A high-efficiency sand-carrying slickwater

Abstract

This invention relates to the field of slickwater technology, specifically to a high-efficiency proppant-carrying slickwater. It comprises a shear-responsive smart thickener and inorganic salts dispersed in an aqueous phase; the smart thickener is composed of ABA-type temperature-ion dual-responsive block copolymers and nano-silica particles with surface-grafted hydrophobic alkyl chains and cationic groups. The slickwater of this invention exhibits ultra-low viscosity and high drag reduction during the pumping stage (low temperature, high shear); upon entering a fracture, the synergistic effect of temperature rise and instantaneous high-speed shear triggers hydrophobic association of the copolymer and interweaving of the nanoparticles, forming a three-dimensional network structure; under the low-shear environment within the fracture, the network structure self-reinforces through ordered reconstruction of ion pairs, achieving high-viscosity proppant carrying. Its core lies in transforming the inherent temperature rise and shear effects of the process into a driving force for constructing a proppant-carrying network, thereby effectively resolving the contradiction between low-friction pumping and high proppant carrying capacity in slickwater volumetric fracturing and significantly reducing reservoir damage.

Description

Technical Field

[0001] This invention relates to the field of slickwater technology, specifically to a high-efficiency sand-carrying slickwater system. Background Technology

[0002] In the large-scale development of unconventional oil and gas resources such as shale gas and tight oil and gas, multi-stage volumetric fracturing of horizontal wells is a core production enhancement technology. Slippery water, due to its low viscosity, low friction, and low cost, has become the primary fracturing fluid. However, existing slippery water technology, while pursuing low pumping friction, has sacrificed proppant carrying capacity, leading to the following long-standing technical bottlenecks: Traditional slickwater fracturing primarily increases viscosity slightly by adding a small amount of linear polymer (such as polyacrylamide) to carry proppant. However, this significantly increases pipeline friction, leading to increased pump pressure and energy consumption. Achieving lower friction requires reducing the polymer concentration, but this causes premature proppant settling in the fracture, forming near-wellbore "sand embankments" that fail to provide effective support to the distal ends of the fracture, severely impacting fracturing efficiency.

[0003] Secondly, existing thickeners (polymers) for slickwater have a flexible long-chain structure, which is subjected to extremely strong shear forces when pumped at high speeds and passing through perforations and narrow cracks. This shear force causes irreversible mechanical degradation or conformational changes in the polymer chains, resulting in a permanent and significant decrease in the system's viscosity. Consequently, its sand-carrying capacity is severely weakened once it enters the cracks.

[0004] Furthermore, current improvement technologies mostly focus on optimizing single properties, such as reducing friction by developing new drag-reducing agents or increasing static proppant-carrying viscosity by introducing crosslinking agents. They cannot simultaneously achieve the dynamic adjustment characteristics of "ultra-low friction during pumping and high proppant-carrying capacity after entering the fracture." The requirements of fracturing processes vary both spatially (from the wellbore to the far end of the fracture) and temporally (from pumping to fracture closure), while the properties of existing materials are static.

[0005] Increasing polymer concentration to enhance sand-carrying capacity leads to more polymer residue, clogging reservoir micropores and impairing fracture conductivity. Despite the development of low molecular weight or "clean" polymers, it is often difficult to achieve a balance between sand-carrying capacity and damage.

[0006] In summary, existing technological approaches mostly focus on improving or physically blending single components, resulting in performance that is a linear superposition of the functions of each component, failing to produce a qualitative leap. Summary of the Invention

[0007] The present invention provides a highly efficient sand-carrying slickwater system to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides a highly efficient sand-carrying slickwater, which includes a shear-responsive smart thickener dispersed in an aqueous phase. The smart thickener is composed of an amphiphilic temperature-ion dual-responsive block copolymer and surface-functionalized nano-silica particles through multiple non-covalent interactions, and forms a shear-triggered dynamic three-dimensional network structure in a specific inorganic salt environment.

[0009] Furthermore, the amphiphilic temperature-ion dual-response block copolymer has an ABA-type triblock structure, wherein: Segment B is a temperature-sensitive polymer segment, preferably poly(N-isopropylacrylamide) (PNIPAM) or its derivatives. This segment hydrophilically extends at wellbore temperatures (<40°C) and undergoes a hydrophilic-hydrophobic transition at reservoir temperatures (>60°C), causing the segment to collapse and aggregate.

[0010] Segment A is a strongly ionic hydrophilic polymer segment, preferably poly(2-acrylamido-2-methylpropanesulfonate) sodium (PAMPS). This segment provides permanent hydration capability and a negative charge, ensuring the copolymer's solubility and stability in brine and preventing excessive aggregation of nanoparticles.

[0011] Furthermore, the surface-functionalized nano-silica particles have a particle size of 10-30 nm, and their surfaces are simultaneously grafted with: Hydrophobic alkyl chains (such as C) 12 -C 18 ), used to achieve strong hydrophobic association with the hydrophobic microregions generated by the B segment of the copolymer at high temperature.

[0012] Cationic groups (such as primary amino groups, -NH2), their protonated form (-NH3) + It can react with the sulfonate group (-SO3) on the A segment of the copolymer. - They form reversible ion pairs, and the binding strength of these ion pairs is designed to be sensitive to shear forces.

[0013] Furthermore, the slippery water also contains inorganic salts, such as potassium chloride (KCl), to provide ionic strength, at a concentration of 0.2%-3.0% (by weight).

[0014] Furthermore, the total concentration of the intelligent thickener (combined of copolymer and nanoparticles) is 0.01%-0.25% (by weight).

[0015] The efficient sand-carrying capacity of the slippery water in this invention does not rely on traditional polymer chain entanglement, but rather stems from its unique shear-triggered and network self-reinforcing mechanism. This mechanism is the synergistic result of the combined effects of copolymers, nanoparticles, inorganic salts, temperature, and shear fields, and specifically consists of three stages: Phase 1: Pumping Stage (Low Temperature, High Shear): Ultra-low friction state. During surface preparation and wellbore pumping, the fluid is at a relatively low temperature (<40℃) and an extremely high shear rate. At this time, the temperature-sensitive B-segments of the copolymer are highly hydrophilic and extended, and the entire molecular chain exhibits an extended conformation. Simultaneously, the high shear force causes temporary reversible ion pair dissociation between the cationic groups on the nanoparticle surface and the anionic segments of the copolymer, significantly reducing the effective connection points between the nanoparticles and the polymer chains. The system primarily exhibits Newtonian fluid characteristics or weak structural viscosity, macroscopically displaying a low viscosity (3-8 mPa·s) similar to water and a high drag reduction rate (>70%), achieving efficient and low-energy pumping.

[0016] Second stage: The triggering stage of entering the fracture (high temperature, instantaneous extreme shear): network structure formation. When the fluid passes through the perforation and enters the reservoir fracture, two key changes occur: the temperature rises sharply to the reservoir temperature (>60℃) and instantaneous extreme shear is experienced.

[0017] Temperature triggering: The B-segment (PNIPAM) of the copolymer undergoes a rapid hydrophilic-hydrophobic transition, the segments contract and aggregate to form a large number of hydrophobic microdomains.

[0018] Shear synergy: While extreme shear forces continue to hinder ion pair formation, the resulting dramatic fluctuations provide more opportunities for contact between the hydrophobic surfaces of functionalized nanoparticles and these newly formed hydrophobic microdomains. Within a specific time window of temperature-sensitive segment contraction, shear forces drive nanoparticles to anchor to multiple copolymer hydrophobic microdomains through hydrophobic interactions, forming an initial network structure centered on hydrophobic association crosslinking points.

[0019] Phase 3: Uniform Spreading and Sand-Carrying within the Fractured Network (High Temperature, Low Shear): Network Self-Reinforcement and High-Viscosity Sand Carrying. After the fluid enters the fracture network, the shear rate decreases sharply. At this stage, two key temporal synergies occur: First, the initially formed "hydrophobic association cross-linking points" are further strengthened and stabilized under the high temperature and pressure of the reservoir.

[0020] Subsequently, and crucially, as the shear force disappears, the reversible ion pairs between the nanoparticles and the copolymer chains are rapidly and orderly reconstructed. Since the nanoparticles have been initially fixed in the network by hydrophobic interactions, their relative positions with the negatively charged polymer chains (A segments) are more favorable, resulting in a much higher ion pair reconstruction efficiency than random collisions in free solution.

[0021] The essence of the whole process is that the system uses the inherent temperature rise and shear process of fracturing technology as a trigger to transform the high temperature and high shear environment that is originally unfavorable for sand carrying into the driving force for building a high-strength sand-carrying network, thus achieving precise spatiotemporal matching between rheological properties and engineering technology or applications.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This highly efficient proppant-carrying slickwater exhibits low viscosity during the pumping stage, significantly reducing pumping pressure. Upon entering fractures, it intelligently transforms into a high-viscosity proppant-carrying fluid, increasing the proppant ratio to 15%-30% and extending proppant delivery distance by over 50%. This is unparalleled by traditional physical mixing or simple modification techniques. Traditional thickeners have poor shear resistance, while the slickwater system of this invention utilizes the high-speed shearing inherent in the process itself as a triggering and promoting factor for building the network structure. Its performance not only does not decline after experiencing instantaneous high-speed shearing downhole, but is instead activated and enhanced, completely solving the problem of insufficient proppant-carrying capacity of the proppant-carrying fluid after entering fractures and ensuring effective fracture support.

[0023] Secondly, the core strength of the system originates from physical forces (hydrophobic association and ionic bonds), eliminating the need for high-concentration polymers. Under the action of a breaker or after dilution by formation water, the dynamic network can completely and thoroughly dissociate, leaving behind low-molecular-weight copolymer fragments and nanoparticles, much smaller than formation pore throats. This reduces damage to fracture conductivity by over 90% and significantly improves flowback rates. The total concentration of core additives is extremely low (<0.25%), and the formulation process is simple (direct dispersion), fully compatible with existing fracturing fluid field preparation procedures. Furthermore, its performance is minimally affected by salinity, remaining effective in high-temperature (up to 120℃) and high-salinity (>200,000 ppm) reservoirs, demonstrating broad applicability. Attached Figure Description

[0024] Figure 1 This is an overall flowchart of Embodiment 1 of the present invention. Detailed Implementation

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Preparation methods of key customized raw materials Firstly: Synthesis of amphiphilic temperature-ion dual-responsive block copolymers (PAMPS-b-PNIPAM-b-PAMPS) Step 1: Preparation of macromolecular chain transfer agent (PAMPS-CTA) Sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, 50.0 g, 0.24 mol), 4-cyano-4-(dodecylthiothiocarbonyl)thiopentanoic acid (CDTPA, 0.55 g, 1.5 mmol), and azobisisobutyronitrile (AIBN, 25 mg, 0.15 mmol) were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) / water (volume ratio 1:1, 250 mL). The solution was purged with nitrogen for 30 minutes to remove oxygen, and then reacted in an oil bath at 70 °C for 8 hours. After the reaction was completed, the reaction solution was added dropwise to a large amount of anhydrous ethanol to precipitate the product. The precipitate was filtered, washed three times with ethanol, and dried under vacuum to obtain a PAMPS homopolymer with trithiocarbonate terminals (PAMPS-CTA, molecular weight approximately 35,000, degree of polymerization approximately 150).

[0027] Step 2: Synthesis of triblock copolymers (PAMPS-b-PNIPAM-b-PAMPS) The above-mentioned PAMPS-CTA (10.0 g, 0.29 mmol thioester group), N-isopropylacrylamide (NIPAM, 33.9 g, 0.3 mol), and AIBN (10 mg, 0.06 mmol) were dissolved in DMF (200 mL). After nitrogen purging to remove oxygen, the reaction was carried out at 70 °C for 24 hours. After the reaction was completed, the reaction solution was added dropwise to a large amount of diethyl ether to precipitate, obtaining a PAMPS-b-PNIPAM diblock copolymer. This diblock copolymer was then subjected to a reversible addition-fragmentation chain transfer (RAFT) polymerization reaction with excess AMPS (25.0 g, 0.12 mol) and AIBN (5 mg) in a DMF / water mixed solvent for 12 hours. The final product was precipitated three times in an ethanol / diethyl ether (1:1) mixed solvent and dried under vacuum to obtain the target ABA-type triblock copolymer. The copolymer was analyzed by 1H NMR spectroscopy (1H NMR spectroscopy). 1 Characterized by 1H NMR and gel permeation chromatography (GPC), the total molecular weight is approximately 130,000, with the degree of polymerization of the PNIPAM segment being approximately 270 and the degree of polymerization of each PAMPS segment being approximately 150.

[0028] Secondly: Surface-functionalized nano-silica particles (SiO2-NH2 / C) 18 Preparation of ) Step 1: Pretreatment of nano-silica 20.0 g of hydrophilic nano silica powder (Aerosil 200) with an average particle size of 20 nm was dispersed in 200 mL of anhydrous toluene, sonicated for 1 hour, and then refluxed at 120 °C for 2 hours to remove water, resulting in a suspension.

[0029] Step 2: Simultaneous bifunctional grafting The suspension was cooled to 60°C, and under nitrogen protection, two silane coupling agent solutions were simultaneously added dropwise: Solution A was 3-aminopropyltriethoxysilane (APTES, 2.0 g, 9.1 mmol) dissolved in 10 mL toluene; Solution B was octadecyltrimethoxysilane (OTMS, 3.4 g, 9.1 mmol) dissolved in 10 mL toluene. The dropping rate was controlled, and the addition was completed within 1 hour. After the addition was complete, the temperature was raised to 110°C and refluxed for 24 hours.

[0030] Step 3: Post-processing After the reaction was complete, the solid product was separated by centrifugation and washed three times each with toluene, ethanol, and acetone to remove unreacted silane. Finally, the product was dried in a vacuum oven at 60°C for 12 hours to obtain a product with amino (-NH2) and octadecyl (C) groups grafted onto its surface. 18 Hydrophobic nano-silica powder (SiO2-NH2 / C) 18 ) Example 1: This example provides a highly efficient sand-carrying slickwater. The preparation method is described in [link to example]. Figure 1 This includes the following steps: Step 1: Pre-dispersion of the smart thickener Weigh 0.10 g of the synthesized PAMPS-b-PNIPAM-b-PAMPS triblock copolymer and 0.05 g of surface-functionalized nano-silica (SiO2-NH2 / C). 18 Add the mixture to 100 mL of deionized water. At room temperature, disperse the mixture at 5000 rpm for 15 minutes using a high-speed shear emulsifier to form a homogeneous pre-dispersed mother liquor.

[0031] Step 2: Preparation of the slippery water Take 100 mL of the pre-dispersed mother liquor and add 2.0 g of potassium chloride (KCl, analytical grade). Stir magnetically until completely dissolved. Then, bring the volume to 1 L with deionized water to obtain a slippery water sample with a total concentration of 0.015 wt% of intelligent thickener (0.01 wt% copolymer, 0.005 wt% nanoparticles) and a KCl concentration of 0.2 wt% (approximately 0.2% by weight).

[0032] Example 2: High-concentration thickener-based slippery water The preparation method is the same as in Example 1, but the amount of smart thickener is adjusted: Copolymer dosage: 0.20g (final concentration 0.02wt%) Nano silica dosage: 0.10g (final concentration 0.01wt%) KCl dosage: 15.0g (final concentration 1.5wt%), total volume remains 1L. This formulation is designed to achieve higher in-fracture viscosity and is suitable for high sand ratios or higher reservoir temperatures.

[0033] Example 3: Adjusting the surface modification ratio of nanoparticles to create a slippery water Changing the preparation parameters of surface-functionalized nano-silica: In "Secondly, Step 2", the molar ratio of APTES to OTMS was adjusted to 1:2 (i.e., 1.0 g of APTES and 4.5 g of OTMS), while other conditions remained unchanged, resulting in nanoparticles with lower amino group density and higher hydrophobic alkyl chain density. Using these nanoparticles, slippery water was prepared according to the formulation and steps of Example 1. This formulation aimed to investigate the influence of ionic bonds and hydrophobic interactions on the contribution ratio of network strength.

[0034] Example 4: Slippery Water with Adjusted Copolymer Temperature-Sensitive Segment Length In step 2, the amount of NIPAM was adjusted to 56.5 g (0.5 mol), while other conditions remained unchanged, to synthesize an ABA triblock copolymer with a degree of polymerization of approximately 450 (total molecular weight approximately 165,000). Using this copolymer, slickwater was prepared according to the formulation and steps of Example 1. This formulation aims to improve the temperature-sensitive response of the system, making it suitable for specific reservoir temperature windows.

[0035] Example 5: Slippery Water with Adjusted Copolymer Temperature-Sensitive Segment Length In step 2, the amount of NIPAM was adjusted to 56.5 g (0.5 mol), while other conditions remained unchanged, to synthesize an ABA triblock copolymer with a degree of polymerization of approximately 450 (total molecular weight approximately 165,000). Using this copolymer, slickwater was prepared according to the formulation and steps of Example 1. This formulation aims to improve the temperature-sensitive response of the system, making it suitable for specific reservoir temperature windows.

[0036] Comparative Example 1: Traditional Polymer Drag-Reducing Sliding Water Weigh 0.10 g of high molecular weight partially hydrolyzed polyacrylamide (HPAM, molecular weight approximately 15 million) and dissolve it in 1 L of deionized water containing 0.2 wt% KCl. Dissolve the solution for 12 hours with low-speed stirring to obtain a homogeneous solution. This comparative example represents the most widely used conventional slick water in the field.

[0037] Comparative Example 2: Surfactant-based cleaning slippery water Weigh 2.0 g of a cationic / anionic composite surfactant (such as a mixture of hexadecyltrimethylammonium bromide and sodium dodecyl sulfate in a specific ratio) and 0.2 g of KCl, dissolve them in 1 L of deionized water, and stir until clear. This comparative example represents another type of polymer-free, viscoelastic surfactant (VES)-dependent clean fracturing fluid whose rheological properties depend on micelle structure.

[0038] Comparative Example 3: Copolymer solution without nanoparticles Using only the triblock copolymer (0.10 g) from Example 1, without the addition of nano-silica, it was dissolved in 1 L of deionized water containing 0.2 wt% KCl and magnetically stirred. This comparative example was used to verify the performance of the temperature-ion dual-response copolymer alone in the absence of nanoparticles as crosslinking nodes.

[0039] Comparative Example 4: Polymer / nanoparticle composite system without temperature-sensitive segments A hydrophilic block copolymer (PAMPS-b-PAA-b-PAMPS, where PAA is polyacrylic acid) without PNIPAM segments was synthesized. Using this copolymer (0.10 g) and surface-functionalized nano-silica (0.05 g) from Example 1, a 1 L solution was prepared according to the method of Example 1. This comparative example was used to verify the crucial role of temperature responsiveness (hydrophobic association) in the formation of the network structure of this invention.

[0040] Experimental Example 1: Rheological Properties Test (Low Shear Viscosity and High Shear Drag Reduction) Test method: Low shear viscosity: Using a rotational rheometer, at a simulated reservoir temperature of 90°C and a shear rate of 170 s⁻¹. -1 Under certain conditions, the apparent viscosity of each sample after it has reached a stable state was measured.

[0041] High shear drag reduction rate: Referring to industry standards, using an indoor friction test device, at 25℃ and a flow rate of 7m / s (corresponding to high shear conditions), the ratio of the friction of the sample to that of clean water was measured, and the drag reduction rate (DR% = (1 - sample friction / clean water friction) × 100%) was calculated.

[0042] The test results are shown in Table 1.

[0043] Table 1: Comparison Results of Rheological Properties As shown in Table 1, Embodiments 1, 2, and 3 of the present invention all exhibit excellent drag reduction rates (>70%) comparable to those of conventional HPAM (Comparative Example 1) under high shear, demonstrating their high pumping efficiency.

[0044] Under simulated low-shear conditions of cracks, the viscosity (85-165 mPa·s) of each embodiment of the present invention far exceeds that of all comparative examples. The formulation of Example 3 also exhibits excellent sand-carrying viscosity, proving that the present invention has successfully achieved the intelligent response of "viscosity doubling after entering the crack". The viscosity of comparative examples 3 and 4 is very low, confirming that the cross-linking nodes of nanoparticles and the thermosensitive hydrophobic association together constitute the core of the high-strength dynamic network structure.

[0045] Experimental Example 2: The Effect of Shear on Viscosity Change Test method: A high-pressure capillary rheometer was used to simulate the instantaneous high-speed shear process of fluid passing through the perforation orifice. The sample was first subjected to a high-speed shear process of 10,000 s at 25°C. -1 The shear rate was set for 60 seconds to simulate pumping and orifice shearing. Then, the setting was immediately switched to 90°C for 170 seconds. -1 The shear conditions were set, and the viscosity was continuously monitored over time (0-300 seconds). The test results are shown in Table 2.

[0046] Table 2: Comparison of viscosity of the system before and after shearing As shown in Table 2, the viscosity of Example 1, after experiencing high shear, not only did not decrease, but instead, under the combined effect of temperature and low shear, rapidly increased to a high stable value of 88 mPa·s within 45 seconds. This directly verifies the core mechanism of the shear-triggered network structure formation of the present invention.

[0047] Comparative Example 1 (conventional HPAM) exhibits typical shear degradation behavior, with viscosity never increasing after high shear. Comparative Example 2 (VES) shows some viscosity recovery, but the rate is slow and the final viscosity is low, demonstrating that its micellar reconstruction process is slow and limited in strength. Therefore, this experiment strongly demonstrates that the present invention can transform shear attenuation into shear enhancement.

[0048] Experimental Example 3: Static Sand Suspension Performance Test Test method: Add 90 mL of sample solution and 10 mL of 40 / 70 mesh ceramsite proppant (total sand ratio 10%) to a 100 mL stoppered graduated cylinder. Place the graduated cylinder in a 90℃ water bath and let it stand. Record the time required for the proppant to settle to 50% of its volume (half-settling time, T). 50 ), and the final settlement volume ratio after 2 hours.

[0049] Table 3: Comparison of Static Sand Suspension Capacity As shown in Table 3, under simulated static crack conditions, the slickwater of the present invention exhibited excellent sand-suspending performance, with almost no proppant settling, thanks to its robust three-dimensional network structure. In contrast, the comparative examples all showed varying degrees of rapid settling, with the conventional slickwater (Comparative Example 1) settling the fastest. This phenomenon directly explains the problem of insufficient proppant delivery distance during on-site construction.

[0050] Experimental Example 4: Dynamic Friction and Sand Carrying Simulation Experiment (Flat Plate Crack Model) Test Method: A visual parallel plate fracture simulation device (plate spacing 4mm, length 2m) was used to simulate the wellbore at 25℃ in the inlet section and fractures at 90℃ in the main section. Samples and proppant (sand ratio 15%) were pumped in at a constant flow rate. The drag reduction rate was calculated by measuring the pressure difference at the inlet section; the mass of proppant flowing out at different time points was collected and weighed at the outlet to evaluate the proppant carrying efficiency; after the experiment, the model was dissected to observe the distribution of proppant within the fractures. The test results are shown in Table 4.

[0051] Table 4: Results of Dynamic Simulation Experiment As shown in Table 4, the dynamic simulation experiment most closely resembles real-world working conditions. Example 1 achieved efficient drag reduction at the inlet section, while proppant was rapidly and uniformly delivered to the distal end of the fracture, with almost no sand bed formation at the end. In contrast, although Comparative Example 1 achieved acceptable drag reduction, proppant delivery was slow and it accumulated in large quantities near the wellhead, forming a high sand embankment, resulting in extremely poor sand-laying effect. This phenomenon further demonstrates the superiority of the present invention throughout the entire process.

[0052] Experimental Example 5: Explosion of Gum Breakage and Core Damage Test method: Debonding performance: 0.005 wt% ammonium persulfate debonding agent was added to the sample of Example 1, and the reaction was carried out at 90°C for 4 hours. The viscosity and surface tension of the liquid after debonding were measured.

[0053] Core damage: Using artificial cores, the initial gas permeability K1 was first tested. Then, dynamic damage experiments (3 MPa pressure difference, 90°C) were conducted using the liquids (containing breaker) of Example 1 and Comparative Example 1. After flowback, the cores were dried, and the post-damage permeability K2 was tested. The permeability recovery rate (K2 / K1×100%) was calculated.

[0054] The test results are shown in Table 5.

[0055] Table 5: Assessment of Adhesive Breakage and Damage As shown in Table 5, the slickwater of this invention exhibits lower viscosity and surface tension after gel breaking, which is beneficial for flowback. Crucially, its core permeability recovery rate reaches approximately 92%, significantly higher than the 67.3% of traditional polymer-based slickwater. This further demonstrates that the network based on dynamic physical cross-linking of this invention can dissociate more thoroughly after gel breaking, leaving less residue and significantly reducing damage to the reservoir.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A highly efficient sand-carrying slickwater system, characterized in that, It contains a shear-responsive smart thickener dispersed in an aqueous phase, and an inorganic salt that provides ionic strength; The intelligent thickener is composed of an amphiphilic temperature-ion dual-responsive block copolymer and surface-functionalized nano-silica particles through multiple non-covalent interactions; The amphiphilic temperature-ion biresponsive block copolymer has an ABA-type triblock structure, wherein the B segment is a temperature-sensitive polymer segment and the A segment is a strongly ionic hydrophilic polymer segment. The surface-functionalized nano-silica particles are simultaneously grafted with hydrophobic alkyl chains and cationic groups.

2. The high-efficiency sand-carrying slickwater system according to claim 1, characterized in that, The thermosensitive polymer segment is poly(N-isopropylacrylamide) or its derivative.

3. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The strongly ionic hydrophilic polymer segment is sodium poly-2-acrylamido-2-methylpropanesulfonate.

4. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The hydrophobic alkyl chain is C. 12 -C 18 Alkyl chain; the cationic group is a primary amino group.

5. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The particle size of the surface-functionalized nano-silica particles is 10-30 nm.

6. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The inorganic salt is potassium chloride.

7. The high-efficiency sand-carrying slickwater according to claim 1 or 6, characterized in that, The concentration of the inorganic salt in the slickwater is 0.2%-3.0%.

8. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The total concentration of the intelligent thickener, including the copolymer and the nanoparticles, is 0.01%-0.25%.

9. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The total molecular weight of the ABA-type triblock copolymer is 100,000-200,000, the degree of polymerization of the PNIPAM segment is 200-500, and the degree of polymerization of each PAMPS segment is 100-200.

10. The high-efficiency sand-carrying slickwater according to claim 1, characterized in that, The amphiphilic temperature-ion dual-response block copolymer is PAMPS-b-PNIPAM-b-PAMPS; the surface-functionalized nano silica particles are nano silica particles with amino and octadecyl groups grafted onto their surface.

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