Fracturing with suspended emulsions and methods of fracturing oil and gas wells

Abstract

This invention provides a fracturing suspension emulsion and a method for fracturing oil and gas wells. The fracturing suspension emulsion comprises, by mass ratio: 40-48 parts dispersant, 3-5 parts suspending agent, 44-52 parts hydrophobic associating polyacrylamide powder, 5-10 parts emulsifier, and 0.1-0.2 parts preservative; wherein the raw material for preparing the hydrophobic associating polyacrylamide powder includes salt-resistant monomers. The fracturing suspension emulsion of this invention improves the dissolution rate of the suspension emulsion in a high-salt environment, maintains sufficient viscosity, reduces friction, and improves the fracturing effect.

Description

Technical Field

[0001] This application relates to the field of oil and gas well fracturing technology, and in particular to a fracturing suspension emulsion and a method for oil and gas well fracturing. Background Technology

[0002] In the oil and gas extraction industry, with the gradual depletion of conventional oil and gas resources, the development of unconventional resources such as shale oil and gas and tight oil and gas is becoming increasingly important. To improve the production of these unconventional oil and gas wells, hydraulic fracturing technology is widely used. Hydraulic fracturing involves injecting high-pressure fluid downhole to fracture the formation, thereby increasing oil and gas permeability and recovery. In this process, the performance of the fracturing fluid is crucial to the fracturing effect. Polyacrylamide, as a thickener in fracturing fluids, is widely used due to its superior performance. Its main advantages include: rapid dissolution rate, low frictional resistance, high viscoelasticity, and minimal formation damage. These characteristics enable polyacrylamide to effectively improve the proppant-carrying capacity and fracture propagation capacity of fracturing fluids, thereby increasing the production of oil and gas wells.

[0003] However, with increasing environmental awareness and the need for cost control, production water and backflow (hereinafter referred to as backflow) are increasingly used in oilfield operations to prepare fracturing fluids. This backflow typically has a high salinity, usually around 30,000 ppm, and may even exceed 100,000 ppm. This high salinity creates a high-salt environment that poses a significant challenge to the performance of fracturing fluid thickeners.

[0004] Traditional thickeners may exhibit problems such as slow dissolution rate, decreased viscosity, and increased friction under high salinity conditions, thereby affecting fracturing performance. Summary of the Invention

[0005] This application provides a fracturing suspension emulsion and a method for fracturing oil and gas wells, which aims to improve the salt resistance of the fracturing suspension emulsion, increase the dissolution rate of the suspension emulsion in a high-salt environment, maintain sufficient viscosity of the suspension emulsion, reduce friction, and improve the fracturing effect.

[0006] In a first aspect, embodiments of this application provide a fracturing suspension emulsion comprising, by mass ratio: 40 to 48 parts dispersant, 3 to 5 parts suspending agent, 44 to 52 parts hydrophobic associating polyacrylamide powder, 5 to 10 parts emulsifier, and 0.1 to 0.2 parts preservative;

[0007] The raw materials for preparing the hydrophobic associative polyacrylamide powder include salt-resistant monomers;

[0008] The structure of the salt-resistant monomer is shown in Formula 1:

[0009]

[0010] In one possible embodiment, the salt-resistant monomer is prepared by a method comprising the following process: heating a mixture comprising maleic anhydride, sodium hydroxyethyl sulfonate, and a catalyst to obtain the salt-resistant monomer; wherein the molar ratio of maleic anhydride to sodium hydroxyethyl sulfonate is 1:(2-3); and / or, the temperature of the heating treatment is 60°C-80°C; and the heating treatment time is 4h-6h.

[0011] In one possible implementation, the structure of the hydrophobically associating polyacrylamide powder is shown in Formula 2:

[0012]

[0013] In one possible implementation, the hydrophobically associating polyacrylamide powder is prepared by a method comprising the following process:

[0014] 1) A first system comprising urea, disodium ethylenediaminetetraacetate, sodium formate, ammonium persulfate, sodium bisulfite, and azo salt, and a second system comprising acrylamide and the hydrophobic monomer of the salt-resistant monomer are added to water to obtain a mixed solution;

[0015] 2) The mixed solution is subjected to a polymerization reaction to obtain a colloid.

[0016] 3) The colloid is subjected to post-processing including separation, drying, pulverization and sieving to obtain the hydrophobic associating polyacrylamide powder.

[0017] In one possible implementation, the mass ratio of the acrylamide, salt-resistant monomer, hydrophobic monomer, and water is (20-30):(2-4):(0.5-1):(65-75).

[0018] In one possible implementation, the urea constitutes 2%-3% of the mass of the second system; and / or,

[0019] The mass percentage of disodium ethylenediaminetetraacetate in the second system is 0.02%-0.06%; and / or,

[0020] The amount of sodium formate added is 0.05%-0.15% of the mass of the second system; and / or,

[0021] The ammonium persulfate is 0.005%-0.01% of the mass of the second system; and / or,

[0022] The sodium bisulfite is 0.005%-0.01% of the mass of the second system; and / or,

[0023] The azo salt is 0.005%-0.01% of the mass of the second system.

[0024] In one possible implementation, the polymerization reaction is carried out at a temperature of 15°C-25°C and for a duration of 6-8 hours.

[0025] In one possible implementation, the hydrophobic monomer comprises one or more of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, tetradecyl methacrylate, and dodecyl acrylamide.

[0026] In one possible implementation, the dispersant comprises one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, and polypropylene glycol 200 and polypropylene glycol 400; and / or, the suspending agent comprises activated polyamide wax; and / or, the emulsifier comprises one or more of span20, span80, tween80, OP-10, and AEO-9; and / or, the preservative comprises sodium diacetate and / or sodium benzoate.

[0027] Secondly, embodiments of this application also provide a method for fracturing oil and gas wells, which uses a fracturing suspension emulsion including the above-mentioned fracturing agent to fracturing the oil and gas well.

[0028] This application provides a fracturing suspension emulsion and a method for fracturing oil and gas wells. The salt-resistant monomer of the suspension emulsion contains disulfonic acid groups. These disulfonic acid groups have strong hydrophilicity and can form strong hydrogen bonds and ion-dipole interactions with water molecules. In high-salt environments, this helps overcome the inhibitory effect of salt ions on the dissolution process, thereby accelerating the dissolution rate. In high-salt environments, the viscosity of the suspension emulsion decreases because salt ions neutralize the electrostatic repulsion between polymer chains. The disulfonic acid groups, by increasing the electrostatic repulsion between chains to form a more stable network structure, can counteract the neutralization effect of salt ions and electrons, thereby maintaining or even increasing the viscosity of the suspension emulsion. During fluid transport, the disulfonic acid groups can also improve the rheological properties of the fluid, forming a more uniform dispersion system, thus reducing the frictional resistance of the suspension emulsion. Furthermore, the disulfonic acid groups can improve the overall stability of the suspension emulsion, preventing phase separation and sedimentation, which helps maintain the performance of the suspension emulsion in high-salt environments, thereby improving the fracturing effect. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1This is a graph showing the drag reduction rate of the suspension emulsion of Example 1 of this application under different conditions over time.

[0031] Figure 2 This is a comparison chart of the suspension emulsion of this application with traditional thickeners on the market;

[0032] Figure 3 This is a graph showing the results of a residue content test between the suspension emulsion of this application and conventional thickeners on the market.

[0033] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0035] In the oil and gas extraction industry, with the gradual depletion of conventional oil and gas resources, the development of unconventional resources such as shale oil and gas and tight oil and gas is becoming increasingly important. To improve the production of these unconventional oil and gas wells, hydraulic fracturing technology is widely used. Hydraulic fracturing involves injecting high-pressure fluid downhole to fracture the formation, thereby increasing oil and gas permeability and recovery. In this process, the performance of the fracturing fluid is crucial to the fracturing effect. Polyacrylamide, as a thickener in fracturing fluids, is widely used due to its superior performance. Its main advantages include: rapid dissolution rate, low frictional resistance, high viscoelasticity, and minimal formation damage. These characteristics enable polyacrylamide to effectively improve the proppant-carrying capacity and fracture propagation capacity of fracturing fluids, thereby increasing the production of oil and gas wells.

[0036] However, with increasing environmental awareness and the need for cost control, production water and backflow (hereinafter referred to as backflow) are increasingly used in oilfield operations to prepare fracturing fluids. This backflow typically has a high salinity, usually around 30,000 ppm, and may even exceed 100,000 ppm. This high salinity environment poses a significant challenge to the performance of fracturing fluid thickeners.

[0037] High-salt environments contain a large number of salt ions. These ions can shield the charges on thickener molecules, reducing their interaction with water molecules and thus slowing down the dissolution rate of the thickener. Traditional thickeners rely on charge repulsion to maintain their extended molecular chain structure. Under high-salt conditions, salt ions can neutralize these charges, causing the molecular chains to contract and reducing the viscosity of the solution. Furthermore, high concentrations of salt ions may weaken hydrogen bonds and other non-covalent interactions between thickener molecules, leading to the collapse of the traditional thickener's network structure and further reducing its viscosity. In addition, the reduced dissolution rate and decreased viscosity may result in uneven dispersion of the thickener in the fluid, creating localized concentration differences and increasing frictional resistance during flow. All of these factors negatively impact fracturing performance.

[0038] In view of this, embodiments of the present invention provide a suspension emulsion for fracturing and a method for fracturing oil and gas wells. The suspension emulsion is prepared by using a salt-resistant monomer with a disulfonic acid group, which can improve the dissolution rate of the suspension emulsion, increase its viscosity, and reduce friction.

[0039] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0040] In a first aspect, embodiments of this application provide a suspension emulsion for fracturing, wherein the suspension emulsion may include, by mass ratio: 40 to 48 parts of dispersant, 3 to 5 parts of suspending agent, 44 to 52 parts of hydrophobic associating polyacrylamide powder, 5 to 10 parts of emulsifier and 0.1 to 0.2 parts of preservative.

[0041] Dispersants are used to uniformly disperse solid particles in the liquid medium, preventing particle aggregation and sedimentation, thereby improving the stability of the suspension emulsion and ensuring that the components in the suspension emulsion remain uniformly dispersed during storage and use. Suspension agents increase the viscosity of the liquid, thereby improving the suspension capacity of solid particles in the liquid medium, preventing particle sedimentation and maintaining the uniformity and stability of the suspension emulsion. Hydrophobic associating polyacrylamide powder can form a network structure in water, improving the viscoelasticity and rheological properties of the suspension emulsion, and enhancing its stability and durability under high salt and high temperature environments. Emulsifiers reduce the surface tension at the oil-water interface, helping the suspension emulsion to form and improving its stability, ensuring the consistency of the composition during storage and use. Preservatives inhibit microbial growth and extend the shelf life of the suspension emulsion.

[0042] For example, the dispersant may include, but is not limited to, polyethylene glycol, polypropylene glycol, etc., and the amount of dispersant added may be 40 parts, 42 parts, 44 parts, 46 parts, or 48 parts. The suspending agent may include, but is not limited to, activated polyamide wax, and the amount of suspending agent added may be 3 parts, 4 parts, or 5 parts. The preparation process of salt-resistant hydrophobic associating polyacrylamide powder is described later, and the amount of hydrophobic associating polyacrylamide powder added may be 44 parts, 46 parts, 48 ​​parts, 50 parts, or 52 parts. The preservative may include, but is not limited to, sodium diacetate, sodium benzoate, etc., and the amount of preservative added may be 0.1 parts, 0.12 parts, 0.15 parts, 0.16 parts, 0.18 parts, or 0.2 parts.

[0043] The raw materials for preparing hydrophobically associating polyacrylamide powder may include salt-resistant monomers, the structure of which is shown in Formula 1:

[0044]

[0045] The suspension emulsion of this invention contains disulfonic acid groups in its salt-resistant monomer. These disulfonic acid groups possess strong hydrophilicity and can form strong hydrogen bonds and ion-dipole interactions with water molecules. In high-salt environments, this helps overcome the inhibitory effect of salt ions on the dissolution process, thereby accelerating the dissolution rate. In high-salt environments, the viscosity of the suspension emulsion decreases because salt ions neutralize the electrostatic repulsion between polymer chains. The disulfonic acid groups, by increasing the electrostatic repulsion between chains to form a more stable network structure, can counteract the neutralization effect of salt ions and electrons, thus maintaining or even increasing the viscosity of the suspension emulsion. During fluid transport, the disulfonic acid groups can also improve the rheological properties of the fluid, forming a more uniform dispersion system, thereby reducing the frictional resistance of the suspension emulsion. Furthermore, the disulfonic acid groups can improve the overall stability of the suspension emulsion, preventing phase separation and sedimentation, which helps maintain the performance of the suspension emulsion in high-salt environments, thereby improving fracturing efficiency.

[0046] Exemplarily, in one possible implementation, the suspension emulsion can be prepared by the following steps:

[0047] (1) Add the dispersant and suspending agent into the reactor in sequence and start stirring;

[0048] (2) After dispersing evenly, add the emulsifier and stir;

[0049] (3) Add the hydrophobic associative polyacrylamide powder into the reactor and stir;

[0050] (4) Add preservatives and continue stirring. After the temperature drops to room temperature, open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0051] In one possible implementation, the salt-resistant monomer is prepared by a method comprising heating a mixture comprising maleic anhydride, sodium hydroxyethyl sulfonate, and a catalyst to obtain the salt-resistant monomer.

[0052] Maleic anhydride reacts with sodium hydroxyethyl sulfonate to introduce disulfonic acid groups, thereby improving the salt resistance of the salt-resistant monomer and its hydrophilicity, resulting in better solubility of the suspension emulsion. Furthermore, the prepared salt-resistant monomer can form a more stable chain structure during the polymerization reaction, improving the mechanical properties and stability of the hydrophobically associated polyacrylamide. Exemplarily, the catalyst can be an acid catalyst, such as p-benzenesulfonic acid or concentrated sulfuric acid; alternatively, the catalyst can be an alkaline metal hydroxide, such as sodium hydroxide or potassium hydroxide; or, alternatively, an organic catalyst, such as triethylamine or dimethylaminopyridine.

[0053] The molar ratio of maleic anhydride to sodium hydroxyethyl sulfonate is 1:(2-3). This ensures an excess of sodium hydroxyethyl sulfonate during the reaction, allowing the maleic anhydride to react fully and minimizing unreacted maleic anhydride residue, thus improving the purity of the generated salt-resistant monomer. Simultaneously, it ensures that each maleic anhydride molecule can combine with two or more sulfonic acid groups to form a disulfonic acid structure, thereby enhancing the salt resistance of the salt-resistant monomer in high-salt environments. Furthermore, the increased number of sulfonic acid groups also increases the hydrophilicity of the salt-resistant monomer, accelerating the dissolution rate of the formed suspension emulsion.

[0054] The heat treatment temperature is 60℃-80℃, such as 60℃, 65℃, 70℃, 75℃, or 80℃. Preferably, the reaction temperature is 70℃. Of course, the heat treatment temperature can also be other values, and this application does not limit this. 60℃-80℃ can provide sufficient heat energy to accelerate the reaction rate and can also avoid excessive acceleration that could lead to side reactions and reduce the yield of salt-resistant monomers.

[0055] The heat treatment time is 4-6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours. Of course, other values ​​are also possible, and this application does not limit this. This ensures that maleic anhydride and sodium hydroxyethyl sulfonate react fully, minimizing unreacted raw material residue and improving the purity of the generated salt-resistant monomer. At a temperature of 60℃-80℃, a reaction time of 6-8 hours provides a balanced reaction rate, accelerating the reaction process while maintaining high reaction selectivity and reducing the formation of byproducts.

[0056] In one possible implementation, the structure of the hydrophobically associating polyacrylamide powder is shown in Formula 2:

[0057]

[0058] Among them, salt-resistant monomers provide additional ionic or polar groups in the polymer chain, enhancing the stability of the polymer in high-salt environments and effectively reducing the shielding effect of salt ions on the polymer chain. Hydrophobic monomers form micro-associated structures in the polymer, increasing the viscoelasticity and rheological properties of the polymer, resulting in hydrophobically associating polyacrylamide exhibiting excellent thickening effects in aqueous solutions.

[0059] In one possible implementation, the hydrophobically associating polyacrylamide powder is prepared by a method comprising the following process:

[0060] 1) Add the first system, which includes urea, disodium ethylenediaminetetraacetate, sodium formate, ammonium persulfate, sodium bisulfite and azo salt, and the second system, which includes acrylamide and hydrophobic monomers with salt resistance, to water to obtain a mixed solution;

[0061] 2) The mixed solution is subjected to a polymerization reaction to obtain a colloid.

[0062] 3) The colloid is subjected to post-processing including separation, drying, pulverization and sieving to obtain hydrophobic associating polyacrylamide powder.

[0063] In an exemplary embodiment, hydrophobic associating polyacrylamide powder is prepared by the following method: Acrylamide, salt-resistant monomer, and hydrophobic monomer are added to distilled water in a mass ratio of 20-30:2-4:0.5-1:65-75. The mixture is then added to a reaction vessel, and nitrogen is purged to remove oxygen. 2%-3% urea, 0.02%-0.06% EDTA-2Na, 0.05%-0.15% sodium formate, 0.005%-0.01% ammonium persulfate, 0.005%-0.01% sodium bisulfite, and 0.005%-0.01% azo salt are added. The initiation temperature is 15℃-25℃, and the reaction is carried out for 6-8 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed, separated, dried, pulverized, and sieved to obtain the hydrophobic associating polyacrylamide powder.

[0064] In one possible implementation, the mass ratio of acrylamide, salt-resistant monomer, hydrophobic monomer, and water is (20-30):(2-4):(0.5-1):(65-75). Acrylamide, as the main-chain monomer, provides the basic structure and water solubility of the resulting polymer, ensuring good solubility and thickening effect in water. The salt-resistant monomer provides additional ionic or polar groups (bissulfonic acid groups), enhancing the polymer's stability in high-salt environments, preventing the shielding effect of salt ions on the polymer chains, thereby accelerating the dissolution rate of the suspension emulsion and maintaining sufficient viscosity. The hydrophobic monomer facilitates the formation of micro-associated structures in the polymer, increasing the polymer's viscoelasticity and rheological properties, resulting in the hydrophobically associating polyacrylamide exhibiting excellent thickening effects in aqueous solutions without significantly reducing the polymer's water solubility. The high water content ensures the fluidity and homogeneity of the reaction system, promoting thorough mixing of various monomers and the smooth progress of the polymerization reaction.

[0065] In one possible implementation, the mass percentage of urea in the second system is 2%-3%, for example, 2%, 2.5%, or 3% of the mass of the second system. Of course, the mass percentage of urea can also be other values, and this application does not limit this. At this ratio, urea effectively increases the solubility of the polymer, prevents excessive entanglement between polymer chains, and thus improves the dispersibility and solubility of the polymer in water.

[0066] The mass percentage of disodium ethylenediaminetetraacetate (EDTA) in the second system is 0.02%-0.06%. For example, the mass percentage of disodium ethylenediaminetetraacetate can be 0.02%, 0.03%, 0.04%, 0.05%, or 0.06% of the second system. Of course, the mass percentage of disodium ethylenediaminetetraacetate can also be other values, and this application does not limit this. Within the above concentration range, disodium ethylenediaminetetraacetate can effectively chelate metal ion impurities in the reaction system, preventing the catalytic or inhibitory effects of metal ion impurities on the polymerization reaction, and improving the purity and consistency of the generated hydrophobic associating polyacrylamide.

[0067] The amount of sodium formate added is 0.05%-0.15% of the mass of the second system. For example, the mass percentage of sodium formate can be 0.05%, 0.10%, or 0.15% of the mass of the second system. Of course, the mass percentage of sodium formate can also be other values, and this application does not limit this. In this way, sodium formate can adjust the rheological properties of the polymer, enabling the polymer to exhibit stable viscosity characteristics under different shear conditions.

[0068] The ammonium persulfate is present at 0.005%-0.01% of the mass of the second system. For example, the mass percentage of ammonium persulfate can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, or 0.01% of the mass of the second system. Of course, the mass percentage of ammonium persulfate can also be other values, and this application does not limit this. Ammonium persulfate can act as a free radical initiator, initiating the polymerization reaction at this concentration, ensuring the efficient and stable progress of the polymerization reaction, and forming high-molecular-weight hydrophobic associating polyacrylamide.

[0069] Sodium bisulfite constitutes 0.005%-0.01% of the mass of the second system. For example, the mass percentage of sodium bisulfite can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, or 0.01% of the mass of the second system. Of course, the mass percentage of sodium bisulfite can also be other values, and this application does not limit this. Sodium bisulfite can act as a reducing agent, forming a red oxygen initiation system with ammonium persulfate, providing a stable source of free radicals, controlling the polymerization rate, reducing side reactions, and improving the purity of the product.

[0070] The azo salt constitutes 0.005%-0.01% of the mass of the second system. For example, the mass percentage of the azo salt can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, or 0.01% of the mass of the second system. Of course, the mass percentage of the azo salt can also be other values, and this application does not limit this. The azo salt can act as an auxiliary initiator, synergistically working with other initiators (ammonium persulfate) to enhance initiation efficiency and ensure uniform growth of the polymer chains.

[0071] For example, the azo salt may be one or more of azobisisobutyronitrile and azobisisobutyramidine hydrochloride.

[0072] In one possible implementation, the polymerization temperature is between 15°C and 25°C. For example, the polymerization temperature can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, or 25°C. Of course, the polymerization temperature can also be other values, and this application does not limit this. Conducting the polymerization reaction within a lower temperature range (15°C-25°C) helps to reduce the occurrence of side reactions, reduce the formation of by-products, and improve the purity of the product.

[0073] The polymerization reaction time is 6-8 hours; for example, the polymerization reaction duration can be 6, 7, or 8 hours. Of course, the polymerization reaction duration can also be other values, and this application does not limit this. A reaction time of 6 to 8 hours ensures that each monomer is fully polymerized, forming a hydrophobically associating polyacrylamide with a uniform molecular structure, thus improving the physical and chemical properties of the hydrophobically associating polyacrylamide. Furthermore, a suitable combination of reaction time and temperature also helps to form an ideal molecular weight and molecular structure, thereby enhancing the salt resistance and thickening effect of the hydrophobically associating polyacrylamide.

[0074] In one possible implementation, the hydrophobic monomer includes one or more of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, tetradecyl methacrylate, and dodecyl acrylamide. The monomers described above contain long-chain alkyl groups or hydrophobic groups, which can form micro-associated structures in the polymer, increasing the polymer's viscoelasticity and rheological properties.

[0075] In one possible implementation, the dispersant may include one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, and polypropylene glycol 200 and polypropylene glycol 400. Using polyethylene glycol or polypropylene glycol with different molecular weights as dispersants can promote uniform dispersion of particles in the reaction system and prevent aggregation and sedimentation. Polyethylene glycol and polypropylene glycol can also improve the polymer's solubility in water, making it easier to handle and use in applications.

[0076] Existing technologies use white oil as a dispersant, which can increase damage to the reservoir after entering the formation. This application uses polyethylene glycol or polypropylene glycol with different molecular weights as dispersants, resulting in less damage to the reservoir.

[0077] The suspending agent may include activated polyamide wax, which can increase the viscosity and yield stress of the system, helping to stabilize the suspended emulsion and prevent particle sedimentation. In the prior art, organobentonite is commonly used as a suspending agent. After the suspended emulsion enters the formation and breaks down, the organobentonite component is non-degradable, leaving a large amount of residue that can clog seepage channels and severely impair formation permeability. The activated polyamide wax of this application leaves less residue after entering the formation and has degradable properties, thus causing less damage to the formation.

[0078] Emulsifiers can include one or more of Span20, Span80, Tween80, OP-10, and AEO-9. These emulsifiers can reduce interfacial tension, stabilize suspended emulsions and dispersion systems, and prevent phase separation. Furthermore, the Span and Tween series, OP-10, and AEO-9 have different hydrophilic-lipophilic balance (HLB) values, allowing for the selection of appropriate emulsifiers to optimize the emulsification effect of the system.

[0079] Preservatives may include sodium diacetate and / or sodium benzoate. Preservatives effectively inhibit the growth of bacteria, mold, and yeast, thus extending the shelf life of suspension emulsions.

[0080] Secondly, embodiments of this application also provide a method for fracturing oil and gas wells, which uses a fracturing suspension emulsion including the above-mentioned fracturing agent to fracturing the oil and gas well.

[0081] The fracturing suspension emulsion of this application is further described below through several embodiments.

[0082] Example 1: Preparation of Suspension Emulsion A for Fracturing

[0083] (1) Preparation of salt-resistant monomer: Add 200g of pure water to a three-necked flask, add 1.0mol of maleic anhydride and 2.0mol of sodium hydroxyethyl sulfonate, stir at 300r / min for 10min, add a small amount of concentrated sulfuric acid for catalysis, heat to 70℃, continue stirring for 30min, and dry at 70℃ for 2h to obtain salt-resistant monomer.

[0084] (2) Preparation of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 650g of pure water and 21g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 35g of salt-resistant monomer, stir and dissolve evenly, add 279g of acrylamide monomer and 6g of octadecyl dimethyl allyl ammonium chloride, continue stirring and cooling to 20℃, then pour the solution in the three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after it is fully dissolved, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 9.0g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 3mL of initiator ammonium persulfate solution (concentration 0.5%), 6mL of sodium bisulfite solution (concentration 0.2%) and 0.02g of azo salt, while maintaining nitrogen purging and stirring. The initiation temperature is 20-25℃, and the reaction time is 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or larger, and dried at 70℃ for 2 hours. After sieving, hydrophobic associative polyacrylamide powder is obtained.

[0085] (3) Preparation of suspension emulsion A for fracturing: Take 41 parts of polyethylene glycol 200 and stir at 1000 r / min. After stirring for 30 min, add 4 parts of polyamide wax and stir for 30 min. Then add 4 parts of span80 and 1 part of op-10 and continue stirring for 30 min to disperse evenly. Then add 50 parts of hydrophobic associative polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium benzoate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor and discharge the suspension emulsion into the barrel.

[0086] Example 2: Preparation of Suspension Emulsion B for Fracturing

[0087] (1) Preparation of salt-resistant monomer: Add 200g of pure water to a three-necked flask, add 1.0mol of maleic anhydride and 2.0mol of sodium hydroxyethyl sulfonate, stir at 300r / min for 10min, add a small amount of concentrated sulfuric acid for catalysis, heat to 70℃, continue stirring for 30min, and dry at 70℃ for 2h to obtain salt-resistant monomer.

[0088] (2) Preparation of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 700g of pure water and 18g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 30g of salt-resistant monomer, stir and dissolve evenly, add 236g of acrylamide monomer and 7g of octadecyl dimethyl allyl ammonium chloride, continue stirring and cooling to 20℃, then pour the solution in the three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 8g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 4mL of initiator ammonium persulfate solution (concentration 2%), 6mL of sodium bisulfite solution (concentration 1%) and 0.02g of azo salt, while maintaining nitrogen purging and stirring. The initiation temperature is 20-25℃, and the reaction time is 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or larger, and dried at 70℃ for 2 hours. After sieving, hydrophobic associative polyacrylamide powder is obtained.

[0089] (3) Preparation method of suspension emulsion B for fracturing

[0090] Take 43 parts of polypropylene glycol 200 and stir at 1000 r / min for 30 min. Then add 4 parts of polyamide wax and stir for 30 min to disperse evenly. Then add 6 parts of span80 and 1.5 parts of tween80 and continue stirring for 30 min. Then add 45.5 parts of hydrophobic associating polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium benzoate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0091] Example 3: Preparation of Suspension Emulsion C for Fracturing

[0092] (1) Preparation of salt-resistant monomer: Add 200g of pure water to a three-necked flask, add 1.0mol of maleic anhydride and 2.0mol of sodium hydroxyethyl sulfonate, stir at 300r / min for 10min, add a small amount of concentrated sulfuric acid for catalysis, heat to 70℃, continue stirring for 30min, and dry at 70℃ for 2h to obtain salt-resistant monomer.

[0093] (2) Preparation of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 720g of pure water and 12g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 20g of salt-resistant monomer, stir and dissolve evenly, add 231g of acrylamide monomer and 8g of octadecyl dimethyl allyl ammonium chloride, continue stirring and cooling to 20℃, then pour the solution in the three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 8g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 4mL of initiator ammonium persulfate solution (concentration 2%), 6mL of sodium bisulfite solution (concentration 1%) and 0.02g of azo salt, while maintaining nitrogen purging and stirring. The initiation temperature is 20-25℃, and the reaction time is 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or larger, and dried at 70℃ for 2 hours. After sieving, hydrophobic associative polyacrylamide powder is obtained.

[0094] (3) Preparation method of suspension emulsion C for fracturing

[0095] Take 45 parts of polyethylene glycol 400 and stir at 1000 r / min for 30 min. Then add 5 parts of polyamide wax and stir for 10 min. Then add 44 parts of hydrophobic associative polyacrylamide powder and continue stirring for 30 min to disperse evenly. Then add 4 parts of Span80 and 1 part of OP-10 and stir for 20 min. Then add 0.1 parts of sodium diacetate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0096] Comparative Example 1

[0097] The difference from Example 1 is that the hydrophobic associative polyacrylamide powder does not contain salt-resistant monomers, and organic bentonite is used as a suspending agent when the suspension emulsion is prepared.

[0098] (1) Preparation method of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 650g of pure water and 21g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 314g of acrylamide monomer and 6g of octadecyl dimethyl allyl ammonium chloride, stir to dissolve evenly, cool down to 20℃, then pour the solution in the above three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 9g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 3mL of initiator ammonium persulfate solution (concentration 0.5%), 6mL of sodium bisulfite solution (concentration 0.2%) and 0.02g of azo salt, and keep purging with nitrogen and stirring. The initiation temperature is 20-25℃, and the reaction lasts for 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or finer, and dried at 70℃ for 2 hours. After sieving, the hydrophobic associative polymer powder is obtained.

[0099] (2) Preparation method of suspension emulsion

[0100] Take 41 parts of polyethylene glycol 200 and stir at 1000 r / min for 30 min. Then add 4 parts of organic bentonite and stir for 30 min to disperse evenly. Then add 4 parts of Span80 and 1 part of OP-10 and continue stirring for 30 min. Then add 50 parts of hydrophobic associative polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium benzoate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0101] Comparative Example 2

[0102] The difference from Example 2 is that the hydrophobic associative polyacrylamide powder does not contain salt-resistant monomers, and organic bentonite is used as a suspending agent when the suspension emulsion is prepared.

[0103] (1) Preparation method of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 700g of pure water and 18g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 266g of acrylamide monomer and 7g of octadecyl dimethyl allyl ammonium chloride, stir and dissolve evenly, cool down to 20℃, then pour the solution in the above three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 8g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 4mL of initiator ammonium persulfate solution (concentration 2%), 6mL of sodium bisulfite solution (concentration 1%) and 0.02g of azo salt, and keep purging with nitrogen and stirring. The initiation temperature is 20-25℃, and the reaction lasts for 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or finer, and dried at 70℃ for 2 hours. After sieving, the hydrophobic associative polymer powder is obtained.

[0104] (2) Preparation method of suspension emulsion for fracturing

[0105] Take 43 parts of polypropylene glycol 200 and stir at 1000 r / min for 30 min. Then add 4 parts of organic bentonite and stir for 30 min to disperse evenly. Then add 6 parts of span80 and 1.5 parts of tween80 and continue stirring for 30 min. Then add 45.5 parts of hydrophobic associative polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium benzoate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0106] Comparative Example 3

[0107] The difference from Example 3 is that the hydrophobic associative polyacrylamide powder does not contain salt-resistant monomers, and organic bentonite is used as a suspending agent when the suspension emulsion is prepared.

[0108] (1) Preparation method of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 720g of pure water and 12g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 251g of acrylamide monomer and 8g of octadecyl dimethyl allyl ammonium chloride, stir and dissolve evenly, cool down to 20℃, then pour the solution in the above three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 8g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 4mL of initiator ammonium persulfate solution (concentration 2%), 6mL of sodium bisulfite solution (concentration 1%) and 0.02g of azo salt, and keep purging with nitrogen and stirring. The initiation temperature is 20-25℃, and the reaction time is 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or larger, and dried at 70℃ for 2 hours. After sieving, hydrophobic associative polyacrylamide powder is obtained.

[0109] (2) Preparation method of suspension emulsion for fracturing

[0110] Take 45 parts of polyethylene glycol 400 and stir at 1000 r / min for 30 min. Then add 5 parts of organic bentonite and stir for 30 min to disperse evenly. Then add 4 parts of Span80 and 1 part of OP-10 and continue stirring for 10 min. Then add 44 parts of hydrophobic associative polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium diacetate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0111] Comparative Example 4

[0112] The difference from Example 1 is that the salt-resistant monomer is replaced with 2-acrylamide-2-methylpropanesulfonic acid.

[0113] (1) Preparation method of hydrophobic associative polyacrylamide powder: Take 1000mL of three-necked flask, add 650g of pure water and 21g of granular alkali, dissolve evenly, place in a constant temperature water bath, slowly add 35g of 2-acrylamide-2-methylpropanesulfonic acid, stir and dissolve evenly, add 279g of acrylamide monomer and 6g of octadecyl dimethyl allyl ammonium chloride, continue stirring and cooling to 20℃, then pour the solution in the above three-necked flask into a 3.0L reactor, control the external circulating water temperature of the reactor to 20℃, continue stirring for 30min, after dissolving fully, add 0.3g of sodium formate, 0.15g of disodium ethylenediaminetetraacetate and 9g of urea, purge with nitrogen in a high-purity nitrogen cylinder for 60min to remove oxygen, then slowly add 3mL of initiator ammonium persulfate solution (concentration 0.5%), 6mL of sodium bisulfite solution (concentration 0.2%) and 0.02g of azo salt, and keep purging with nitrogen and stirring. The initiation temperature is 20-25℃, and the reaction time is 4-6 hours. When the reaction temperature stops rising, the mixture is allowed to cool naturally for 2 hours. The colloid is then removed from the reactor, granulated into powder particles of 60 mesh or larger, and dried at 70℃ for 2 hours. After sieving, hydrophobic associative polyacrylamide powder is obtained.

[0114] (2) Preparation method of suspension emulsion for fracturing

[0115] Take 41 parts of polypropylene glycol 200 and stir at 1000 r / min for 30 min. Then add 4 parts of polyamide wax and stir for 30 min to disperse evenly. Then add 4 parts of span80 and 1 part of op-10 and continue stirring for 30 min. Then add 50 parts of hydrophobic associative polyacrylamide powder and stir for 60 min. Then add 0.1 parts of sodium benzoate and continue stirring for 30 min. After the temperature drops to below room temperature (25℃), open the bottom valve and discharge port of the reactor to discharge the suspended emulsion into a barrel.

[0116] Performance Evaluation

[0117] (1) Thickening rate test: 500 mL of standard saline solution (mineralization approximately 33,000 ppm, calcium and magnesium ion content 2,000 ppm) was measured in a stirrer. The stirrer speed was adjusted to 1500 r / min ± 90 r / min. 3 mL of the suspension emulsion was weighed, and after stirring for 3 min, its viscosity was measured using a six-speed viscometer and compared with the viscosity after 10 min. The test results of Example 1 were: the viscosity at 3 min was 36 mPa·s, the viscosity at 10 min was 39 mPa·s, and the thickening rate was 39 / 42 = 92.3%, which is greater than 90%.

[0118] (2) Salt tolerance test: Measure another 500 mL of distilled water into a stirrer, adjust the stirrer speed to 1500 r / min ± 90 r / min, weigh 3 mL of the suspension emulsion, stir for 3 min, and then place the solution in a constant temperature water bath at 25℃ ± 1℃ for 2 h. Measure its viscosity using a six-speed viscometer and compare it with the viscosity in standard salt water. The test results for Example 1 are: the viscosity in distilled water is 28.5 mPa·s, and the viscosity retention rate is 28.5 / 39 = 73.1%, which is greater than 70%.

[0119] (3) Drag Reduction Test: 0.10% solutions of the suspension emulsion were prepared using both water and standard saline solution, and tested according to the standard method NB / T14003.1-2015, with a pipe diameter of 14 mm and a flow rate of 100 L / min. The test results for Example 1 are shown below. Figure 1 . Figure 1 These are the drag reduction test results for the suspension emulsion in pure water / standard saline. The maximum drag reduction in pure water is 79.3%, the time required to reach the maximum drag reduction is 48 seconds, and the drag reduction at the end time is 78.4%. The maximum drag reduction in standard saline is 72.3%, the time required to reach the maximum drag reduction is 73 seconds, and the drag reduction at the end time is 71.6%.

[0120] (4) Residue content test: Prepare a 1.0% solution, add 500 ppm of degumming agent, measure an appropriate amount and put it into a sealed container, place it in a water bath at 90℃, and degumme for 120 min. Pour the degummed liquid into a centrifuge tube, centrifuge at 3000 r / min for 20 min, and place it in a constant temperature oven at 105℃ until the mass of the centrifuge tube no longer changes, and calculate the residue content. See Example 1 for test results with other similar products on the market. Figure 2 and Figure 3 See also Figure 2 In the left-middle image, the suspension of this application is clear after gel breaking, with minimal white residue; see also... Figure 2 The image on the right shows a different product on the market. Other similar products have a cloudy liquid with a lot of white residue floating on the surface. (See also...) Figure 3 The centrifuge tube on the left is the residue after the suspension gelling liquid of this application has been dried, and the residue content is significantly less than that of other similar products on the market on the right.

[0121] The results are shown in Table 1.

[0122] Table 1

[0123]

[0124]

[0125] Referring to Examples 1-3 and Comparative Examples 1-3, it is evident that the presence or absence of the salt-resistant monomer of this application has a significant impact on the salt tolerance and maximum drag reduction of the suspension emulsion in brine. The salt tolerance and maximum drag reduction of the suspension emulsion containing the salt-resistant monomer of this application are generally much greater than those without the salt-resistant monomer. That is, the salt-resistant monomer of this application can significantly improve the salt tolerance and maximum drag reduction of the suspension emulsion in brine, thereby increasing the dissolution rate of the suspension emulsion in high-salinity environments and reducing friction.

[0126] Further reference to Examples 1-3, Comparative Examples 1-3 and Comparative Example 4 shows that the number of sulfonic acid groups in the salt-resistant monomer has a significant impact on the salt resistance of the suspension emulsion. As the number of sulfonic acid groups increases, the salt resistance of the suspension emulsion is significantly improved.

[0127] Furthermore, referring to Examples 1-3 and Comparative Examples 1-3, it can be seen that using polyamide wax as a suspending agent can greatly reduce the residue content after the suspension emulsion breaks down, thereby reducing damage to the formation.

[0128] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A suspended emulsion for fracturing, characterized in that, The composition by weight is as follows: 40 to 48 parts dispersant, 3 to 5 parts suspending agent, 44 to 52 parts hydrophobic associating polyacrylamide powder, 5 to 10 parts emulsifier, and 0.1 to 0.2 parts preservative. The raw materials for preparing the hydrophobic associative polyacrylamide powder include salt-resistant monomers; The structure of the salt-resistant monomer is shown in Formula 1:

2. The suspended emulsion for fracturing according to claim 1, characterized by, The salt-resistant monomer is prepared by a method comprising the following process: The salt-resistant monomer is obtained by heating a mixture comprising maleic anhydride, sodium hydroxyethyl sulfonate, and a catalyst. Wherein, the molar ratio of maleic anhydride to sodium hydroxyethyl sulfonate is 1:(2-3); and / or, The temperature of the heat treatment is 60℃-80℃; the time of the heat treatment is 4h-6h.

3. The suspended emulsion for fracturing according to claim 1 or 2, characterized in that, The structure of the hydrophobically associating polyacrylamide powder is shown in Formula 2:

4. The suspended emulsion for fracturing according to any one of claims 1 to 3, characterized in that, The hydrophobically associating polyacrylamide powder is prepared by a method comprising the following steps: 1) A first system comprising urea, disodium ethylenediaminetetraacetate, sodium formate, ammonium persulfate, sodium bisulfite and azo salt, and a second system comprising acrylamide and the hydrophobic monomer of the salt-resistant monomer are added to water to obtain a mixed solution; 2) The mixed solution is subjected to a polymerization reaction to obtain a colloid. 3) The colloid is subjected to post-processing including separation, drying, pulverization and sieving to obtain the hydrophobic associating polyacrylamide powder.

5. The suspended emulsion for fracturing according to claim 4, characterized in that, The mass ratio of acrylamide, salt-resistant monomer, hydrophobic monomer and water is (20-30):(2-4):(0.5-1):(65-75).

6. The fracturing suspension emulsion according to claim 4 or 5, characterized in that, The urea constitutes 2%-3% of the mass of the second system; and / or, The mass percentage of disodium ethylenediaminetetraacetate in the second system is 0.02%-0.06%; and / or, The amount of sodium formate added is 0.05%-0.15% of the mass of the second system; and / or or, The ammonium persulfate is 0.005%-0.01% of the mass of the second system; and / or, The sodium bisulfite is 0.005%-0.01% of the mass of the second system; and / or, The azo salt is 0.005%-0.01% of the mass of the second system.

7. The suspended emulsion for fracturing according to any one of claims 4 to 6, characterized in that, The polymerization reaction is carried out at a temperature of 15℃-25℃ and for a duration of 6h-8h.

8. The suspended emulsion for fracturing according to any one of claims 4 to 7, characterized in that, The hydrophobic monomer includes one or more of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, tetradecyl methacrylate, and dodecyl acrylamide.

9. The fracturing suspension emulsion according to any one of claims 1-8, characterized in that, The dispersant includes one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, and polypropylene glycol 200 and polypropylene glycol 400; and / or, The suspending agent comprises activated polyamide wax; and / or, The emulsifier includes one or more of span20, span80, tween80, OP-10, and AEO-9; and / or, The preservatives include sodium diacetate and / or sodium benzoate.

10. A method of fracturing an oil and gas well, characterized in that, Fracturing a hydrocarbon well using the invert emulsion fluid of any one of claims 1-9.

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