A polymer solution viscosity protection system for oil and gas fields that improves ferrous ion tolerance

Abstract

The application discloses an oil and gas field polymer solution viscosity protection system with improved ferrous ion tolerance, and belongs to the technical field of oil and gas field chemicals.The system comprises the following components in mass percentage: 5-10% of a ferrous ion stabilizer, 10-20% of a free radical capturing agent, 10-20% of a structure reinforcing agent, 5-10% of a synergist, and the balance of water; the ferrous ion stabilizer is at least one selected from sodium gluconate, potassium gluconate, diethylene triamine pentaacetic acid and hydroxyethylidene diphosphonic acid; the free radical capturing agent is a compound containing phenolic hydroxyl; the structure reinforcing agent is an imidazoline compound; and the synergist is an aldehyde compound.The application method of the viscosity protection system is as follows: the viscosity protection system is first added into liquid water, polymer powder is then added, a gel breaker is further added, and stirring is uniformly performed to obtain a polymer solution.The viscosity protection system significantly reduces the influence of ferrous ions on the viscosity of the polymer solution, and improves the application effect of polyacrylamide substances in the field of oil and gas fields.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field chemicals, and in particular to a polymer solution viscosity protection system for improving the tolerance of ferrous ions in oil and gas fields. Background Technology

[0002] In oil and gas field development, polymers, represented by polyacrylamide, are commonly used in polymer flooding to enhance oil recovery and as fracturing fluids for fracturing operations. The main function of polyacrylamide is to form a high-viscosity polymer solution through the combined effects of the spatial effects of polymer molecular chains and the electrostatic repulsion between molecules. After years of research and field application, it has become quite mature and has achieved good economic benefits. However, polyacrylamide encounters some challenges in its application, one of which is the significant impact of ferrous ions on the viscosity of the polymer solution. In many situations, polyacrylamide inevitably comes into contact with ferrous ions, such as pipeline corrosion during polymer solution transportation, contact between the polymer and ferrous-containing formation water after entering the formation, and the presence of ferrous ions in produced water during operations. The presence of ferrous ions acts as a catalytic oxidation agent, causing the long polymer chains of polyacrylamide to break down, resulting in rapid loss of viscosity in the solution. In addition, during the preparation of fracturing fluid, oxidants such as ammonium persulfate are added simultaneously as breaker. In the presence of ammonium persulfate, the catalytic oxidation activity of ferrous ions is enhanced, which further catalyzes the generation of free radicals from ammonium persulfate, thereby intensifying the chain scission of polyacrylamide and causing a rapid decrease in the viscosity of polyacrylamide fracturing fluid. Summary of the Invention

[0003] To reduce or eliminate the influence of ferrous ions on the viscosity of polymer solutions and stabilize the viscosity of polymer solutions, this invention provides a polymer solution viscosity protection system for oil and gas fields that improves the tolerance of ferrous ions.

[0004] The polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields provided by this invention comprises the following components by mass percentage:

[0005] Ferrous ion stabilizer 5%-10%, free radical scavenger 10%-20%, structural enhancer 10%-20%, synergist 5%-10%, balance is water, total 100%.

[0006] The ferrous ion stabilizer is selected from at least one of sodium gluconate, potassium gluconate, diethylenetriaminepentaacetic acid, and hydroxyethylidene diphosphonic acid.

[0007] The free radical scavenger is a compound containing a phenolic hydroxyl group; preferably, the free radical scavenger is selected from at least one of phenol, hydroquinone, resorcinol, catechol, and biphenylpyrogallol.

[0008] The structural reinforcing agent is an imidazoline compound; preferably, the structural reinforcing agent is selected from at least one of imidazoline, imidazoline quaternary ammonium salt, sulfonic acid imidazoline, tall oil imidazoline, and carboxylic acid imidazoline.

[0009] The synergist is an aldehyde compound; preferably, the synergist is selected from at least one of glyoxal, succinaldehyde, glutaraldehyde, adipaldehyde, and furfural.

[0010] The viscosity protection system is prepared by adding ferrous ion stabilizer, free radical trapping agent, structure enhancer and synergist to water, stirring and dissolving to obtain the viscosity protection system.

[0011] This invention also provides an application method for a polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields: first, the viscosity protection system is added to the solution water and stirred evenly; then, polymer powder is added, followed by a desiccant, and stirred evenly to obtain a polymer solution; the polymer powder is a polyacrylamide-based substance.

[0012] The viscosity protection system is added at a rate of 0.5-1.0% of the mass of the water used to prepare the solution.

[0013] The concentration of ferrous ions in the prepared solution is 0-50 ppm.

[0014] The polymer solution can be used as a fracturing fluid for hydraulic fracturing operations, or as a polymer flooding agent for enhanced oil recovery in oil fields.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] (1) The ferrous ion stabilizer mainly maintains the stability of ferrous ions and alleviates their oxidation through its strong interaction with both ferrous and ferric ions. When ferrous ions are oxidized to ferric ions, they simultaneously chelate ferric ions, reducing the interaction between ferric ions and polyacrylamide. The free radical scavenger mainly combines with free radicals generated by ferrous ions catalyzing dissolved oxygen or ammonium persulfate, causing the free radicals to lose activity, terminating the chain reaction of free radicals, preventing polyacrylamide from being oxidized and degraded too quickly, and stabilizing the viscosity of the polyacrylamide solution. The main function of the structural reinforcement is to improve the viscoelasticity of the fracturing fluid under the influence of ferrous ions, so that the polymer solution maintains good viscoelasticity while having a high viscosity. The main function of the synergist is to improve the overall performance of the system, so that the polymer solution maintains a stable viscosity for a longer period of time. The synergist must be used in conjunction with the ferrous ion stabilizer, the free radical scavenger, and the structural reinforcement to exert its effect.

[0017] (2) The polymer solution viscosity protection system for oil and gas fields that improves the tolerance of ferrous ions significantly reduces or even eliminates the influence of ferrous ions on polymer solutions through the synergistic effect of each component, stabilizes the viscosity of polyacrylamide solutions, and improves the application effect of polyacrylamide in oil and gas fields.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the viscosity test results of different polymer solutions in Comparative Example 1 and Example 3.

[0020] Figure 2 These are viscoelastic photographs of the polymer solutions of Comparative Example 1 and Example 3.

[0021] Figure 3 Fe in Comparative Example 8 2+ A comparison of viscosity test results between a polymer solution with a content of 5 ppm and a polymer solution with 0.5% added to the viscosity protection system in Example 6. Detailed Implementation

[0022] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] Polymer Fluid Viscosity Evaluation Method 1: Prepare a simulated brine sample as the flue water. Stir the sample under different water quality conditions at a stirrer speed of 700 r / min. Then, sequentially add the viscosity protection system of this invention, polyacrylamide powder, and a breaker to obtain the fracturing fluid. Test the viscosity after stirring for 2 minutes after adding polyacrylamide powder, and measure the viscosity for 170 seconds using a flow viscometer. -1 The viscosity value (mPa·s) was determined to simulate the application scenario of polyacrylamide in hydraulic fracturing.

[0024] Polymer solution viscosity evaluation method 2: A simulated brine sample was prepared as the solution water. The mixture was stirred at 700 r / min under different water quality conditions. The viscosity protection system of this invention and polyacrylamide powder were added sequentially to prepare the polymer solution. After adding the polyacrylamide powder, the mixture was stirred for 2 minutes, and then the viscosity was measured at 10 min, 20 min, 30 min, and 60 min. The purpose was to simulate the application scenario of polyacrylamide in oilfield polymer flooding.

[0025] Preparation of simulated brine samples: The simulated brine was prepared according to the requirements for oilfield simulated brine preparation, with a total mineralization of 500 ppm, and a ferrous ion concentration in the range of 0-50 ppm. Other ions contained in the simulated brine included 2% NaCl, 0.09% MgCl2·6H2O, 0.2% KCl, and 0.2% CaCl2 by mass fraction.

[0026] Examples 1-4 and Comparative Examples 1-7 were used to simulate the preparation process of polyacrylamide fracturing fluid during hydraulic fracturing operations.

[0027] Comparative Example 1

[0028] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 0, 2, 5, 10, 20, and 50 ppm. Deionized water was added to the simulated brine at a rate of 0.5% of its mass, polyacrylamide powder at a rate of 0.2% of its mass, and APS (a type of polymer thief) at a rate of 0.01% of its mass. The viscosity was measured after stirring for 2 minutes following the addition of polyacrylamide powder, and then measured using a flow viscometer over 170 seconds. -1 Lower viscosity value (mPa·s). No component related to any viscosity protection system was added in this comparative example, serving as a blank control group.

[0029] Comparative Example 2

[0030] The viscosity protection system used in this comparative example consists of: 5% ferrous ion stabilizer, 10% free radical scavenger, 5% synergist, and the balance being water. The ferrous ion stabilizer is composed of sodium gluconate and diethylenetriaminepentaacetic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone and resorcinol in a 2:1 mass ratio; and the synergist is glutaraldehyde.

[0031] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 2, 5, and 10 ppm. A viscosity protection system was added to the simulated brine at a dosage of 0.5% of its mass, polyacrylamide powder at a dosage of 0.2% of its mass, and APS (a type of polymer thief) at a dosage of 0.01% of its mass. The viscosity was tested after stirring for 2 minutes following the addition of polyacrylamide powder, and measured using a flow viscometer over 170 seconds. -1 Lower viscosity value (mPa·s).

[0032] Example 1

[0033] The viscosity protection system used in this embodiment consists of: 5% ferrous ion stabilizer, 10% free radical scavenger, 10% structural enhancer, 5% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:1:1 mass ratio; the structural enhancer is composed of imidazoline and imidazoline quaternary ammonium salt in a 1:1 mass ratio; and the synergist is composed of glutaraldehyde and glyoxal in a 1:1 mass ratio.

[0034] The viscosity of the prepared solution was measured according to Method 1 for evaluating polymer solution viscosity. The simulated brine contained ferrous ions at concentrations of 2, 10, and 20 ppm. A viscosity protection system was added to the simulated brine at a concentration of 0.5% of its mass, polyacrylamide powder at a concentration of 0.2% of its mass, and APS (a type of polymer thief) at a concentration of 0.01% of its mass. The viscosity was measured after stirring for 2 minutes following the addition of polyacrylamide powder, and then measured using a flow viscometer over 170 seconds. -1 Lower viscosity value (mPa·s).

[0035] Example 2

[0036] The viscosity protection system used in this embodiment consists of: 5% ferrous ion stabilizer, 15% free radical scavenger, 15% structural enhancer, 5% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of sodium gluconate and diethylenetriaminepentaacetic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone and resorcinol in a 2:1 mass ratio; the structural enhancer is composed of imidazoline, imidazoline quaternary ammonium salt, and sulfonated imidazoline in a 1:1:1 mass ratio; and the synergist is composed of glutaraldehyde and glyoxal in a 1:1 mass ratio.

[0037] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0038] Example 3

[0039] The viscosity protection system used in this embodiment consists of: 10% ferrous ion stabilizer, 15% free radical scavenger, 15% structural enhancer, 10% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:1:1 mass ratio; the structural enhancer is composed of imidazoline, imidazoline quaternary ammonium salt, and tall oil imidazoline in a 1:1:1 mass ratio; and the synergist is composed of glutaraldehyde and glyoxal in a 1:1 mass ratio.

[0040] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 2, 5, 10, and 50 ppm. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the brine mass, polyacrylamide powder was added at a dosage of 0.2% of the brine mass, and APS (a type of polymer thief) was added at a dosage of 0.01% of the brine mass. The viscosity was tested after stirring for 2 minutes following the addition of polyacrylamide powder, and measured using a flow viscometer over 170 seconds. -1 Lower viscosity value (mPa·s).

[0041] Example 4

[0042] The viscosity protection system used in this embodiment consists of: 5% ferrous ion stabilizer, 20% free radical scavenger, 20% structural enhancer, 5% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:2:1 mass ratio; the structural enhancer is composed of imidazoline, imidazoline quaternary ammonium salt, and tall oil imidazoline in a 1:1:2 mass ratio; and the synergist is composed of glutaraldehyde, glyoxal, and adipaldehyde in a 1:1:1 mass ratio.

[0043] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5, 10, and 20 ppm. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the brine mass, polyacrylamide powder was added at a dosage of 0.2% of the brine mass, and APS (a type of polymer thief) was added at a dosage of 0.01% of the brine mass. The viscosity was tested after stirring for 2 minutes following the addition of polyacrylamide powder, and measured using a flow viscometer over 170 seconds. -1 Lower viscosity value (mPa·s).

[0044] Comparative Example 3

[0045] The viscosity protection system used in this comparative example consists of: 5% ferrous ion stabilizer, 10% structural reinforcing agent, 5% synergist, and the balance being water. The ferrous ion stabilizer is composed of sodium gluconate and diethylenetriaminepentaacetic acid in a 1:1 mass ratio; the structural reinforcing agent is composed of imidazoline, imidazoline quaternary ammonium salt, and tall oil imidazoline in a 1:1:1 mass ratio; and the synergist is glyoxal.

[0046] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0047] Comparative Example 4

[0048] The viscosity protection system used in this comparative example consists of 10% ferrous ion stabilizer, 10% synergist, and the balance being water. The ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio, and the synergist is composed of glutaraldehyde and glyoxal in a 1:1 mass ratio.

[0049] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0050] Comparative Example 5

[0051] The viscosity protection system used in this comparative example consists of: 5% ferrous ion stabilizer, 10% free radical scavenger, 10% structure enhancer, and the balance being water. The ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:1:1 mass ratio; and the structure enhancer is composed of imidazoline and imidazoline quaternary ammonium salt in a 1:1 mass ratio.

[0052] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0053] Comparative Example 6

[0054] The viscosity protection system used in this comparative example consists of: 5% ferrous ion stabilizer, 10% free radical scavenger, and the balance being water. The ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio, and the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:1:1 mass ratio.

[0055] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0056] Comparative Example 7

[0057] The viscosity protection system used in this comparative example consists of 5% ferrous ion stabilizer, 10% structural reinforcing agent, and the balance being water. The ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio, and the structural reinforcing agent is composed of imidazoline and imidazoline quaternary ammonium salt in a 1:1 mass ratio.

[0058] The viscosity of the polymer solution was measured according to Method 1, where the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively. A viscosity protection system was added to the simulated brine at a dosage of 0.5% or 1.0% of the simulated brine mass, polyacrylamide powder was added at a dosage of 0.2% of the simulated brine mass, and the APS breaker was added at a dosage of 0.01% of the simulated brine mass. The viscosity was tested after stirring for 2 minutes after adding the polyacrylamide powder, and measured using a flow viscometer for 170 seconds. -1 Lower viscosity value (mPa·s).

[0059] The specific experimental conditions and corresponding viscosity test results of Examples 1-4 and Comparative Examples 1-7 are shown in Table 1.

[0060] Table 1. Specific experimental conditions and corresponding viscosity test results for Examples 1-4 and Comparative Examples 1-7.

[0061]

[0062] Figure 1 This is a comparison chart of the viscosity test results of different polymer solutions in Comparative Example 1 and Example 3.

[0063] Figure 2 These are viscoelastic photographs of the polymer solutions of Comparative Example 1 and Example 3.

[0064] From Table 1, Figure 1 and Figure 2 It can be seen that the viscosity protection system of the present invention can reduce Fe 2+ The effect of catalytic oxidation on fracturing fluid viscosity, when Fe 2+ At concentrations ≤20 mg / L, the viscosity protection system effectively protects the viscosity of fracturing fluid, reducing the viscosity decrease rate from 50%–90% to 10%–25%. Furthermore, with the addition of the viscosity protection system of this invention, the polymer solution exhibits significantly better viscoelasticity. This demonstrates that the polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields of this invention can be applied to polyacrylamide fracturing fluid systems for hydraulic fracturing operations. Additionally, as shown in Comparative Examples 2 and 3–7, the viscosity protection system of this invention requires the simultaneous presence of four components: a ferrous ion stabilizer, a free radical scavenger, a structural enhancer, and a synergistic agent. Only under synergistic conditions can the ferrous ion tolerance be maximized and the polymer solution viscosity stabilized. If one or two of these components are missing, the resulting viscosity protection system only slightly improves ferrous ion tolerance, and the viscosity of the polymer solution is significantly lower than in Examples 1–4.

[0065] Examples 5-7 and Comparative Examples 8 and 9 are used to simulate the polymer solution preparation process for polymer flooding in oilfield enhanced oil recovery.

[0066] Comparative Example 8

[0067] The viscosity of the prepared solution was measured according to Polymer Solution Viscosity Evaluation Method 2. The ferrous ion content in the simulated brine was 0, 5, 10, and 20 ppm. Deionized water was added to the simulated brine at a rate of 0.5% of its mass, and polyacrylamide powder was added at a rate of 0.2% of its mass. After adding the polyacrylamide powder, the mixture was stirred for 2 minutes, and then the viscosity was measured at 10, 20, 30, and 60 minutes. This comparative example did not include any components related to the viscosity protection system and served as a blank control group.

[0068] Comparative Example 9

[0069] The viscosity protection system used in this comparative example consists of 10% ferrous ion stabilizer, 10% synergist, and the balance being water. The ferrous ion stabilizer is composed of sodium gluconate and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio, and the synergist is glyoxal.

[0070] The viscosity of the prepared solution was measured according to the polymer solution viscosity evaluation method 2, wherein the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively, the amount of viscosity protection system added to the simulated brine was 0.5% of the mass of the simulated brine, the amount of polyacrylamide powder added was 0.2% of the mass of the simulated brine, no de-gelling agent was added, and after adding polyacrylamide powder, the mixture was stirred for 2 min, and then the viscosity was measured at 10 min, 20 min, 30 min and 60 min respectively.

[0071] Example 5

[0072] The viscosity protection system used in this embodiment consists of: 5% ferrous ion stabilizer, 10% free radical scavenger, 10% structure enhancer, 5% synergist, and the balance being water. The ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 2:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and pyrogallol in a 1:1:1 mass ratio; and the synergist is composed of glyoxal and glutaraldehyde in a 1:1 mass ratio.

[0073] The viscosity of the prepared solution was measured according to the polymer solution viscosity evaluation method 2, wherein the ferrous ion content in the simulated brine was 5 and 10 ppm, respectively, the amount of viscosity protection system added to the simulated brine was 0.5% of the mass of the simulated brine, the amount of polyacrylamide powder added was 0.2% of the mass of the simulated brine, no de-gelling agent was added, and after adding polyacrylamide powder, the mixture was stirred for 2 min, and then the viscosity was measured at 10 min, 20 min, 30 min and 60 min respectively.

[0074] Example 6

[0075] The viscosity protection system used in this embodiment consists of: 5% ferrous ion stabilizer, 20% free radical scavenger, 20% structural enhancer, 5% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of sodium gluconate, diethylenetriaminepentaacetic acid, and hydroxyethylidene diphosphonic acid in a mass ratio of 2:1:1; the free radical scavenger is composed of hydroquinone, resorcinol, catechol, and biphenylol in a mass ratio of 1:2:1:1; the structural enhancer is composed of imidazoline, imidazoline quaternary ammonium salt, and tall oil imidazoline in a mass ratio of 1:1:1; and the synergist is composed of glutaraldehyde and glyoxal in a mass ratio of 1:1.

[0076] The viscosity of the prepared solution was measured according to the polymer solution viscosity evaluation method 2, wherein the ferrous ion content in the simulated brine was 5 ppm, the amount of viscosity protection system added to the simulated brine was 0.5% or 1.0% of the mass of the simulated brine, the amount of polyacrylamide powder added was 0.2% of the mass of the simulated brine, no de-gelling agent was added, and after adding polyacrylamide powder, the mixture was stirred for 2 min, and then the viscosity was measured at 10 min, 20 min, 30 min and 60 min respectively.

[0077] Example 7

[0078] The viscosity protection system used in this embodiment consists of: 10% ferrous ion stabilizer, 20% free radical scavenger, 20% structural enhancer, 10% synergist, and the balance being water. Specifically, the ferrous ion stabilizer is composed of diethylenetriaminepentaacetic acid and hydroxyethylidene diphosphonic acid in a 1:1 mass ratio; the free radical scavenger is composed of hydroquinone, resorcinol, and catechol in a 1:2:1 mass ratio; the structural enhancer is composed of imidazoline quaternary ammonium salt, tall oil imidazoline, and carboxylic acid imidazoline in a 1:2:1 mass ratio; and the synergist is composed of glutaraldehyde, glyoxal, and adipaldehyde in a 2:1:1 mass ratio.

[0079] The viscosity of the prepared solution was measured according to the polymer solution viscosity evaluation method 2, wherein the ferrous ion content in the simulated brine was 5, 10, and 20 ppm, the amount of viscosity protection system added to the simulated brine was 0.5% or 1.0% of the mass of the simulated brine, the amount of polyacrylamide powder added was 0.2% of the mass of the simulated brine, no de-gelling agent was added, and after adding polyacrylamide powder, the mixture was stirred for 2 min, and then the viscosity was measured at 10 min, 20 min, 30 min, and 60 min respectively.

[0080] The specific experimental conditions and corresponding viscosity test results for Examples 5-7 and Comparative Examples 8 and 9 are shown in Table 2.

[0081] Table 2 shows the specific experimental conditions and corresponding viscosity test results for Examples 5-7 and Comparative Examples 8 and 9.

[0082]

[0083] Figure 3 Fe in Comparative Example 8 2+ A comparison of viscosity test results between a polymer solution with a content of 5 ppm and a polymer solution with 0.5% added to the viscosity protection system in Example 6.

[0084] From Table 2 and Figure 3 It can be seen that the viscosity protection system of the present invention can reduce Fe 2+The effect of catalytic oxidation on the viscosity of the polymer solution: Compared with the embodiment without the viscosity protection system of this invention, the viscosity of the polymer solution with the viscosity protection system is significantly increased by 20-35%, and the viscosity of the polymer solution can be protected for a longer period of time, keeping the viscosity of the polymer solution stable. This indicates that the polymer solution viscosity protection system for oil and gas fields that improves ferrous ion tolerance of this invention can be applied to polyacrylamide as a polymer flooding system for tertiary oil recovery polymer flooding operations.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polymer solution viscosity protection system for oil and gas fields to improve ferrous ion tolerance, characterized in that, Includes the following components by mass percentage: Ferrous ion stabilizer 5%-10%, free radical scavenger 10%-20%, structural enhancer 10%-20%, synergist 5%-10%, balance water, total 100%; The ferrous ion stabilizer is selected from at least one of sodium gluconate, potassium gluconate, diethylenetriaminepentaacetic acid, and hydroxyethylidene diphosphonic acid. The free radical scavenger is a compound containing a phenolic hydroxyl group; The structural reinforcing agent is selected from at least one of imidazoline, imidazoline quaternary ammonium salt, sulfonic acid imidazoline, tall oil imidazoline, and carboxylic acid imidazoline; The synergist is selected from at least one of glyoxal, succinaldehyde, glutaraldehyde, adipaldehyde, and furfural.

2. The polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields as described in claim 1, characterized in that, Ferrous ion stabilizer, free radical scavenger, structure enhancer and synergist were added to water and stirred to dissolve, thus obtaining a viscosity protection system.

3. The polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields as described in claim 2, characterized in that, The free radical scavenger is selected from at least one of phenol, hydroquinone, resorcinol, catechol, and biphenyl pyrogallol.

4. A method for applying the polymer solution viscosity protection system for improving ferrous ion tolerance in oil and gas fields as described in any one of claims 1-3, characterized in that, First, the viscosity protection system is added to the solution water and stirred evenly. Then, the polymer powder is added, followed by the desiccant, and stirred evenly to obtain a polymer solution. The polymer powder is a polyacrylamide-based substance.

5. The application method as described in claim 4, characterized in that, The amount of the viscosity protection system added is 0.5-1.0% of the mass of the water used to prepare the solution.

6. The application method as described in claim 4, characterized in that, The concentration of ferrous ions in the prepared solution is 0-50 ppm.

7. The application method as described in claim 4, characterized in that, The polymer solution is used as a fracturing fluid for hydraulic fracturing operations or as a polymer flooding agent for enhanced oil recovery in oil fields.

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