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1. Miscible gas injection Part 3:
Nitrogen Injection
By: Salem Eljareh

2. Nitrogen miscible injection is a process whereby nitrogen gas is injected into
an oil reservoir above the Minimum Miscibility Pressure (MMP) to create a
miscible vaporizing drive and increase the oil recovery factor.

4. Advantages
Nitrogen is the optimum EOR method for many reservoirs and has
been chosen for the following reasons:
• By applying nitrogen given the fact that a significant increase in
oil production has been realized
• Nitrogen is economical (cheaper than CO2)
• Nitrogen has good injectivity in low permeability reservoirs

5. Advantages
► Nitrogen can be generated and therefore can be injected
wherever, whenever, and whatever quantities are needed
► Nitrogen is friendly to environment, completely inert, and
remains inert in the presence of water
► Nitrogen is non-corrosive to field equipment
► Nitrogen vaporizes the lighter components of the crude oil and
generates miscibility if the pressure is high enough

6. Mechanisms That Improve Recovery
• Vaporizes the lighter components of the crude oil and
generates miscibility if the pressure is high enough.
• Provides a gas drive where a significant portion of the reservoir
volume is filled with low cost gases

7. Limitations
• Miscibility can only be achieved with light oils at high
pressures; therefore, deep reservoirs are needed.
• Steeply dipping reservoir is desired to permit gravity
stabilization of the displacement, which has a very unfavorable
mobility ratio.

8. • Challenges
• Viscous fingering results in poor vertical and horizontal sweep
efficiency.
• gas injection can cause corrosion.
• Nonhydrocarbon gases must be separated from saleable gas.

9. Mechanism
This technique based on the
vaporization of intermediate
components from the reservoir oil to
the injected gas creating a miscible
transition zone.

10. Mechanism
When Nitrogen is injected at high
pressure, it can form a miscible slug
which aids in freeing the oil from
the reservoir rock

11. Reservoir Screening Criteria
Nitrogen Miscible Injection Screening Criteria
API gravity 35-48
Viscosity <10 cp
Composition C1 – C7
Oil saturation >30 %
Formation type sand stone/carbonate
Permeability not critical
Transmissibility not critical
Temperature not critical
Depth >6000 ft
Thickness thin unless dipping