Enhanced oil recovery with high-pressure nitrogen injection

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.