Oil was discovered in November 1959 at Amal field, Libya, located in the eastern part of the Sirte basin, in well B1-Concession 12. The exploration technique utilized was reflection seismic because there is no surface topographic expression in this area. The field now includes more than 100,000 acres and extends north-south for 30 mi and east-west for approximately 10 mi. To date 81 wells have been drilled in the field, 76 of these being producers. The outer configuration of the gross reservoir has been defined on the north and on the southeast. The gross oil column is as thick as 600 ft in the most favorable areas.

The Amal field accumulation is on a plunging horst block extending northwest from the old ancestral basement knob, the Rakb high. The field is interpreted from seismic and gravity data to be bounded on the west and east flanks by large fault systems.

The principal reserves in the field are contained in the Amal Formation, a fractured, quartzose sandstone of Cambro-Ordovician age and the Early Cretaceous Maragh Formation, a sandstone interbedded with siltstone and shale. The Amal Formation in most of the field is unconformable below the Cretaceous Rakb Formation, and is at a depth of 10,000 ft. The Maragh Formation is on the north and east flanks of the main horst block; it is a transgressive marine Lower Cretaceous unit.

Several prolific oil fields have been discovered in association with the ancestral Rakb high. These are the Amal field (1959), the Nafoora field (1965), and the Augila field (1966). Several hundred million barrels of reserves have been established by the operating companies in this geological province since Mobil's first discovery. Additional exploration within this general area will discover new and additional petroleum accumulations.

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