BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of extracting oil from a subsurface reservoir. More specifically, the invention relates to a method of extracting oil from a subsurface reservoir by injecting a waterflooding composition into the subsurface reservoir.

2. Discussion of the Related Art

Methods of extracting oil from subsurface reservoirs are known in the art. More specifically, methods of extracting oil from a subsurface reservoir by injecting water into the reservoir, are being used to extract oil from oil reservoirs. The water that is injected into the oil reservoir may contain additives.

U.S. Pat. No. 7,789,144B2 describes a method of flooding an oil reservoir for oil recovery. The method includes the steps of introducing a flooding fluid into the reservoir, along with a non-polymeric viscoelastic surfactant.

Chinese patent CN107794019A describes a composite oil displacement agent that controls the degree of emulsification of the crude oil, for enhancing oil recovery. In this reference, the composite oil displacement agent includes a non-ionic surfactant and an anionic surfactant. The anionic surfactant used herein is sodium alkyl benzene sulfonate and the nonionic surfactant is octylphenol polyoxyethylene ether and/or nonylphenol polyoxyethylene ether.

Non-patent literature report “Crude Oil—Water Interfacial Viscoelasticity in Waterflooding Performance, AIChE Annual Meeting, Nov. 10, 2015” describes an analysis of the interfacial viscoelasticity of oil and low-salinity brine for enhanced oil recovery. The reference mentions that the use of a low concentration (about 100 parts per million) of anionic surfactant with high salinity brine is reported to increase oil recovery by 10%.

Similarly, the non-patent reference “Interfacial Viscoelasticity of Crude Oil/Brine: An Alternative Enhanced-Oil-Recovery Mechanism in Smart Waterflooding, SPE Improved Oil Recovery Symposium, Tulsa, 12-16 Apr. 2014, and subsequently published in SPE Journal, Volume 23, Issue 03, June 2018” describes the correlation between dynamic interfacial viscoelasticity and oil recovery.

Although these methods are useful in improving the rates of oil recovery from oil reservoirs, a large amount of oil is still not recoverable from the oil reservoirs.

Thus, there is a need in the art for a method of extracting oil from a subsurface reservoir by waterflooding, that is capable of a higher efficiency of oil extraction from a subsurface reservoir.

SUMMARY OF THE INVENTION

These and other needs are met by the present invention.

One embodiment of the present invention describes a method of extracting oil from a subsurface reservoir, the method consisting essentially of, accessing the subsurface reservoir by means of a well, injecting a waterflooding composition comprising water and a functional molecule, into the subsurface reservoir through the well, altering the viscoelasticity of the oil-injected water interface; and extracting the oil through the well.

