Low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water and preparation method thereof

Abstract

The present application relates to the field of oil and gas production, in particular to a low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water and a preparation method thereof; the preparation raw materials include the following mass fractions: high salt-resistant thickening agent containing strong hydrophilic groups and betaine zwitterionic groups 30-55 parts; salt-resistant filtration reducer 5-10 parts; organic phosphonic acid or organic phosphonate 1-5 parts; suspending agent 30-64 parts; the low filtration loss salt-resistant thickening agent of the present application realizes strong viscosity increase, strong drag reduction and strong sand carrying performance under high salinity and complex water quality through the carboxylic acid anion and quaternary ammonium cation of the high salt-resistant thickening agent, can greatly improve the high salt resistance, high valence metal ion interference resistance and filtration loss of the fracturing fluid, and solve the problems of insufficient salt resistance, poor high valence metal ion interference resistance and large filtration loss of the fracturing fluid in the prior art when directly matched with flowback fluid and produced water.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas stimulation, in particular to a low filtration loss anti-salt thickening agent for direct matching of flowback fluid and produced water and a preparation method thereof. BACKGROUND

[0002] With the continuous progress and improvement of oil and gas exploration and development technology and means, a large amount of unconventional oil and gas (tight gas, shale oil and gas, coal rock gas, etc.) has been continuously discovered and has become an important replacement field for oil and gas development, making a great contribution to global energy supply. Unconventional oil and gas reservoirs are dense, and it is difficult to develop recoverable reserves. Large-scale volume fracturing has become a necessary way for the development and production of unconventional oil and gas.

[0003] During fracturing and production, a large amount of high salinity flowback fluid and produced water is discharged from the well bottom or produced to the ground in an explosive trend. Under the current environmental protection requirements, direct matching of flowback fluid and produced water for fracturing fluid is the best technical approach. However, flowback fluid and produced water generally have the characteristics of complex composition, high salinity, high content of high-valence metal ions (Ca 2+ , Mg 2+ , Fe 2+ , Fe 3+ ), high content of solid suspended matter and high oil content. During the reuse of flowback fluid and produced water, high salinity (especially high-valence metal ions) can significantly weaken the hydration swelling ability and dissolution performance of the fracturing thickening agent, cause the molecular chain of polyacrylamide thickening agent to curl, and cause the viscosity increasing ability, drag reduction effect, sand carrying performance and temperature resistance and shear resistance performance of the fracturing fluid to decrease significantly, and even Ca 2+ , Mg 2+ , Fe 3+ , etc. can produce flocculation with the fracturing fluid and pollute and block the formation. At the same time, due to the decrease in the viscosity increasing ability of the flowback fluid and produced water directly matched fracturing fluid, the viscoelasticity of the medium and low viscosity system is insufficient, and the filtration loss of the fracturing fluid is significantly increased (more prominent when there are developed natural fractures in the reservoir), which significantly affects the overall fracture stimulation and production increasing effect. Therefore, it is urgent to develop a low filtration loss anti-salt fracturing thickening agent and fracturing fluid suitable for direct matching of flowback fluid and produced water.

[0004] At present, the development of anti-salt fracturing thickening agent and fracturing fluid for flowback fluid and produced water is the main technical means, in which the main way is to introduce anti-salt monomers containing sulfonic acid groups, amphiphilic monomers containing hydrophobic groups and other groups that can increase the rigidity of the molecular chain into the molecular structure of the thickening agent, use the salt tolerance of the sulfonic acid group, the self-association of the hydrophobic group and the rigidity of the molecular chain to improve the anti-salt performance, and then construct an anti-salt fracturing fluid system based on the thickening agent.

[0005] However, the above technical means can solve the problems under the condition of direct matching of flowback fluid and produced water to a certain extent, but there are still problems such as limited increase in viscosity, reduction in resistance, limited improvement in sand carrying performance, high additive amount, high filtration loss when the viscosity is low, etc., so it is difficult to realize the application of low additive amount under the condition of direct matching of flowback fluid and produced water. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water and a preparation method thereof, which combines a high salt-resistant thickening agent containing strong hydrophilic groups and betaine zwitterion groups, a salt-resistant filtration reducer with strong filtration reduction performance, and an organic phosphonic acid or organic phosphonate with excellent chelation and scale inhibition ability. The carboxylate anion (-COO - ) and quaternary ammonium cation of the high salt-resistant thickening agent form an internal salt, and the sulfonic acid group and the associated group synergistically resist salt to achieve strong viscosity increase, high resistance reduction, and strong sand carrying performance under high salinity and complex water quality. The salt-resistant filtration reducer achieves low filtration performance under high salinity and complex water quality. The organic phosphonic acid or organic phosphonate has a strong binding ability to high-valence metal ions such as Ca 2+ , Mg 2+ , Fe 3+ , etc., which can inhibit the adverse effects of high-valence ions on the performance of directly matched fracturing fluid, greatly improve the anti-high salt and anti-high valence metal ion interference ability of the fracturing fluid, and reduce the filtration loss, thereby solving the problems of insufficient salt resistance, poor anti-high valence metal ion interference ability, and large filtration loss of the fracturing fluid in the prior art when directly matched with flowback fluid and produced water.

[0007] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0008] The present application provides a low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water, which comprises the following preparation raw materials in mass fraction:

[0009] A high salt-resistant thickening agent containing strong hydrophilic groups and betaine zwitterion groups, 30-55 parts;

[0010] A salt-resistant filtration reducer, 5-10 parts;

[0011] An organic phosphonic acid or organic phosphonate, 1-5 parts;

[0012] A suspending agent, 30-64 parts;

[0013] The high salt-resistant thickening agent containing strong hydrophilic groups and betaine zwitterion groups is obtained by copolymerization of acrylamide, a salt-resistant monomer, sodium acrylamide long-chain alkyl sulfonate, and a carboxyl betaine containing an unsaturated double bond, and has a viscosity average molecular weight in the range of 10-150 million Daltons;

[0014] wherein the salt-resistant fluid loss additive is a copolymer of 2-acrylamido-2-methylpropane sulfonic acid, acrylic acid, N,N-dimethyl acrylamide and maleic anhydride, and has a viscosity average molecular weight ranging from 2 to 35 million Daltons;

[0015] wherein the suspending agent is a mixture of an organic phase, an emulsifier, a stabilizer and a dispersing surfactant;

[0016] The salt-resistant monomer is sodium 2-acrylamido-2-methylpropane sulfonate, sodium p-acrylamidobenzenesulfonate, sodium p-styrenesulfonate or sodium p-allylbenzenesulfonate.

[0017] As a further improvement of the present application, the mass ratio of the acrylamide, the salt-resistant monomer, the sodium acrylamido long chain alkyl sulfonate and the carboxybetaine containing unsaturated double bond is 1:(0.02-0.06):(0.005-0.012):(0.003-0.008).

[0018] As a further improvement of the present application, the mass ratio of the 2-acrylamido-2-methylpropane sulfonic acid, the acrylic acid, the N,N-dimethyl acrylamide and the maleic anhydride is 1:(0.02-0.03):(0.06-0.08):(0.01-0.012).

[0019] As a further improvement of the present application, the molecular structure of the high salt-resistant thickening agent containing strong hydrophilic group and betaine zwitterion group is:

[0020] .

[0021] As a further improvement of the present application, the structure of R1 is:

[0022] .

[0023] As a further improvement of the present application, the structure of R2 is:

[0024]

[0025] wherein m is 9-13.

[0026] As a further improvement of the present application, the structure of R3 is:

[0027]

[0028] wherein n is 1-2.

[0029] As a further improvement of the present application, the sodium acrylamido long chain alkyl sulfonate is sodium 2-acrylamidododecyl sulfonate, sodium 2-acrylamidotetradecyl sulfonate or sodium 2-acrylamido hexadecyl sulfonate.

[0030] As a further improvement of the present application, the carboxybetaine containing unsaturated double bond is carboxybetaine acrylamide or allyl carboxybetaine.

[0031] As a further improvement of the present application, the molecular structure of the salt-resistant fluid loss additive is:

[0032] .

[0033] As a further improvement of the present application, the mass ratio of the organic phase, emulsifier, stabilizer, and dispersing surfactant is 1:0.02:0.01:0.015.

[0034] The present application provides a preparation method of a low filtration salt-resistant thickening agent for direct matching of flowback fluid and produced water as described above, comprising the following steps:

[0035] S1, acrylamide, salt-resistant monomer, acrylamide-based long-chain alkyl sodium sulfonate, and carboxybetaine containing unsaturated double bond are stirred and dissolved in deionized water, the pH is adjusted to 8.5-8.8, and a mixed solution with a total monomer mass concentration of 25%-30% is formed;

[0036] S2, the mixed solution is cooled to 3-5°C, a molecular regulator and an inorganic compound oxidant are sequentially added, an oxidation / reduction initiator is added after 2 minutes, an azo initiator is added after 4 minutes to initiate polymerization, and a reaction product is obtained; the reaction product is placed in an adiabatic condition and reacted for 6-7 hours to obtain a colloidal product;

[0037] S3, the colloidal product is cut and dried at 95-100°C for 6-8 hours, and after crushing and sieving, a high-salt-resistant thickening agent in powder form is obtained;

[0038] S4, at room temperature, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, N,N-dimethyl acrylamide, and maleic anhydride are dissolved and stirred in deionized water containing ultra-fine calcium sulfate, the pH is adjusted to 6.2-6.5, and a molecular regulator is added to form a reaction mixture;

[0039] S5, the reaction mixture is heated to 63-65°C, an initiator is added and stirred, the temperature is raised to 80-82°C after 6-7 minutes of reaction, and the reaction is kept for 75-85 minutes to obtain a viscous product;

[0040] S6, the viscous product is dried at 115-120°C for 7.5-8 hours, and sieved to obtain a salt-resistant fluid loss additive in powder form;

[0041] S7, at room temperature, an organic phase, an emulsifier, a stabilizer, and a dispersing surfactant are mixed and emulsified by stirring for 2-3 hours to obtain a suspending agent;

[0042] S8, the high salt resistance thickening agent obtained in S3 and the salt resistance filtrate reducer obtained in S6 are added into the suspending agent, mixed for 1.5h-2h, then the organic phosphonic acid or the organic phosphonic acid salt is added, and the stirring is continued for 30min-40min, to obtain the low filtrate salt resistance thickening agent.

[0043] As a further improvement of the present application, the pH adjusting agent for adjusting pH in S1 is one or more of acetic acid, citric acid, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium hydroxide.

[0044] As a further improvement of the present application, the molecular regulator in S2 is one or more of sodium formate, thiourea, isopropyl alcohol or urea.

[0045] The inorganic compound oxidant is one or more of ammonium metavanadate, ammonium cerium sulfate or cerium ammonium nitrate.

[0046] The oxidation / reduction initiator is one or both of hydrogen peroxide / ferrous chloride mixture or tert-butyl hydroperoxide / ferrous ammonium sulfate / sodium bisulfite mixture.

[0047] The azo initiator is one or more of azobisdiisopropylimidazoline, azobisdiisobutylamidine hydrochloride, azobisdiisobutylimidazoline hydrochloride or azobiscyanopentanoic acid.

[0048] As a further improvement of the present application, the addition amount of the molecular regulator in S2 is 0.04%-0.042% of the mass of the acrylamide monomer.

[0049] The total addition amount of the oxidation / reduction initiator and the azo initiator is 0.05%-0.055% of the mass of the acrylamide monomer.

[0050] The mass ratio of the inorganic compound oxidant, the oxidation / reduction initiator and the azo initiator is 0.1:1:0.2.

[0051] As a further improvement of the present application, the pH adjusting agent for adjusting pH in S4 is one or more of sodium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonia, sodium hydroxide, potassium hydroxide or triethanolamine.

[0052] The molecular regulator in S4 is one or more of mercaptoethanol, mercaptoacetic acid, tert-dodecyl mercaptan, dodecyl mercaptan, n-butyl mercaptan or sodium hypophosphite.

[0053] As a further improvement of the present application, the initiator in S5 is one or more of sodium persulfate, ammonium persulfate, potassium persulfate, sodium persulfate / sodium bisulfite mixture, ammonium persulfate / sodium bisulfite mixture or potassium persulfate / sodium bisulfite mixture.

[0054] As a further improvement of the application, the organic phase in S7 is one or more of kerosene, white oil No. 5, white oil No. 10, white oil No. 15 or transformer oil;

[0055] The emulsifier is one or more of sorbitan monooleate, polyoxyethylene sorbitan monooleate, sorbitan ester or sodium dioctyl sulfosuccinate;

[0056] The stabilizer is one or more of organically modified bentonite, organically modified attapulgite or organically modified nanocellulose;

[0057] The dispersible surfactant is one or both of alkylphenol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

[0058] As a further improvement of the application, the organic phosphonic acid in S8 is one or more of diethylenetriamine pentamethylene phosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, hydroxyl phosphonoacetic acid, aminotrimethylene phosphonic acid; the organic phosphonate is one or both of hydroxyethylidene diphosphonic acid sodium or ethylenediamine tetraamine methylene phosphonic acid sodium.

[0059] The application has the following technical effects relative to the prior art:

[0060] The application introduces a high-salt-tolerant thickening agent containing a strong hydrophilic group and a betaine zwitterion group, a salt-tolerant fluid loss additive with strong fluid loss reduction performance, and an organic phosphonic acid or organic phosphonate with excellent chelation and scale inhibition capacity; the carboxylate anion and quaternary ammonium cation of the high-salt-tolerant thickening agent form an internal salt, and the carboxyl group and the associated group synergistically resist salt to achieve strong viscosity increase, high drag reduction and strong sand carrying performance in high salinity complex water, the salt-tolerant fluid loss additive is used to achieve low fluid loss performance in high salinity complex water, and the organic phosphonic acid or organic phosphonate is used to inhibit the adverse effects of high-valence metal ions such as Ca 2+ , Mg 2+ , Fe 3+ on the performance of the straight fracturing fluid, greatly improve the high-salt resistance, high-valence metal ion interference resistance and fluid loss reduction capacity of the fracturing fluid, and simultaneously solve the problems of insufficient salt resistance, poor high-valence metal ion interference resistance and large fluid loss of the existing fracturing fluid when directly matched with flowback fluid and produced water.

[0061] The low fluid loss salt-tolerant thickening agent of the application has the following performance under the conditions of 150,000 mg / L salinity (calcium and magnesium ion content of 8,000 mg / L, iron ion content of 500 mg / L) flowback fluid and produced water:

[0062] The viscosity increase time is less than 18 s;

[0063] The viscosity release rate at 1 min 30 s is greater than 90%;

[0064] The low filtration loss salt-resistant thickening agent has a mass concentration of 0.12%, and the drag reduction rate is greater than 76.8%; the static filtration coefficient is less than 0.89*10 -4 m / min 1 / 2 ; the dynamic filtration coefficient is less than 1.07*10 -4 m / min 1 / 2 ;

[0065] The low filtration loss salt-resistant thickening agent has a mass concentration of 1.0%, and the viscosity at room temperature is greater than 102 mPa·s;

[0066] The stable viscosity after shearing at 120 DEG C for 170 s -1 is greater than 56.1 mPa·s; the viscosity of the gel breaking liquid is less than 4.82 mm 2 / s, and the residue content is less than 50 mg / L within 2 h under the condition of 90 DEG C and 0.025% ammonium persulfate. DETAILED DESCRIPTION

[0067] Hereinafter, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application.

[0068] In the present application, unless specifically defined and limited otherwise, the terms "mount", "connect", "connection", "fixed", and the like should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection, and can also be communication; can be directly connected, can also be indirectly connected through an intermediate medium, and can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0069] In the present application, unless specifically defined and limited otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or can include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0070] It should be understood that the terms "comprises" and "comprising," when used in this specification and the following claims, indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0071] It should also be understood that the terms used in the specification and the appended claims are intended to describe particular embodiments and do not intend to limit the present application. As used in the specification and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0072] It should further be understood that the term "and / or" used in the specification and the appended claims means one or more of the associated listed items and all possible combinations of the items, and includes these combinations.

[0073] Embodiment 1

[0074] The embodiment provides a preparation method of a high salt-resistant thickening agent in a low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water, and the specific steps are as follows:

[0075] Acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, 2-acrylamide tetradecyl sodium sulfonate and carboxy betaine acrylamide are weighed according to the mass ratio of 1:0.02:0.005:0.003, to obtain 275.23 g of acrylamide, 5.5 g of 2-acrylamide-2-methylpropanesulfonic acid sodium, 1.38 g of 2-acrylamide tetradecyl sodium sulfonate and 0.83 g of carboxy betaine acrylamide. 694 g of deionized water is added into a 1000 mL beaker, and the above monomers are sequentially added into the deionized water, stirred uniformly until completely dissolved, to obtain a mixed solution with a total mass concentration of 30%.

[0076] 1.05 g of sodium hydroxide and 5 g of sodium carbonate are added into the mixed solution, and the pH value of the solution is adjusted to 8.6; then the obtained solution is cooled to 5°C in an ice-salt water bath; 0.11 g of sodium formate and 0.01 g of ammonium metavanadate are sequentially added, stirred for 2 min, and then 0.1 g of a hydrogen peroxide / ferrous chloride mixture is added; after continuing to react for 4 min, 0.02 g of azobis diisopropyl imidazoline is added to initiate the polymerization reaction, to obtain a reaction product.

[0077] The reaction product is transferred into an adiabatic polymerization device, and the reaction is continued for 6 h to obtain a colloidal product. The colloidal product is cut into pieces, dried at 100°C for 6 hours, and finally crushed and passed through an 80 mesh sieve, to obtain a high salt-resistant thickening agent GKY-1 in powder form;

[0078] The high salt-resistant thickening agent GKY-1 obtained in Example 1 was determined by a Ubbelohde viscometer according to the standard of GB / T 12005.10-1992 to have a viscosity average molecular weight of 15 million Daltons.

[0079] Example 2

[0080] The Example 2 is basically the same as Example 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium salt, 2-acrylamidoglycol sulfonic acid sodium salt, and carboxybetaine acrylamide in the Example 2 is 1:0.06:0.005:0.003.

[0081] The high salt-resistant thickening agent GKY-2 obtained in Example 2 was determined by a Ubbelohde viscometer according to the standard of GB / T 12005.10-1992 to have a viscosity average molecular weight of 14.56 million Daltons.

[0082] Example 3

[0083] The Example 3 is basically the same as Example 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium salt, 2-acrylamidoglycol sulfonic acid sodium salt, and carboxybetaine acrylamide in the Example 3 is 1:0.02:0.012:0.003.

[0084] The high salt-resistant thickening agent GKY-3 obtained in Example 3 was determined by a Ubbelohde viscometer according to the standard of GB / T 12005.10-1992 to have a viscosity average molecular weight of 13.24 million Daltons.

[0085] Example 4

[0086] The Example 4 is basically the same as Example 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium salt, 2-acrylamidoglycol sulfonic acid sodium salt, and carboxybetaine acrylamide in the Example 4 is 1:0.06:0.012:0.003.

[0087] The high salt-resistant thickening agent GKY-4 obtained in Example 4 was determined by a Ubbelohde viscometer according to the standard of GB / T 12005.10-1992 to have a viscosity average molecular weight of 12.11 million Daltons.

[0088] Example 5

[0089] The embodiment is basically the same as embodiment 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, 2-acrylamidyl tetradecyl sodium sulfonate, and carboxy betaine acrylamide in the embodiment is 1:0.02:0.005:0.008;

[0090] The high salt-resistant thickening agent GKY-5 in powder form is prepared in the embodiment, and the viscosity average molecular weight of the high salt-resistant thickening agent GKY-5 obtained in embodiment 5 is determined to be 14 million Dalton by using an Ubbelohde viscometer according to the standard of “GB / T12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0091] Embodiment 6

[0092] The embodiment is basically the same as embodiment 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, 2-acrylamidyl tetradecyl sodium sulfonate, and carboxy betaine acrylamide in the embodiment is 1:0.06:0.005:0.008;

[0093] The high salt-resistant thickening agent GKY-6 in powder form is prepared in the embodiment, and the viscosity average molecular weight of the high salt-resistant thickening agent GKY-6 obtained in embodiment 6 is determined to be 13.78 million Dalton by using an Ubbelohde viscometer according to the standard of “GB / T12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0094] Embodiment 7

[0095] The embodiment is basically the same as embodiment 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, 2-acrylamidyl tetradecyl sodium sulfonate, and carboxy betaine acrylamide in the embodiment is 1:0.02:0.012:0.008;

[0096] The high salt-resistant thickening agent GKY-7 in powder form is prepared in the embodiment, and the viscosity average molecular weight of the high salt-resistant thickening agent GKY-7 obtained in embodiment 7 is determined to be 11.79 million Dalton by using an Ubbelohde viscometer according to the standard of “GB / T12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0097] Embodiment 8

[0098] The embodiment is basically the same as embodiment 1, except that the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, 2-acrylamidyl tetradecyl sodium sulfonate, and carboxy betaine acrylamide in the embodiment is 1:0.06:0.012:0.008;

[0099] The high salt-resistant thickening agent GKY-8 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-8 obtained in Example 8 is determined to be 11 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0100] Example 9

[0101] This example is basically the same as Example 1, except that an equal amount of sodium p-acrylamidobenzenesulfonate is used instead of sodium 2-acrylamido-2-methylpropanesulfonate in this example.

[0102] The high salt-resistant thickening agent GKY-9 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-9 obtained in Example 9 is determined to be 14.23 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0103] Example 10

[0104] This example is basically the same as Example 8, except that an equal amount of sodium p-acrylamidobenzenesulfonate is used instead of sodium 2-acrylamido-2-methylpropanesulfonate in this example.

[0105] The high salt-resistant thickening agent GKY-10 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-10 obtained in Example 10 is determined to be 10.43 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0106] Example 11

[0107] This example is basically the same as Example 1, except that an equal amount of sodium p-styrenesulfonate is used instead of sodium 2-acrylamido-2-methylpropanesulfonate in this example.

[0108] The high salt-resistant thickening agent GKY-11 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-11 obtained in Example 11 is determined to be 14.76 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0109] Example 12

[0110] This example is basically the same as Example 8, except that an equal amount of sodium p-styrenesulfonate is used instead of sodium 2-acrylamido-2-methylpropanesulfonate in this example.

[0111] The high salt-resistant thickening agent GKY-12 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-12 obtained in Example 12 is determined to be 10.74 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0112] Example 13

[0113] This example is basically the same as Example 1, except that an equal amount of sodium p-allylbenzenesulfonate is used instead of sodium 2-acrylamido-2-methylpropane sulfonate in this example.

[0114] The high salt-resistant thickening agent GKY-13 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-13 obtained in Example 13 is determined to be 14.82 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0115] Example 14

[0116] This example is basically the same as Example 8, except that an equal amount of sodium p-allylbenzenesulfonate is used instead of sodium 2-acrylamido-2-methylpropane sulfonate in this example.

[0117] The high salt-resistant thickening agent GKY-14 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-14 obtained in Example 14 is determined to be 10.54 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0118] Example 15

[0119] This example is basically the same as Example 1, except that an equal amount of allyl carboxybetaine is used instead of carboxybetaine acrylamide in this example.

[0120] The high salt-resistant thickening agent GKY-15 in powder form is prepared in this example. The viscosity average molecular weight of the high salt-resistant thickening agent GKY-15 obtained in Example 15 is determined to be 14.12 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0121] Example 16

[0122] This example is basically the same as Example 8, except that an equal amount of allyl carboxybetaine is used instead of carboxybetaine acrylamide in this example.

[0123] The high salt-resistant thickening agent GKY-16 in powder form is prepared in this example. The viscosity-average molecular weight of the high salt-resistant thickening agent GKY-16 obtained in Example 16 is determined to be 10.13 million Dalton by using an Ubbelohde viscometer according to the standard of “GB / T 12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0124] Example 17

[0125] The preparation method of the salt-resistant fluid loss additive in the low fluid loss salt-resistant thickening agent for direct matching of flowback fluid and produced water is provided in this example, and the specific steps are as follows:

[0126] The mass concentration of the salt-resistant fluid loss additive in this example is fixed at 20%. 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride are weighed according to a mass ratio of 1:0.02:0.06:0.01 to obtain 275.2 g of 2-acrylamide-2-methylpropanesulfonic acid, 5.5 g of acrylic acid, 16.5 g of N,N-dimethylacrylamide, and 2.75 g of maleic anhydride. At room temperature, 6.7 g of ultra-fine calcium sulfate is added to a 1000 mL beaker containing deionized water, and stirred thoroughly. The above monomers are sequentially added to the deionized water, stirred uniformly until completely dissolved, and then 81.2 g of sodium carbonate is slowly added. The pH value is adjusted to 6.5, and then 1.4 g of mercaptoethanol is added. The reaction mixture is formed by thoroughly stirring and dissolving.

[0127] The reaction mixture is placed in a constant-temperature water bath and heated to a temperature of 63°C under continuous stirring. Then, 0.12 g of ammonium persulfate / sodium bisulfite mixture is slowly added. After uniform stirring, the stirring is stopped, and the mixture is left to stand for 6 min before starting the reaction. The temperature is quickly raised to 80°C, and the reaction is kept at this temperature for 75 min to obtain a viscous product. The viscous product is dried at 120°C for 8 h, and finally sieved through an 80-mesh screen to obtain the salt-resistant fluid loss additive KYJS-1 in powder form.

[0128] The viscosity-average molecular weight of the salt-resistant fluid loss additive KYJS-1 obtained in Example 17 is determined to be 3.5 million Dalton by using an Ubbelohde viscometer (0.55 mm inner diameter of capillary) according to the standard of “GB / T 12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0129] Example 18

[0130] This example is basically the same as Example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.03:0.06:0.01.

[0131] The anti-salt type fluid loss additive KYJS-2 in powder form is prepared in this example, and the viscosity average molecular weight of the high salt-resistant thickening agent KYJS-2 obtained in Example 18 is determined to be 3.2 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0132] Example 19

[0133] This example is basically the same as Example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.02:0.08:0.01.

[0134] The anti-salt type fluid loss additive KYJS-3 in powder form is prepared in this example, and the viscosity average molecular weight of the high salt-resistant thickening agent KYJS-3 obtained in Example 19 is determined to be 2.86 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0135] Example 20

[0136] This example is basically the same as Example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.03:0.08:0.01.

[0137] The anti-salt type fluid loss additive KYJS-4 in powder form is prepared in this example, and the viscosity average molecular weight of the high salt-resistant thickening agent KYJS-4 obtained in Example 20 is determined to be 2.86 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0138] Example 21

[0139] This example is basically the same as Example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.02:0.06:0.012.

[0140] The anti-salt type fluid loss additive KYJS-5 in powder form is prepared in this example, and the viscosity average molecular weight of the high salt-resistant thickening agent KYJS-5 obtained in Example 21 is determined to be 2.57 million Dalton by using an Ubbelohde viscometer according to the standard of "GB / T12005.10-1992 Determination of molecular weight of polyacrylamide".

[0141] Example 22

[0142] This example is basically the same as example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.03:0.06:0.012;

[0143] In this example, the high-salt-resistant fluid loss additive KYJS-6 obtained in example 22 is in powder form. The viscosity average molecular weight of the high-salt-resistant fluid loss additive KYJS-6 obtained in example 22 is determined to be 2.39 million Daltons by a Ubbelohde viscometer according to the standard of “GB / T 12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0144] Example 23

[0145] This example is basically the same as example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.02:0.08:0.012;

[0146] In this example, the high-salt-resistant fluid loss additive KYJS-7 obtained in example 23 is in powder form. The viscosity average molecular weight of the high-salt-resistant fluid loss additive KYJS-7 obtained in example 23 is determined to be 2.15 million Daltons by a Ubbelohde viscometer according to the standard of “GB / T 12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0147] Example 24

[0148] This example is basically the same as example 17, except that the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and maleic anhydride in this example is 1:0.03:0.08:0.012;

[0149] In this example, the high-salt-resistant fluid loss additive KYJS-8 obtained in example 24 is in powder form. The viscosity average molecular weight of the high-salt-resistant fluid loss additive KYJS-8 obtained in example 24 is determined to be 2 million Daltons by a Ubbelohde viscometer according to the standard of “GB / T 12005.10-1992 Determination of molecular weight of polyacrylamide”.

[0150] Example 25

[0151] The embodiment provides a preparation method of low filtration loss salt-resistant thickening agent for direct matching of flowback fluid and produced water. 95.7 g of No. 15 white oil is formed into a vortex under high-speed stirring in a 500 mL beaker at room temperature, 1.9 g of sorbitan monooleate, 0.96 g of organically modified attapulgite and 1.44 g of alkylphenol polyoxyethylene ether are sequentially added, and the mixture is stirred and emulsified for more than 2 h to obtain a suspending agent; under continuous stirring, 125 g of powdered high-salt-resistant thickening agent GKY-1 and 12.5 g of salt-resistant filtration reducer KYJS-1 are sequentially and slowly added into the suspending agent, 12.5 g of aminotrimethylene phosphonic acid is further added after the mixture is sufficiently mixed for 1.5 h, and the mixture is continuously stirred and mixed for 30 min to obtain the low filtration loss salt-resistant thickening agent DLKY-1 for direct matching of flowback fluid and produced water.

[0152] Embodiment 26

[0153] The embodiment is basically the same as embodiment 25, except that the embodiment uses equal amounts of high-salt-resistant thickening agent GKY-2 instead of high-salt-resistant thickening agent GKY-1, and equal amounts of salt-resistant filtration reducer KYJS-2 instead of salt-resistant filtration reducer KYJS-1, to prepare the low filtration loss salt-resistant thickening agent DLKY-2 for direct matching of flowback fluid and produced water.

[0154] Embodiment 27

[0155] The embodiment is basically the same as embodiment 25, except that the embodiment uses equal amounts of high-salt-resistant thickening agent GKY-3 instead of high-salt-resistant thickening agent GKY-1, and equal amounts of salt-resistant filtration reducer KYJS-3 instead of salt-resistant filtration reducer KYJS-1, to prepare the low filtration loss salt-resistant thickening agent DLKY-3 for direct matching of flowback fluid and produced water.

[0156] Embodiment 28

[0157] The embodiment is basically the same as embodiment 25, except that the embodiment uses equal amounts of high-salt-resistant thickening agent GKY-4 instead of high-salt-resistant thickening agent GKY-1, and equal amounts of salt-resistant filtration reducer KYJS-4 instead of salt-resistant filtration reducer KYJS-1, to prepare the low filtration loss salt-resistant thickening agent DLKY-4 for direct matching of flowback fluid and produced water.

[0158] Embodiment 29

[0159] The embodiment is basically the same as embodiment 25, except that the embodiment uses equal amounts of high-salt-resistant thickening agent GKY-5 instead of high-salt-resistant thickening agent GKY-1, and equal amounts of salt-resistant filtration reducer KYJS-5 instead of salt-resistant filtration reducer KYJS-1, to prepare the low filtration loss salt-resistant thickening agent DLKY-5 for direct matching of flowback fluid and produced water.

[0160] Embodiment 30

[0161] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-6 is used instead of high salt-tolerant thickening agent GKY-1, and an equal amount of salt-tolerant fluid loss additive KYJS-6 is used instead of salt-tolerant fluid loss additive KYJS-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-6 for direct blending of flowback fluid and produced water.

[0162] Example 31

[0163] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-7 is used instead of high salt-tolerant thickening agent GKY-1, and an equal amount of salt-tolerant fluid loss additive KYJS-7 is used instead of salt-tolerant fluid loss additive KYJS-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-7 for direct blending of flowback fluid and produced water.

[0164] Example 32

[0165] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-8 is used instead of high salt-tolerant thickening agent GKY-1, and an equal amount of salt-tolerant fluid loss additive KYJS-8 is used instead of salt-tolerant fluid loss additive KYJS-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-8 for direct blending of flowback fluid and produced water.

[0166] Example 33

[0167] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-9 is used instead of high salt-tolerant thickening agent GKY-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-9 for direct blending of flowback fluid and produced water.

[0168] Example 34

[0169] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-10 is used instead of high salt-tolerant thickening agent GKY-1, and an equal amount of salt-tolerant fluid loss additive KYJS-8 is used instead of salt-tolerant fluid loss additive KYJS-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-10 for direct blending of flowback fluid and produced water.

[0170] Example 35

[0171] This example is basically the same as example 25, except that in this example, an equal amount of high salt-tolerant thickening agent GKY-11 is used instead of high salt-tolerant thickening agent GKY-1, to prepare a low fluid loss salt-tolerant thickening agent DLKY-11 for direct blending of flowback fluid and produced water.

[0172] Example 36

[0173] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of high-salt-resistant thickening agent GKY-12 is used instead of high-salt-resistant thickening agent GKY-1, and an equal amount of salt-resistant fluid loss additive KYJS-8 is used instead of salt-resistant fluid loss additive KYJS-1, to prepare a low-filtering salt-resistant thickening agent DLKY-12 for direct mixing of flowback fluid and produced water.

[0174] Embodiment 37

[0175] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of high-salt-resistant thickening agent GKY-13 is used instead of high-salt-resistant thickening agent GKY-1, to prepare a low-filtering salt-resistant thickening agent DLKY-13 for direct mixing of flowback fluid and produced water.

[0176] Embodiment 38

[0177] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of high-salt-resistant thickening agent GKY-14 is used instead of high-salt-resistant thickening agent GKY-1, and an equal amount of salt-resistant fluid loss additive KYJS-8 is used instead of salt-resistant fluid loss additive KYJS-1, to prepare a low-filtering salt-resistant thickening agent DLKY-14 for direct mixing of flowback fluid and produced water.

[0178] Embodiment 39

[0179] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of high-salt-resistant thickening agent GKY-15 is used instead of high-salt-resistant thickening agent GKY-1, to prepare a low-filtering salt-resistant thickening agent DLKY-15 for direct mixing of flowback fluid and produced water.

[0180] Embodiment 40

[0181] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of high-salt-resistant thickening agent GKY-16 is used instead of high-salt-resistant thickening agent GKY-1, and an equal amount of salt-resistant fluid loss additive KYJS-8 is used instead of salt-resistant fluid loss additive KYJS-1, to prepare a low-filtering salt-resistant thickening agent DLKY-16 for direct mixing of flowback fluid and produced water.

[0182] Embodiment 41

[0183] This embodiment is basically the same as embodiment 25, except that in this embodiment, an equal amount of diethylenetriamine pentamethylene phosphonic acid is used instead of amino trimethylene phosphonic acid, to prepare a low-filtering salt-resistant thickening agent DLKY-17 for direct mixing of flowback fluid and produced water.

[0184] Embodiment 42

[0185] This embodiment is basically the same as embodiment 32, except that: in this embodiment, an equal amount of diethylenetriaminepentamethylenephosphonic acid is used instead of aminotrimethylphosphonic acid to prepare a low filtration loss salt-resistant thickener DLKY-18 for direct mixing of backflow fluid and produced water.

[0186] Example 43

[0187] This embodiment is basically the same as embodiment 25, except that: in this embodiment, an equal amount of sodium hydroxyethylidene diphosphonate is used instead of aminotrimethylphosphonic acid to prepare a low filtration loss salt thickener DLKY-19 for direct mixing of backflow fluid and produced water.

[0188] Example 44

[0189] This embodiment is basically the same as embodiment 32, except that: in this embodiment, an equal amount of sodium hydroxyethylidene diphosphonate is used instead of aminotrimethylphosphonic acid to prepare a low filtration loss salt-resistant thickener DLKY-20 for direct mixing of backflow fluid and produced water.

[0190] Comparative Example 1

[0191] This comparative example is basically the same as Example 1, except that carboxybetaine acrylamide was not added in this comparative example.

[0192] In this comparative example, a powdered high salt-resistant thickener DB-1 was prepared. The viscosity-average molecular weight of the high salt-resistant thickener DB-1 obtained in Comparative Example 1 was determined to be 16.5 million Daltons using an Ubbelohde viscometer according to the standard GB / T12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0193] Comparative Example 2

[0194] This comparative example is basically the same as Example 2, except that carboxybetaine acrylamide was not added in this comparative example.

[0195] In this comparative example, a powdered high salt-resistant thickener DB-2 was prepared. The viscosity-average molecular weight of the high salt-resistant thickener DB-2 obtained in Comparative Example 2 was determined to be 15.87 million Daltons using an Ubbelohde viscometer according to the standard GB / T12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0196] Comparative Example 3

[0197] This comparative example is basically the same as Example 7, except that carboxybetaine acrylamide was not added in this comparative example.

[0198] The comparative example 3 obtains the high salt-resistant thickening agent DB-3 in powder form, and the viscosity average molecular weight of the high salt-resistant thickening agent DB-3 obtained in the comparative example 3 is 15.1 million Dalton, which is determined by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0199] Comparative example 4

[0200] The comparative example 4 is basically the same as the example 8, except that the carboxybetaine acrylamide is not added in the comparative example 4.

[0201] The comparative example 4 obtains the high salt-resistant thickening agent DB-4 in powder form, and the viscosity average molecular weight of the high salt-resistant thickening agent DB-4 obtained in the comparative example 4 is 14.57 million Dalton, which is determined by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0202] Comparative example 5

[0203] The comparative example 5 is basically the same as the example 9, except that the carboxybetaine acrylamide is not added in the comparative example 5.

[0204] The comparative example 5 obtains the high salt-resistant thickening agent DB-5 in powder form, and the viscosity average molecular weight of the high salt-resistant thickening agent DB-5 obtained in the comparative example 5 is 16.21 million Dalton, which is determined by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0205] Comparative example 6

[0206] The comparative example 6 is basically the same as the example 10, except that the carboxybetaine acrylamide is not added in the comparative example 6.

[0207] The comparative example 6 obtains the high salt-resistant thickening agent DB-6 in powder form, and the viscosity average molecular weight of the high salt-resistant thickening agent DB-6 obtained in the comparative example 6 is 15.46 million Dalton, which is determined by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0208] Comparative example 7

[0209] The comparative example 7 is basically the same as the example 11, except that the carboxybetaine acrylamide is not added in the comparative example 7.

[0210] The high salt-resistant viscosifier DB-7 in powder form is prepared in this comparative example, and the viscosity-average molecular weight of the high salt-resistant viscosifier DB-7 obtained in Comparative Example 7 is determined to be 16.34 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0211] Comparative Example 8

[0212] This comparative example is basically the same as Example 12, except that no carboxybetaine acrylamide is added in this comparative example.

[0213] The high salt-resistant viscosifier DB-8 in powder form is prepared in this comparative example, and the viscosity-average molecular weight of the high salt-resistant viscosifier DB-8 obtained in Comparative Example 8 is determined to be 15.55 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0214] Comparative Example 9

[0215] This comparative example is basically the same as Example 13, except that no carboxybetaine acrylamide is added in this comparative example.

[0216] The high salt-resistant viscosifier DB-9 in powder form is prepared in this comparative example, and the viscosity-average molecular weight of the high salt-resistant viscosifier DB-9 obtained in Comparative Example 9 is determined to be 16.01 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0217] Comparative Example 10

[0218] This comparative example is basically the same as Example 14, except that no carboxybetaine acrylamide is added in this comparative example.

[0219] The high salt-resistant viscosifier DB-10 in powder form is prepared in this comparative example, and the viscosity-average molecular weight of the high salt-resistant viscosifier DB-10 obtained in Comparative Example 10 is determined to be 15.23 million Dalton by using an Ubbelohde viscometer according to the standard of GB / T12005.10-1992 Determination of molecular weight of polyacrylamide.

[0220] Comparative Example 11

[0221] This comparative example is basically the same as Example 32, except that an equal amount of the high salt-resistant viscosifier DB-1 is used instead of the high salt-resistant viscosifier GKY-8, and no amino-trimethylene phosphonic acid is added; the high salt-resistant viscosifier BJKY-1 in powder form is prepared in this comparative example.

[0222] Comparative Example 12

[0223] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-2 instead of high salt-tolerant thickening agent GKY-8, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-2.

[0224] Comparative example 13

[0225] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-3 instead of high salt-tolerant thickening agent GKY-8, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-3.

[0226] Comparative example 14

[0227] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-4 instead of high salt-tolerant thickening agent GKY-8, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-4.

[0228] Comparative example 15

[0229] The comparative example is basically the same as example 34, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-5 instead of high salt-tolerant thickening agent GKY-10, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-5.

[0230] Comparative example 16

[0231] The comparative example is basically the same as example 34, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-6 instead of high salt-tolerant thickening agent GKY-10, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-6.

[0232] Comparative example 17

[0233] The comparative example is basically the same as example 36, except that the comparative example uses an equal amount of high salt-tolerant thickening agent DB-7 instead of high salt-tolerant thickening agent GKY-12, and no amino-trimethylene phosphonic acid is added; the comparative example prepares a powder of high salt-tolerant thickening agent BJKY-7.

[0234] Comparative example 18

[0235] The comparative example is basically the same as example 36, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-8 instead of high salt-resistant thickening agent GKY-12, and no amino trimethylene phosphonic acid is added; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-8.

[0236] Comparative example 19

[0237] The comparative example is basically the same as example 38, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-9 instead of high salt-resistant thickening agent GKY-14, and no amino trimethylene phosphonic acid is added; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-9.

[0238] Comparative example 20

[0239] The comparative example is basically the same as example 38, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-10 instead of high salt-resistant thickening agent GKY-14, and no amino trimethylene phosphonic acid is added; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-10.

[0240] Comparative example 21

[0241] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-1 instead of high salt-resistant thickening agent GKY-8; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-11.

[0242] Comparative example 22

[0243] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-2 instead of high salt-resistant thickening agent GKY-8; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-12.

[0244] Comparative example 23

[0245] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-3 instead of high salt-resistant thickening agent GKY-8; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-13.

[0246] Comparative example 24

[0247] The comparative example is basically the same as example 32, except that the comparative example uses an equal amount of high salt-resistant thickening agent DB-4 instead of high salt-resistant thickening agent GKY-8; the comparative example prepares a powdery high salt-resistant thickening agent BJKY-14.

[0248] Comparative Example 25

[0249] The comparative example is basically the same as example 34, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-5 is used instead of high salt-tolerant thickening agent GKY-10; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-15 is prepared.

[0250] Comparative Example 26

[0251] The comparative example is basically the same as example 34, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-6 is used instead of high salt-tolerant thickening agent GKY-10; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-16 is prepared.

[0252] Comparative Example 27

[0253] The comparative example is basically the same as example 36, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-7 is used instead of high salt-tolerant thickening agent GKY-12; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-17 is prepared.

[0254] Comparative Example 28

[0255] The comparative example is basically the same as example 36, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-8 is used instead of high salt-tolerant thickening agent GKY-12; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-18 is prepared.

[0256] Comparative Example 29

[0257] The comparative example is basically the same as example 38, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-9 is used instead of high salt-tolerant thickening agent GKY-14; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-19 is prepared.

[0258] Comparative Example 30

[0259] The comparative example is basically the same as example 38, except that: in the comparative example, an equal amount of high salt-tolerant thickening agent DB-10 is used instead of high salt-tolerant thickening agent GKY-14; and in the comparative example, a powder-like high salt-tolerant thickening agent BJKY-20 is prepared.

[0260] Comparative Example 31

[0261] The comparative example is basically the same as example 25, except that no salt-resistant fluid loss additive KYJS-1 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-21 is prepared in the comparative example.

[0262] Comparative example 32

[0263] The comparative example is basically the same as example 26, except that no salt-resistant fluid loss additive KYJS-2 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-22 is prepared in the comparative example.

[0264] Comparative example 33

[0265] The comparative example is basically the same as example 27, except that no salt-resistant fluid loss additive KYJS-3 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-23 is prepared in the comparative example.

[0266] Comparative example 34

[0267] The comparative example is basically the same as example 28, except that no salt-resistant fluid loss additive KYJS-4 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-24 is prepared in the comparative example.

[0268] Comparative example 35

[0269] The comparative example is basically the same as example 29, except that no salt-resistant fluid loss additive KYJS-5 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-25 is prepared in the comparative example.

[0270] Comparative example 36

[0271] The comparative example is basically the same as example 30, except that no salt-resistant fluid loss additive KYJS-6 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-26 is prepared in the comparative example.

[0272] Comparative example 37

[0273] The comparative example is basically the same as example 31, except that no salt-resistant fluid loss additive KYJS-7 is added in the comparative example; and the powder-like high-salt-resistant viscosifier BJKY-27 is prepared in the comparative example.

[0274] Comparative example 38

[0275] The comparative example is basically the same as example 32, except that no salt-resistant fluid loss additive KYJS-8 is added in the comparative example; and the high-salt-resistant thickening agent BJKY-28 in powder form is prepared in the comparative example.

[0276] The testing process of the examples and the comparative example of the present application is as follows:

[0277] (1) The tack-up time: accurately weigh the low-filter-loss salt-resistant thickening agent in powder form, and place it in a 500 mL beaker pre-loaded with an appropriate amount of flowback fluid (total salinity 150000 mg / L, wherein the calcium and magnesium ion content is 8000 mg / L, and the iron ion content is 500 mg / L), and dissolve it by stirring at a speed of 600±50 rad / min at room temperature by using a powerful stirrer. The time corresponding to the stringing of the glass rod is the tack-up time.

[0278] (2) Viscosity release rate: the flowback fluid is used to prepare the low-filter-loss salt-resistant thickening agent with the target mass concentration according to the method in (1), and the viscosity values of the low-filter-loss salt-resistant thickening agent dissolved for different time are tested at 100 r / min (170 s -1 ) at room temperature by using a six-speed rotary viscometer, and the viscosity release rate is calculated according to the following formula. When the viscosity is lower than 10 mPa·s, the kinematic viscosity of the product is tested by using a capillary viscometer.

[0279]

[0280] In the formula, V R is the real-time viscosity before stabilization, mPa·s (or mm 2 / s); V F is the final stable viscosity, mPa·s (or mm 2 / s); R V is the viscosity release rate, %.

[0281] (3) Drag reduction rate: the drag reduction rate of the low-filter-loss salt-resistant thickening agent is tested by using a flow loop friction testing device (pipe diameter 10 mm) according to the provisions for determining the drag reduction rate in the industry standard SY / T 6376-2008 “General Technical Conditions for Fracturing Fluids”, and the change curve of the drag reduction rate with time is recorded, and the drag reduction rate at 10 min is taken as the final drag reduction rate value.

[0282] (4) Temperature resistance and shear resistance: the low-filter-loss salt-resistant thickening agent is tested for temperature resistance and shear resistance by using an RS6000 senior rheometer PZ38 coaxial cylinder rotor system at 120 o C and 170 s -1 , the change curve of the viscosity with time is recorded, and the final stable viscosity value is recorded, and the duration from the temperature rise to the end of the test is 2 hours.

[0283] (5) Static / dynamic filtration performance: the static filtration coefficient and dynamic filtration coefficient of the low filtration anti-salt thickening agent were calculated after the filtration amount of the low filtration anti-salt thickening agent prepared according to the low filtration anti-salt thickening agent in the returned fluid was tested by a static filtration instrument and a dynamic filtration testing device respectively according to the provisions of the industry standard SY / T 5107-2016 “Method for evaluating the performance of water-based fracturing fluid”.

[0284] (6) Gel breaking performance: 100 g of the low filtration anti-salt thickening agent prepared in the returned fluid was placed in a metal sealed tank, and ammonium persulfate with a mass concentration of 0.025% was added, and then the tank was sealed and aged at 90 o C for different time, and then the tank was taken out, and the viscosity and residue content of the gel breaking liquid were tested at room temperature according to the provisions of the industry standard SY / T 5107-2016 “Method for evaluating the performance of water-based fracturing fluid”.

[0285] The tack-up time, viscosity at 1 min 30 s and viscosity release rate of the low filtration anti-salt fracturing thickening agent obtained from the low filtration anti-salt thickening agent in the examples 25 to 44 and the low filtration anti-salt thickening agent obtained from the low filtration anti-salt thickening agent in the comparative examples 11 to 30 were tested by the above method, and the results are shown in Table 1:

[0286] Table 1 Test results of tack-up time, viscosity at 1 min 30 s and viscosity release rate of the thickening agent

[0287]

[0288] As shown in Table 1, the low filtration anti-salt fracturing thickening agent (DLKY-1 to DLKY-20) obtained after the high salt-resistant thickening agent containing betaine zwitterion groups, the salt-resistant filtration reducer, the organic phosphonic acid or the organic phosphonate in the examples 25 to 44 were introduced, the tack-up time at the mass concentration of 0.12 wt% and 1.0 wt% was less than 18 s, and the viscosity release rate at 1 min 30 s was greater than 90%.

[0289] The tack-up time of the low filtration anti-salt fracturing thickening agent (BJKY-1 to BJKY-10) obtained after the high salt-resistant thickening agent not containing betaine zwitterion groups and the organic phosphonic acid were introduced in the comparative examples 11 to 20 was greater than 35 s, and the viscosity release rate at 1 min 30 s was less than 79.5%.

[0290] The tack-up time of the low filtration anti-salt fracturing thickening agent (BJKY-11 to BJKY-20) obtained after the high salt-resistant thickening agent not containing betaine zwitterion groups was introduced in the comparative examples 21 to 30 was greater than 24 s, and the viscosity release rate at 1 min 30 s was less than 85%.

[0291] In addition, the 1 min 30 s viscosity of the low fluid loss salt-tolerant fracturing thickening agents (DLKY-8, DLKY-10, DLKY-12, DLKY-14, DLKY-16, DLKY-18 and DLKY-20) obtained in Example 32, Example 34, Example 36, Example 38, Example 40, Example 42 and Example 44 is at least 54.9% and 37.6% higher than the viscosity of the thickening agents (DB-1 to DB-10) obtained in Comparative Example 11 to Comparative Example 20, respectively, at a mass concentration of 0.12 wt% to 1.0 wt%; and is at least 45.4% and 19.4% higher than the viscosity of the low fluid loss salt-tolerant fracturing thickening agents (DB-11 to DB-20) obtained in Comparative Example 21 to Comparative Example 30, respectively.

[0292] Therefore, according to the above experimental data, it is shown that the high-salt-tolerant thickening agent containing the betaine zwitterion group and the organic phosphonic acid or organic phosphonate can significantly improve the viscosity performance and viscosity increasing ability of the low fluid loss salt-tolerant fracturing thickening agent in the high-salinity flowback fluid, and achieve excellent solubility and high salt tolerance in the high-salinity flowback fluid.

[0293] At room temperature, the drag reduction rate of the low fluid loss salt-tolerant fracturing thickening agents obtained in Example 25 to Example 44 and the low fluid loss salt-tolerant fracturing thickening agents obtained in Comparative Example 11 to Comparative Example 30 was tested at a mass concentration of 0.12% by the above method, and the results are shown in Table 2:

[0294] Table 2 Test results of drag reduction rate

[0295]

[0296] As shown in Table 2, the low fluid loss salt-tolerant fracturing thickening agents (DLKY-1 to DLKY-20) obtained in Example 25 to Example 44 by introducing the high-salt-tolerant thickening agent containing the betaine zwitterion group, the salt-tolerant fluid loss reducer and the organic phosphonic acid or organic phosphonate; the drag reduction rate at a mass concentration of 0.12 wt% is at least 8.3% higher than the drag reduction rate of the low fluid loss salt-tolerant fracturing thickening agents (BJKY-1 to BJKY-10) obtained in Comparative Example 11 to Comparative Example 20 by introducing the high-salt-tolerant thickening agent not containing the betaine zwitterion group and not introducing the organic phosphonic acid; and is at least 5.3% higher than the drag reduction rate of the low fluid loss salt-tolerant fracturing thickening agents (BJKY-11 to BJKY-20) obtained in Comparative Example 21 to Comparative Example 30 by introducing the high-salt-tolerant thickening agent not containing the betaine zwitterion group.

[0297] Therefore, according to the above experimental data, it is shown that after the introduction of the high-salt-tolerant thickening agent containing betaine zwitterion groups and the organic phosphonic acid or the organic phosphonate, the salt resistance of the low fluid loss salt-tolerant fracturing thickening agent in the high-salinity flowback fluid can be greatly improved, the molecular chain of the thickening agent is more relaxed, the tackifying capacity is stronger, and the viscoelasticity reduction is achieved.

[0298] The low fluid loss salt-tolerant fracturing thickening agents obtained in Examples 25 to 44 and the low fluid loss salt-tolerant fracturing thickening agents obtained in Comparative Examples 11 to 30 are tested for the temperature resistance and shear resistance at a mass concentration of 1.0% by the above method, and the results are shown in Table 3.

[0299] Table 3: Test results of temperature resistance and shear resistance

[0300]

[0301] As shown in Table 3, the low fluid loss salt-tolerant fracturing thickening agents (DLKY-1 to DLKY-20) obtained in Examples 25 to 44 after the introduction of the high-salt-tolerant thickening agent containing betaine zwitterion groups, the salt-tolerant fluid loss reducer and the organic phosphonic acid or the organic phosphonate have a temperature resistance and shear resistance stable viscosity at least 32% higher than that of the fracturing thickening agents (BJKY-1 to BJKY-10) obtained in Comparative Examples 11 to 20 after the introduction of the high-salt-tolerant thickening agent not containing betaine zwitterion groups and the non-introduction of the organic phosphonic acid; and at least 18% higher than that of the low fluid loss salt-tolerant fracturing thickening agents (BJKY-11 to BJKY-20) obtained in Comparative Examples 21 to 30 after the introduction of the high-salt-tolerant thickening agent not containing betaine zwitterion groups.

[0302] More obviously, the temperature resistance and shear resistance stable viscosity of the low fluid loss salt-tolerant fracturing thickening agents (DLKY-8, DLKY-10, DLKY-12, DLKY-14, DLKY-16, DLKY-18 and DLKY-20) obtained in Examples 32, 34, 36, 38, 40, 42 and 44 is more than 51.4% higher than that of the low fluid loss salt-tolerant fracturing thickening agent (BJKY-10) obtained in Comparative Example 20; and 35.4% higher than that of the low fluid loss salt-tolerant fracturing thickening agent (BJKY-18) obtained in Comparative Example 28.

[0303] Therefore, according to the above experimental data, it is shown that after the introduction of the high-salt-tolerant thickening agent containing betaine zwitterion groups and the organic phosphonic acid or the organic phosphonate, the temperature resistance and shear resistance of the low fluid loss salt-tolerant fracturing thickening agent in the high-salinity flowback fluid can be greatly improved.

[0304] The low filtration anti-salt fracturing thickening agents obtained from Examples 25 to 44 and the low filtration anti-salt fracturing thickening agents obtained from Comparative Examples 11 to 38 were tested for static filtration performance and dynamic filtration performance at a mass concentration of 0.12% by the above method, and the results are shown in Table 4.

[0305] Table 4 Test results of static filtration performance and dynamic filtration performance

[0306]

[0307] As shown in Table 4, the static filtration coefficients and dynamic filtration coefficients of the low filtration anti-salt fracturing thickening agents (DLKY-1 to DLKY-20) obtained by introducing the high-salt-tolerant thickening agent containing betaine zwitterion groups, the salt-tolerant filtration reducer and the organic phosphonic acid or organic phosphonate in Examples 25 to 44 were at least 9.2% and 8.5% lower than the static filtration coefficients and dynamic filtration coefficients of the fracturing thickening agents (BJKY-1 to BJKY-10) obtained by introducing the high-salt-tolerant thickening agent not containing betaine zwitterion groups and without introducing the organic phosphonic acid in Comparative Examples 11 to 20, respectively.

[0308] The static filtration coefficients and dynamic filtration coefficients of the low filtration anti-salt fracturing thickening agents (DLKY-8, DLKY-10, DLKY-12, DLKY-14, DLKY-16, DLKY-18 and DLKY-20) obtained from Examples 32, 34, 36, 38, 40, 42 and 44 were at least 12.9% and 9.9% lower than the static filtration coefficients and dynamic filtration coefficients of the low filtration anti-salt fracturing thickening agents (BJKY-11 to BJKY-20) obtained by introducing the high-salt-tolerant thickening agent not containing betaine zwitterion groups in Comparative Examples 21 to 30, respectively.

[0309] More obviously, the static filtration coefficients and dynamic filtration coefficients of the low filtration anti-salt fracturing thickening agents (DLKY-1 to DLKY-8) obtained from Examples 25 to 32 were at least 10.1% and 8.5% lower than the static filtration coefficients and dynamic filtration coefficients of the low filtration anti-salt fracturing thickening agents (BJKY-21 to BJKY-28) obtained by not introducing the salt-tolerant filtration reducer in corresponding Comparative Examples 31 to 38, respectively.

[0310] Therefore, according to the above experimental data, it is shown that after introducing the high-salt-tolerant thickening agent containing betaine zwitterion groups, the salt-tolerant fluid loss reducer and the organic phosphonic acid or organic phosphonate, the low fluid loss and salt-tolerant fracturing thickening agent can greatly improve the fluid loss performance in the high-salinity flowback fluid through the synergistic effect of the salt-tolerant ability of the high-salt-tolerant thickening agent, the weakening effect of the organic phosphonic acid or phosphonate on the adverse effect of high-valence ions and the fluid loss reduction ability of the salt-tolerant fluid loss reducer.

[0311] The low fluid loss and salt-tolerant fracturing thickening agents obtained in Examples 25 to 44 and the low fluid loss and salt-tolerant fracturing thickening agents obtained in Comparative Examples 11 to 30 are tested for the gel breaking performance under the condition of 1.0% mass concentration and 0.025% ammonium persulfate addition by the above method, and the results are shown in Table 5:

[0312] Table 5 Gel breaking performance test results

[0313]

[0314] As shown in Table 5, the low fluid loss and salt-tolerant fracturing thickening agents (DLKY-1 to DLKY-20) obtained in Examples 25 to 44 after introducing the high-salt-tolerant thickening agent containing betaine zwitterion groups, the salt-tolerant fluid loss reducer and the organic phosphonic acid or organic phosphonate can completely break the gel in 2h under the condition of 1.0wt% mass concentration, 90 o C and 0.025wt% ammonium persulfate addition, and the viscosity of the gel breaking liquid is less than 4.82mm 2 / s and the residue content is less than 50mg / L, which is equivalent to the gel breaking performance of the fracturing thickening agents (BJKY-11 to BJKY-20) obtained in Comparative Examples 21 to 30 after introducing the high-salt-tolerant thickening agent not containing betaine zwitterion groups.

[0315] The gel breaking liquid viscosity of the low fluid loss and salt-tolerant fracturing thickening agents (BJKY-1 to BJKY-10) obtained in Comparative Examples 11 to 20 after introducing the high-salt-tolerant thickening agent not containing betaine zwitterion groups and without introducing the organic phosphonic acid is greater than 5.82mm 2 / s and the residue content is greater than 67.6mg / L.

[0316] Therefore, according to the above experimental data, it is shown that after introducing the high-salt-tolerant thickening agent containing betaine zwitterion groups, the salt-tolerant fluid loss reducer and the organic phosphonic acid or organic phosphonate to obtain the low fluid loss and salt-tolerant fracturing thickening agent, the gel breaking performance of the thickening agent in the high-salinity flowback fluid can be improved, and the residue content and the risk of reservoir damage can be reduced.

[0317] In summary, the above data results show that by introducing the high salt-tolerant thickening agent containing betaine zwitterion group, the salt-tolerant fluid loss additive and the organic phosphonic acid or organic phosphonate, the low filtration salt-tolerant fracturing thickening agent of the present application is obtained, which can not only greatly improve the high salt tolerance and fluid loss performance, significantly enhance the sand carrying ability in complex water quality direct matching conditions such as flowback fluid, obviously reduce the fracturing fluid loss, but also improve the gel breaking performance of the thickening agent in high salinity complex water quality.

[0318] The basic principles and main features of the present application and the advantages of the present application are shown and described above, and it is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present application.

[0319] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application, and any modification made on the basis of the technical solutions according to the technical idea of the present application falls within the protection scope of the claims of the present application.

Claims

1. A method for preparing a low filtration loss anti-salt thickening agent for direct spiking of flowback and produced water, characterized in that, The preparation raw materials include the following parts by weight: 30-55 parts of a highly salt-resistant thickener containing strong hydrophilic groups and betaine zwitterionic groups; 5-10 parts of salt-resistant filtration loss reducer; 1 to 5 parts of organophosphonic acid or organophosphonate; 30-64 parts of suspension concentrate; The high salt-resistant thickener containing strong hydrophilic groups and betaine zwitterionic groups is obtained by copolymerization of acrylamide, salt-resistant monomer, sodium acrylamide long-chain alkyl sulfonate and carboxybetaine containing unsaturated double bonds, with a viscosity-average molecular weight range of 10.13 to 15 million Daltons. The salt-resistant filtration loss reducer is obtained by copolymerizing 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide and maleic anhydride, with a viscosity-average molecular weight range of 2 million to 3.5 million Daltons. The suspending agent is a mixture of organic phase, emulsifier, stabilizer and dispersing surfactant; The salt-resistant monomer is sodium 2-acrylamido-2-methylpropanesulfonate, sodium p-acrylamidobenzenesulfonate, sodium p-styrenesulfonate, or sodium p-allylbenzenesulfonate. The mass ratio of acrylamide, salt-resistant monomer, sodium acrylamide-based long-chain alkyl sulfonate, and carboxybetaine containing unsaturated double bonds is 1:(0.02-0.06):(0.005-0.012):(0.003-0.008). The mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide and maleic anhydride is 1:(0.02~0.03):(0.06~0.08):(0.01~0.012); The acrylamide-based long-chain alkyl sulfonate sodium is 2-acrylamidododecyl sulfonate sodium, 2-acrylamidotetradecyl sulfonate sodium or 2-acrylamidohexadecyl sulfonate sodium; The carboxybetaine containing unsaturated double bonds is carboxybetaine acrylamide or allyl carboxybetaine; The preparation method of the low filtration loss anti-salt thickener includes the following steps: S1. Dissolve acrylamide, salt-resistant monomer, sodium acrylamide long-chain alkyl sulfonate, and carboxybetaine containing unsaturated double bonds in deionized water by stirring, and adjust the pH to 8.5-8.8 to form a mixed solution with a total monomer mass concentration of 25%-30%. S2. Cool the mixed solution to 3℃~5℃, add the molecular regulator and inorganic compound oxidant in sequence, add the oxidation / reduction initiator after 2 min interval, and add the azo initiator after 4 min interval to initiate the polymerization reaction and obtain the reaction product; place the reaction product under adiabatic conditions for 6h~7h to obtain the colloidal product. S3. Chop the colloidal product and dry it at 95℃~100℃ for 6h~8h. After pulverizing, sieve to obtain a powdered high salt-resistant thickener. S4. At room temperature, 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide and maleic anhydride are dissolved in deionized water containing ultrafine calcium sulfate and stirred until dissolved. The pH is adjusted to 6.2-6.5, and a molecular regulator is added to form a reaction mixture. S5, the reaction mixture is heated to 63-65 DEG C, after adding initiator stirring, interval 6-7 min reaction after heating to 80-82 DEG C, incubation reaction 75-85 min, get sticky product; S6, the sticky product is dried at 115-120 DEG C for 7.5-8 h, sieving to get powder salt-resistant fluid loss additive; S7, at room temperature, the organic phase, emulsifier, stabilizer and dispersing surfactant are mixed and stirred for 2-3 h to get a suspension agent; S8, the high salt-resistant thickening agent obtained in S3 and the salt-resistant fluid loss additive obtained in S6 are added to the suspension agent, mixed for 1.5-2 h, then organic phosphonic acid or organic phosphonate is added, and stirring is continued for 30-40 min to obtain a low filtration salt-resistant thickening agent.

2. The method for preparing the low filtration loss and salt-resistant thickening agent for direct matching of flowback fluid and produced water according to claim 1, characterized in that, The mass ratio of the organic phase, emulsifier, stabilizer and dispersing surfactant is 1:0.02:0.01:0.

015.

3. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The pH regulator for adjusting pH in S1 is one or more of acetic acid, citric acid, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium hydroxide.

4. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The molecular regulator in S2 is one or more of sodium formate, thiourea, isopropyl alcohol or urea. The inorganic compound oxidant is one or more of ammonium metavanadate, cerium ammonium sulfate or cerium nitrate. The oxidation / reduction initiator is one or both of hydrogen peroxide / ferrous chloride mixture or tert-butyl hydroperoxide / ferrous ammonium sulfate / sodium bisulfite mixture. The azo initiator is one or more of azobis isopropyl imidazoline, azobis isobutyl amidine hydrochloride, azobis isobutyl imidazoline hydrochloride or azobis dicyanopentanoic acid.

5. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The addition amount of the molecular regulator in S2 is 0.04-0.042% of the mass of acrylamide monomer. The total addition amount of oxidation / reduction initiator and azo initiator is 0.05-0.055% of the mass of acrylamide monomer. The mass ratio of inorganic compound oxidant, oxidation / reduction initiator and azo initiator is 0.1:1:0.

2.

6. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The pH regulator for adjusting pH in S4 is one or more of sodium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonia, sodium hydroxide, potassium hydroxide or triethanolamine. The molecular regulator in S4 is one or more of mercaptoethanol, mercaptoacetic acid, tert-dodecyl mercaptan, dodecyl mercaptan, n-butyl mercaptan or sodium hypophosphite.

7. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The initiator in S5 is one or more of sodium persulfate, ammonium persulfate, potassium persulfate, sodium persulfate / sodium bisulfite mixture, ammonium persulfate / sodium bisulfite mixture or potassium persulfate / sodium bisulfite mixture.

8. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The organic phase in S7 is one or more of kerosene, No. 5 white oil, No. 10 white oil, No. 15 white oil or transformer oil. The emulsifier is one or more of sorbitan monooleate, polyoxyethylene sorbitan monooleate, sorbitan ester or sodium sulfosuccinic acid dioctyl ester. The stabilizer is one or more of organic modified bentonite, organic modified attapulgite or organic modified nanocellulose. The dispersing surfactant is one or both of alkyl phenol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

9. The method for preparing the low fluid loss anti-salt thickening agent for flowback fluid and produced water direct matching of claim 1, characterized in that, The organic phosphonic acid in S8 is one or more of diethylenetriamine pentamethylene phosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, hydroxyl phosphono acetic acid, aminotrimethylene phosphonic acid; the organic phosphonic acid salt is one or both of hydroxyethylidene diphosphonic acid sodium or ethylenediamine tetraamine sodium methylidene phosphonic acid.

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