A comprehensive treatment agent for fracturing flowback fluid recycling

Abstract

The application discloses a comprehensive treatment agent for recycling fracturing flowback fluid, which comprises the following components: boron shielding agent, metal ion chelating dispersant, bactericide, pH regulator, clay stabilizer, filtrate reducer and water. The application can form a spatial net structure by using a composite multi-hydroxyl molecule to shield residual boron crosslinking agent, use a multi-metal chelating dispersant to treat high-valence metal ions such as iron, calcium and magnesium, use a high-efficiency bactericide to reduce the influence of bacteria on the prepared liquid, use a slow-release acid to properly adjust the pH value of the prepared liquid system, and add a clay stabilizer and a filtrate reducer to cope with the adverse influence of the formation on the fracturing fluid. The above additives jointly form the comprehensive treatment agent for recycling fracturing flowback fluid. The treatment agent can treat the influence of residual boron, iron, calcium, magnesium and other elements in the fracturing flowback fluid by a small amount of addition, kill bacteria, adjust the pH value and ensure the successful recycling of the fracturing flowback fluid after treatment.

Description

Technical Field

[0001] This invention relates to the field of fracturing flowback fluid recycling technology during the development of oil and gas fields and coalbed methane fields, and particularly to a comprehensive treatment agent for fracturing flowback fluid recycling. Background Technology

[0002] Currently, most oil and gas, and coalbed methane development in my country is gradually shifting from shallow to deep reservoirs and from structurally simple to structurally complex areas. This leads to changes in development conditions, such as increased reservoir pressure, decreased permeability, and deterioration of reservoir structure, posing challenges to the economical and efficient development of these oil and gas deposits. Hydraulic fracturing is a crucial measure for developing these complex reservoir structures, and large-scale, high-volume fracturing technology is increasingly widely used. However, this has also resulted in a sharp increase in fracturing water consumption and flowback fluid volume.

[0003] Numerous scholars both domestically and internationally have proposed technologies for the reuse of treated fracturing flowback fluid in fracturing fluid formulation. Currently, technologies for the reuse of fracturing flowback fluid mainly include two aspects: first, the development of recyclable fracturing fluid systems, including modified guar gum, small-molecule thickeners, and viscoelastic surfactants, primarily aimed at increasing the recyclability and reusability of fracturing fluids; second, flowback fluid treatment technologies, which remove factors affecting re-mixing through a series of physicochemical methods, thereby improving the secondary mixing performance of the flowback fluid. Regarding the second type of fracturing flowback fluid reuse technology, the flowback fluid contains a large amount of polymers, inorganic salts, residual additives, suspended solid particles, crude oil, bacteria, and other substances, exhibiting characteristics such as high mineralization, complex properties, high viscosity, and difficulty in processing. This leads to numerous challenges in the reuse of fracturing flowback fluid. Even after employing conventional treatment steps such as degumming, hardening removal, flocculation sedimentation, and filtration, successful re-mixing and reuse of the fracturing flowback fluid cannot be guaranteed.

[0004] For example, due to the presence of residual boron crosslinking agent, the compounded fracturing fluid base fluid will immediately form a gel in a slightly alkaline environment before new crosslinking agent is added, leading to premature crosslinking and failing to achieve the purpose of delaying crosslinking. This may not only cause blockage of the fluid preparation pipeline, but also result in a gel with poor temperature resistance and shear resistance, thus affecting normal fracturing operations. Furthermore, metal ions such as iron, calcium, and magnesium can severely affect the hydration of thickener molecules, preventing them from fully swelling and expanding. Additionally, bacteria can degrade the thickener molecules, leading to a decrease in fracturing fluid viscosity. The increase in bacteria, especially SRB bacteria, exacerbates the corrosion of reinjected water, which in turn leads to a surge in suspended solids. Unremoved suspended solids aggregate and settle in the pipeline, causing bacterial growth and reproduction, resulting in the proliferation of sulfides, which also severely affects the viscosity of the fracturing fluid base fluid. Furthermore, pH value also affects the reuse of fracturing flowback fluid. Generally, weakly acidic conditions are conducive to the swelling and thickening of the thickener, while appropriate alkaline conditions are conducive to the boron cross-linking process. Simultaneously, pH value affects bacterial growth and clay swelling caused by post-fracturing filtrate. Additionally, the hydration, swelling, and migration of formation clay particles can lead to formation blockage, thus affecting fracturing efficiency. Finally, fracturing fluid loss increases fracturing fluid usage, reduces fracturing fluid efficiency, and consequently increases fracturing fluid costs. It also hinders the creation of long and wide fractures with high conductivity. Poorly controlled filtrate loss can also increase fracturing fluid seepage and retention in oil and gas reservoirs, causing damage to the reservoir.

[0005] To address the aforementioned difficulties in recycling fracturing flowback fluid, proposing a comprehensive treatment agent for fracturing flowback fluid recycling is of great significance. Summary of the Invention

[0006] This invention addresses the problem that fracturing flowback fluid, after undergoing conventional processing steps such as degelatinization, hardening removal, flocculation sedimentation, and filtration, still contains residual polymers, inorganic salts, additives, bacteria, and other substances. It also addresses the challenges of high mineralization, complex properties, high viscosity, and processing difficulty, making successful reuse of the treated fluid uncertain. This invention proposes a comprehensive treatment agent for the recycling of fracturing flowback fluid. The agent contains a boron shielding agent to remove the influence of residual boron crosslinking agents, a metal ion chelating and dispersing agent to remove the influence of high-valence metal ions such as iron, calcium, and magnesium, a bactericide to remove bacterial influence, a slow-release acid to adjust the pH of the system, and a clay stabilizer and filtration loss reducer to further ensure the effectiveness of the recycled fracturing flowback fluid injected into the formation. Through the combined action of these components, the problem of fracturing flowback fluid recycling is effectively solved, thus contributing to the full utilization of valuable water resources and the protection of the ecological environment.

[0007] The present invention is achieved by the following technical solution.

[0008] A comprehensive treatment agent for the recycling of fracturing flowback fluid comprises the following components by weight percentage: 10-40% boron shielding agent, 5-40% metal ion chelating dispersant, 5-25% bactericide, 5-25% pH adjuster, 1-10% clay stabilizer, 1-10% filtration loss reducer, and 10-60% water.

[0009] Furthermore, the boron shielding agent is selected from one or more of the following: glycerol, pentaerythritol, polyglucosamine (1-4)-2-amino-BD glucose, hydroxyethyl cellulose, and glucose.

[0010] By adopting the above technical solution, the boron shielding agent of the present invention is a complex of a group of polyhydroxy molecules. The polyhydroxy cellulose is a macromolecule, and its numerous hydroxyl groups encapsulate the residual boron crosslinking agent and crosslink it with it through esterification. The small polyol molecules enter the gap between the cellulose molecules and the borate molecules and esterify with the unesterified hydroxyl groups in the borate molecule structure. They also form a network structure with the cellulose molecules through hydrogen bonds, which firmly controls the free residual borate crosslinking agent molecules, thereby achieving a good boron shielding effect. Even if the pH value of the environment changes, the borate ions in the network structure of cellulose molecules and polyol molecules are difficult to be released, thus effectively avoiding their influence on the swelling of the thickener molecules and inhibiting the occurrence of premature crosslinking.

[0011] Furthermore, the metal ion chelating dispersant is selected from one or more of the following: sodium polycisinate, fumaric acid-propylene sulfonic acid copolymer, 1,3-propanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, tetrahydropyrrole-3-acetic acid, sodium gluconate, tetrasodium hydroxyethylidene diphosphonate, and sodium polyvinyl sulfonate.

[0012] By adopting the above technical solution, the metal ion chelating dispersant in this invention is a combination of high molecular polymer and phosphonate. The molecular combination contains a large number of carboxyl or hydroxyl groups, which can coordinate with metal ions to form chelates, forming stable five-membered ring and six-membered ring chelates with high chemical stability, thereby effectively preventing the influence of metal ions such as iron, calcium and magnesium on the hydration and swelling of thickener molecules.

[0013] Furthermore, 2,2-dibromo-3-nitropropionamide was selected as the bactericide.

[0014] Through this technical solution, the bactericide component in this invention kills bacteria through multiple mechanisms, such as disrupting bacterial cell metabolism, damaging DNA and cell membrane structure, and synergizing with other antibacterial agents. It has the advantages of high efficiency, speed, and odorlessness, and effectively prevents bacteria from consuming and degrading organic polymer thickeners, which would have an adverse effect on the viscosity of fracturing fluid.

[0015] Furthermore, the pH adjuster is a slow-release acid, which is selected from one or both of ethyl acetate and propyl acetate.

[0016] By adopting the above technical solution, the pH value adjusting agent component in this invention adjusts the pH value of the fracturing flowback fluid by adding slow-release organic acid. On the one hand, the slow-release organic acid can adjust the pH value of the fracturing flowback fluid by releasing moderate-strength organic acid at a uniform hydrolysis rate. On the other hand, the organic acid also has a certain chelating effect, which can further reduce the mineralization of the fracturing flowback fluid.

[0017] Furthermore, the clay stabilizer is selected from one or more of the following: polyhydroxypropyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, (3-methacrylamidopropyl)trimethylammonium chloride and acrylamide polymer, poly(1,3-propylene pyridine chloride), and polyepoxychloropropane-dimethylamine.

[0018] By adopting the above technical solution, the clay stabilizer in this invention helps to stabilize the formation and prevent damage from water-sensitive formations when fracturing fluid is injected into the formation.

[0019] Furthermore, the filtration loss reducing agent is selected from one or more of sodium humate, polyvinyl alcohol, and acrylamide-methacrylate-sodium propylene sulfonate copolymer.

[0020] By adopting the above technical solution, the filtration loss reducing agent component in this invention is beneficial to reducing the filtration loss of fracturing fluid in the formation, reducing the amount of fracturing fluid used, and reducing the cost of fracturing fluid; it is beneficial to create long and wide fractures, increase the sand ratio, and make the fractures have higher conductivity; it is beneficial to reduce the seepage and retention of fracturing fluid in oil and gas reservoirs, and reduce damage to the reservoir.

[0021] Preferably, a comprehensive treatment agent for the recycling of fracturing flowback fluid comprises the following components by mass percentage:

[0022] A compound of 15%~25% glycerol, glucose, and hydroxyethyl cellulose, with a mass ratio of 1:1:2.

[0023] A compound of 10%~25% sodium polybutadiene and fumaric acid-propylene sulfonic acid copolymer, with a mass ratio of 3:1;

[0024] 10%~15% 2,2-Dibromo-3-nitropropionamide;

[0025] 10%~15% propyl acetate;

[0026] 3%~8% (3-methacrylamidopropyl)trimethylammonium chloride and acrylamide polymer;

[0027] 3%~8% Acrylamide-methacrylate-sodium propylene sulfonate copolymer;

[0028] 25%–45% water.

[0029] This application has the following beneficial effects.

[0030] This invention's treatment agent effectively controls key factors that cause low viscosity in fracturing fluid base fluid, such as residual boron crosslinking agent, metal ions, and bacterial content in the flowback fluid. It also adjusts the pH value through slow-release acid, ensuring a suitable pH environment during the viscosity formation and gelation processes of the fracturing fluid base fluid. Furthermore, it prevents adverse effects from formation clay, filtration loss, and other factors after the fracturing fluid enters the formation, further guaranteeing the effectiveness of the fracturing fluid. By implementing preventative measures against adverse factors from the viscosity formation and crosslinking of the fracturing fluid base fluid to its entry into the formation, it ensures a good recycling effect for the fracturing flowback fluid. Detailed Implementation

[0031] The present patent application will be further described below with reference to the embodiments.

[0032] Unless otherwise specified, the experimental methods used in the following preparation examples and embodiments are conventional methods; the materials and reagents used in the following preparation examples and embodiments are commercially available unless otherwise specified.

[0033] Example 1

[0034] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0035] 3% glycerol;

[0036] 9% polyglucosamine (1-4)-2-amino-BD glucose (purchased from Hebei Chujun Biotechnology Co., Ltd.);

[0037] 6% Sodium polycis-butenedioate;

[0038] 2% Tetrahydropyrrole-3-acetic acid (CAS: 89203-64-5);

[0039] 5% 2,2-Dibromo-3-nitropropionamide (CAS: 10222-01-2)

[0040] 5% ethyl acetate;

[0041] 1% polyhydroxypropyl dimethylammonium chloride (CAS: 39660-17-8).

[0042] 1% sodium humate;

[0043] The remainder is water;

[0044] After adding the treatment agent and stirring thoroughly, add 2g of hydroxypropyl-modified guar gum (CAS: 39421-75-5) and continue stirring until the thickener is fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid is measured to be 32 mPa·s using a rotational viscometer. Add 0.5g of organoboron crosslinking agent until crosslinking occurs, and then heat at 100℃ for 170 seconds. -1 After continuous shearing for 60 minutes, the final viscosity was 52 mPa·s, indicating good temperature resistance and shear strength.

[0045] Example 2

[0046] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0047] 10% glucose;

[0048] 10% polyglucosamine (1-4)-2-amino-BD glucose;

[0049] 15% fumaric acid-propylene sulfonic acid copolymer (purchased from Tianmen Hengchang Chemical Co., Ltd.);

[0050] 5% 1,3-Propanediaminetetraacetic acid (CAS: 1939-36-2).

[0051] 5% diethylenetriaminepentaacetic acid;

[0052] 15% 2,2-Dibromo-3-nitropropionamide (CAS: 10222-01-2);

[0053] 5% ethyl acetate;

[0054] 5% propyl acetate;

[0055] 3% Dodecyl dimethyl benzyl ammonium chloride;

[0056] 3% polyvinyl alcohol;

[0057] The remainder is water;

[0058] After adding the treatment agent and stirring thoroughly, add 2g of hydroxypropyl-modified guar gum and continue stirring until the thickener is fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid is measured to be 36 mPa·s using a rotational viscometer. Add 0.5g of organoboron crosslinking agent until crosslinking occurs. Then, at 100℃ for 170s... -1 After continuous shearing for 60 minutes, the final viscosity was 57 mPa·s, indicating good temperature resistance and shear strength.

[0059] Example 3

[0060] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0061] 4% glycerol;

[0062] 4% glucose;

[0063] 8% polyglucosamine (1-4)-2-amino-BD glucose;

[0064] 15% Sodium Polyethylene Sulfonate (CAS: 9002-97-5);

[0065] 5% diethylenetriaminepentaacetic acid;

[0066] 13% 2,2-Dibromo-3-nitropropionamide (CAS: 10222-01-2);

[0067] 13% propyl acetate;

[0068] Polymer of 5% (3-methacrylamidopropyl)trimethylammonium chloride and acrylamide (CAS: 58627-30-8).

[0069] 5% Acrylamide, methacrylate, sodium propylene sulfonate terpolymer (purchased from Shandong Yonglida New Material Technology Co., Ltd.);

[0070] The remainder is water;

[0071] After adding the treatment agent and stirring thoroughly, 2g of hydroxypropyl-modified guar gum was added and stirring continued until the thickener was fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid was measured to be 41 mPa·s using a rotational viscometer. 0.5g of organoboron crosslinking agent was added until crosslinking occurred. The mixture was then subjected to a 170s reaction at 110℃. -1 After continuous shearing for 60 minutes, the final viscosity was 56 mPa·s, indicating good temperature resistance and shear strength.

[0072] Example 4

[0073] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0074] 4% glycerol;

[0075] 4% glucose;

[0076] 8% hydroxyethyl cellulose;

[0077] 9% Sodium polycis-butenedioate;

[0078] 3% fumaric acid-propylene sulfonic acid copolymer;

[0079] 10% 2,2-Dibromo-3-nitropropionamide (10222-01-2);

[0080] 10% ethyl acetate;

[0081] 3% Poly(1,3-propylidene) pyridine chloride (This polymer can be found in Chapter 7, Drilling Fluid Materials Chemistry and Treatment Agents, page 285 of "Principles of Drilling Fluid Technology" edited by Huang Hanren, published in August 2016).

[0082] 3% Acrylamide-methacrylate-sodium propylene sulfonate copolymer;

[0083] The remainder is water;

[0084] After adding the treatment agent and stirring thoroughly, add 2g of hydroxypropyl-modified guar gum and continue stirring until the thickener is fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid is measured to be 37 mPa·s using a rotational viscometer. Add 0.5g of organoboron crosslinking agent until crosslinking occurs. Then, at 110℃ for 170s... -1 After continuous shearing for 60 minutes, the final viscosity was 55 mPa·s, indicating good temperature resistance and shear strength.

[0085] Example 5

[0086] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0087] 6% glycerol;

[0088] 6% glucose;

[0089] 12% hydroxyethyl cellulose;

[0090] 18% fumaric acid-propylene sulfonic acid copolymer;

[0091] 6% Tetrasodium Hydroxyethylidene Diphosphonate, CAS: 3794-83-0;

[0092] 10% 2,2-Dibromo-3-nitropropionamide (CAS: 10222-01-2);

[0093] 15% ethyl acetate;

[0094] 6% polyepoxychloropropane-dimethylamine (purchased from Hubei Darli Chemical Co., Ltd.);

[0095] 6% Acrylamide-methacrylate-sodium propylene sulfonate copolymer;

[0096] The remainder is water;

[0097] After adding the treatment agent and stirring thoroughly, add 2g of hydroxypropyl-modified guar gum and continue stirring until the thickener is fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid is measured to be 39 mPa·s using a rotational viscometer. Add 0.5g of organoboron crosslinking agent until crosslinking occurs. Then, at 120℃ for 170s...-1 After continuous shearing for 60 minutes, the final viscosity was 53 mPa·s, indicating good temperature resistance and shear strength.

[0098] Example 6

[0099] Take 494.5 ml of pre-treated fracturing flowback fluid and add 3 g of fracturing flowback fluid recycling and reuse comprehensive treatment agent. The composition is as follows:

[0100] 5% glycerol;

[0101] 5% glucose;

[0102] 10% hydroxyethyl cellulose;

[0103] 9% Sodium polycis-butenedioate;

[0104] 3% fumaric acid-propylene sulfonic acid copolymer;

[0105] 8% 2,2-Dibromo-3-nitropropionamide (CAS: 10222-01-2);

[0106] 6% propyl acetate;

[0107] 6% (3-methacrylamidopropyl)trimethylammonium chloride polymer with acrylamide;

[0108] 6% Acrylamide-methacrylate-sodium propylene sulfonate copolymer;

[0109] The remainder is water;

[0110] After adding the treatment agent and stirring thoroughly, add 2g of hydroxypropyl-modified guar gum and continue stirring until the thickener is fully dissolved to obtain the fracturing fluid base. The viscosity of the base fluid was measured to be 43 mPa·s using a rotational viscometer. Add 0.5g of organoboron crosslinking agent until crosslinking occurs. Then, at 120℃ for 170 seconds... -1 After continuous shearing for 60 minutes, the final viscosity was 61 mPa·s, indicating good temperature resistance and shear strength.

[0111] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A comprehensive treatment agent for recycling of fracturing flowback fluid, characterized in that: The composition comprises the following components by mass percentage: 15%~25% boron shielding agent, the boron shielding agent comprising a compound of glycerol, glucose and hydroxyethyl cellulose, the mass ratio of the three being 1:1:2; 10%~25% metal ion chelating dispersant, the metal ion chelating dispersant comprising a compound of poly sodium maleic acid and fumaric acid-acryl sulfonic acid copolymer, the mass ratio of the two being 3:1; 10%~15% bactericide, the bactericide being 2,2-dibromo-3-nitropropionamide; 10%~15% pH value regulator, the pH value regulator comprising propyl acetate; 3%~8% clay stabilizer, the clay stabilizer comprising a polymer of (3-methyl acrylamide propyl) trimethyl ammonium chloride and acrylamide; 3%~8% fluid loss additive, the fluid loss additive comprising acrylamide-methyl methacrylate-sodium acryl sulfonate copolymer; 25%~45% water.