Grand Isle Block 16 field is a large offshore oil field with an estimated 277 million bbl of ultimately recoverable oil. The field, located in the Gulf of Mexico 7 mi (11 km) offshore from Grand Isle, Louisiana, was discovered in 1948. Oil is trapped in 26 poorly consolidated upper Miocene sandstones located in peripheral fault blocks on the flanks of a shallow piercement salt dome. The Block 16 salt diapir is circular in plan, and has a maximum diameter of 4.75 mi (7.6 km) and a shallow crest at −1,700 ft (518 m). The field is on one of several large, oil-productive piercements located offshore along a deep-seated, regional salt-ridge trend oriented east-west. The salt-ridge trend and a related regional salt-withdrawal syncline to the north cause a reversal from normal south dip to steep north dip across the field. Deposition of the producing section, which thins toward the salt, was contemporaneous with domal growth. The major oil accumulation is on the southeast flank at depths from −6,500 to −11,000 ft (−1,980 to −3,350 m). Wells typically flow 500-800 BOPD. All wells are directionally drilled from a limited number of platforms in 40-60 ft (12-18 m) of water. As a result, not all well-bore penetrations are ideal for 100-percent primary recovery. Therefore, careful planning and secondary-recovery techniques have been utilized for optimum oil recovery and well-bore utility.