A reservoir containing approximately 12 billion bbl of original oil in plac
e (OOIP) has produced only 1 billion bbl after 15 years of primary producti
on, with the reservoir pressure declining from 11,500 to 4,100 psi, rapidly
approaching the bubblepoint pressure of 3,750 psi. Miscible displacement w
ith high-pressure nitrogen injection has been selected as an enhanced-oil-r
ecovery (EOR) process for the naturally fractured thick carbonate reservoir
containing light oil underlain by an aquifer. The objectives are to mainta
in the reservoir pressure and increase the ultimate recovery.