 1995. On June 25, 1995 Saudi Aramco awarded the project management and FEED contract, worth SR300m, to Ralph M. Parsons Co. The field's development and related infrastructure have cost about $2.5 bn. The field has three GOSPs and a 640 km pipeline to Abqaiq's gathering centre. Shaybah's crude, 40-42 deg. API with 0.7% sulphur, is piped to Abqaiq for blending and has improved the quality of Arabian Extra Light. Oil at Shaybah occurs in reefal facies of the Shuaiba formation, with the reservoir being 122m thick at a depth of 1,494m, the origin of which is similar to that of Abu Dhabi's large fields in swells developed over salt pillows triggered by deeper basement faulting. Work on the field has included 3D seismic surveys and extensive horizontal drilling. A 385 km access road from Dhahran to Shaybah was completed in late November 1996.