Oil was discovered in November 1959 in well B1 concession 12, Amal field, Libya, in the eastern part of the Sirte basin. The reflection seismic exploration technique was used because there is very little surface 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, 76 of which are 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 nose 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 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 in the Early Cretaceous Maragh Formation, a sandstone interbedded with siltstone and shale. The Amal Formation in most of the field unconformably underlies the Cretaceous Rakb Formation at a depth of 10,000 ft. The Maragh Formation is on the north and east flanks of the crest of the plunging nose; it is a transgressive marine Lower Cretaceous unit.