Polymer viscosifier and method for its preparation

Abstract

This invention provides a polymer thickener and filtration loss reducer. The polymer thickener and filtration loss reducer is prepared by copolymerization of monomers under the action of an initiator; wherein the monomers include: acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, monomer A, and monomer B, wherein the structure of monomer A is shown in Formula I, and the structure of monomer B is shown in Formula II. This invention also provides a method for preparing the above-mentioned polymer thickener and filtration loss reducer, which can effectively thicken the polymer and exhibits good temperature and salt resistance.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a polymer thickener and filtration loss reducer and its preparation method. Background Technology

[0002] Under high temperature and high salinity conditions, the viscosity and shear stress of the drilling fluid must be maintained within a suitable range to ensure wellbore cleanliness and safe drilling. When the viscosity is too low, it can be increased by increasing the bentonite content; however, this method increases the solid content in the drilling fluid, which is detrimental to improving mechanical drilling speed and protecting oil and gas reservoirs. Therefore, viscosifiers are usually added to increase the viscosity of the drilling fluid and improve its rheological properties. Besides increasing viscosity, viscosifiers also have coating inhibition and filtration loss reduction effects, thus contributing to wellbore stability.

[0003] Currently used water-based drilling fluid thickeners such as carboxymethyl cellulose and modified guar gum have good salt resistance, capable of withstanding salt saturation, but their temperature resistance is below 150℃. Synthetic polymers, mainly partially hydrolyzed polyacrylamide and its derivatives, can effectively thicken fluids with molecular weights greater than 1 million, but their salt resistance is poor. Furthermore, these thickeners lack inhibition effects when facing shale formations, easily causing wellbore instability. For example, patent CN103113518 B provides a drilling fluid thickener and its preparation method, producing an amphoteric hydrophobic associative thickener. This thickener exhibits excellent temperature resistance but poor salt resistance and lacks shale inhibition properties. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a polymer thickener and filtration loss reducer and its preparation method, wherein the polymer thickener and filtration loss reducer can effectively thicken and has good temperature and salt resistance.

[0005] To achieve the above objectives, the present invention provides a polymer thickener and filtration loss reducer, which is prepared by copolymerization of monomers under the action of an initiator;

[0006] The monomers include: acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, monomer A, and monomer B. The structure of monomer A is shown in Formula I, and the structure of monomer B is shown in Formula II.

[0007]

[0008] According to a specific embodiment of the present invention, preferably, the molar ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, monomer A and monomer B is (50-65):(10-25):(10-15):(3-6).

[0009] According to a specific embodiment of the present invention, preferably, the initiator is selected from the ammonium persulfate and sodium bisulfite system, the potassium persulfate and sodium bisulfite system, the manganese chloride and sodium bisulfite system, ammonium persulfate alone, potassium persulfate alone, or azobisisobutyrazoline hydrochloride.

[0010] According to a specific embodiment of the present invention, preferably, the initiator is azobisisobutyrazoline hydrochloride.

[0011] According to a specific embodiment of the present invention, preferably, the ratio of the total mass of the monomer to the mass of the initiator is 100:(0.2-0.5).

[0012] The present invention also provides a method for preparing the above-mentioned polymer thickener and filtration loss reducer, which includes the following steps:

[0013] (1) Dissolve the raw materials 2-acrylamido-dimethylpropanesulfonic acid, acrylamide, and monomer A in water, and adjust the pH of the solution to 6-9;

[0014] (2) Add monomer B to the solution, pass nitrogen gas to remove oxygen, and heat to 40-60℃ at the same time;

[0015] (3) Add an initiator to the solution, continue to pass nitrogen gas through, react under stirring conditions, add ethanol, take out the solid product, dry and pulverize it to obtain the polymer thickening and filtration loss reducing agent.

[0016] According to a specific embodiment of the present invention, preferably, in step (1), the total mass ratio of the three monomers 2-acrylamido-dimethylpropanesulfonic acid, acrylamide and monomer A to the mass ratio of water is 1:(3-4).

[0017] According to a specific embodiment of the present invention, preferably, in step (3), the drying is drying until the solvent content is less than 7%, more preferably, the drying is carried out at 60-80°C.

[0018] According to a specific embodiment of the present invention, preferably, in step (1), the pH of the solution is adjusted using NaOH or ammonia.

[0019] According to a specific embodiment of the present invention, preferably, in step (3), ethanol is added after stirring the reaction for 4-8 hours.

[0020] According to a specific embodiment of the present invention, the above preparation method can be carried out according to the following specific steps:

[0021] (1) Under stirring conditions, dissolve the raw materials 2-acrylamido-dimethylpropanesulfonic acid, acrylamide, and monomer A in water; add NaOH or ammonia to the solution to adjust its pH value to 6-9;

[0022] (2) Add monomer B to the solution, pass nitrogen gas to remove oxygen, and heat to 40-60℃ at the same time;

[0023] (3) Add an initiator to the solution, continue to pass nitrogen gas through, react for 4-8 hours under stirring, add ethanol, take out the solid product, dry and crush it to obtain a polymer thickening and filtration loss reducing agent.

[0024] The molecular structure of the polymer thickener and filtration loss reducer prepared in this invention is shown in Formula III:

[0025]

[0026] In Equation III, a, b, c, and d are natural numbers.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] The polymer thickener and filtration loss reducer of this invention uses two novel monomers. Monomer A contains two anionic groups, namely a carboxyl group and a sulfonic acid group, which have good temperature and salt resistance. Monomer B contains a cationic adsorption group, which has good clay inhibition properties. Furthermore, due to the presence of a rigid and hydrophobic benzene ring at the end position, it has good hydrophobic association, which can thicken the polymer through hydrophobic association. The polymer thickener and filtration loss reducer prepared by this invention has good temperature and salt resistance, can effectively thicken, and has a temperature resistance of up to 200°C and a salt resistance of up to saturated NaCl. Detailed Implementation

[0029] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0030] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0031] The chemical name of monomer A used in the following examples is: N-benzyl-2-(methacryloyloxy)-N,N-dimethylethan-1-aminium (CAS No.: 784131-86-8), purchased from Mitsubishi Petrochemical Corporation, Japan.

[0032] The chemical name of monomer B is 4-(2-(methacryloyloxy)ethoxy)-4-oxo-2-sulfobutanoic acid, CAS No.: 62849-97-2, purchased from Mitsubishi Petrochemical Corporation, Japan.

[0033] Example 1

[0034] This embodiment provides a polymer thickener and filtration loss reducer, which is prepared by the following method:

[0035] Add 127g of water, 12g (0.169mol) of acrylamide, 17.5g (0.0845mol) of 2-acrylamido-2-methylpropanesulfonic acid, and 10.47g (0.033mol) of monomer A to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Then add NaOH to adjust the pH to 6.0, followed by adding 2.37g (0.010mol) of monomer B and purging with nitrogen to remove oxygen. After purging with nitrogen, heat the flask until it reaches 40°C, then add 0.0847g of azobisisobutyrazoline hydrochloride and continue purging with nitrogen to remove oxygen.

[0036] The reaction lasted for 4 hours. After 4 hours, the semi-solid polymer was poured into an ethanol solution for purification, cut into small pieces and granulated, and then dried in a 50°C oven to obtain polymer thickener and filtration loss reducer A.

[0037] Example 2

[0038] This embodiment provides a polymer thickener and filtration loss reducer, which is prepared by the following method:

[0039] Add 118.5 g of water, 12 g (0.169 mol) of acrylamide, 8.75 g (0.042 mol) of 2-acrylamido-2-methylpropanesulfonic acid, and 10.47 g (0.033 mol) of monomer A to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Add NaOH to adjust the pH to 7.0, then add 2.63 g (0.011 mol) of monomer B and purge with nitrogen gas to remove oxygen. After purging with nitrogen, heat the flask until it reaches 50°C. Add 0.101 g of azobisisobutyrazoline hydrochloride and continue purging with nitrogen gas. Stop purging after half an hour.

[0040] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was poured into an ethanol solution for purification, cut into small pieces and granulated. Then it was placed in a 65°C oven to dry. The white granules obtained after drying were the polymer thickener and filtration loss reducer B.

[0041] Example 3

[0042] This embodiment provides a polymer thickener and filtration loss reducer, which is prepared by the following method:

[0043] Add 132g of water, 12g (0.169mol) of acrylamide, 5.38g (0.026mol) of 2-acrylamido-2-methylpropanesulfonic acid, and 12.09g (0.039mol) of monomer A to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Then add NaOH to adjust the pH to 9, followed by adding 3.65g (0.0156mol) of monomer B and purging with nitrogen gas to remove oxygen. After purging with nitrogen gas, heat the flask until it reaches 60°C, then add 0.165g of azobisisobutyrazoline hydrochloride. Continue purging with nitrogen gas and stop after half an hour.

[0044] The reaction lasted for 8 hours. After 8 hours, the semi-solid polymer was poured into an ethanol solution for purification, cut into small pieces and granulated. Then it was placed in an 80°C oven to dry. The white granules obtained after drying were the polymer thickener and filtration loss reducer C.

[0045] Comparative Example 1

[0046] This comparative example provides a polymer prepared by the following method:

[0047] Add 48.7g of water, 10g (0.14mol) of acrylamide, and 6.23g (0.020mol) of monomer A to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Add NaOH to adjust the pH to 7, then purge with nitrogen to remove oxygen. After purging with nitrogen, heat until the temperature reaches 50°C. Add 0.0487g of azobisisobutyrazoline hydrochloride and continue purging with nitrogen. Stop after half an hour.

[0048] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was purified by pouring it into an ethanol solution, then granulated and dried in an 80°C oven. The resulting white granules were polymer control sample 1. The molecular structure of polymer control sample 1 is shown in Formula IV:

[0049]

[0050] In Equation IV, a and b are both constants.

[0051] Comparative Example 2

[0052] This comparative example provides a polymer prepared by the following method:

[0053] Add 48.7 g of water, 10 g (0.14 mol) of acrylamide, and 4.16 g (0.020 mol) of 2-acrylamido-2-methylpropanesulfonic acid to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Then add NaOH to adjust the pH to 7, followed by purging with nitrogen gas to remove oxygen. After purging with nitrogen gas, heat the flask until it reaches 50°C, then add 0.0424 g of azobisisobutyrazoline hydrochloride. Continue purging with nitrogen gas, and stop after half an hour.

[0054] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was purified by pouring it into an ethanol solution, then granulated and dried in an 80°C oven. The resulting white granules were polymer control sample 2. The molecular structure of this polymer is shown in Formula V.

[0055]

[0056] In equation V, a and b are both natural numbers.

[0057] Comparative Example 3

[0058] This comparative example provides a polymer prepared by the following method:

[0059] Add 48.86 g of water, 10 g (0.14 mol) of acrylamide, 4.16 g (0.020 mol) of 2-acrylamido-2-methylpropanesulfonic acid, and 2.12 g of p-vinylbenzyltrimethylammonium chloride to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Then add NaOH to adjust the pH to 7, followed by purging with nitrogen gas to remove oxygen. After purging with nitrogen gas, heat the flask until it reaches 50°C, then add 0.048 g of azobisisobutyrazoline hydrochloride. Continue purging with nitrogen gas for half an hour, then stop.

[0060] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was purified by pouring it into an ethanol solution, then granulated and dried in an 80°C oven. The resulting white granules were polymer control sample 3. The molecular structure of the polymer is shown in Formula VI:

[0061]

[0062] In Equation VI, a, b, and c are all natural numbers.

[0063] Comparative Example 4

[0064] This comparative example provides a polymer prepared by the following method:

[0065] Add 49.5 g of water, 10 g (0.14 mol) of acrylamide, and 4.16 g (0.020 mol) of 2-acrylamido-2-methylpropanesulfonic acid to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and stir until all monomers are dissolved. Add NaOH to adjust the pH to 7, then add 2.35 g (0.010 mol) of monomer B and purge with nitrogen gas to remove oxygen. After purging with nitrogen, heat the flask until it reaches 50°C. Add 0.0495 g of azobisisobutyrazoline hydrochloride and continue purging with nitrogen gas. Stop purging after half an hour.

[0066] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was poured into an ethanol solution for purification, granulated, and then dried in an 80°C oven. The resulting white granules were polymer control sample 4. The polymer structure is shown in formula VII.

[0067]

[0068] In equation VII, a, b, and c are all natural numbers.

[0069] Comparative Example 5

[0070] This comparative example provides a polymer prepared by the following method:

[0071] Add 51.84 g of water, 10 g (0.14 mol) of acrylamide, 4.16 g (0.020 mol) of 2-acrylamido-2-methylpropanesulfonic acid, and 3.12 g (0.010 mol) of monomer A to a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and heating device. Start the stirrer and wait for all monomers to dissolve. Then add NaOH to adjust the pH to 7, followed by purging with nitrogen gas to remove oxygen. After purging with nitrogen gas, heat the flask until it reaches 50°C, then add 0.0518 g of azobisisobutyrazoline hydrochloride. Continue purging with nitrogen gas for half an hour, then stop.

[0072] The reaction lasted for 6 hours. After 6 hours, the semi-solid polymer was purified by pouring it into an ethanol solution, then granulated and dried in an 80°C oven. The resulting white granules were polymer control sample 5. The polymer structure is shown in formula VIII.

[0073]

[0074] In equation VIII, a, b, and c are all natural numbers.

[0075] Performance testing experiment

[0076] Experiments were conducted using the products prepared in Examples 1-3 (filtration loss reducer A, filtration loss reducer B, and filtration loss reducer C) and the polymers prepared in Comparative Examples 1-5 (comparative samples 1-5).

[0077] Preparation of freshwater-based slurry: Add 400g of tap water to an enamel cup, add 16g of bentonite and 0.8g of sodium carbonate while stirring continuously, stir at 600r / min for 30min, then transfer to a mixing cup and stir at 12000r / min for 10min, and cure at room temperature for 24h to obtain freshwater-based slurry.

[0078] (1) Take 8 portions of pre-hydrated freshwater-based slurry, and add 1 wt% of filtration loss reducer (filtration loss reducer A, filtration loss reducer B, filtration loss reducer C, control sample 1, control sample 2, control sample 3, control sample 4, and control sample 5) to the freshwater-based slurry under continuous stirring. Stir at high speed until homogeneous, and label them as filtration loss reducer A freshwater-based slurry, filtration loss reducer B freshwater-based slurry, filtration loss reducer C freshwater-based slurry, control sample 1 freshwater-based slurry, control sample 2 freshwater-based slurry, control sample 3 freshwater-based slurry, control sample 4 freshwater-based slurry, and control sample 5 freshwater-based slurry, respectively. Rheological tests and filtration loss tests were performed on these eight polymer-containing freshwater-based slurries and the original freshwater-based slurry at room temperature. The results are shown in Table 1.

[0079] Table 1. Test results of rheological properties and filtrate loss of experimental slurry at room temperature.

[0080] Experimental Slurry <![CDATA[AV(mPa . S)]]> <![CDATA[PV(mPa . S)]]> YP(Pa) <![CDATA[FL API (mL)]]> Original freshwater-based pulp 3 2.5 0.5 26 Filtration Loss Reducer A (Fresh Water-Based Slurry) 60 39 21 6.2 Filtration Loss Reducer B - Freshwater-Based Slurry 62 46 16 5.6 Filtration Loss Reducer C - Freshwater-Based Slurry 66 42 24 4.8 Comparison Sample 1: Freshwater-based slurry 30 21 9 9.4 Comparison Sample 2: Freshwater-based slurry 41 34 7 12.8 Comparison Sample 3: Freshwater-based slurry 28 16 12 11.8 Comparison Sample 4: Freshwater-based slurry 46 30 8 8.8 Comparison Sample 5: Freshwater-based slurry 43 26 17 8.2

[0081] In Table 1, AV represents apparent viscosity, PV represents plastic viscosity, YP refers to dynamic shear stress, and FL... API This refers to the filtration loss of drilling fluid at normal temperature and pressure. As shown in Table 1, the filtration loss reducer of the present invention has good filtration loss reduction performance and significant viscosity-increasing effect even with a very small dosage. After adding the filtration loss reducer of the present invention to the freshwater-based slurry, its viscosity is significantly improved compared to the original freshwater-based slurry.

[0082] Comparison of Examples 1 and 2 shows that monomer A has a significantly better effect on the polymer's filtration loss reduction performance than 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0083] Comparison of Examples 3 and 4 shows that monomer B has a significantly better effect on reducing polymer filtration loss and increasing viscosity than p-vinylbenzyltrimethylammonium chloride. Furthermore, the benzene ring of monomer B is located at the end position, thus exhibiting good hydrophobic association effect.

[0084] (2) Eight pre-hydrated freshwater-based slurries were mixed with 1 wt% of a filtration loss reducer (filtration loss reducer A, filtration loss reducer B, filtration loss reducer C, control sample 1, control sample 2, control sample 3, control sample 4, and control sample 5) under continuous stirring. The mixture was stirred at high speed until homogeneous and labeled as filtration loss reducer A freshwater-based slurry, filtration loss reducer B freshwater-based slurry, filtration loss reducer C freshwater-based slurry, control sample 1 freshwater-based slurry, control sample 2 freshwater-based slurry, control sample 3 freshwater-based slurry, control sample 4 freshwater-based slurry, and control sample 5 freshwater-based slurry. A hot rolling aging test at 200℃ was conducted on these eight polymer-containing freshwater-based slurries and the original freshwater-based slurry. Rheological tests and filtration loss tests were then performed. The results are shown in Table 2.

[0085] Table 2. Test results of rheological properties and filtrate loss of experimental slurry at high temperature.

[0086] Experimental Slurry <![CDATA[AV(mPa . S)]]> <![CDATA[PV(mPa . S)]]> YP(Pa) <![CDATA[FL API (mL)]]> Original freshwater-based pulp 5 4 1 66 Filtration Loss Reducer A (Fresh Water-Based Slurry) 21 17 4 8.0 Filtration Loss Reducer B - Freshwater-Based Slurry 18 16 2 7.6 Filtration Loss Reducer C - Freshwater-Based Slurry 28 22 6 6.2 Comparison Sample 1 8 6 2 13.4 Comparison Sample 2 9 8 1 15.9 Comparison Sample 3 12 11 1 14.8 Comparison Sample 4 15 13 2 10.4 Comparison Sample 5 16 14 2 10.0

[0087] As shown in Table 2, the filtration loss reducer of the present invention still has good filtration loss reduction performance under fresh water-based slurry and 200°C conditions, indicating that the filtration loss reducer has good temperature resistance.

[0088] (3) Preparation of 36% sodium chloride brine base slurry: Add 400g of tap water to an enamel cup, add 16g of bentonite, 0.8g of sodium carbonate and 144g of sodium chloride while stirring continuously. Stir at 600r / min for 30min, then transfer to a high-speed stirring cup and stir at 12000r / min for 10min. Cure at room temperature for 24h to obtain brine base slurry.

[0089] Preparation of experimental slurry: Take eight portions of pre-hydrated brine-based slurry and add 2 wt% of filtration loss reducers (filtration loss reducer A, filtration loss reducer B, filtration loss reducer C, control sample 1, control sample 2, control sample 3, control sample 4, and control sample 5) to the brine-based slurry under continuous stirring. Stir at high speed until homogeneous. Rheological tests and filtration loss tests are performed on the brine-based slurry and the eight polymer-containing brine-based slurries, respectively. The results are shown in Table 3.

[0090] Table 3. Test results of rheological properties and filtrate loss of experimental slurry under normal temperature and high salinity conditions.

[0091] Experimental Slurry <![CDATA[AV(mPa . S)]]> <![CDATA[PV(mPa . S)]]> YP(Pa) <![CDATA[FL API (mL)]]> brine-based slurry 5 5 0 92 Filtration Loss Reducer A (Brine-Based Slurry) 38 32 6 8.4 Filtration Loss Reducer B B-Based Slurry 24 20 4 7.8 Filtration Loss Reducer C Brine-Based Slurry 44 34 10 6.2 Comparison Sample 1 14 12 2 22.2 Comparison Sample 2 15 11 4 26.4 Comparison Sample 3 18 15 3 28.8 Comparison Sample 4 22 16 6 14.0 Comparison Sample 5 24 17 7 12.8

[0092] As shown in Table 3, the filtration loss reducing agent of the present invention has good filtration loss reducing performance in saturated brine and requires a small dosage.

[0093] (4) Take four portions of freshwater-based slurry and add 1 wt% of the filtration loss reducer prepared in Example 3 and three imported filtration loss reducers (Driscal-D, Dristemp, and Polydrill) to the pre-hydrated freshwater-based slurry under continuous stirring. Driscal-D and Dristemp are acrylamide polymer filtration loss reducers, and Polydrill is a sulfonated polymer filtration loss reducer. Stir at high speed until homogeneous, and label the slurry as filtration loss reducer C freshwater-based slurry, Driscal-D freshwater-based slurry, Dristemp freshwater-based slurry, and Polydrill freshwater-based slurry. Test their rheological properties and filtration loss. The results are shown in Table 4.

[0094] Table 4. Room temperature rheological properties and filtration loss of experimental slurries containing different filtration loss reducers.

[0095] Experimental Slurry <![CDATA[AV(mPa . S)]]> <![CDATA[PV(mPa . S)]]> YP(Pa) <![CDATA[FL API (mL)]]> Filtration Loss Reducer C - Freshwater-Based Slurry 66 42 24 4.8 Driscal-D Freshwater-Based Pulp 46 21 25 13.5 Dristemp Freshwater-Based Pulp 47 26 21 8.4 Polydrill freshwater-based pulp 3.5 3 0.5 15.6

[0096] As shown in Table 4, under normal temperature conditions, the filtration loss reducing agent prepared in this invention is superior to the imported filtration loss reducing agent at the same concentration, proving that it has a better filtration loss reducing effect.

[0097] (5) Take 4 portions of freshwater-based slurry and add 1 wt% of the filtration loss reducer prepared in Example 3 and three imported filtration loss reducers (Driscal-D, Dristemp, and Polydrill) to the pre-hydrated freshwater-based slurry under continuous stirring. Driscal-D and Dristemp are acrylamide polymer filtration loss reducers, and Polydrill is a sulfonated polymer filtration loss reducer. Stir at high speed until homogeneous, and label them as filtration loss reducer C freshwater-based slurry, Driscal-D freshwater-based slurry, Dristemp freshwater-based slurry, and Polydrill freshwater-based slurry. Perform a 200℃ hot rolling aging test on each of the four freshwater-based slurries. After aging, test their rheological properties and filtration loss. The results are shown in Table 5.

[0098] Table 5. High-Temperature Rheological Properties and Filtration Loss Tests with Different Filtration Loss Reducers

[0099] Experimental Slurry <![CDATA[AV(mPa . S)]]> <![CDATA[PV(mPa . S)]]> YP(Pa) <![CDATA[FL API (mL)]]> Filtration Loss Reducer C - Freshwater-Based Slurry 28 22 6 10 Driscal-D Freshwater-Based Pulp 8 7 1 38 Dristemp Freshwater-Based Pulp 22.5 20 2.5 16.2 Polydrill freshwater-based pulp 12.5 11 1.5 74

[0100] As shown in Table 5, the temperature- and salt-resistant filtration loss reducer prepared in this invention is significantly superior to the imported filtration loss reducer after aging, and has good temperature resistance.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polymer viscosifier fluid loss additive, which is prepared by copolymerization of monomers under the action of an initiator; wherein the monomers comprise acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, monomer A and monomer B in a molar ratio of (50-65):(10-25):(10-15):(3-6), the structure of monomer A is shown in formula I, and the structure of monomer B is shown in formula II:

2. The polymeric viscosifying fluid loss agent of claim 1, wherein, the initiator is selected from the group consisting of ammonium persulfate and sodium bisulfite system, potassium persulfate and sodium bisulfite system, manganese chloride and sodium bisulfite system, ammonium persulfate single agent, potassium persulfate single agent or azobisimidozoline hydrochloride.

3. The polymeric viscosifying fluid loss agent of claim 1, wherein, the initiator is azobisimidozoline hydrochloride.

4. The polymeric viscosifier fluid loss additive of any of claims 1-3, wherein, the mass ratio of the total mass of monomers to the mass of initiator is 100:(0.2-0.5).

5. A method for preparing the polymer viscosifier fluid loss additive according to any one of claims 1-4, comprising the following steps: (1) dissolving raw materials 2-acrylamido-dimethylpropane sulfonic acid, acrylamide and monomer A in water, and adjusting the pH value of the solution to 6-9; (2) adding monomer B to the solution, deoxygenating by nitrogen blowing, and heating to 40-60℃ at the same time; (3) adding the initiator to the solution, continuing to blow nitrogen, and adding ethanol after reaction under stirring, drying and crushing the solid product to obtain the polymer viscosifier fluid loss additive.

6. The production method according to claim 5, wherein In step (1), the mass ratio of the total mass of 2-acrylamido-dimethylpropane sulfonic acid, acrylamide and monomer A to the mass of water is 1:(3-4).

7. The production method according to claim 5, wherein In step (3), the drying is performed until the solvent content is less than 7%.

8. The production method according to claim 7, wherein The drying is performed at 60-80℃.

9. The production method according to claim 5, wherein In step (1), the pH value of the solution is adjusted by NaOH or ammonia.

10. The production method according to claim 5, wherein, In step (3), ethanol is added after stirring for 4-8h. In step (1), the pH value of the solution is adjusted by NaOH or ammonia. In step (3), ethanol is added after stirring for 4-8h.

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