Oil recovery using non-cryogenically produced nitrogen and off-gas recycling

Abstract

An enhanced oil recovery process includes non-cryogenically generating a relatively inert gas, such as nitrogen, or nitrogen-enriched air, near the site of an oil-bearing formation. The relatively inert gas is injected into the formation, so as to displace oil from the formation. One or more off-gases, also obtained from the formation with the oil, are separated from the oil, compressed, and recycled into the formation. The use of the compressed off-gas therefore reduces the amount of relatively inert gas required, and reduces the required size and energy consumption of the equipment used to produce the inert gas. The invention therefore substantially reduces the cost of an enhanced oil recovery process.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to the field of recovery of oil from oil wells, and provides an improved method for enhanced oil recovery. [0002] Enhanced oil recovery means the recovery of oil with the assistance of a compressed fluid which is pumped into a well so as to force the oil out. Such a technique is appropriate where the oil in the reservoir exists naturally in liquid form, but where the pressure of the oil is too low to cause the oil to exit the reservoir spontaneously. Such reservoirs typically include a mixture of liquid oil and natural gas, and may have some oxygen mixed therewith. [0003] In the prior art, it has been known to use a relatively inert gas, such as nitrogen or nitrogen-enriched air, to force the oil out of a reservoir. An inert gas, or relatively inert gas, is preferred, so as to prevent the fluid from reacting with the contents of the reservoir. A stream of compressed nitrogen, or other relatively inert gas, effectively ...

AI Technical Summary

Benefits of technology

[0007] The present invention comprises an improved process for enhanced oil recovery. A relatively inert gas, such as nitrogen, or nitrogen-enriched air, is generated by a non-cryogenic process, at or near the site of an oil-bearing formation. This inert gas is compressed and injected into the formation, displacing liquid oil in the formation, and causing the liquid oil to flow out. Also exiting the formation are one or more off-gases. The off-gases are separated from the liquid oil, so that the liquid oil can be recovered as the final product.

[0008] Meanwhile, the separated off-gases are compressed and re-injected into the formation. Preferably, the off-gases are conveyed to the same conduit used to inject the inert gas. The off-gases therefore become mixed with the inert gas while being injected into the formation. Recycling of the off-gases in this manner reduces the requirement for inert gas. Essentially, the system need only supply “make-up” inert gas, thus reducing the size and power consumption requirements of the equipment for generating the inert gas.

Problems solved by technology

But providing gaseous nitrogen in cylinders is cumbersome and expensive, especially where the well site is remote.

It is also expensive to produce, handle, and store cryogenic liquids at a well site.

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