Salt-tolerant hydrophobic association polymer suspension emulsion and preparation method and application thereof

Abstract

The invention provides a salt-tolerant hydrophobic association polymer suspension emulsion and a preparation method and application thereof, and belongs to the technical field of oil and gas well fracturing, the suspension emulsion comprises the following components by weight: 40-50 parts of white oil, 4-6 parts of a suspending agent, 40-50 parts of hydrophobic association polymer powder, 5-10 parts of an emulsifier, 1-2 parts of a conditioning agent, and 0.1-0.2 part of a preservative. The preparation method comprises the following steps: adding the white oil into a reaction kettle, and starting stirring for 30 minutes; sequentially adding the suspending agent and the hydrophobic association polymer powder into the reaction kettle, and stirring for 30 minutes; after uniformly dispersing, adding an emulsifier, and stirring for 30 minutes; adding a conditioning agent, continuously and circularly stirring for 30 minutes, and then adding a preservative to obtain the hydrophobic association polymer suspension emulsion for fracturing. The suspension emulsion provided by the invention has the advantages of rapid dissolution and tackification and good salt tolerance, and meets the technical requirements of large-displacement hydraulic fracturing construction for continuous mixing by using flow-back fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well fracturing, and particularly to a salt-tolerant hydrophobically associating polymer suspension emulsion, a preparation method thereof, and an application thereof. Background Art

[0002] With the large-scale exploitation of shale oil and gas and tight oil and gas, fracturing and reforming of oil and gas wells can effectively increase production, and continuous mixing of large-displacement hydraulic fracturing has become the preferred choice for more. Polyacrylamide is one of the main raw materials of fracturing fluid thickeners, and has advantages such as fast dissolution rate, low friction, high viscoelasticity, and low formation damage, and has been promoted and applied. In order to save fracturing costs and reduce the damage to the environment near the well site at the same time, currently, oilfields will preferentially use produced water and return flow water for liquid preparation (hereinafter collectively referred to as return flow water). And the salinity of these return flow waters is relatively high, generally about 10,000 ppm, and the highest is above 50,000 ppm. This has higher requirements for the polymer thickeners used, that is, under the conditions of high salinity water quality, they can dissolve and thicken quickly, have a high viscosity retention rate, and low friction.

[0003] Currently, the mainstream polyacrylamide polymer thickeners used are mainly divided into two types: solid dry powder and water-in-oil emulsion. There are problems such as slow dissolution rate and easy generation of "fish eyes" during the dissolution and thickening process of solid dry powder in water, which cannot meet the requirements of rapid thickening of continuous mixing in fracturing construction. Although the water-in-oil emulsion can meet the requirements of continuous mixing for the thickening speed and has the characteristics of being ready to use on-site. However, the solid content of such products is at most about 35%, and the problem of poor salt tolerance has been difficult to solve. Therefore, a new polymer thickener for fracturing is needed to meet the requirements of both rapid dissolution and salt tolerance. Summary of the Invention

[0004] The present invention solves the problem that the existing emulsion-type polymer fracturing fluid has poor salt tolerance and cannot meet the requirements of large-displacement continuous mixing fracturing construction under the conditions of high salinity return flow fluid. The suspension emulsion is a new type of polymer thickener, which has the advantages of rapid dissolution and thickening and good salt tolerance, and meets the technical requirements of large-displacement hydraulic fracturing construction using return flow fluid for continuous mixing.

[0005] One of the purposes of the present invention is to provide a salt-tolerant hydrophobically associating polymer suspension emulsion.

[0006] Another purpose of the present invention is to provide a preparation method of the salt-tolerant hydrophobically associating polymer suspension emulsion.

[0007] The third purpose of the present invention is to provide an application of the salt-tolerant hydrophobically associating polymer suspension emulsion.

[0008] In order to achieve the above purposes of the present invention, the following technical solutions are specifically adopted:

[0009] In a first aspect, the present invention provides a salt-tolerant hydrophobically associating polymer suspension emulsion, which comprises the following components in parts by weight: 40-50 parts of white oil, 4-6 parts of suspending agent, 40-50 parts of salt-tolerant hydrophobically associating polymer, 5-10 parts of emulsifier, 1-2 parts of regulator, and 0.1-0.2 parts of preservative.

[0010] The following is a detailed description of each component:

[0011] White oil:

[0012] The white oil includes but is not limited to 3# white oil, 5# white oil, etc.

[0013] The addition amount of the white oil can be, for example, 40, 42, 44, 45, 46, 48, 50 parts by weight.

[0014] Suspending agent:

[0015] The suspending agent includes but is not limited to carboxymethyl cellulose, bentonite, etc.

[0016] The addition amount of the suspending agent can be, for example, 4, 5, 6 parts by weight.

[0017] Salt-tolerant hydrophobically associating polymer:

[0018] The salt-tolerant hydrophobically associating polymer is prepared by the following method:

[0019] Mix acrylamide, salt-resistant monomer, hydrophobic monomer and water, add urea, disodium ethylenediaminetetraacetate, sodium formate, ammonium persulfate, sodium bisulfite and azo salt to initiate a polymerization reaction. After the reaction, naturally cool down, take out the colloid, separate, dry, pulverize, and sieve to obtain the salt-tolerant hydrophobically associating polymer;

[0020] Wherein the structure of the salt-resistant monomer is as follows:

[0021]

[0022] The hydrophobic monomer is one or more selected from cetyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, tetradecyl methacrylate, dodecyl acrylamide.

[0023] In some embodiments, the mass ratio of acrylamide, salt-resistant monomer, hydrophobic monomer and water is 20-30: 2-4: 0.5-1: 65-75.

[0024] In some embodiments, the addition amount of urea is 2-3% of the total mass of the monomers (acrylamide, salt-resistant monomer, hydrophobic monomer);

[0025] The addition amount of disodium ethylenediaminetetraacetate is 0.02 - 0.06% of the total mass of the monomers (acrylamide, salt - resistant monomer, hydrophobic monomer);

[0026] The addition amount of sodium formate is 0.05 - 0.15% of the total mass of the monomers (acrylamide, salt - resistant monomer, hydrophobic monomer);

[0027] The addition amounts of ammonium persulfate, sodium bisulfite and azo salt are each independently 0.005 - 0.01% of the total mass of the monomers (acrylamide, salt - resistant monomer, hydrophobic monomer).

[0028] Preferably, the azo salt is one or more selected from azobisisobutyronitrile and azobis (isobutyramidine) hydrochloride.

[0029] In some embodiments, the initiation temperature is 20 - 25 °C and the reaction time is 4 - 6 hours.

[0030] In some embodiments, the salt - resistant monomer is prepared by the following method:

[0031] Mix maleic anhydride and sodium hydroxyethyl sulfonate, add a small amount of concentrated sulfuric acid as a catalyst, and heat for reaction to obtain the salt - resistant monomer;

[0032] Preferably, the molar ratio of maleic anhydride to sodium hydroxyethyl sulfonate is 1:2 - 3;

[0033] Preferably, the reaction temperature is 70 °C and the reaction time is 4 - 8 h.

[0034] In a specific embodiment, the salt - resistant hydrophobically associating polymer is prepared by the following method:

[0035] Add acrylamide, salt - resistant monomer, and hydrophobic monomer into distilled water. The mass ratio of acrylamide, salt - resistant monomer, hydrophobic monomer to water is 20 - 30:2 - 4:0.5 - 1:65 - 75. Add them into a reaction kettle, keep purging with nitrogen to remove oxygen, add 2 - 3% urea, 0.02 - 0.06% EDTA - 2Na, 0.05 - 0.15% sodium formate, 0.005 - 0.01% ammonium persulfate, 0.005 - 0.01% sodium bisulfite and 0.005 - 0.01% azo salt. The initiation temperature is 20 - 25 °C, and react for 4 - 6 hours. When the reaction temperature no longer rises, after naturally cooling for 2 h, take out the colloid, separate, dry, pulverize, and sieve to obtain the salt - resistant hydrophobically associating polymer powder.

[0036] The addition amount of the salt - resistant hydrophobically associating polymer can be, for example, 40, 42, 44, 45, 46, 48, 50 parts by weight.

[0037] In a specific embodiment, the structure of the salt - resistant hydrophobically associating polymer is as follows:

[0038]

[0039] Emulsifier:

[0040] The emulsifier includes, but is not limited to, span20, span80, tween80, OP-10, AEO-9, etc.

[0041] The addition amount of the emulsifier can be, for example, 5, 6, 7, 8, 9, 10 parts by weight.

[0042] Regulator:

[0043] The regulator includes, but is not limited to, propylene glycol, glycerol, etc.

[0044] The addition amount of the regulator can be, for example, 1, 1.2, 1.5, 1.6, 1.8, 2 parts by weight.

[0045] Preservative:

[0046] The preservative includes, but is not limited to, sodium diacetate, sodium benzoate, etc.

[0047] The addition amount of the preservative can be, for example, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2 parts by weight.

[0048] In a second aspect, the present invention provides a method for preparing the above-mentioned salt-tolerant hydrophobically associating polymer suspension emulsion, comprising the following steps:

[0049] Disperse white oil, suspending agent and salt-tolerant hydrophobically associating polymer evenly, then add emulsifier, and then add regulator and preservative to obtain the salt-tolerant hydrophobically associating polymer suspension emulsion.

[0050] In some embodiments, the method for preparing the salt-tolerant hydrophobically associating polymer suspension emulsion comprises the following steps:

[0051] (1) Add white oil into the reaction kettle, and start stirring;

[0052] (2) Add the suspending agent and the hydrophobically associating polymer powder into the reaction kettle in sequence, and stir;

[0053] (3) After dispersing evenly, add emulsifier and stir;

[0054] (4) Add regulator and preservative, continue stirring, after the temperature drops to normal temperature, open the bottom valve and the discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into barrels.

[0055] In a third aspect, the present invention provides an application of the above-mentioned salt-tolerant hydrophobically associating polymer suspension emulsion in preparing fracturing fluid.

[0056] Beneficial effects

[0057] (1) The hydrophobic associating polymer suspension emulsion formulated in the present invention has rapid dissolution, good fluidity and stability. According to the construction requirements, the use concentration can be adjusted to be used as slick water or sand-carrying fluid to meet the technical requirements for the performance of fracturing fluids at different stages in continuous mixing fracturing construction, and it is convenient for on-site use.

[0058] (2) The salt-resistant monomer with double sulfonic groups self-made in the present invention is used to prepare a hydrophobic associating polymer suspension emulsion with a long-chain hydrophobic monomer, effectively improving the salt tolerance of the thickener, and still having a high viscosity under the conditions of high salinity water with a TDS of 50000 ppm or produced water (where the total content of calcium and magnesium ions is greater than 2000 ppm).

[0059] (3) The solid content of the hydrophobic associating polymer suspension emulsion prepared in the present invention can reach more than 40%, and good performance can be obtained at low concentrations, reducing the use cost of fracturing fluids.

[0060] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art, invention content or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Shows the test results of the drag reduction rate of the suspension emulsion in fresh water.

[0062] Figure 2 Shows the test results of the drag reduction rate of the suspension emulsion in brine.

[0063] Figure 3 Shows the rheological curve of the suspension emulsion in fresh water at 120 °C for 2 h.

[0064] Figure 4 Shows the rheological curve of the suspension emulsion in brine at 120 °C for 2 h. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0065] The present invention will be further described below in conjunction with the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed by the present invention.

[0066] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, methods in the art.

[0067] The raw materials involved in the examples and comparative examples are as follows:

[0068] Acrylic acid (AA) was purchased from Nantong Runfeng Petrochemical Co., Ltd.

[0069] Acrylamide (AM) was purchased from Nantong Runfeng Petrochemical Co., Ltd.

[0070] The hydrophobic monomer was purchased from Zhangjiagang Renda Chemical Co., Ltd.

[0071] The emulsifier was purchased from Jiangsu Haian Petrochemical Factory.

[0072] White oil was purchased from Kunshan Ocean Lubricating Oil Co., Ltd.

[0073] Example 1: Preparation of Hydrophobically Associating Polymer Suspension Emulsion A for Fracturing

[0074] (1) Preparation method of salt-resistant monomer: Add 200 g of pure water to a three-necked flask, add 1.0 mol of maleic anhydride and 2.0 mol of sodium hydroxyethyl sulfonate, stir at a speed of 300 r / min for 10 min, add a small amount of concentrated sulfuric acid as a catalyst, and heat to 70 °C. Continue stirring for 30 min and dry at 70 °C for 2 h to obtain the salt-resistant monomer.

[0075] (2) Preparation method of salt-tolerant hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 650 g of pure water and 21 g of granular caustic soda, dissolve evenly, place it in a constant temperature water bath, slowly add 35 g of salt-resistant monomer, stir and dissolve evenly, then add 279 g of acrylamide monomer and 6 g of octadecyl dimethyl allyl ammonium chloride. Continue stirring and cooling to 20 °C. Then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the external circulation water temperature of the reaction kettle to 20 °C, continue stirring for 30 min, and after sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 9.0 g of urea. After purging with nitrogen from a high-purity nitrogen cylinder for 60 min, slowly add 3 mL of ammonium persulfate solution (concentration 0.5%), 6 mL of sodium bisulfite solution (concentration 0.2%), and 0.02 g of azo salt, and keep purging with nitrogen and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles larger than 60 mesh, and dry at 70 °C for 2 h. After sieving, the salt-tolerant hydrophobically associating polymer powder is obtained.

[0076] (3) Preparation method of salt-tolerant hydrophobically associating polymer suspension emulsion

[0077] Take 40 parts of No. 5 white oil, stir at a speed of 1000 r / min. After stirring for 30 min, add 4 parts of carboxymethyl cellulose. After stirring for 10 min, add 50 parts of salt-tolerant hydrophobically associating polymer powder. After continuing to stir for 30 min until evenly dispersed, add 4 parts of span80 and 1 part of op-10. After stirring for 20 min, add 1 part of propylene glycol and 0.1 part of sodium benzoate. Continue stirring for 30 min. After the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0078] Example 2: Preparation of Hydrophobically Associating Polymer Suspension Emulsion B for Fracturing

[0079] (1) Preparation method of salt-resistant monomer: Add 200 g of pure water into a three-necked flask, add 1.0 mol of maleic anhydride and 2.0 mol of sodium hydroxyethyl sulfonate, stir at a speed of 300 r / min for 10 min, add a small amount of concentrated sulfuric acid as a catalyst, heat to 70 °C, continue to stir for 30 min, and dry at 70 °C for 2 h to obtain the salt-resistant monomer.

[0080] (2) Preparation method of salt-tolerant hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 700 g of pure water and 18 g of solid caustic soda, dissolve evenly, place it in a constant temperature water bath, slowly add 30 g of salt-resistant monomer, stir and dissolve evenly, then add 236 g of acrylamide monomer and 7 g of octadecyl dimethyl allyl ammonium chloride, continue to stir and cool down to 20 °C, then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the external circulation water temperature of the reaction kettle at 20 °C, continue to stir for 30 min, after sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 8 g of urea, purge with nitrogen from a high-purity nitrogen cylinder for 60 min, then slowly dropwise add 4 mL of ammonium persulfate solution (concentration 2%) and 6 mL of sodium bisulfite solution (concentration 1%), and 0.02 g of azo salt, while maintaining nitrogen purging and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles larger than 60 mesh, and dry at 70 °C for 2 h, and sieve to obtain the salt-tolerant hydrophobically associating polymer powder.

[0081] (3) Preparation method of salt-tolerant hydrophobically associating polymer suspension emulsion

[0082] Take 44 parts of No. 5 white oil, stir at a speed of 1000 r / min, after stirring for 30 min, add 4 parts of carboxymethyl cellulose, after stirring for 10 min, add 43 parts of salt-tolerant hydrophobically associating polymer powder, continue to stir for 30 min until evenly dispersed, then add 6 parts of span80 and 1.5 parts of tween80, after stirring for 20 min, add 1.5 parts of glycerol and 0.1 part of sodium benzoate, continue to stir for 30 min, after the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0083] Example 3: Preparation of Hydrophobically Associating Polymer Suspension Emulsion C for Fracturing

[0084] (1) Preparation method of salt-resistant monomer: Add 200 g of pure water into a three-necked flask, add 1.0 mol of maleic anhydride and 2.0 mol of sodium hydroxyethyl sulfonate, stir at a speed of 300 r / min for 10 min, add a small amount of concentrated sulfuric acid as a catalyst, heat to 70 °C, continue to stir for 30 min, and dry at 70 °C for 2 h to obtain the salt-resistant monomer.

[0085] (2) Preparation method of hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 720 g of pure water and 12 g of solid caustic soda, dissolve evenly, place it in a constant temperature water bath, slowly add 20 g of salt-resistant monomer, stir until dissolved evenly, then add 231 g of acrylamide monomer and 8 g of octadecyl dimethyl allyl ammonium chloride, continue to stir and cool down to 20 °C. Then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the outer circulation water temperature of the reaction kettle at 20 °C, continue to stir for 30 min, after sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 8 g of urea. After purging oxygen with high-purity nitrogen gas for 60 min, slowly dropwise add 4 mL of ammonium persulfate solution (concentration 2%) and 6 mL of sodium bisulfite solution (concentration 1%), and 0.02 g of azo salt, while maintaining nitrogen purging and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles larger than 60 mesh, and dry at 70 °C for 2 h, and then sieve to obtain the hydrophobically associating polymer powder.

[0086] (3) Preparation method of hydrophobically associating polymer suspension emulsion

[0087] Take 48 parts of No. 3 white oil, stir at a speed of 1000 r / min, after stirring for 30 min, add 6 parts of carboxymethyl cellulose, after stirring for 10 min, add 40 parts of hydrophobically associating polymer powder, continue to stir for 30 min until evenly dispersed, then add 4 parts of span80 and 1 part of op-10, after stirring for 20 min, add 1 part of propylene glycol and 0.1 part of sodium diacetate, continue to stir for 30 min. After the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0088] Comparative Example 1

[0089] The difference from Example 1 is that the salt-resistant monomer is not added.

[0090] (1) Preparation method of hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 650 g of pure water and 21 g of granular caustic soda. After dissolving evenly, place it in a constant temperature water bath, and slowly add 314 g of acrylamide monomer and 6 g of octadecyl dimethyl allyl ammonium chloride. Stir to dissolve evenly, cool down to 20 °C, then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the outer circulation water temperature of the reaction kettle to be 20 °C, and continue stirring for 30 min. After sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 9 g of urea. After purging oxygen with high-purity nitrogen for 60 min, slowly dropwise add 3 mL of ammonium persulfate solution (concentration 0.5%), 6 mL of sodium bisulfite solution (concentration 0.2%), and 0.02 g of azo salt, and keep purging nitrogen and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles larger than 60 mesh, and dry it at 70 °C for 2 h. After sieving, the hydrophobically associating polymer powder is obtained.

[0091] (2) Preparation method of hydrophobically associating polymer suspension emulsion

[0092] Take 40 parts of No. 5 white oil, stir at a speed of 1000 r / min. After stirring for 30 min, add 4 parts of carboxymethyl cellulose. After stirring for 10 min, add 50 parts of hydrophobically associating polymer powder. Continue stirring for 30 min until evenly dispersed, then add 4 parts of span80 and 1 part of op-10. After stirring for 20 min, add 1 part of propylene glycol and 0.1 part of sodium benzoate. Continue stirring for 30 min. After the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0093] Comparative Example 2

[0094] The difference from Example 2 is that the anti-salt monomer is not added.

[0095] (1) Preparation method of hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 700 g of pure water and 18 g of granular caustic soda. After dissolving evenly, place it in a constant temperature water bath. Slowly add 266 g of acrylamide monomer and 7 g of octadecyl dimethyl allyl ammonium chloride. After stirring and dissolving evenly, cool down to 20 °C. Then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the external circulation water temperature of the reaction kettle at 20 °C, and continue stirring for 30 min. After sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 8 g of urea. After purging oxygen with high-purity nitrogen for 60 min, slowly dropwise add 4 mL of ammonium persulfate solution (concentration 2%), 6 mL of sodium bisulfite solution (concentration 1%), and 0.02 g of azo salt, and keep purging nitrogen and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles with a mesh size of over 60 meshes, and dry it at 70 °C for 2 h. After sieving, the hydrophobically associating polymer powder is obtained.

[0096] (2) Preparation method of hydrophobically associating polymer suspension emulsion

[0097] Take 44 parts of No. 5 white oil, stir at a speed of 1000 r / min. After stirring for 30 min, add 4 parts of carboxymethyl cellulose. After stirring for 10 min, add 43 parts of hydrophobically associating polymer powder. After continuing to stir for 30 min until evenly dispersed, add 6 parts of span80 and 1.5 parts of tween80. After stirring for 20 min, add 1.5 parts of glycerol and 0.1 part of sodium benzoate. Continue to stir for 30 min. After the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0098] Comparative Example 3

[0099] The difference from Example 3 is that the anti-salt monomer is not added.

[0100] (1) Preparation method of hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 720 g of pure water and 12 g of granular caustic soda. After dissolving evenly, place it in a constant temperature water bath. Slowly add 251 g of acrylamide monomer and 8 g of octadecyl dimethyl allyl ammonium chloride. After stirring and dissolving evenly, cool down to 20 °C. Then pour the solution in the above three-necked flask into a 3.0 L reaction kettle, control the external circulation water temperature of the reaction kettle at 20 °C, and continue stirring for 30 min. After sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 8 g of urea. After purging oxygen with high-purity nitrogen for 60 min, slowly dropwise add 4 mL of ammonium persulfate solution (concentration 2%), 6 mL of sodium bisulfite solution (concentration 1%), and 0.02 g of azo salt, and keep purging nitrogen and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles with a mesh size of more than 60 meshes, and dry it at 70 °C for 2 h. After sieving, the hydrophobically associating polymer powder is obtained.

[0101] (2) Preparation method of hydrophobically associating polymer suspension emulsion

[0102] Take 48 parts of No. 3 white oil, stir at a speed of 1000 r / min. After stirring for 30 min, add 6 parts of carboxymethyl cellulose. After stirring for 10 min, add 40 parts of hydrophobically associating polymer powder. After continuing to stir for 30 min until evenly dispersed, add 4 parts of span80 and 1 part of op-10. After stirring for 20 min, add 1 part of propylene glycol and 0.1 part of sodium diacetate. Continue stirring for 30 min. After the temperature drops below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0103] Comparative Example 4

[0104] The difference from Example 1 is that the anti-salt monomer is replaced with 2-acrylamido-2-methylpropanesulfonic acid.

[0105] (1) Preparation method of hydrophobically associating polymer powder: Take a 1000 mL three-necked flask, add 650 g of pure water and 21 g of granular caustic soda. After dissolving evenly, place it in a constant temperature water bath. Slowly add 35 g of 2-acrylamido-2-methylpropanesulfonic acid. After stirring and dissolving evenly, add 279 g of acrylamide monomer and 6 g of octadecyl dimethyl allyl ammonium chloride. Continue to stir and cool down to 20 °C. Then pour the solution in the above three-necked flask into a 3.0 L reaction kettle. Control the external circulation water temperature of the reaction kettle at 20 °C. Continue to stir for 30 min. After sufficient dissolution, add 0.3 g of sodium formate, 0.15 g of disodium ethylenediaminetetraacetate, and 9 g of urea. After purging oxygen with high-purity nitrogen for 60 min, slowly dropwise add 3 mL of ammonium persulfate solution (concentration 0.5%), 6 mL of sodium bisulfite solution (concentration 0.2%), and 0.02 g of azo salt. Keep purging nitrogen and stirring. The initiation temperature is 20 - 25 °C, and the reaction lasts for 4 - 6 hours. When the reaction temperature no longer rises, after natural cooling for 2 h, take out the colloid from the reaction kettle, granulate it into powder particles larger than 60 mesh, and dry it at 70 °C for 2 h. After sieving, the hydrophobically associating polymer powder is obtained.

[0106] (2) Preparation method of hydrophobically associating polymer suspension emulsion

[0107] Take 40 parts of No. 5 white oil, stir at a speed of 1000 r / min. After stirring for 30 min, add 4 parts of carboxymethyl cellulose. After stirring for 10 min, add 50 parts of hydrophobically associating polymer powder. After continuing to stir for 30 min until evenly dispersed, add 4 parts of span80 and 1 part of op-10. After stirring for 20 min, add 1 part of propylene glycol and 0.1 part of sodium benzoate. Continue to stir for 30 min. After the temperature drops to below normal temperature of 25 °C, open the bottom valve and discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into a barrel.

[0108] Performance Evaluation

[0109] (1) Viscosity increasing rate test: Measure 500 m of standard brine (salinity about 33000 ppm, calcium and magnesium ion content 2000 ppm) in a stirrer, adjust the rotation speed of the stirrer to 1500 r / min ± 90 r / min, weigh 3 mL of suspension emulsion, measure its viscosity with a six-speed viscometer after stirring for 3 min, and compare it with the viscosity after 10 min. The test result of Example 1 is: the viscosity at 3 min is 36 mPa·s, the viscosity at 10 min is 39 mPa·s, and the viscosity increasing speed is 39 / 42 = 92.3%, which is greater than 90%.

[0110] (2) Salt tolerance test: Measure 500 mL of distilled water into a stirrer, adjust the stirrer speed to 1500 r / min ± 90 r / min, weigh 3 mL of the suspension emulsion, stir for 3 min, then place the solution in a constant temperature water bath at 25°C ± 1°C for 2 h, and use a six-speed viscometer to measure its viscosity and compare it with the viscosity in standard salt water. The test result of Example 1 is: the viscosity in distilled water is 28.5 mPa·s, and the viscosity retention rate is 28.5 / 39 = 73.1%, which is greater than 70%.

[0111] (3) Drag reduction rate test: Prepare 0.10% solutions of the suspension emulsion using clear water and standard salt water respectively, and detect them according to the standard method of NB / T14003.1 - 2015, with a pipe diameter of 14 mm and a displacement of 100 L / min. The test results of Example 1 are shown in Figure 1 、 Figure 2 。 Figure 1 are the drag reduction rate test results of the suspension emulsion in clear water. The maximum drag reduction rate is 76.3%, the time required to reach the maximum drag reduction rate is 54 s, and the drag reduction rate at the end time is 74.5%. Figure 2 are the drag reduction rate test results of the suspension emulsion in standard salt water. The maximum drag reduction rate is 72.1%, the time required to reach the maximum drag reduction rate is 69 s, and the drag reduction rate at the end time is 70.8%.

[0112] (4) Temperature and shear resistance test: Prepare a 1.0% solution, measure an appropriate amount and put it into a HAAKE MARSⅢ rheometer, with a 38# rotor, a shear rate of 170 s -1 , a temperature of 120°C, and a shear time of 120 min, and read the apparent viscosity value after shearing for 120 min. The test results of Example 1 are shown in Figure 3 、 Figure 4 : The final viscosity is 75.8 mPa·s.

[0113] The results are shown in Table 1.

[0114] Table 1

[0115]

[0116]

[0117] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: without departing from the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing examples can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A salt-tolerant hydrophobically associating polymer suspension emulsion, characterized in that, It comprises the following components in parts by weight: 40 - 50 parts of white oil, 4 - 6 parts of suspending agent, 40 - 50 parts of salt - tolerant hydrophobically associating polymer, 5 - 10 parts of emulsifier, 1 - 2 parts of regulator, and 0.1 - 0.2 parts of preservative; Wherein the salt - tolerant hydrophobically associating polymer is prepared by the following method: Mix acrylamide, salt - resistant monomer, hydrophobic monomer and water, add urea, disodium ethylenediaminetetraacetate, sodium formate, ammonium persulfate, sodium bisulfite and azo salt to initiate polymerization reaction. After the reaction, cool naturally, take out the colloid, separate, dry, pulverize and sieve to obtain the salt - tolerant hydrophobically associating polymer; Wherein the structure of the salt - resistant monomer is as follows: The hydrophobic monomer is one or more selected from cetyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, tetradecyl methacrylate, dodecyl acrylamide.

2. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, wherein The white oil is one or more selected from 3# white oil and 5# white oil; and / or The suspending agent is one or more selected from carboxymethyl cellulose and bentonite; and / or The emulsifier is one or more selected from span20, span80, tween80, OP - 10 and AEO - 9; and / or The regulator is one or more selected from propylene glycol and glycerol; and / or The preservative is one or more selected from sodium diacetate and sodium benzoate.

3. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, wherein The mass ratio of acrylamide, salt - resistant monomer, hydrophobic monomer and water is 20 - 30:2 - 4:0.5 - 1:65 - 75.

4. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, characterized in that, The addition amount of urea is 2 - 3% of the total mass of monomers; The addition amount of disodium ethylenediaminetetraacetate is 0.02 - 0.06% of the total mass of monomers; The addition amount of sodium formate is 0.05 - 0.15% of the total mass of monomers; The addition amounts of ammonium persulfate, sodium bisulfite and azo salt are each independently 0.005 - 0.01% of the total mass of monomers.

5. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, characterized in that, The initiation temperature is 20 - 25°C and the reaction time is 4 - 6 hours.

6. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, wherein The salt - resistant monomer is prepared by the following method: Mix maleic anhydride and sodium hydroxyethyl sulfonate, add a small amount of concentrated sulfuric acid as a catalyst, heat and react to obtain the salt - resistant monomer; Preferably, the molar ratio of maleic anhydride to sodium hydroxyethyl sulfonate is 1:2 - 3; Preferably, the reaction temperature is 60 - 80°C and the reaction time is 4 - 8 h.

7. The salt-tolerant hydrophobically associating polymer suspension emulsion according to claim 1, wherein The structure of the salt - tolerant hydrophobically associating polymer is as follows:

8. A method for preparing a salt-tolerant hydrophobically associating polymer suspension emulsion according to any one of claims 1-7, characterized in that, It includes the following steps: Disperse white oil, suspending agent and salt - tolerant hydrophobically associating polymer evenly, then add emulsifier, and then add regulator and preservative to obtain a salt - tolerant hydrophobically associating polymer suspension emulsion.

9. The preparation method according to claim 8, wherein It includes the following steps: (1) Add white oil into the reaction kettle and start stirring; (2) Add the suspending agent and the powder of hydrophobically associating polymer into the reaction kettle in sequence and stir; (3) After dispersing evenly, add emulsifier and stir; (4) Add regulator and preservative, continue stirring. After the temperature drops to room temperature, open the bottom valve and the discharge port of the reaction kettle, and discharge the suspension emulsion in the kettle into barrels.

10. Use of the salt - tolerant hydrophobically associating polymer suspension emulsion according to any one of claims 1 - 7 in the preparation of fracturing fluid.

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