Nitrogen has recently emerged in the Rockies as an alternative to natural gas and carbon dioxide. A number of fields, particularly in the overthrust, are using large volumes of nitrogen to increase the recovery of oil. The application of nitrogen in four Rocky Mountain nitrogen injection projects is described, giving reservoir parameters, quantities of gas injected and some early predictions.

In many gas injection projects an operator usually has a choice among alternative gases. After determining for each alternative the incremental barrels of oil recovered per thousand standard cubic foot (MSCF) of gas injected and the rate of recovery, the operator should consider the following factors; the cost per MCF at delivery pressure at the field, the long term availability and reliability of supply, the physical and chemical properties, the incremental cost for corrosion and produced gas clean-up, and the impact of the Windfall Profits Tax. These factors are presented, discussed and compared for natural gas, nitrogen and carbon dioxide.

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