Salt-resistant hydrophobically modified copolymer nanostructures as viscosity increasing agents for enhanced oil recovery

Abstract

A hydrophobically modified copolymer nanostructure includes a first monomer and a second monomer. The first monomer is a hydrophilic monomer. The second monomer is a non-ionic short-chain hydrophobic monomer. The first monomer and the second monomer form a microblock structure, forming nanoparticles. The microblock structure is the hydrophobically modified copolymer nanostructure.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of priority to an Iran patent application having serial number 139450140003003488 filed on Jun. 22, 2015, which is incorporated by reference herein in its entirety.TECHNICAL FIELD[0002]The present disclosure relates generally to oil extraction and, more particularly, to polymer flooding processes for oil recovery. Also it relates to other applications such as cosmetics, coatings and drilling fluids.BACKGROUND[0003]In the context of oil extraction, oil reservoirs can be fractured, thereby trapping oil even upon completion of classical oil recovery processes, such as water flooding, gas injection and in-situ combustion. There are known processes, sometimes referred to as “secondary” and “tertiary” oil recovery, aimed at recovering portions of this trapped oil. One such process is polymer flooding. This is a flooding process that uses natural polymers, such as xanthan and starch, and synthetic polymers, for...

AI Technical Summary

Benefits of technology

The patent describes a new type of polymer that can resist salt and other damage, and also increase the viscosity of oil to improve its recovery from underground reservoirs. This polymer is produced by modifying an existing polymer with a special process. One important feature is that it protects other polymers from damage in underground reservoirs. This modified polymer is also easier to separate from unreacted components. Overall, this new polymer can provide a more effective way to recover oil from underground reservoirs.

Problems solved by technology

A limitation of traditional polymer flooding, however, is that the polymer chains exhibit degradations during the flooding process.

In addition, shearing and heating in wellbores and reservoirs often decrease the polymer viscosity.

The chain extension approach leads to one of the greatest disadvantages of using PAM and HPAM in oil reservoirs.

The polymer chains no longer extend fully, which can cause the solution to have decreased viscosity due to the ion-dipole interaction between the salt cations and the oxygen atoms in polyacrylamide molecules.

Second, mechanical, thermal and bacterial damages, as well as surface absorption, can result in the particular disadvantages in the use of hydrophilic polymers, such as PAM, HPAM, TVP, and xanthan during the traditional polymer flooding.

Third, an increase in the water viscosity in undesired directions before reaching the remaining oil areas, and use of excessive polymers to increase viscosity in heavy oil reservoirs are other limitations of this traditional polymer flooding technique and approach.

The result has susceptibility to temperature degradation, as well as mechanical, salinity, shear and biological degradations of polymer chains during the flooding process.

At the critical concentration, the hydrophobic intra-actions of the hydrophobic groups change to molecular interactions, which lead to sudden increase in viscosity of the copolymer.

The chain extension approach, though, creates inherent vulnerability to degradations during flooding processes.

The polymer chains, as a result, no longer extend fully.

The weakened bond strengths can cause chemical degradation of polymer molecules and an associated decrease of the polymer solution viscosity.

In addition, shearing and heating in wellbores and reservoirs often decrease the polymer viscosity.

In case of conventional polymers such as HPAM, in hard water (with high contents of Ca2+ and Mg2+) precipitation may occur due to complexing ability of the carboxylate groups of HPAM and resulting in a rapid decreasing of viscosity.

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