Composite fracturing fluid thickening agent for oil and gas well and preparation process thereof

Abstract

The application relates to the technical field of thickening agents for fracturing fluids, and particularly discloses a composite fracturing fluid thickening agent for oil and gas wells and a preparation process thereof.The composite fracturing fluid thickening agent for oil and gas wells comprises the following components: 30-50 parts of acrylamide, 20-35 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10-25 parts of acryloyl morpholine, 3-8 parts of polyether amine modified organic zirconium crosslinking agent, 2-6 parts of sulfonated konjak gum, 1-5 parts of salt-resistant synergistic additive, 0.5-2 parts of composite initiator, 0.1-0.8 parts of inhibitor and 150-180 parts of deionized water.The fracturing fluid thickening agent has the advantages of high viscosity, high temperature resistance and high salt resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of thickening agents for fracturing fluids, in particular to a composite fracturing fluid thickening agent for oil and gas wells and a preparation process thereof. BACKGROUND

[0002] In the field of oil and gas resource exploration and development, with the continuous consumption of conventional oil and gas reserves, the focus of mining is gradually shifting to tight sandstone gas, coalbed methane, shale gas and other low-permeability, ultra-low-permeability and deep high-temperature unconventional oil and gas reservoirs. As the core means for efficient development of such difficult-to-mine oil and gas resources, the operation effect of hydraulic fracturing technology directly depends on the comprehensive performance of the fracturing fluid, and the thickening agent, as a key functional component of the water-based gel fracturing fluid, plays an important role in improving the viscosity of the fracturing fluid, reducing the filtration loss, suspending and carrying proppants into the formation fractures. The water-based gel fracturing fluid forms a gel system with a specific viscoelasticity through the incomplete crosslinking reaction of the thickening agent high molecular polymer and the crosslinking agent, and with the advantages of high viscosity, low friction, strong sand suspension capacity, etc., has been applied in the yield-increasing operations of domestic major oil and gas fields, especially in low-permeability oil reservoir blocks such as Changqing Oilfield, the contribution rate of fracturing operations to the improvement of oil recovery rate is more than 30%, and it has become the core technical support for ensuring the stability of oil and gas production.

[0003] In the related art, the application file with the publication number CN119614177A discloses a fracturing fluid thickening agent and a preparation method thereof. The thickening agent includes liquid material and solid material with a mass ratio of 1: (2.2-2.4). The liquid material is composed of deionized water and N-methyl pyrrolidone, and the mass ratio of deionized water to N-methyl pyrrolidone is 8.5:1.5. The solid material includes the following raw materials by weight: 20-30 parts of 2-acrylamide-2-methylpropane sulfonic acid, 10-20 parts of acrylic acid, 10-20 parts of acrylamide, 8-10 parts of hydroxypropyl methacrylate, 4-6 parts of konjac gum, 2-4 parts of chitosan, 1-3 parts of diatomite, 0.4-0.6 parts of ceramsite, 0.4-0.6 parts of disodium ethylenediaminetetraacetate, 0.2-0.4 parts of a chain transfer agent and 0.2-0.4 parts of an initiator. By adding konjac powder in the preparation of the thickening agent, the amino functional groups in the konjac molecules can crosslink with the aldehyde groups of glutaraldehyde after mixing reaction and solidification treatment, so that water molecules are wrapped in the crosslinked network structure, increasing the internal friction when the fluid flows, i.e. playing a role in improving the viscosity of the thickening agent. The condensation reaction between the hydroxyl groups on the konjac gum molecular chain and the aldehyde groups of glutaraldehyde forms a covalent bond, which plays a crosslinking role, forming a stable chemical crosslinking network structure between the konjac gum molecular chains, effectively improving the crosslinking performance of the thickening agent.

[0004] However, the existing thickening agent still has obvious performance short board in the face of complex geological conditions. Due to the insufficient adaptation of the molecular structure to the high temperature and high salt synergistic environment, and the insufficient synergistic resistance of the functional components, the performance is easy to decay rapidly under the working conditions of high temperature (some blocks are more than 200 DEG C) and high salinity (formation water salinity is more than 5*10 4 mg / L), resulting in the inability to meet the fracturing operation requirements. From the temperature resistance, the existing thickening agent is mostly linear high molecular structure, and high temperature will intensify the thermal motion of molecular chain, destroy the weak interaction between molecules, cause the decrease of chain entanglement degree and the rapid reduction of viscosity; from the salt resistance, the metal cations in high salt environment will complex with the hydrophilic groups of the thickening agent, compress the hydration layer, make the molecular chain curl and aggregate, weaken the thickening effect and even produce flocculation and sedimentation. Even if natural components such as konjac gum are introduced, it is also difficult to resist high salt erosion due to the lack of salt-resistant functional groups. In summary, the thickening agent in the related art has the defects of insufficient temperature resistance and salt resistance. SUMMARY

[0005] In order to enhance the temperature resistance and salt resistance of the composite fracturing fluid thickening agent for oil and gas wells, the application provides a composite fracturing fluid thickening agent for oil and gas wells and a preparation process thereof.

[0006] The composite fracturing fluid thickening agent for oil and gas wells provided by the application adopts the following technical scheme:

[0007] A composite fracturing fluid thickening agent for oil and gas wells is prepared from the following components:

[0008] 30-50 parts of acrylamide;

[0009] 20-35 parts of 2-acrylamide-2-methylpropane sulfonic acid;

[0010] 10-25 parts of acryloyl morpholine;

[0011] 3-8 parts of polyether amine modified organic zirconium crosslinking agent;

[0012] 2-6 parts of sulfonated konjac gum;

[0013] 1-5 parts of salt-resistant synergistic adjuvant;

[0014] 0.5-2 parts of composite initiator;

[0015] 0.1-0.8 parts of inhibitor;

[0016] 150-180 parts of deionized water;

[0017] The polyether amine modified organic zirconium crosslinking agent is obtained by coordination polymerization reaction of zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine;

[0018] The sulfonated konjac gum is obtained by modifying konjac gum with chlorosulfonic acid.

[0019] By adopting the technical scheme, acrylamide (AM) provides a basic polymer skeleton, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) contains a strong hydrophilic sulfonic acid group (-SO3H), and the negative charge layer formed after ionization can resist the erosion of metal cations in a high-salt environment and avoid the curling of molecular chains; acryloyl morpholine contains a six-membered heterocyclic structure, and the conjugated system formed by the nitrogen atom and the oxygen atom in the ring can enhance the rigidity of the molecular chain and inhibit thermal motion at high temperatures, and the three are matched to ensure the viscosity-increasing basis of the polymer and to improve the temperature resistance and salt resistance through functional groups. The polyether amine modified organic zirconium crosslinking agent molecule formed by the coordination polymerization of zirconium oxychloride, polyether amine D230 and the like contains a zirconium-oxygen-carbon covalent bond, a polyether segment and an amino functional group. At high temperatures, the zirconium-oxygen-carbon bond is not easy to break, and the integrity of the crosslinking network can be maintained; in a high-salt environment, the steric hindrance effect of the polyether segment can hinder the contact between metal cations and the hydrophilic groups of the polymer, solving the problem of crosslinking failure of traditional crosslinking agents under complex working conditions. The natural konjac gum is easy to agglomerate in a high-salt environment due to the lack of salt-resistant functional groups, and the sulfonated konjac gum modified by chlorosulfonic acid introduces sulfonic acid groups, and the negative charges form a "double salt-resistant barrier" with the sulfonic acid groups of AMPS, and the polysaccharide chains of the konjac gum can form an interpenetrating network with the polymer skeleton, further enhancing the viscosity stability of the system and avoiding the viscosity attenuation caused by the decrease in the entanglement degree of the molecular chains at high temperatures.

[0020] In summary, the design of the above raw materials solves the core defects of the existing thickening agents in terms of molecular structure, crosslinking network and environmental adaptation, and can meet the fracturing requirements of deep oil and gas reservoirs under high-temperature and high-salt conditions.

[0021] Optionally, the polyether amine modified organic zirconium crosslinking agent is prepared by the following method:

[0022] Zirconium oxychloride is dissolved in ethylene glycol monomethyl ether, stirred at 40-60℃ for 30-60min until completely dissolved to obtain a zirconium salt solution; polyether amine D230 is added dropwise to the zirconium salt solution, the dropwise adding time is controlled for 30-45min, after the dropwise adding is completed, the temperature is raised to 70-85℃, and the reaction is kept for 2-4h; then triethanolamine is added, and the reaction is continued for 1-2h, and then cooled to room temperature, and rotary evaporation is performed to remove unreacted ethylene glycol monomethyl ether to obtain the polyether amine modified organic zirconium crosslinking agent.

[0023] Optionally, the molar ratio of the zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine is 1: (0.8-1.2): (1.5-2.5): (0.5-1).

[0024] By adopting the technical scheme, the zirconium oxychloride is dissolved in ethylene glycol monomethyl ether to form a zirconium salt solution, then polyetheramine D230 is added dropwise to perform a coordination polymerization reaction, then triethanolamine is added to continue the reaction, and finally a polyetheramine modified organic zirconium crosslinking agent is obtained. The step-by-step reaction mode can accurately control the reaction progress and degree between the raw materials, and ensure the formation of a stable coordination structure. At high temperatures, the zirconium-oxygen-carbon bond has high stability and is not easy to break, thereby maintaining the integrity of the crosslinking network and preventing the performance of the thickening agent from being attenuated due to the destruction of the crosslinking structure caused by high temperatures; in a high-salt environment, the steric hindrance effect of the polyether chain segment can effectively hinder the contact between metal cations and the hydrophilic groups of the polymer, avoiding the problem that the traditional crosslinking agent fails to crosslink under high-salt conditions due to the interference of metal cations, and further improving the temperature resistance and salt tolerance of the thickening agent.

[0025] Optionally, the sulfonated konjac gum is prepared by the following method:

[0026] The konjac gum is dissolved in deionized water, stirred at 30-40 DEG C to form a colloidal solution, then chlorosulfonic acid is added, heated to 55-65 DEG C, and kept for 3-5 h; after the reaction is completed, the pH is adjusted to neutral with a 10%-15% sodium hydroxide solution, centrifuged, washed until there is no chloride ion, dried and crushed to obtain the sulfonated modified konjac gum.

[0027] Optionally, the mass ratio of the konjac gum, deionized water and chlorosulfonic acid is 1: (12-18): (1.2-1.8).

[0028] By adopting the technical scheme, the konjac gum is first dissolved in deionized water to form a colloidal solution, then chlorosulfonic acid is added to perform a sulfonation reaction, then the pH is adjusted to neutral, and the sulfonated modified konjac gum is obtained through centrifugal separation, washing, drying and crushing. By modifying with chlorosulfonic acid, sulfonic acid groups are introduced into the konjac gum molecules. The natural konjac gum is prone to aggregation in a high-salt environment due to the lack of salt-resistant functional groups, while the sulfonic acid groups introduced in the modified sulfonated konjac gum have negative charges, and the negative charge layer formed after ionization can synergize with the sulfonic acid groups of AMPS to form a "double salt-resistant barrier" to effectively resist the erosion of metal cations in a high-salt environment and prevent the molecular chain from curling and aggregating. At the same time, the polysaccharide chains of the konjac gum can form an interpenetrating network with the polymer backbone, further enhancing the viscosity stability of the system, preventing the viscosity from attenuating due to the decrease in the entanglement degree of the molecular chain at high temperatures, and improving the temperature resistance and salt tolerance of the thickening agent.

[0029] Optionally, the salt-tolerant synergistic additive is prepared by the following method:

[0030] The montmorillonite is added into deionized water, ultrasonic dispersion is carried out for 20-30 min to form a montmorillonite suspension; amino trimethylene phosphonic acid is added, and stirring reaction is carried out at 70-85 DEG C for 4-6 h; after cooling, centrifugal separation is carried out, washing is carried out 3-5 times with deionized water, vacuum drying is carried out at 80-90 DEG C for 8-10 h, and grinding is carried out through a 200 mesh screen to obtain amino trimethylene phosphonic acid modified montmorillonite.

[0031] Optionally, the mass ratio of the montmorillonite, deionized water and amino trimethylene phosphonic acid is 1:(30-50):(0.3-0.6).

[0032] By using the above technical solution, the montmorillonite is ultrasonic dispersed in deionized water to form a suspension, amino trimethylene phosphonic acid is added to carry out stirring reaction, and then centrifugal separation, washing, drying and grinding are carried out to obtain amino trimethylene phosphonic acid modified montmorillonite. The amino trimethylene phosphonic acid can modify the montmorillonite and endow it with new properties. The amino trimethylene phosphonic acid can fully react with the montmorillonite, so that the surface properties of the montmorillonite are improved. The modified montmorillonite can play a synergistic role in the thickening agent system, enhance the tolerance of the thickening agent to high salt environment, further improve the salt tolerance of the thickening agent, and meet the use requirements of the thickening agent under high temperature and high salt working conditions of deep oil and gas reservoirs.

[0033] Optionally, the composite initiator is potassium sulfite and sodium bisulfite with a mass ratio of (2-3):1.

[0034] By using the above technical solution, the composite initiator with the above mass ratio can provide suitable initiation conditions, the reaction rate and polymerization degree can be accurately controlled in the polymerization process, the monomers such as acrylamide, AMPS and acryloyl morpholine can be fully polymerized to form a polymer skeleton with good molecular structure and properties, the thickening agent is provided with a stable tackifying base, and meanwhile, the composite initiator is also helpful for synergistic action with other functional components to improve the overall temperature resistance and salt tolerance of the thickening agent.

[0035] Optionally, the inhibitor is any one of sodium formate and hydroxypropyl methyl cellulose.

[0036] In a second aspect, the application provides a preparation method of a composite fracturing fluid thickening agent for oil and gas wells, which adopts the following technical solution:

[0037] The preparation method of the composite fracturing fluid thickening agent for oil and gas wells comprises the following steps:

[0038] S1, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acryloyl morpholine, an inhibitor and deionized water are mixed according to a proportion, stirring is carried out for 1-2 h to obtain a prepolymer solution, the composite initiator is added into the prepolymer solution, and polymerization is carried out at 40-50 DEG C under nitrogen protection for 4-8 h to obtain a polymer gel;

[0039] S2, adding sulfonated konjac gum, salt-tolerant synergistic additive and polyether amine modified organic zirconium crosslinking agent into the polymer gel, heating to 50-60 DEG C, continuing to stir for 1-3h, and then drying at 80-100 DEG C for 6-12h to obtain the thickening agent for composite fracturing fluid of oil and gas well.

[0040] By adopting the technical scheme, S1 mixes acrylamide, AMPS, acryloyl morpholine and inhibitor with deionized water to obtain a prepolymer solution, and then adds a composite initiator to polymerize under nitrogen protection to obtain a polymer gel. In this step, by accurately controlling the reaction conditions and the raw material ratio, the three monomers are polymerized under the action of the initiator to form a polymer skeleton with a specific molecular structure. Acrylamide provides a basic polymer skeleton, the strong hydrophilic sulfonic acid group of AMPS and the six-membered heterocyclic structure of acryloyl morpholine synergize to not only ensure the viscosity of the polymer but also improve the temperature resistance and salt tolerance through functional group synergy. S2 adds sulfonated konjac gum, salt-tolerant synergistic additive and polyether amine modified organic zirconium crosslinking agent into the polymer gel, heats and stirs to react, and then blows dry to obtain the thickening agent. In this step, the sulfonated konjac gum, the salt-tolerant synergistic additive and the polyether amine modified organic zirconium crosslinking agent are fully mixed with the polymer gel. The "double salt resistance barrier" and the interpenetrating network structure of the sulfonated konjac gum, the synergistic effect of the salt-tolerant synergistic additive and the stable crosslinking network of the polyether amine modified organic zirconium crosslinking agent together improve the temperature resistance and salt tolerance of the thickening agent, so that the thickening agent can meet the fracturing construction requirements under the high-temperature and high-salt working conditions of deep oil and gas reservoirs.

[0041] In summary, the present application has the following beneficial effects:

[0042] 1. In the present application, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and acryloyl morpholine are used as the basic polymer components. Acrylamide provides a basic polymer skeleton, 2-acrylamide-2-methylpropanesulfonic acid contains a strong hydrophilic sulfonic acid group, and the negative charge layer formed after ionization can resist the erosion of metal cations in a high-salt environment and avoid the curling of the molecular chain. Acryloyl morpholine contains a six-membered heterocyclic structure, and the conjugated system formed by the nitrogen atom and the oxygen atom in the ring can enhance the rigidity of the molecular chain and inhibit thermal motion at high temperatures. The three components synergize to not only ensure the viscosity of the polymer but also significantly improve the temperature resistance and salt tolerance of the thickening agent, effectively solving the defects of the existing thickening agents in terms of temperature resistance and salt tolerance under complex geological conditions, and meeting the fracturing requirements under the high-temperature and high-salt working conditions of deep oil and gas reservoirs.

[0043] 2, The polyether amine modified organic zirconium crosslinking agent is preferably adopted in the application, and is obtained by coordination polymerization reaction of zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine. The molecule contains zirconium-oxygen-carbon covalent bond, polyether segment and amino functional group at the same time. At high temperature, the zirconium-oxygen-carbon bond is not easy to break, and the crosslinking network integrity can be maintained. In a high salt environment, the steric hindrance effect of the polyether segment can hinder the contact between metal cations and polymer hydrophilic groups, solving the crosslinking failure problem of traditional crosslinking agents under complex working conditions, further enhancing the temperature resistance and salt resistance of the thickening agent, and ensuring the stability and effectiveness of the thickening agent under extreme working conditions. DETAILED DESCRIPTION

[0044] The application will be further described in detail below in combination with examples.

[0045] Preparation example of polyether amine modified organic zirconium crosslinking agent

[0046] Preparation example 1

[0047] The polyether amine modified organic zirconium crosslinking agent is prepared by the following method:

[0048] The raw materials zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine are weighed according to the molar ratio of 1:0.8:1.5:0.5, zirconium oxychloride is dissolved in ethylene glycol monomethyl ether, stirred at 40°C for 30 min until completely dissolved to obtain a zirconium salt solution; polyether amine D230 is added dropwise to the zirconium salt solution, the dropwise adding time is controlled for 30 min, after the dropwise adding is completed, the temperature is raised to 70°C, and the reaction is kept for 2 h; then triethanolamine is added, and the reaction is continued for 1 h, and then cooled to room temperature, and the unreacted ethylene glycol monomethyl ether is removed by rotary evaporation to obtain the polyether amine modified organic zirconium crosslinking agent.

[0049] Preparation example 2

[0050] The polyether amine modified organic zirconium crosslinking agent is prepared by the following method:

[0051] The raw materials zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine are weighed according to the molar ratio of 1:0.8:1.5:0.5, zirconium oxychloride is dissolved in ethylene glycol monomethyl ether, stirred at 40°C for 30 min until completely dissolved to obtain a zirconium salt solution; polyether amine D230 is added dropwise to the zirconium salt solution, the dropwise adding time is controlled for 30 min, after the dropwise adding is completed, the temperature is raised to 70°C, and the reaction is kept for 2 h; then triethanolamine is added, and the reaction is continued for 1 h, and then cooled to room temperature, and the unreacted ethylene glycol monomethyl ether is removed by rotary evaporation to obtain the polyether amine modified organic zirconium crosslinking agent.

[0052] Preparation example 3

[0053] The polyether amine modified organic zirconium crosslinking agent is prepared by the following method:

[0054] The raw materials zirconium oxychloride, polyetheramine D230, ethylene glycol monomethyl ether and triethanolamine were weighed according to a molar ratio of 1:1.2:2.5:1, zirconium oxychloride was dissolved in ethylene glycol monomethyl ether, and stirring was performed at 60℃ for 60 min until complete dissolution to obtain a zirconium salt solution; polyetheramine D230 was added dropwise into the zirconium salt solution, the dropwise adding time was controlled for 45 min, after the dropwise adding was completed, the temperature was increased to 78℃, and the reaction was performed for 3 h; then triethanolamine was added, and the reaction was continued for 1.5 h, and the reaction was cooled to room temperature; unreacted ethylene glycol monomethyl ether was removed by rotary evaporation to obtain a polyetheramine modified organic zirconium crosslinking agent.

[0055] Preparation example of sulfonated konjac gum

[0056] Preparation example 4

[0057] Sulfonated konjac gum was prepared by the following method:

[0058] 10 kg of konjac gum was dissolved in 120 kg of deionized water, and stirring was performed at 30℃ to form a colloidal solution, then 12 kg of chlorosulfonic acid was added, the temperature was increased to 55℃, and the reaction was performed for 3 h; after the reaction was completed, the pH was adjusted to neutral by using a sodium hydroxide solution with a mass concentration of 10%, and centrifugal separation and washing were performed until there was no chloride ion, and drying and crushing were performed to obtain sulfonated modified konjac gum.

[0059] Preparation example 5

[0060] Sulfonated konjac gum was prepared by the following method:

[0061] 10 kg of konjac gum was dissolved in 150 kg of deionized water, and stirring was performed at 35℃ to form a colloidal solution, then 15 kg of chlorosulfonic acid was added, the temperature was increased to 60℃, and the reaction was performed for 4 h; after the reaction was completed, the pH was adjusted to neutral by using a sodium hydroxide solution with a mass concentration of 12%, and centrifugal separation and washing were performed until there was no chloride ion, and drying and crushing were performed to obtain sulfonated modified konjac gum.

[0062] Preparation example 6

[0063] Sulfonated konjac gum was prepared by the following method:

[0064] 10 kg of konjac gum was dissolved in 180 kg of deionized water, and stirring was performed at 40℃ to form a colloidal solution, then 18 kg of chlorosulfonic acid was added, the temperature was increased to 65℃, and the reaction was performed for 5 h; after the reaction was completed, the pH was adjusted to neutral by using a sodium hydroxide solution with a mass concentration of 15%, and centrifugal separation and washing were performed until there was no chloride ion, and drying and crushing were performed to obtain sulfonated modified konjac gum.

[0065] Preparation example of salt-tolerant synergistic adjuvant

[0066] Preparation example 7

[0067] The salt-tolerant synergistic adjuvant was prepared by the following method:

[0068] 1 kg of montmorillonite was added to 30 kg of deionized water, ultrasonic dispersion for 20 min to form a montmorillonite suspension; amino trimethylene phosphonic acid was added, and stirred at 70℃ for 4h; after cooling, centrifugal separation, washed with deionized water 3 times, vacuum drying at 80℃ for 8h, grinding through 200 mesh sieve, to obtain amino trimethylene phosphonic acid modified montmorillonite.

[0069] Preparation Example 8

[0070] Salt-tolerant synergistic adjuvant, prepared by the following method:

[0071] 1 kg of montmorillonite was added to 40 kg of deionized water, ultrasonic dispersion for 25 min to form a montmorillonite suspension; amino trimethylene phosphonic acid was added, and stirred at 75℃ for 5h; after cooling, centrifugal separation, washed with deionized water 4 times, vacuum drying at 85℃ for 9h, grinding through 200 mesh sieve, to obtain amino trimethylene phosphonic acid modified montmorillonite.

[0072] Preparation Example 9

[0073] Salt-tolerant synergistic adjuvant, prepared by the following method:

[0074] 1 kg of montmorillonite was added to 50 kg of deionized water, ultrasonic dispersion for 30 min to form a montmorillonite suspension; amino trimethylene phosphonic acid was added, and stirred at 85℃ for 6h; after cooling, centrifugal separation, washed with deionized water 5 times, vacuum drying at 90℃ for 10h, grinding through 200 mesh sieve, to obtain amino trimethylene phosphonic acid modified montmorillonite.

[0075] Example

[0076] Example 1

[0077] A composite fracturing fluid thickening agent for oil and gas wells, the raw material components and the ratio are shown in Table 1, wherein the polyether amine modified organic zirconium crosslinking agent is selected from the polyether amine modified organic zirconium crosslinking agent prepared in Preparation Example 1, the sulfonated konjac gum is selected from the sulfonated konjac gum prepared in Preparation Example 4, the salt-tolerant synergistic adjuvant is selected from the salt-tolerant synergistic adjuvant prepared in Preparation Example 7, the composite initiator is potassium sulfite and sodium bisulfite with a mass ratio of 2:1, and the inhibitor is selected from sodium formate.

[0078] A composite fracturing fluid thickening agent for oil and gas wells, the preparation method comprises the following steps:

[0079] S1, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acryloyl morpholine, inhibitor and deionized water are mixed according to the ratio, stirred for 1h to obtain a prepolymer solution, the composite initiator is added to the prepolymer solution, and the polymer gel is obtained by polymerization at 40℃ for 4h under nitrogen protection;

[0080] S2, sulfonated konjac gum, salt-tolerant synergistic additive and polyether amine modified organic zirconium crosslinking agent are added into the polymer gel, the temperature is increased to 50 DEG C, and the stirring reaction is continued for 1h; then, air blowing drying is carried out at 80 DEG C for 6h, and an oil and gas well composite fracturing fluid thickening agent is obtained.

[0081] Example 2

[0082] An oil and gas well composite fracturing fluid thickening agent, raw material components and proportions are shown in Table 1, wherein the polyether amine modified organic zirconium crosslinking agent is selected from the polyether amine modified organic zirconium crosslinking agent prepared in Preparation Example 2, the sulfonated konjac gum is selected from the sulfonated konjac gum prepared in Preparation Example 5, the salt-tolerant synergistic additive is selected from the salt-tolerant synergistic additive prepared in Preparation Example 8, the composite initiator is potassium sulfite and sodium bisulfite with a mass ratio of 2.5:1, and the inhibitor is selected from hydroxypropyl methyl cellulose.

[0083] An oil and gas well composite fracturing fluid thickening agent, a preparation method thereof comprises the following steps:

[0084] S1, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acryloyl morpholine, inhibitor and deionized water are mixed according to the proportion, stirring is carried out for 1.5h, a prepolymer solution is obtained, the composite initiator is added into the prepolymer solution, and the polymer gel is obtained by polymerization under nitrogen protection at 45 DEG C for 6h;

[0085] S2, sulfonated konjac gum, salt-tolerant synergistic additive and polyether amine modified organic zirconium crosslinking agent are added into the polymer gel, the temperature is increased to 55 DEG C, and the stirring reaction is continued for 2h; then, air blowing drying is carried out at 90 DEG C for 9h, and an oil and gas well composite fracturing fluid thickening agent is obtained.

[0086] Example 3

[0087] An oil and gas well composite fracturing fluid thickening agent, raw material components and proportions are shown in Table 1, wherein the polyether amine modified organic zirconium crosslinking agent is selected from the polyether amine modified organic zirconium crosslinking agent prepared in Preparation Example 3, the sulfonated konjac gum is selected from the sulfonated konjac gum prepared in Preparation Example 6, the salt-tolerant synergistic additive is selected from the salt-tolerant synergistic additive prepared in Preparation Example 9, the composite initiator is potassium sulfite and sodium bisulfite with a mass ratio of 3:1, and the inhibitor is selected from hydroxypropyl methyl cellulose.

[0088] An oil and gas well composite fracturing fluid thickening agent, a preparation method thereof comprises the following steps:

[0089] S1, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acryloyl morpholine, inhibitor and deionized water are mixed according to the proportion, stirring is carried out for 2h, a prepolymer solution is obtained, the composite initiator is added into the prepolymer solution, and the polymer gel is obtained by polymerization under nitrogen protection at 50 DEG C for 8h;

[0090] S2, adding sulfonated konjac gum, salt-tolerant synergistic additive and polyether amine modified organic zirconium crosslinking agent into the polymer gel, and continuing to stir and react for 3 h at 60 DEG C; then drying at 100 DEG C for 12 h under air blowing to obtain a composite fracturing fluid thickening agent for oil and gas wells.

[0091] Table 1 Raw material components and proportions (kg) of the composite fracturing fluid thickening agent for oil and gas wells in Examples 1-3

[0092]

[0093] Example 4

[0094] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that the inhibitor used in the present example is hydroxypropyl methyl cellulose.

[0095] Example 5

[0096] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that the composite initiator used in the present example is potassium sulfite and sodium bisulfite in a mass ratio of 1:1.

[0097] Example 6

[0098] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that the salt-tolerant synergistic additive used in the present example is untreated montmorillonite.

[0099] Comparative Example

[0100] Comparative Example 1

[0101] A fracturing fluid thickening agent is prepared according to the method of Example 1 in the application file with the publication number CN119614177A and the name of a fracturing fluid thickening agent and its preparation method.

[0102] Comparative Example 2

[0103] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that an equal amount of sodium tetraborate decahydrate crosslinking agent is used instead of polyether amine modified organic zirconium crosslinking agent in the present comparative example.

[0104] Comparative Example 3

[0105] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that an equal amount of unmodified konjac gum is used instead of sulfonated konjac gum in the present comparative example.

[0106] Comparative Example 4

[0107] A composite fracturing fluid thickening agent for oil and gas wells, which is different from Example 1 in that no salt-tolerant synergistic additive is added in the present comparative example, and the difference is made up with acrylamide.

[0108] Performance test

[0109] I. Viscosity detection of thickening agent

[0110] The initial viscosity of the thickening agent prepared into fracturing fluid base fluid was determined according to SY / T5107-2016 "Water-based Fracturing Fluid Performance Evaluation Method", and the detection results are shown in Table 2.

[0111] II. Detection of temperature resistance of thickening agent

[0112] According to SY / T5107-2016 "Water-based Fracturing Fluid Performance Evaluation Method", the viscosity retention rate of the gel after cross-linking of the thickening agent was determined by simulating the high temperature environment (220℃) of deep oil and gas reservoirs, and the temperature resistance stability was evaluated. The detection results are shown in Table 2.

[0113] III. Detection of salt resistance of thickening agent

[0114] According to SY / T5107-2016 "Water-based Fracturing Fluid Performance Evaluation Method", NaCl, CaCl2 and MgCl2 were mixed in a mass ratio of 8:1:1 to prepare a simulated salinity brine, simulate the high salt environment (salinity 8x10 4 ~9x10 4 mg / L) of deep oil and gas reservoirs, and determine the viscosity retention rate of the gel after cross-linking of the thickening agent to evaluate its salt resistance stability. The detection results are shown in Table 2.

[0115] Table 2 Detection results

[0116]

[0117] As can be seen from Table 2, the viscosity of the thickening agent of Examples 1-3 is between 132-137 mPa·s, the temperature viscosity retention rate is between 90.8%-93.1%, and the salt viscosity retention rate is between 91.6%-94.7%, indicating that the thickening agent prepared by different raw material ratios has good viscosity, temperature resistance and salt resistance, and the adjustment of the raw material ratio within a certain range has a relatively stable effect on the performance.

[0118] The difference between Example 4 and Example 1 is that the inhibitor is hydroxypropyl methyl cellulose. The detection results show that the viscosity, temperature viscosity retention rate and salt viscosity retention rate are not much different from Example 1, indicating that in the technical scheme of the present application, the use of sodium formate or hydroxypropyl methyl cellulose as an inhibitor has little effect on the overall performance of the thickening agent.

[0119] The difference between Example 5 and Example 1 is that the mass ratio of the composite initiator is different. The detection results show that the viscosity, temperature viscosity retention rate and salt viscosity retention rate are all lower than Example 1, indicating that when the mass ratio of the composite initiator is 2:1, it can better provide suitable initiation conditions, accurately control the reaction rate and polymerization degree, and make the performance of the thickening agent better.

[0120] Example 6 is different from Example 1 in that the salt-resistant synergistic additive is untreated montmorillonite, and the test results show that the salt-resistant viscosity retention rate is significantly lower than that of Example 1, indicating that the amino-trimethylene phosphonic acid modified montmorillonite as a salt-resistant synergistic additive can better enhance the tolerance of the thickening agent to high-salt environment and improve the salt-resistant performance.

[0121] The test results of the thickening agent of Comparative Example 1 show that the viscosity, temperature-resistant viscosity retention rate and salt-resistant viscosity retention rate are all lower than those of the examples of the present application, indicating that the thickening agent prepared by the technical scheme of the present application is superior to the thickening agent in the related art in terms of temperature-resistant and salt-resistant performance.

[0122] Comparative Example 2 uses an equal amount of sodium tetraborate decahydrate crosslinking agent instead of polyether amine modified organic zirconium crosslinking agent, and the test results show that the viscosity, temperature-resistant viscosity retention rate and salt-resistant viscosity retention rate are all lower than those of Example 1, indicating that the polyether amine modified organic zirconium crosslinking agent has obvious advantages in improving the temperature-resistant and salt-resistant performance of the thickening agent, and the traditional crosslinking agent is prone to crosslinking failure under complex working conditions.

[0123] Comparative Example 3 uses an equal amount of unmodified konjac gum instead of sulfonated konjac gum, and the test results show that the temperature-resistant viscosity retention rate and salt-resistant viscosity retention rate are both lower than those of Example 1, indicating that the "double salt-resistant barrier" formed by the sulfonic acid group introduced by the sulfonated konjac gum and the interpenetrating network structure formed with the polymer skeleton play an important role in improving the temperature-resistant and salt-resistant performance of the thickening agent, and the natural konjac gum cannot meet the requirements.

[0124] Comparative Example 4 does not add a salt-resistant synergistic additive, and the test results show that the salt-resistant viscosity retention rate is significantly lower than that of Example 1, indicating that the salt-resistant synergistic additive is indispensable to improve the salt-resistant performance of the thickening agent.

[0125] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A composite fracturing fluid viscosifier for oil and gas wells, characterized in that, The raw material is prepared by including the following components: Acrylamide 30-50 parts; 2-Acrylamide-2-methylpropane sulfonic acid 20-35 parts; Acryloyl morpholine 10-25 parts; Polyether amine modified organic zirconium crosslinking agent 3-8 parts; Sulfonated konjac gum 2-6 parts; Salt-tolerant synergistic aid 1-5 parts; Composite initiator 0.5-2 parts; Inhibitor 0.1-0.8 parts; Deionized water 150-180 parts; The polyether amine modified organic zirconium crosslinking agent is prepared by the following method: Dissolve zirconium oxychloride in ethylene glycol monomethyl ether, stir at 40-60℃ for 30-60min until completely dissolved to obtain a zirconium salt solution; add polyether amine D230 dropwise to the zirconium salt solution, the dropwise adding time is controlled at 30-45min, after the dropwise adding is completed, warm to 70-85℃, and keep the temperature for 2-4h; then add triethanolamine, continue to react for 1-2h, cool to room temperature, and rotary evaporate to remove unreacted ethylene glycol monomethyl ether to obtain the polyether amine modified organic zirconium crosslinking agent; the molar ratio of the zirconium oxychloride, polyether amine D230, ethylene glycol monomethyl ether and triethanolamine is 1:(0.8-1.2):(1.5-2.5):(0.5-1); The sulfonated konjac gum is obtained by modifying konjac gum with chlorosulfonic acid.

2. The viscosifier for composite fracturing fluid for oil and gas wells according to claim 1, characterized in that, The sulfonated konjac gum is prepared by the following method: Dissolve konjac gum in deionized water, stir to form a colloidal solution at 30-40℃, then add chlorosulfonic acid, warm to 55-65℃, and keep the temperature for 3-5h; after the reaction is completed, adjust the pH to neutral with 10%-15% sodium hydroxide solution, centrifugal separation, wash until no chloride ions, dry and crush to obtain the sulfonated modified konjac gum.

3. The viscosifier for composite fracturing fluid for oil and gas wells according to claim 2, characterized in that, The mass ratio of the konjac gum, deionized water and chlorosulfonic acid is 1:(12-18):(1.2-1.8).

4. The viscosifier for composite fracturing fluid for oil and gas wells according to claim 1, characterized in that, The salt-tolerant synergistic aid is prepared by the following method: Add montmorillonite to deionized water, ultrasonic dispersion for 20-30min to form a montmorillonite suspension; add amino trimethylene phosphonic acid, stir and react at 70-85℃ for 4-6h; after cooling, centrifugal separation, wash with deionized water for 3-5 times, vacuum dry at 80-90℃ for 8-10h, and grind through a 200 mesh sieve to obtain amino trimethylene phosphonic acid modified montmorillonite.

5. The complex fracturing fluid viscosifier for oil and gas wells according to claim 4, characterized in that, The mass ratio of the montmorillonite, deionized water and amino trimethylene phosphonic acid is 1:(30-50):(0.3-0.6).

6. The viscosifier for composite fracturing fluid for oil and gas wells as claimed in claim 1, wherein, The composite initiator is potassium sulfite and sodium bisulfite with a mass ratio of (2-3):

1.

7. The complex fracturing fluid viscosifier for oil and gas wells as claimed in claim 1, wherein, The inhibitor is any one of sodium formate and hydroxypropyl methyl cellulose.

8. A process for the preparation of the composite fracturing fluid viscosifier for oil and gas wells as claimed in any one of claims 1 to 7, wherein, Including the following steps: S1, mix acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acryloyl morpholine, inhibitor and deionized water according to the ratio, stir for 1-2h to obtain a prepolymer solution, add a composite initiator to the prepolymer solution, and keep the temperature at 40-50℃ for 4-8h under nitrogen protection to obtain a polymer gel; S2, adding sulfonated konjac gum, salt-tolerant synergistic adjuvant and polyether amine modified organic zirconium crosslinking agent into the polymer gel, heating to 50-60℃ and continuing to stir for 1-3h; then drying at 80-100℃ with air blowing for 6-12h to obtain the composite fracturing fluid thickening agent for oil and gas wells.

Images