To select the optimum process for Neptune II, we evaluated refrigerated GSP, which Neptune I uses, and other proprietary NGL recovery processes. Inlet gas to the Neptune plants is projected to average more than 4 GPM for many years after start-up. Technip-Coflexip, which also built the first unit, is the contractor for Neptune II. To process newer discoveries from the Southern Canyon of the Gulf of Mexico, another nominal 300 MMcfd train, Neptune II, is currently under construction (Fig. To improve ethane and propane recoveries, mechanical refrigeration was later added to make Neptune I a refrigerated GSP plant.Īt times, the plant has processed inlet gas volumes of up to 330 MMcfd with an ethane recovery of 70-80%. When the plant started up in February 2000, the inlet gas was significantly richer than the design anticipated (4+ GPM vs. C-406 centrifugal compressor, driven by a Mars 100 gas turbine, recompresses the residue gas. Neptune I uses a standard gas subcooled process (GSP) to treat 300 MMcfd of 2.8-GPM (gal/Mcf) gas. Photo courtesy of Enterprise Products Operating LP (Fig. 18, 2003, shows the Neptune II plant under construction in the foreground. This plant, Neptune I, processes Gulf of Mexico natural gas produced by Shell Oil Co., Marathon, and others. Neptune gas plantĮnterprise and Marathon started up a cryogenic NGL recovery plant at St. The new train is scheduled to start up by the end of 2003. The two enhancements should allow ethane recoveries of 90+% and maintain the flexibility to maximize propane recovery during ethane-rejection mode. A novel demethanizer reflux design was also incorporated into the unit.

IPSI's technology replaces conventional propane refrigeration with a self-refrigeration and stripping gas package that allows up to 20% more processing capacity with the same residue-gas compression horsepower as in the existing train. The companies selected IPSI LLC's Enhanced NGL-Recovery Process after comparing available NGL recovery technologies for the new train. conducted a study for the design and construction of a second 300 MMcfd NGL-recovery train at the Neptune plant in St.

Enterprise Products Operating LP and partner Marathon Oil Co.

Neptunes gas