Fracturing thickening agent, its preparation method and application

Abstract

This invention provides a thickener for fracturing, its preparation method, and its application. The preparation method includes: reacting monomers in an aqueous environment using an azo initiator and a redox initiator; the resulting product is then granulated, hydrolyzed, dried, and powdered to obtain the thickener for fracturing; wherein, based on the total monomer mass of 100%, the monomers include 64.5%-70.5% hydrophilic monomers, 5.5%-7% cationic monomers, 18%-24.5% anionic monomers, and 4.5%-7.0% composite supramolecular interaction monomers; the hydrophilic monomer is acrylamide; the cationic monomer is dimethyl diallyl ammonium chloride and / or acryloyloxyethyltrimethylammonium chloride; the anionic monomer is sodium acrylate; the composite supramolecular interaction monomers include a mixture of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and silane monomers in a mass ratio of 4.1-4.5:1:0.3-0.7.

Description

Technical Field

[0001] This invention relates to a thickener for fracturing, its preparation method, and its application. Background Technology

[0002] Volumetric fracturing thickeners have undergone multiple generations of product iterations, achieving "one agent, multiple uses" and exhibiting temperature and salt resistance. However, the proppant delivery capacity (i.e., proppant carrying capacity) of thickeners across various viscosity ranges (low, medium, and high viscosity) still needs further improvement. This is particularly true in deep shale gas fracturing operations, where the deep reservoirs and high in-situ stress make fractures easier to close, placing higher demands on the proppant carrying capacity of the fracturing fluid (full-area fracture support under high in-situ stress conditions).

[0003] In the low viscosity range, when used as slickwater, its proppant-carrying capacity needs further improvement to carry more proppant into the far end of fractures and enhance reservoir stimulation. Currently, increasing the viscosity of slickwater is a common method to improve its proppant-carrying capacity. However, numerous studies have shown that simply increasing the viscosity of slickwater to improve its proppant-carrying capacity leads to a decrease in the complexity of volumetric fracturing fractures and the length of connecting natural fractures, which is detrimental to improving the stimulation effect. Therefore, there is an urgent need to develop new thickeners that, when used as slickwater, can significantly increase its proppant-carrying capacity without significantly increasing the viscosity of the slickwater, enabling volumetric fracturing to create complex fracture networks using low-viscosity fracturing fluid while carrying more proppant into the far end of fractures.

[0004] In the medium to high viscosity range, linear adhesives and gels are used to provide matching fracturing fluids for the dynamic fracture full-domain proppant fracturing process with "ultra-low pre-position, real-time viscosity change, combined support, and dynamic placement" as the core of the current unconventional reservoir. Compared with conventional proppant-carrying fluids with medium to high viscosity, it can further improve proppant carrying performance and carry more proppant into the far end of the fracture to improve the volumetric modification effect.

[0005] In summary, further research is needed on new thickeners for strong proppant fracturing that can be used to formulate slickwater fracturing fluids and gel fracturing fluids with strong proppant carrying capacity, thereby enabling propulsion of the proppant into the depths of the fracture and achieving full-domain fracture support. Summary of the Invention

[0006] The purpose of this invention is to provide a thickener technology for strong suspended proppant fracturing that can be used to prepare slickwater fracturing fluid and gel fracturing fluid with strong proppant carrying capacity to propel proppant deep into fractures.

[0007] To achieve the above objectives, the present invention provides the following technical solution.

[0008] In a first aspect, the present invention provides a method for preparing a thickener for fracturing, wherein the preparation method includes:

[0009] The monomer is reacted in an aqueous environment using an azo initiator and a redox initiator. The resulting product is then granulated, hydrolyzed, dried, and powdered to obtain the fracturing thickener.

[0010] The monomers, based on a total mass of 100%, comprise 64.5%-70.5% hydrophilic monomers, 5.5%-7% cationic monomers, 18%-24.5% anionic monomers, and 4.5%-7.0% complex supramolecular interaction monomers. The hydrophilic monomer is selected from acrylamide; the cationic monomer is selected from at least one of dimethyl diallyl ammonium chloride and acryloyloxyethyltrimethyl ammonium chloride; the anionic monomer is selected from sodium acrylate; and the complex supramolecular interaction monomer comprises a mixture of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and silane monomers in a mass ratio of 4.1-4.5:1:0.3-0.7.

[0011] The fracturing thickener preparation method provided by this invention utilizes a special hydrophilic monomer, cationic monomer, anionic monomer, and composite supramolecular interaction monomer with specific monomer ratios, employing a segmented initiation process followed by hydrolysis to prepare the fracturing thickener. The fracturing thickener prepared by this method exhibits strong proppant-carrying capacity throughout the fracturing process, and can be used to formulate slickwater fracturing fluids and gel fracturing fluids with strong proppant-carrying properties, thereby advancing the proppant deeper into the fracture and achieving full-domain fracture support.

[0012] The invention provides a method for preparing a fracturing thickener. During synthesis, a segmented initiation process significantly increases the molecular weight and conversion rate of the prepared thickener, enhancing its thickening properties and reducing dosage. Furthermore, by finely adjusting the type, ratio, and amount of composite supramolecular monomers, the prepared thickener achieves a substantial increase in proppant-carrying capacity across all viscosity ranges without significantly increasing viscosity. This allows it to carry more proppant into the far end of the fracture, effectively improving reservoir stimulation. Moreover, through the increase in molecular weight and the introduction of temperature- and salt-resistant monomers, it achieves salt tolerance exceeding 60,000 ppm, making it suitable for direct preparation of flowback fluids and with a temperature resistance of 180°C, greatly expanding its application scenarios.

[0013] The fracturing thickener preparation method provided by this invention utilizes a special composite supramolecular monomer. The composite supramolecular monomer functions by achieving hydrophobic association between thickener molecules. When the thickener aqueous solution reaches the critical association concentration (CAC), a spatial network structure begins to form within the solution. This network structure macroscopically manifests as a significant increase in the solution's elasticity without a substantial increase in viscosity. This, in turn, significantly enhances the sand-suspending performance through an elastic sand-suspending mechanism, and is beneficial for increasing the complexity of volumetric fracture modification and the length of naturally occurring fractures, without affecting drag reduction performance. This invention employs a composite supramolecular interaction monomer consisting of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and silane monomers in a specific ratio selected through extensive research. Compared to conventional hydrophobic monomers, this composite supramolecular interaction monomer allows for precise control of intermolecular supramolecular forces. In particular, the introduction of trace amounts of silane supramolecular interaction monomers, through the synergistic effect between the two types and three supramolecular interaction monomers, not only significantly reduces the critical association concentration (CAC) of the thickener aqueous solution, thereby significantly reducing the amount of thickener required, but also significantly increases the intermolecular forces and the elasticity and strength of the network structure, thereby greatly improving the suspension performance of the thickener.

[0014] According to a preferred embodiment of the first aspect, preferably, the silane monomer includes at least one of vinyltrimethylsilane and allyltrimethylsilane.

[0015] According to a preferred embodiment of the first aspect, preferably, the azo initiator is azobisisobutyramidine hydrochloride.

[0016] According to a preferred embodiment of the first aspect, preferably, the amount of azo initiator is 0.02%-0.035% based on the total mass of the monomers as 100%.

[0017] According to a preferred embodiment of the first aspect, preferably, the redox reaction initiator includes sodium hypophosphite, sodium metabisulfite, and sodium persulfate;

[0018] More preferably, based on the total mass of the monomers as 100%, the amount of sodium hypophosphite is 0.02%-0.035%, the amount of sodium metabisulfite is 0.005%-0.015%, and the amount of sodium persulfate is 0.015%-0.03%.

[0019] According to a preferred embodiment of the first aspect, preferably, the mass content of the monomer is 25.5%-28% based on the total mass of water and monomer in the aquatic environment as 100%.

[0020] According to a preferred embodiment of the first aspect, preferably, the aquatic environment further contains a solubility regulator, said solubility regulator comprising urea and sodium formate;

[0021] More preferably, the mass ratio of urea to sodium formate is 18-22:1;

[0022] More preferably, the total amount of urea and sodium formate is 5%-10% based on the total mass of the monomers, which is 100%.

[0023] Adding urea and sodium formate as solubility modifiers can adjust the solubility and speed of the prepared fracturing thickener. Compared with the conventional use of a single solubility modifier, under the same concentration conditions, the solubility and speed of the prepared fracturing thickener are significantly improved, effectively reducing the dissolution time of the prepared fracturing thickener. This better meets the rapid dissolution requirements of fracturing fluids, especially those used for fracturing fluids in unconventional reservoirs such as shale gas. When 5%-10% of the total mass of monomers are added at a mass ratio of 20:1 (urea and sodium formate), the dissolution time of the prepared fracturing thickener can be achieved within 30 seconds, meeting the requirements for 20m fracturing fluids in unconventional reservoirs such as shale gas. 3 The requirement for continuous mixing of slickwater fracturing fluid and gel fracturing fluid under high-displacement construction conditions (<30s).

[0024] According to a preferred embodiment of the first aspect, preferably, the aquatic environment further contains a polymerization reaction stabilizer, said polymerization reaction stabilizer comprising EDTA-2Na and EDTA-5Na;

[0025] More preferably, the mass ratio of EDTA-2Na to EDTA-5Na is 1.5-2.5:1;

[0026] More preferably, the total amount of EDTA-2Na and EDTA-5Na is 0.1%-0.2% based on the total mass of the monomers (100%).

[0027] Adding EDTA-2Na and EDTA-5Na as polymerization stabilizers can control the polymerization rate and improve the stability of the prepared product by chelating metal ions. Compared with the conventional use of a single polymerization stabilizer, the polymerization rate control effect is stronger, the molecular weight of the polymerized product is larger, and the viscosity is significantly increased under the same concentration conditions, which significantly reduces the amount of thickener used.

[0028] According to the preferred embodiment of the first aspect, hydrolysis is preferably carried out by adding an aqueous sodium hydroxide solution;

[0029] More preferably, the mass concentration of sodium hydroxide in the sodium hydroxide aqueous solution is 35%-45%;

[0030] More preferably, the amount of sodium hydroxide aqueous solution used is 2%-5% based on the mass of the granulated particles (100%).

[0031] More preferably, hydrolysis is carried out at 80-90°C;

[0032] More preferably, the hydrolysis time is 1.5-2.5 hours.

[0033] According to a preferred embodiment of the first aspect, preferably, the method for preparing the thickener for fracturing includes:

[0034] 1) Prepare a first solution; wherein the first solution contains various components, monomers, and azo initiators in an aqueous environment;

[0035] 2) Heat the first solution to the target temperature; under heat preservation conditions, deoxygenate the first solution and mix it with the redox reaction initiator, and then carry out the reaction in an oxygen-free atmosphere;

[0036] 3) The product obtained from the reaction in step 2) is granulated, hydrolyzed, dried, and powdered in sequence to obtain the thickener for fracturing.

[0037] According to a preferred embodiment of the first aspect, preferably, the method for preparing the thickener for fracturing includes:

[0038] 1) Prepare a first solution; wherein the first solution contains all components in the aqueous environment, monomers, azo initiators, and part or all of the reducing agent in redox reaction initiators;

[0039] 2) Heat the first solution to the target temperature; under heat preservation conditions, deoxygenate the first solution and mix it with the remaining part of the redox reaction initiator, and then carry out the reaction in an oxygen-free atmosphere;

[0040] 3) The product obtained from the reaction in step 2) is granulated, hydrolyzed, dried, and powdered in sequence to obtain the thickener for fracturing.

[0041] According to a preferred embodiment of the first aspect, preferably, the pH value of the first solution is 6.85-7.25.

[0042] According to a preferred embodiment of the first aspect, preferably, the target temperature is 18-22°C.

[0043] According to the preferred embodiment of the first aspect, preferably, the deoxygenation process is carried out by introducing nitrogen gas; more preferably, the nitrogen gas is introduced for 30-45 minutes.

[0044] According to a preferred embodiment of the first aspect, preferably, a nitrogen atmosphere is used for the oxygen-free atmosphere.

[0045] According to the preferred embodiment of the first aspect, preferably, the reaction time is 3.5-4.5 hours during the reaction process carried out in an oxygen-free atmosphere.

[0046] In a second aspect, the present invention provides a thickener for fracturing, wherein the thickener for fracturing can be prepared by the preparation method of the thickener for fracturing provided in the first aspect of the invention.

[0047] The thickener for fracturing provided by this invention is a quaternary copolymer produced by a segmented initiation process using special proportions of hydrophilic monomers, cationic monomers, anionic monomers, and composite supramolecular monomers.

[0048] Thirdly, the present invention provides the application of the fracturing thickener provided in the second aspect of the present invention as a thickener in slickwater fracturing fluid and / or gel fracturing fluid.

[0049] According to the preferred embodiment of the third aspect, preferably, the amount of the thickener for fracturing provided in the second aspect of the present invention is 0.01%-0.1% based on the total mass of the slickwater fracturing fluid as 100%.

[0050] According to a preferred embodiment of the third aspect, preferably, the amount of the thickener for fracturing provided in the second aspect of the present invention is 0.1%-0.6% based on the total mass of the fracturing fluid as 100%.

[0051] The fracturing thickener provided by this invention possesses strong proppant-carrying capacity throughout the fracturing process. It can be used to formulate slickwater fracturing fluids and gel fracturing fluids with strong proppant-carrying properties, thereby advancing the proppant deeper into the fracture and achieving full-area fracture support. Compared with existing technologies, the technical solution provided by this invention has the following beneficial effects:

[0052] 1. The thickener for fracturing provided by this invention can be used to prepare slickwater fracturing fluid and gel fracturing fluid by changing its concentration. The slickwater fracturing fluid prepared by this invention has a drag reduction of over 70%, a salt tolerance of over 60,000 ppm, and a viscosity that is linearly adjustable from 2 to 30 mPa·s. The gel fracturing fluid prepared by this invention has a temperature resistance of over 180℃.

[0053] 2. The thickener for fracturing provided by the present invention, when formulated into a slickwater fracturing fluid with a low viscosity range (2-20 mPa.s), compared with slickwater fracturing fluid formulated with conventional thickeners (such as reverse emulsion drag reducers), satisfies the requirement of significantly increasing its proppant carrying capacity (60%-120% increase in suspension shear force) without significantly increasing the viscosity of slickwater (viscosity increase of 0%-20%). This achieves the effect of creating complex fracture networks through low-viscosity fracturing fluid while carrying more proppant into the far end of the fracture.

[0054] A specific embodiment of the fracturing thickener provides a 5 mPa·s slickwater fracturing fluid with a suspension shear force 79.8% higher than that of a conventional thickener fracturing fluid with the same viscosity. In dynamic sand suspension experiments, it exhibits stronger sand suspension capacity, carries sand over a longer distance, and distributes sand more evenly.

[0055] 3. When the thickener for fracturing provided by the present invention is formulated into a gel fracturing fluid with a medium to high viscosity range (20-50 mPa.s), the suspension shear force is increased by 10%-50% compared with gel fracturing fluids formulated with conventional thickeners (such as inverse emulsion thickeners).

[0056] A specific embodiment of the fracturing thickener provides a 50 mPa·s viscosity gel fracturing fluid with increased suspension shear force by 33.2% compared to gel fracturing fluid with conventional thickener of the same viscosity. In dynamic sand suspension experiments, it exhibits stronger sand suspension capacity, carries sand over a longer distance, and distributes sand more evenly.

[0057] 4. A comparison of the static sand suspension performance of the fracturing thickener provided by the technical solution of this invention with that of the thickener currently used in the field shows that, under the same concentration conditions, the sand suspension performance of the thickener for different specifications of proppant is stronger than that of the thickener currently used in the field. The proppant is more evenly distributed, and the sand does not easily settle after 2 hours. The sand suspension capacity of the fracturing thickener provided by the technical solution of this invention at 0.4% is even stronger than that of the thickener currently used in the field at 0.6% (e.g., reverse emulsion thickener). Attached Figure Description

[0058] Figure 1 The graph shows the drag reduction rate of the fracturing thickener provided in Example 1 in water over time.

[0059] Figure 2 The graph shows the drag reduction rate of the fracturing thickener provided in Example 1 in 60,000 ppm brine over time.

[0060] Figure 3 This is a comparison chart of the thickening properties of the fracturing thickener provided in Example 1 and a conventional fracturing thickener.

[0061] Figure 4 The temperature and shear resistance of the gel fracturing fluid prepared with the fracturing thickener provided in Example 2 is shown in the figure.

[0062] Figure 5 A comparison chart of the dynamic proppant carrying capacity of 5 mPa·s slickwater fracturing fluid prepared with the fracturing thickener provided in Example 1 and slickwater fracturing fluid of the same viscosity prepared with conventional fracturing thickener.

[0063] Figure 6This is a comparison chart of the dynamic proppant carrying capacity of the 50 mPa·s gel fracturing fluid prepared with the fracturing thickener provided in Example 2 and the gel fracturing fluid of the same viscosity prepared with a conventional fracturing thickener.

[0064] Figure 7 This is a comparison chart showing the proppant suspension performance of the fracturing fluid prepared with the fracturing thickener provided in Example 2 and the fracturing fluid prepared with the same concentration of conventional fracturing thickener for proppant with different specifications.

[0065] Figure 8 This is a comparison chart of the proppant suspension performance of the fracturing fluid prepared with the fracturing thickener provided in Example 2 and the fracturing fluid prepared with conventional fracturing thickeners of the same and different concentrations. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0067] Example 1

[0068] This embodiment provides a thickener for fracturing.

[0069] This fracturing thickener is prepared by the following method:

[0070] Add 550 kg of water to the reactor, along with 134 kg of acrylamide, 11 kg of acryloyloxyethyltrimethylammonium chloride, 46 kg of sodium acrylate, and 9 kg of a mixture obtained by mixing hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and vinyltrimethylsilane in a mass ratio of 4.2:1:0.5. Then add 10.48 kg of urea, 0.52 kg of sodium formate, 0.05 kg of sodium hypophosphite, and EDTA-2Na. 0.17 kg of EDTA-5Na and 0.08 kg of azobisisobutyramidine hydrochloride were added, and the mixture was dissolved in pure water and the pH was adjusted to 6.91 to obtain the first solution. The reaction vessel containing the first solution was heated to 21°C. Under the heat preservation condition, nitrogen gas was introduced for 40 min to remove oxygen. Then, redox reaction initiators, sodium metabisulfite and sodium persulfate, were added. The nitrogen gas flow rate was increased to 50 L / min, and nitrogen was continued to be introduced until no more nitrogen could be introduced. The reaction was continued to be kept at the heat for 4 hours to complete the reaction. The obtained product was granulated, and 4% sodium hydroxide aqueous solution (sodium hydroxide concentration in the sodium hydroxide aqueous solution was 42%) of the granulated granules were added. The mixture was mixed evenly and hydrolyzed in an oven at 80°C for 2 h. The product was then dried and pulverized through a 100-mesh sieve to obtain the fracturing thickener.

[0071] The fracturing thickener provided in this embodiment was dissolved in clean water to prepare a slickwater fracturing fluid with a thickener mass concentration of 0.02% (based on the total mass of the slickwater fracturing fluid being 100%). The drag reduction rate of the fracturing thickener in clean water reached 75.56%, and the dissolution time of the fracturing thickener in clean water was 23 seconds. The change in drag reduction rate of the fracturing thickener in clean water over time is shown below. Figure 1 As shown.

[0072] The fracturing thickener provided in this embodiment was dissolved in 60,000 ppm sodium chloride brine to prepare slickwater fracturing fluid A with a thickener mass concentration of 0.03% (based on the total mass of the slickwater fracturing fluid being 100%). The viscosity of slickwater fracturing fluid A at room temperature and pressure was 5 mPa·s. The drag reduction rate of the fracturing thickener in 60,000 ppm sodium chloride brine reached 74.23%, and the dissolution time of the fracturing thickener in 60,000 ppm sodium chloride brine was 25 s. The change in drag reduction rate of the fracturing thickener in 60,000 ppm sodium chloride brine over time is shown below. Figure 2 As shown, the suspension shear force of the slickwater fracturing fluid B with the same viscosity was increased by 79.8% when the relatively inverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.) was dissolved in 60,000 ppm sodium chloride brine.

[0073] Fracturing fluids with different mass concentrations (0.03%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.4%, 0.6%) were prepared by dissolving the fracturing thickener provided in this embodiment in water. Similarly, fracturing fluids with different mass concentrations (0.03%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.4%, 0.6%) were prepared by dissolving the reverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.) in water. The concentrations of these fracturing fluids were then tested, and the results are as follows: Figure 3 As shown.

[0074] The fracturing thickener provided in this embodiment was dissolved in water to prepare a slickwater fracturing fluid C with a viscosity of 5 MPa·s at room temperature and pressure. An inverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.) was dissolved in water to prepare a slickwater fracturing fluid D with a viscosity of 5 MPa·s at room temperature and pressure. The dynamic proppant carrying capacity of both was tested, and the results are as follows. Figure 5 As shown. By Figure 5 It can be seen that the slickwater fracturing fluid prepared with the fracturing thickener provided in this embodiment is significantly better at pushing the proppant into the depth of the fracture, making the sandbank more gentle.

[0075] Example 2

[0076] This embodiment provides a thickener for fracturing.

[0077] This fracturing thickener is prepared by the following method:

[0078] Add 520 kg of water to the reactor, along with 130 kg of acrylamide, 12 kg of acryloyloxyethyltrimethylammonium chloride, 47 kg of sodium acrylate, and 11 kg of a mixture obtained by mixing hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and vinyltrimethylsilane in a mass ratio of 4.3:1:0.5. Then add 15.24 kg of urea, 0.76 kg of sodium formate, 0.06 kg of sodium hypophosphite, and EDTA-2Na. 0.2 kg of EDTA-5Na and 0.1 kg of azobisisobutyramidine hydrochloride were added, and the mixture was dissolved in pure water and the pH was adjusted to 6.91 to obtain the first solution. The reaction vessel containing the first solution was heated to 21°C. Under the heat preservation condition, nitrogen gas was introduced for 40 min to remove oxygen. Then, redox reaction initiators: sodium metabisulfite 0.02 kg and sodium persulfate 0.035 kg were added. The nitrogen gas flow rate was increased to 45 L / min, and nitrogen was continued until no more nitrogen could be introduced. The reaction was continued to be heated for 4 hours to complete the reaction. The obtained product was granulated, and 4.5% sodium hydroxide aqueous solution (sodium hydroxide concentration in the sodium hydroxide aqueous solution was 40%) of the granulated granules was added. The mixture was mixed evenly and hydrolyzed in an oven at 80°C for 2 h. The product was then dried and pulverized through a 100-mesh sieve to obtain the fracturing thickener.

[0079] In this embodiment, the fracturing thickener was dissolved in water to prepare a fracturing fracturing fluid with a thickener mass concentration of 0.3% (based on the total mass of the fracturing fluid being 100%). A Hacker rheometer was used to increase the test temperature to 180°C at a heating rate of 3°C / min, and the result was obtained within 100 seconds. -1 The shear test of the prepared gel hydraulic fracturing fluid for 2 hours yielded the following results: Figure 4 As shown, the viscosity of the prepared gel hydraulic fracturing fluid remains above 50 mPa·s, and its temperature resistance can reach 180℃.

[0080] The fracturing thickener provided in this embodiment was dissolved in water to prepare a gel-fracturing fluid A with a viscosity of 50 MPa·s at room temperature and pressure. The reverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.) was dissolved in water to prepare a gel-fracturing fluid B with a viscosity of 50 MPa·s at room temperature and pressure. The dynamic proppant carrying capacity of both fluids was tested, and the results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the gel-fracturing fluid B prepared with a conventional fracturing thickener carries proppant and accumulates in the middle of the flat plate to form a peak-shaped slope, while the gel-fracturing fluid A prepared with a fracturing thickener provided in this embodiment carries proppant and mainly accumulates in the middle and rear of the flat plate. Although the spreading distance is similar, the gel-fracturing fluid prepared with a fracturing thickener provided in this embodiment carries proppant further into the fracture depth, the sandbank height is reduced, and the proppant settlement height in the deeper part of the fracture is increased.

[0081] The fracturing thickener provided in this embodiment was dissolved in water to prepare fracturing fluid C with a thickener mass concentration of 0.4% (based on 100% of the total mass of the fracturing fluid). A reverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.) was dissolved in water to prepare fracturing fluid D with a thickener mass concentration of 0.4% (based on 100% of the total mass of the fracturing fluid). The sand suspension performance (sand suspension for 2 hours) of both fluids with different specifications of proppant at a sand ratio of 20% was tested. The results are as follows: Figure 7 As shown. Among them, Figure 7 Figure a shows a comparison of the effects of two different adhesive fracturing fluids on 40-70 mesh ceramsite proppant with a sand ratio of 20% after suspension for 2 hours. Figure 7 Figure b shows a comparison of the effects of two types of adhesive hydraulic fracturing fluids on quartz sand proppant with a sand ratio of 20% after suspension for 2 hours. Figure 7 Figure c shows a comparison of the effects of two different adhesive fracturing fluids on 20-40 mesh ceramsite proppant with a sand ratio of 20% after suspension for 2 hours. Figure 7 It can be seen that, under the same thickener concentration, the thickener provided in this embodiment exhibits stronger sand suspension performance for proppant of different specifications than conventional fracturing thickeners. The proppant distribution is more uniform, and the sand does not easily settle after 2 hours of suspension. The proppant is also less likely to form linear adhesions to the cylinder wall. A fracturing fluid E with a thickener concentration of 0.6% (based on the total mass of the fracturing fluid being 100%) was prepared by dissolving a conventional fracturing thickener in water. The sand suspension performance (sand suspension for 4 hours) of fracturing fluids C, D, and E on 40-70 mesh ceramsite proppant with a sand ratio of 20% was tested respectively. The results are as follows: Figure 8 As shown. By Figure 8 It can be seen that the fracturing thickener C prepared using the fracturing thickener provided in this embodiment, with a fracturing thickener mass concentration of 0.4% (based on the total mass of the fracturing fluid being 100%), has stronger sand-suspending performance than the fracturing thickener E prepared using a conventional fracturing thickener, with a fracturing thickener mass concentration of 0.6% (based on the total mass of the fracturing fluid being 100%).

[0082] Comparative Example 1

[0083] This comparative example provides a thickener for fracturing.

[0084] The preparation method of the fracturing thickener provided in this comparative example differs from the preparation method of the fracturing thickener provided in Example 1 only in that: octadecyl dimethyl allyl ammonium chloride and vinyltrimethylsilane are not added, and the amount of hexadecyl dimethyl allyl ammonium chloride used is 9 kg.

[0085] Comparative Example 2

[0086] This comparative example provides a thickener for fracturing.

[0087] The difference between the preparation method of the fracturing thickener provided in this comparative example and the preparation method of the fracturing thickener provided in Example 1 is only that: vinyltrimethylsilane is not added, and the mass ratio of octadecyl dimethyl allyl chloride to hexadecyl dimethyl allyl chloride is 1:1, and the sum of the amounts of octadecyl dimethyl allyl chloride and hexadecyl dimethyl allyl chloride is 9 kg.

[0088] Comparative Example 3

[0089] This comparative example provides a thickener for fracturing.

[0090] The preparation method of the fracturing thickener provided in this comparative example differs from the preparation method of the fracturing thickener provided in Example 1 only in that: vinyltrimethylsilane is not added, and the total amount of octadecyl dimethyl allyl ammonium chloride and hexadecyl dimethyl allyl ammonium chloride is 9 kg.

[0091] Comparative Example 4

[0092] This comparative example provides a thickener for fracturing.

[0093] The preparation method of the fracturing thickener provided in this comparative example differs from the preparation method of the fracturing thickener provided in Example 1 only in that the mass ratio of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride and vinyltrimethylsilane is 4.2:1:1, and the total mass of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride and vinyltrimethylsilane is 9 kg.

[0094] Experimental Example 1

[0095] The critical association concentrations of the fracturing thickeners provided in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 in water were tested respectively, and the results are shown in Table 1.

[0096] The fracturing thickeners provided in Examples 1, 1, 2, 3, and 4, as well as the reverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.), were dissolved in water to prepare slickwater fracturing fluids with a viscosity of 5 mPa·s at room temperature and pressure. The suspension shear force enhancement rate of the slickwater fracturing fluids prepared with the fracturing thickeners provided in Examples 1, 1, 2, 3, and 4, compared with that of the slickwater fracturing fluids prepared with conventional fracturing thickeners, was tested. The results are shown in Table 1.

[0097] The fracturing thickeners provided in Examples 1, 1, 2, 3, and 4, as well as the reverse emulsion thickener (purchased from Sichuan Chuanqing Well Technology Co., Ltd.), were dissolved in water to prepare gel-fracturing fluids with a viscosity of 50 mPa·s at room temperature and pressure. The suspension shear force enhancement rate of the gel-fracturing fluids prepared with the fracturing thickeners provided in Examples 1, 1, 2, 3, and 4, compared with that of the gel-fracturing fluids prepared with conventional fracturing thickeners, was tested. The results are shown in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] Example 3

[0102] This embodiment provides a thickener for fracturing.

[0103] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that sodium formate is not added.

[0104] Example 4

[0105] This embodiment provides a thickener for fracturing.

[0106] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that urea is not added.

[0107] Example 5

[0108] This embodiment provides a thickener for fracturing.

[0109] The preparation method of the fracturing thickener provided in this embodiment differs from the preparation method of the fracturing thickener provided in Example 1 only in that the mass ratio of urea to sodium formate is 1:1, and the total mass of urea and sodium formate is 11 kg.

[0110] Example 6

[0111] This embodiment provides a thickener for fracturing.

[0112] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that: 0.52 kg of urea and 10.48 kg of sodium formate are used.

[0113] Experimental Example 2

[0114] The dissolution time of the fracturing thickeners provided in Examples 1, 3, 4, 5, and 6 in water was tested (with the sum of the masses of water and the fracturing thickeners to be tested being 100%, and the mass concentration of the fracturing thickeners to be tested being 0.05 wt%). The results are shown in Table 2.

[0115] Table 2

[0116] Sources of thickeners for fracturing Dissolution time of 0.05wt% fracturing thickener in water / s Example 3 60 Example 4 77 Example 5 54 Example 6 45 Example 1 25

[0117] Example 7

[0118] This embodiment provides a thickener for fracturing.

[0119] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that EDTA-5Na is not added.

[0120] Example 8

[0121] This embodiment provides a thickener for fracturing.

[0122] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that EDTA-2Na is not added.

[0123] Example 9

[0124] This embodiment provides a thickener for fracturing.

[0125] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that the mass ratio of EDTA-2Na and EDTA-5Na is 1:1, and the total mass of EDTA-2Na and EDTA-5Na is 0.25 kg.

[0126] Example 10

[0127] This embodiment provides a thickener for fracturing.

[0128] The only difference between the preparation method of the fracturing thickener provided in this embodiment and the preparation method of the fracturing thickener provided in Example 1 is that the mass of EDTA-2Na is 0.17 kg and the mass of EDTA-5Na is 0.08 kg.

[0129] Experimental Example 3

[0130] The thickeners for fracturing provided in Examples 1, 7, 8, 9, and 10 were dissolved in water to prepare fracturing fluids with a thickener mass concentration of 0.2% (based on the total mass of the fracturing fluid being 100%). The viscosity of each fracturing fluid at room temperature and pressure was then tested, and the results are shown in Table 3.

[0131] Table 3

[0132]

[0133] The embodiments described above are for the purpose of better explaining the present invention. For those skilled in the art, it is not difficult to make various modifications to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and variations made to the present invention by those skilled in the art based on the principles and spirit of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a thickener for fracturing, wherein, The preparation method includes: The monomer is reacted in an aqueous environment using an azo initiator and a redox initiator. The resulting product is then granulated, hydrolyzed, dried, and powdered to obtain the fracturing thickener. The monomers, based on a total mass of 100%, comprise 64.5%-70.5% hydrophilic monomers, 5.5%-7% cationic monomers, 18%-24.5% anionic monomers, and 4.5%-7.0% complex supramolecular interaction monomers. The hydrophilic monomer is selected from acrylamide; the cationic monomer is selected from at least one of dimethyl diallyl ammonium chloride and acryloyloxyethyltrimethyl ammonium chloride; the anionic monomer is selected from sodium acrylate; and the complex supramolecular interaction monomer comprises a mixture of hexadecyl dimethyl allyl ammonium chloride, octadecyl dimethyl allyl ammonium chloride, and silane monomers in a mass ratio of 4.1-4.5:1:0.3-0.

7.

2. The preparation method according to claim 1, wherein, Silane monomers include at least one of vinyltrimethylsilane and allyltrimethylsilane.

3. The preparation method according to claim 1, wherein, The azo initiator selected is azobisisobutyramidine hydrochloride; and / or Based on the total mass of monomers as 100%, the amount of azo initiator used is 0.02%-0.035%.

4. The preparation method according to claim 1, wherein, Redox initiators include sodium hypophosphite, sodium metabisulfite, and sodium persulfate; Preferably, based on the total mass of the monomers (100%), the amount of sodium hypophosphite is 0.02%-0.035%, the amount of sodium metabisulfite is 0.005%-0.015%, and the amount of sodium persulfate is 0.015%-0.03%.

5. The preparation method according to claim 1, wherein, Based on the total mass of water and monomers in the aquatic environment being 100%, the mass content of monomers is 25.5%-28%.

6. The preparation method according to claim 1, wherein, The aquatic environment also contains solubility regulators, which include urea and sodium formate; Preferably, the mass ratio of urea to sodium formate is 18-22:1; Preferably, the total amount of urea and sodium formate is 5%-10% based on the total mass of the monomers, which is 100%.

7. The preparation method according to claim 1, wherein, The aquatic environment also contains polymerization reaction stabilizers, which include EDTA-2Na and EDTA-5Na; The mass ratio of EDTA-2Na to EDTA-5Na is 1.5-2.5:1; Based on the total mass of the monomers (100%), the total amount of EDTA-2Na and EDTA-5Na used is 0.1%-0.2%.

8. The preparation method according to claim 1, wherein, Hydrolysis is carried out by adding an aqueous sodium hydroxide solution; The mass concentration of sodium hydroxide in the sodium hydroxide aqueous solution is 35-45%. Based on the mass of the granulated particles obtained by granulation as 100%, the amount of sodium hydroxide aqueous solution used is 2%-5%; Preferably, hydrolysis is carried out at 80-90°C; Preferably, the hydrolysis time is 1.5-2.5 hours.

9. The preparation method according to any one of claims 1-8, wherein, The preparation method of the thickener for fracturing includes either step one or step two: Method 1: 1) Prepare a first solution; wherein the first solution contains various components, monomers, and azo initiators in an aqueous environment; 2) Heat the first solution to the target temperature; under heat preservation conditions, deoxygenate the first solution and mix it with the redox reaction initiator, and then carry out the reaction in an oxygen-free atmosphere; 3) The product obtained from the reaction is successively granulated, hydrolyzed, dried, and powdered to obtain the thickener for fracturing; Method 2: 1) Prepare a first solution; wherein the first solution contains all components in the aqueous environment, monomers, azo initiators, and part or all of the reducing agent in redox reaction initiators; 2) Heat the first solution to the target temperature; under heat preservation conditions, deoxygenate the first solution and mix it with the remaining part of the redox reaction initiator, and then carry out the reaction in an oxygen-free atmosphere; 3) The product obtained from the reaction is successively granulated, hydrolyzed, dried, and powdered to obtain the thickener for fracturing.

10. The preparation method according to claim 9, wherein, The pH value of the first solution is 6.85-7.

25.

11. The preparation method according to claim 9, wherein, The target temperature is 18-22℃; and / or During the reaction process under an oxygen-free atmosphere, the reaction time is 3.5-4.5 hours.

12. The preparation method according to claim 9, wherein, During the deoxygenation process, nitrogen gas is introduced to remove oxygen; preferably, the nitrogen gas introduction time is 30-45 minutes; and / or Nitrogen atmosphere is used for oxygen-free atmosphere.

13. A thickener for fracturing, wherein, The thickener for fracturing can be prepared by the method for preparing the thickener for fracturing according to any one of claims 1-12.

14. An application of the fracturing thickener of claim 13, wherein the application is the use of the fracturing thickener of claim 13 as a thickener in slickwater fracturing fluid and / or gel fracturing fluid.

15. The application according to claim 14, wherein, Based on the total mass of the slickwater fracturing fluid being 100%, the amount of the thickener used for fracturing is 0.01-0.1%. Based on the total mass of the fracturing fluid as 100%, the amount of the thickener used for fracturing is 0.1-0.6%.

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