Saudi Arabia's Oil & Gas Fields - The Najd Fields.
The Najd reservoirs in the centre 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 found in that area since 1994. The fields need gas re-injection to maintain reservoir pressure.
Most of the gas is produced from the Nu'ayyem 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. Nu'ayyem, 250 km south of Riyadh found in April 1990, has been developed to 100,000 b/d of Arab Super Light (ASL) - on stream since May 2009.
The Nu'ayyem plant has the latest smart-field technology, enabling operators to view a variety of relevant down-hole and surface data and make adjustments from their control-room desks. Production and reservoir engineers can monitor well performance and acquire real-time information which allows them to perform better reservoir management. The GOSP has compressors capable of pumping gas through a 300-km pipeline to the Haradh gas plant.
Recoverable reserves of oil and condensates in the Najd area have been put at 10bn barrels. Saudi Aramco experts still point to an earlier estimate that the Najd fields could have up to 30bn barrels of liquids and major reserves of natural gas. The liquids and gas are reservoired in Paleozoic Fms older than the Khuff, at depths ranging from 7,900 to more than 9,000 ft. Some reservoirs are more than 150 ft thick. About 85-90% of the liquids and gas tested had no traces of hydrogen sulphide. Some crudes are free of sulphur and have been tested as a motor fuel.
The main producing Najd fields are: Hawtah, 190 km south of Riyadh, on stream since late 1994 with a capacity of 150,000 b/d, and its reserve of liquids has been put at about 1.5 bn barrels; Nu'ayyem, 25 km east of Hawtah, which came on stream with a limited capacity in January 1997, using facilities at Hawtah; Hazmiyah, south of Hawtah; and Ghinah, whose liquid reserves have been estimated at almost 1bn barrels.
These and several other Najd fields are linked to Petroline (the east-west pipeline) by a 325-km spur 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 has been partly converted to pump natural gas from the east to Yanbu'.