US-12618312-B2 - Systems and methods for performing a polymer flood having a graded polymer concentration

US12618312B2US 12618312 B2US12618312 B2US 12618312B2US-12618312-B2

Abstract

A method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir. The method includes injecting a polymer solution from an injection well ( 32 ) into the subterranean reservoir to form a polymer slug in the subterranean reservoir, wherein the polymer slug has a leading front and a trailing rear ( 48 ), and a graded viscosity profile which decreases in viscosity from the front of the polymer slug to the rear of the polymer slug. The method additionally includes injecting an aqueous solution ( 50 ) from the injection well into the subterranean reservoir following to displace the polymer slug through the subterranean reservoir.

Inventors

Stephane Jouenne
Alexandra Klimenko
Khalid Mateen
Kun Ma
Haishan LUO

Assignees

TOTALENERGIES E&P RESEARCH & TECHNOLOGY USA, LLC

Dates

Publication Date: 20260505
Application Date: 20221221

Claims (8)

1 . A method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir, the method comprising: (a) injecting a polymer solution from an injection well into the subterranean reservoir to form a polymer slug in the subterranean reservoir; (b) linearly reducing a polymer concentration of the polymer solution over time during (a) beginning with a leading front of the polymer slug and concluding at a trailing rear of the polymer slug to provide the polymer slug with a and a graded viscosity profile which decreases in viscosity from the leading front of the polymer slug to the trailing rear of the polymer slug; and (c) injecting an aqueous solution from the injection well into the subterranean reservoir following (a) to displace the polymer slug through the subterranean reservoir.
2 . The method of claim 1 , wherein the viscosity of the polymer slug at the front thereof is greater than the viscosity of the polymer slug at a midpoint between the front and the rear of the polymer slug.
3 . The method of claim 1 , wherein a mobility ratio (M) between the front of the polymer slug and hydrocarbons present in the subterranean reservoir is less than or equal to one.
4 . The method of claim 1 , wherein the graded viscosity profile is S-shaped such that the polymer slug decreases convexly in viscosity from the leading front to an inflection point and concavely in viscosity from the inflection point to the trailing rear, and wherein the inflection point of the polymer slug is located at a midpoint between the front and the rear of the polymer slug.
5 . The method of claim 1 , wherein the polymer of the polymer solution comprises an acrylamide-based polymer.
6 . The method of claim 1 , further comprising: (d) heating a heating fluid by a surface heating system to a temperature that is greater than the temperature of at least some of the hydrocarbons present in the subterranean reservoir; and (e) injecting the heated heating fluid into the subterranean reservoir.
7 . The method of claim 1 , further comprising: (d) determining a nonlinear dependence of the viscosity of the polymer solution to a polymer concentration of the polymer solution, wherein the nonlinear dependence comprises a nonlinear dependence of a specific viscosity at zero shear rate (η sp ) of the polymer solution on the polymer concentration of the polymer solution.
8 . The method of claim 1 , wherein the polymer slug has a pore volume (PV) equal to at least 0.5 of the subterranean reservoir.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application 35 U.S.C. § 371 national stage application of PCT/US2022/053708 filed Dec. 21, 2022, entitled “Systems and Methods for Performing a Polymer Flood Having a Graded Polymer Concentration” which claims benefit of U.S. provisional patent application Ser. No. 63/292,485 filed Dec. 22, 2021, entitled “Systems and Methods for Performing a Polymer Flood Having a Graded Polymer Concentration,” both of which are hereby incorporated herein by reference in their entirety for all purposes. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable. BACKGROUND Hydrocarbons may be produced from a porous, subterranean hydrocarbon bearing reservoir by drilling a production well into the subterranean reservoir and flowing hydrocarbons from the reservoir into the production well, and then flowing the hydrocarbons through the production well to the surface. Particularly, following the drilling of the production well into the subterranean reservoir, the pressure within the subterranean reservoir drives hydrocarbons therein into the production well as part of a “primary recovery” process of producing hydrocarbons from the formation. However, typically only a fraction of the hydrocarbons originally present within the subterranean reservoir are produced during the primary recovery phase. In at least some applications, the primary recovery phase may be followed by an improved oil recovery (IOR) or enhanced oil recovery (EOR) operation in which a fluid is injected into the subterranean reservoir from one or more injection wells (separate and spaced from the production well) to thereby force hydrocarbons remaining within the subterranean reservoir into the production well. For example, as part of a “waterflooding” process, the fluid injected into the subterranean reservoir from the one or more injection wells may comprise an aqueous solution intended to maintain a desired pressure within the subterranean reservoir. In some applications, a polymer may be added to the injection fluid as part of a “polymer flooding” process to control the mobility of the injection fluid and thereby increase the amount of hydrocarbons recovered from the subterranean reservoir as part of the EOR operation. Particularly, compared to waterflooding, the addition of a polymer to the injection fluid as part of a flooding process may increase the sweep efficiency of the reservoir, which refers to the fraction of the subterranean reservoir swept by the injection fluid. SUMMARY An embodiment of a method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir comprises (a) injecting a polymer solution from an injection well into the subterranean reservoir to form a polymer slug in the subterranean reservoir, wherein the polymer slug has a leading front and a trailing rear, and an S-shaped graded viscosity profile which decreases convexly in viscosity from the front of the polymer slug to an inflection point and concavely in viscosity from the inflection point to the rear of the polymer slug, and (b) injecting an aqueous solution from the injection well into the subterranean reservoir following (a) to displace the polymer slug through the subterranean reservoir. In some embodiments, the viscosity of the polymer slug at the front thereof is greater than the viscosity of the polymer slug at a midpoint between the front and the rear of the polymer slug. In some embodiments, a mobility ratio (M) between the front of the polymer slug and hydrocarbons present in the subterranean reservoir is less than or equal to one. In certain embodiments, the inflection point of the polymer slug is located at a midpoint between the front and the rear of the polymer slug. In certain embodiments, the polymer of the polymer solution comprises an acrylamide-based polymer. In some embodiments, (a) comprises continuously reducing the polymer concentration of the polymer solution over time while injecting the polymer solution from the injection well into the subterranean reservoir. In some embodiments, the method comprises (c) heating a heating fluid by a surface heating system to a temperature that is greater than the temperature of at least some of the hydrocarbons present in the subterranean reservoir, and (d) injecting the heated heating fluid into the subterranean reservoir. In certain embodiments, the nonlinear dependence comprises a nonlinear dependence of a specific viscosity at zero shear rate (ηsp) of the polymer solution on the polymer concentration of the polymer solution. An embodiment of a method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir comprises (a) determining a nonlinear dependence of a viscosity of a polymer solution to a polymer concentration of the polymer solution, (b) simulating the injection of a graded polymer slug into the subterranean reservoir based on the nonlinear dependence of the viscosity of the polymer solution to the poly