Triple-responsive wide-temperature-range in-situ phase-transition self-supporting fracturing fluid and preparation and application thereof

Abstract

The application discloses a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid and a preparation and application thereof, and belongs to the technical field of oil and gas field development. The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid comprises a phase change component and a water-based dispersion and stabilization component. The phase change component comprises a thermosetting resin prepolymer, a diluent, a thermal initiator composite system, a salinity-sensitive curing agent microcapsule, a shear response type rheological modifier and a functional monomer. The water-based dispersion and stabilization component comprises a dispersant, a surfactant and a thickening stabilizer. Through triple synergistic effect of temperature gradient, salinity delay and shear intelligent response, phase change in a wide temperature range of 30 DEG C to 150 DEG C is realized, the curing time is adjustable in a range of 5 min to 150 min, the breakage rate of the proppant after curing is less than 6.5% under 69 MPa, and the mid-far end proppant coverage rate is more than 86%. The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid solves the problems of narrow phase change window, limited curing time regulation and difficulty in adapting to complex reservoir conditions.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, specifically relating to triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid and its preparation and application. Background Technology

[0002] With the continuous advancement and improvement of oil and gas exploration and development technologies and methods, a large number of unconventional oil and gas resources (tight gas, shale oil and gas, coalbed methane, etc.) have been continuously discovered, becoming an important replacement area for oil and gas development. Unconventional oil and gas reservoirs are tight, and the exploitable reserves are difficult to access; therefore, hydraulic fracturing has become an essential path for their efficient development and production. In fracturing operations, proppant acts as the "skeleton" of the fracture wall, continuously widening the fracture after the fracturing fluid is flowed back, maintaining a highly conductive oil and gas flow channel. Traditional hydraulic fracturing mainly uses conventional proppants such as quartz sand and ceramsite. However, with the expansion of development scale and the deepening of technology, the inherent defects of conventional proppants have become increasingly prominent, seriously restricting the production enhancement effect and development efficiency of oil and gas wells. First, conventional proppant usage is huge and the cost is high, urgently requiring new cost reduction methods. Second, conventional proppant has a high density (around 1.5 g / cm³). 3 The above-mentioned factors (significant gravity differentiation and excessively rapid settling velocity) make it difficult to effectively deliver proppant to the mid-to-far regions of fracture branches and complex fracture networks, resulting in insufficient support for distal and secondary fractures and inadequate establishment of flow channels. Third, to deliver conventional proppant, high-volume, high-viscosity fracturing fluid must be used in conjunction with large-capacity pumps, leading to high costs, significant reservoir damage, high water consumption, and difficulties in flowback fluid treatment, posing multiple challenges to the green and efficient development of oil and gas. To address these difficulties, domestic scholars have proposed the core concept of "in-situ liquid-solid phase self-proppant," breaking the traditional logic of fracturing's "sand-carrying for increased production." Theoretically, it possesses potential advantages such as no need for external conventional proppant, achieving "liquid-to-sand" delivery, high mid-to-far fracture network support, low reservoir damage, low water consumption, and small flowback fluid volume, making it one of the most theoretically valuable and practically promising research directions in recent years.

[0003] Numerous explorations have been conducted in this direction. Chinese patent documents with authorization announcement numbers CN110591684B and CN106190086B disclose phase change fracturing fluid systems based on supramolecular building blocks or two-phase temperature-responsive systems. Chinese patent documents with authorization announcement numbers CN112727429B and CN112795376B disclose self-supporting fracturing fluid systems for modifying the main fracture segment and fracture network segment, with curing temperatures ranging from 60 ℃ to 150 ℃ and curing times ranging from 5 min to 30 min and 15 min to 60 min, respectively. Chinese patent documents with application publication numbers CN111410948A and CN117247773A disclose temperature-responsive phase change fracturing fluids and liquid-solid phase change self-generated proppant systems, respectively. Chinese patent document CN116925730B discloses a fully fractured mesh supported phase change fracturing fluid system, including modified hydrophobic epoxy resin and various curing agents.

[0004] In summary, existing technologies have made significant progress in the preparation of in-situ phase change fracturing fluids and self-supporting agents. However, comprehensive analysis reveals that most existing technologies employ a single thermal initiation (temperature response) mechanism, which still suffers from problems such as a narrow phase change temperature window, a limited range of adjustable solidification time, and difficulty in adapting to complex reservoir conditions with different burial depths, temperature gradients, and formation water salinity. There is an urgent need to develop an in-situ phase change self-supporting fracturing fluid system that can overcome the limitations of single thermal solidification, utilize the synergistic regulation of multiple environmental factors such as temperature, salinity, and shear force to achieve precise control of a wide window and gradient solidification time, and possess intelligent rheological response characteristics. Summary of the Invention

[0005] To address the technical problems of existing in-situ phase change self-supporting fracturing fluids, which suffer from narrow phase change temperature windows, limited adjustable curing time ranges, and difficulty in adapting to complex reservoir conditions such as different burial depths, temperature gradients, and mineralization due to a single thermal initiation mechanism, the present invention aims to provide a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid and its preparation and application.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid, the raw materials of which include a phase changeable component and a water-based dispersion stable component, in parts by mass. The phase changeable component includes: 50-60 parts of thermosetting resin prepolymer, 15-27 parts of diluent, 4.5-5.5 parts of thermal initiator composite system, 8-12 parts of salinity-sensitive curing agent microcapsules, 1.5-2.5 parts of shear-responsive rheology modifier, and 5-8 parts of functional monomer. The water-based dispersion stabilizing component comprises: 93-95 parts water, 3-4 parts dispersant, 1-2 parts surfactant, and 0.5-1 part thickening stabilizer; the functional monomer is selected from one or more of triallyl isocyanurate, glycidyl methacrylate, and vinyltriethoxysilane. The thermal initiator composite system is composed of benzoyl peroxide, a low activation energy initiator, and dicumyl peroxide, a high activation energy initiator; the salt-sensitive curing agent microcapsules use polyamide or m-phenylenediamine as the core material and salt-sensitive polyelectrolyte as the shell; the shear-responsive rheology modifier is selected from one or more of hydrophobic modified polyacrylamide, hydrophobic modified hydroxyethyl cellulose, and cationic polyelectrolyte.

[0007] The thermosetting resin prepolymer is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin; the diluent is selected from one or more of styrene, methyl methacrylate, and diallyl phthalate. The viscosity, permeability, crosslinking density, and interfacial bonding performance with formation rocks of the fracturing fluid can be flexibly adjusted according to the reservoir temperature, pressure, and other environmental conditions, thereby further optimizing the mechanical strength, temperature resistance, toughness, and compressive strength of the cured proppant. Experimental data show that the proppant exhibits a fragmentation rate of less than 6.5% and a conductivity exceeding 72 D·cm at 69 MPa.

[0008] In the aforementioned thermal initiator composite system, the mass ratio of the low-activation-energy initiator benzoyl peroxide to the high-activation-energy initiator dicumyl peroxide is (0.5~3):(1~5). This achieves gradient solidification of the fracturing fluid within different temperature ranges: the low-activation-energy initiator can initiate the reaction at lower temperatures, ensuring that solidification can begin even in low-temperature formations; the high-activation-energy initiator is activated at higher temperatures, ensuring continuous solidification and achieving higher strength in high-temperature formations, thereby widening the solidification temperature window and expanding the adjustable range of solidification time.

[0009] The salt-sensitive polyelectrolyte is one or more of the following: alginate-chitosan complex, polyacrylic acid-chitosan complex, and sodium polystyrene sulfonate-polydiallyldimethylammonium chloride complex.

[0010] The shear-responsive rheology modifier is a shear-time dual-responsive rheology modifier.

[0011] The water is selected from one or more of deionized water, tap water, river water, lake water, well water, formation water, salt lake water, and seawater; the dispersant is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and polycarboxylic acid dispersants; the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, and sorbitan monooleate; and the thickening and stabilizing agent is selected from one or more of xanthan gum, guar gum, and carboxymethyl cellulose.

[0012] The fracturing fluid exhibits a triple response characteristic of temperature, salinity, and shear, with a phase transition temperature of 30 ℃ to 150 ℃ and an adjustable curing time range of 5 min to 150 min.

[0013] The proppant formed after the fracturing fluid solidifies has a breakage rate of less than 6.5% at 69 MPa, a mid-to-far end support coverage of more than 86%, and a flow conductivity of more than 72 D·cm.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid, comprising: Thermosetting resin prepolymer and diluent are added to a reaction vessel, inert gas is introduced, and the mixture is stirred until dissolved. Then, functional monomers, thermal initiator composite system, and shear-responsive rheology modifier are added. Stirring is continued, the temperature is lowered, and salt-sensitive curing agent microcapsules are added. The mixture is stirred and dispersed to obtain a phase change component. After heating water from different sources, dispersants, surfactants, and thickeners / stabilizers are added, stirred to dissolve, and cooled to room temperature to obtain a water-based dispersion and stabilization component. The phase change component is mixed evenly with the water-based dispersion stabilizer component to obtain the final product.

[0015] The inert gas is high-purity nitrogen or high-purity argon. The inert gas is introduced and stirred at 50 ℃~60 ℃.

[0016] The mass ratio of the phase change component to the water-based dispersed stable component is 1:(2~3).

[0017] Thirdly, the present invention provides the application of the above-mentioned triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid in hydraulic fracturing of deep, ultra-deep or complex-salinity reservoirs.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid provided by this invention introduces a thermal initiator composite system composed of low-activation-energy benzoyl peroxide and high-activation-energy dicumyl peroxide, a salinity-sensitive curing agent microcapsule with polyamide or m-phenylenediamine as the core material and a salt-sensitive polyelectrolyte as the shell, and a shear-responsive rheology modifier selected from hydrophobically modified polyacrylamide, along with thermosetting resin prepolymer, diluent, functional monomers, and water-based dispersion stabilizing components. This allows the fracturing fluid to achieve the synergistic effect of a triple mechanism of "temperature gradient response - salinity delayed response - shear intelligent response" for the first time. This significantly widens the phase change window to 30~150℃, expands the adjustable curing time range to 5~150min, and greatly reduces the sensitivity to single formation conditions. It effectively solves the technical problems of existing technologies, such as narrow phase change window, limited curing time control, and difficulty in adapting to complex reservoir conditions such as different burial depths, temperature gradients, and mineralization.

[0019] The preparation method provided by this invention employs a stepwise preparation method, first preparing a phase change component and a water-based dispersion stabilizing component separately, and then mixing them in proportion. In the preparation of the phase change component, an inert gas is introduced for protection, and after stirring until dissolved, each component is added sequentially. After cooling, microcapsules are added at a low speed. The water-based dispersion stabilizing component is heated to dissolve and then cooled to room temperature. This method effectively prevents early reactions between components and damage to microcapsules due to high-speed shearing, ensuring the storage stability and consistency of solidification performance of the fracturing fluid. Moreover, the process is simple, the conditions are mild, and it is suitable for large-scale industrial production.

[0020] The application provided by this invention utilizes the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid in hydraulic fracturing of deep, ultra-deep, or complex-salinity reservoirs. By leveraging the synergistic effects of reservoir temperature, formation water salinity, and pumping shear force, a triple mechanism of temperature gradient response, salinity delay response, and shear intelligent response is triggered in the fracturing fluid. This ensures that the fluid maintains low viscosity and easy flow during pumping, moderately recovers viscosity upon entering the fracture, and ultimately solidifies in-situ into a high-strength solid proppant, achieving effective support for the main fracture and mid-to-far-end microfractures. Compared to existing single-temperature-responsive fracturing fluids, the application of this invention can significantly improve the success rate and effectiveness of fracturing stimulation in complex reservoirs, reduce construction risks and water consumption, and has broad prospects for industrial application. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for the preparation of a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid.

[0022] Figure 2 The graph shows a comparison of viscosity and mid-to-far end support coverage before and after high and low shear rates in Examples 1-4 and Comparative Example 2.

[0023] Figure 3The graph shows a comparison of phase change temperature, curing time, compressive strength, and breakage rate between Examples 1-4 and Comparative Example 3.

[0024] Figure 4 The graph shows a comparison of phase change temperature, curing time, mid-to-far end support coverage, and flow conduction capacity between Examples 1-4 and Comparative Example 1.

[0025] Figure 5 The chart shows a comparison of the compressive strength and breakage rate of Examples 1-4 and Comparative Examples 1-3.

[0026] Figure 6 The diagram shows a comparison of the mid-to-far end support coverage and flow guiding capacity between Examples 1-4 and Comparative Examples 1-2. Detailed Implementation

[0027] To enable those skilled in the art to understand the features and effects of the present invention, the following descriptions and definitions are only general descriptions of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0028] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0029] This invention provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid and its preparation method. The core invention lies in the simultaneous introduction of a thermosetting resin prepolymer, a composite initiation system composed of low-activation-energy and high-activation-energy initiators, salinity-sensitive curing agent microcapsules, and a shear-responsive rheology modifier. This achieves the synergistic effect of a triple response mechanism of "temperature gradient response - salinity delayed response - shear intelligent response", thereby widening the phase change temperature window to 30 ℃~150 ℃ and expanding the adjustable curing time range to 5 min~150 min. This significantly reduces the sensitivity to single formation conditions and enables it to adapt to complex reservoir conditions with different burial depths, different temperature gradients, and different formation water salinity.

[0030] I. Raw Material Sources and Specifications Unless otherwise specified, all chemical reagents and chemicals used in this invention are commercially available and well-known in the art. Specifically: bisphenol A epoxy resin (brand E-51, epoxy value 0.48~0.54 eq / 100g), bisphenol F epoxy resin (brand NPEF-170, epoxy value 0.55~0.65 eq / 100g), and phenolic epoxy resin (brand F-51, epoxy value 0.50~0.56). (eq / 100g) was purchased from Nantong Xingchen Synthetic Materials Co., Ltd.; styrene (analytical grade), methyl methacrylate (analytical grade), and diallyl phthalate (analytical grade) were purchased from Aladdin Reagent (Shanghai) Co., Ltd.; benzoyl peroxide (BPO, purity ≥98%) and dicumyl peroxide (DCP, purity ≥98%) were purchased from Sinopharm Chemical Reagent Co., Ltd.; triallyl isocyanurate (TAIC, purity ≥98%) and glycidyl methacrylate (GMA) were purchased from Sinopharm Chemical Reagent Co., Ltd. The following were purchased from Maclean Biochemical Technology Co., Ltd.: (purity ≥97%) and vinyltriethoxysilane (VTES, purity ≥97%); (hydrophobically modified polyacrylamide (molecular weight 8-12 million, degree of hydrolysis 20-30%), hydrophobically modified hydroxyethyl cellulose (degree of substitution 1.5-2.0), and cationic polyelectrolyte (polydiallyl dimethyl ammonium chloride, molecular weight 200,000-300,000); (sodium alginate (viscosity 200-400 mPa·s), chitosan (degree of deacetylation ≥90%), polyacrylic acid (molecular weight 5000), sodium polystyrene sulfonate (molecular weight 70,000), and polydiallyl dimethyl ammonium chloride (molecular weight 200,000); (Sigma-Aldrich (Shanghai) Trading Co., Ltd.); (m-phenylenediamine (purity ≥99%) and polyamide (amine value 200-300 mg)). KOH (g) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; polyvinylpyrrolidone (K30), polyvinyl alcohol (type 1788), polyethylene glycol (PEG-4000), and polycarboxylic acid dispersant (PC-101) were purchased from BASF (China) Co., Ltd.; sodium dodecylbenzenesulfonate (SDBS, purity ≥95%), hexadecyltrimethylammonium bromide (CTAB, purity ≥99%), and sorbitan monooleate (Span80, chemically pure) were purchased from Sinopharm Chemical Reagent Co., Ltd.; xanthan gum (food grade), guar gum (food grade), and carboxymethyl cellulose (degree of substitution 0.8~1.0) were purchased from Henan Wanbang Industrial Co., Ltd.; deionized water was prepared in the laboratory, and simulated formation water and simulated seawater were prepared according to the formula. The water quality parameters of each water source are described in the specific examples.

[0031] II. Preparation method of salt-sensitive curing agent microcapsules The salt-sensitive curing agent microcapsules used in this invention are prepared by complex coagulation or interfacial polymerization, using m-phenylenediamine or polyamide as the core material and salt-sensitive polyelectrolyte as the shell. A typical preparation method for microcapsules with an alginate-chitosan complex shell is as follows: 5g of sodium alginate is dissolved in 500mL of deionized water, and 10g of core material (m-phenylenediamine or polyamide) is added. The mixture is emulsified at high speed (10000 rpm, 5min) to form an oil-in-water emulsion. 500mL of an acetic acid solution containing 2g of chitosan (acetic acid concentration 1%) is slowly added dropwise, adjusting the pH to 5.0-5.5. The mixture is stirred at 40℃ for 30min to allow the sodium alginate and chitosan to undergo a complex coagulation reaction on the oil droplet surface to form the shell. The temperature is lowered to below 10℃, and 2mL of glutaraldehyde (25% aqueous solution) is added for crosslinking and curing for 2h. The mixture is then filtered, washed, and freeze-dried under vacuum to obtain microcapsule powder with a particle size controlled at 10-50μm. Microcapsules with polyacrylic acid-chitosan complex or sodium polystyrene sulfonate-polydiallyl dimethylammonium chloride complex as the shell can be prepared by similar methods. Those skilled in the art can adjust the specific process parameters according to the existing technology.

[0032] III. Performance Testing Methods The performance tests of the fracturing fluid in this invention were conducted according to the following methods: (1) Apparent viscosity: At room temperature, a six-speed rotational viscometer (ZNN-D6 type, Qingdao Haitongda Special Instrument Co., Ltd.) was used at 100 rpm (corresponding to a shear rate of 170 s). - ¹) The viscosity of the fracturing fluid was measured.

[0033] (2) Shear response performance: Using an RS6000 advanced rheometer (Harker, Germany) equipped with a PZ38 coaxial cylindrical rotor system, the shear response performance was measured at 1000 s. -1 Shear the fracturing fluid for 1 minute, then at 170 s. -1 The viscosity after high shear was measured; the same method was used to measure the viscosity at 10 s. -1 Shear for 1 minute, then at 170 s. -1 The viscosity was measured after low shear. By comparing the viscosity changes before and after high shear and before and after low shear, the shear response characteristics of the fracturing fluid were evaluated.

[0034] (3) Phase change initiation temperature and curing time: Place the fracturing fluid in a constant temperature water bath or oil bath, and gradually increase the temperature at a rate of 1 °C / min starting from room temperature (25 °C). Observe the temperature at which the fracturing fluid begins to undergo phase change (from liquid to non-flowing gel state) and record it as the phase change initiation temperature. Continue to maintain the constant temperature and observe once every 5 min until the phase change product is stable and there is no obvious change. Record the time taken from the start of phase change to the morphology stabilization as the curing time.

[0035] (4) Average particle size of solidified proppant: The proppant particles formed after the phase transformation of fracturing fluid are dispersed on a glass slide and observed under an optical microscope (BX53 type, Olympus Corporation, Japan) at magnification of 200 to 500 times. At least 100 particles are randomly selected and the average particle size is calculated using image analysis software.

[0036] (5) Single-particle compressive strength and breakage rate: The tests were conducted in accordance with the industry standard SY / T 5108-2014 "Test Methods for Performance of Proppants for Hydraulic Fracturing and Gravel Packing Operations". The single-particle compressive strength was tested using a single-particle strength tester (KY-Ⅲ type, Jiangsu Keyuan Electronic Instruments Co., Ltd.). At least 30 particles were tested for each sample, and the average value was taken. Breakage rate test: A certain mass of proppant was weighed, placed in a standard crushing chamber, a pressure of 69 MPa was applied and maintained for 5 min, and the mass percentage of broken particles was calculated after sieving.

[0037] (6) Mid-to-far end proppant coverage: A self-designed simulated fracture device was used for testing. This device is made of transparent plexiglass and has adjustable fracture width (2~6 mm) and fracture length (3~6 m). The prepared fracturing fluid was injected into the simulated fracture device at a constant flow rate. After the fracturing fluid was completely discharged, the inlet and outlet were closed, and the device was heated to above the phase transition temperature and maintained for more than the curing time to allow the fracturing fluid to fully solidify in the device. The fracture device was divided into three sections along its length: proximal end (0~1 / 3 of the fracture length), middle end (1 / 3~2 / 3 of the fracture length), and distal end (2 / 3~the end of the fracture length). The proppant in each section was collected and weighed, and the mid-to-far end proppant coverage was calculated using the following formula: Mid-to-far end proppant coverage = (middle end proppant mass + distal end proppant mass) / total mass of proppant in the entire fracture section × 100%.

[0038] (7) Conductivity: The conductivity of the proppant-filled sand layer was measured with reference to the provisions of the industry standard SY / T 6302-2019 "Test Method for Conductivity of Fracturing Proppant". The conductivity tester (FCES-100, Jiangsu Huaan Scientific Instrument Co., Ltd.) was used to measure the conductivity of the proppant-filled sand layer under a closing pressure of 52 MPa.

[0039] Example 1 This embodiment provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid IPSSF-1, the raw material composition and preparation method of which are as follows.

[0040] See Figure 1Preparation of the phase change component: 55.0 g of bisphenol A epoxy resin and 20.0 g of styrene were added to a reaction vessel, and high-purity nitrogen gas (purity ≥99.999%) was introduced. The mixture was stirred continuously at 400 rpm at 50℃ until completely dissolved to form a homogeneous system. Under stirring conditions, 5.0 g of triallyl isocyanurate, 3.0 g of glycidyl methacrylate, 4.0 g of benzoyl peroxide, 1.5 g of dicumyl peroxide, and 1.5 g of hydrophobically modified polyacrylamide were added sequentially. The mixture was stirred for 30 min to ensure that the components were fully mixed and homogeneous. The temperature was lowered to 30℃, and 10.0 g of salt-sensitive curing agent microcapsules (core material is m-phenylenediamine, shell layer is alginate-chitosan complex, average particle size 25 μm) were added. The mixture was dispersed by low-speed stirring at 300 rpm for 10 min to obtain the phase change component.

[0041] Preparation of the water-based dispersion stabilizer: 95.0 g of deionized water was added to a preparation vessel and heated to 40 °C. Under stirring, 3.0 g of polyvinylpyrrolidone (K30), 1.5 g of sodium dodecylbenzenesulfonate, and 0.5 g of xanthan gum were added sequentially. Stirring continued for 30 min until all components were completely dissolved, forming a homogeneous and stable aqueous phase system. The mixture was cooled to room temperature to obtain the water-based dispersion stabilizer.

[0042] Preparation of in-situ phase change self-supporting fracturing fluid: The two components prepared above were mixed evenly at 300 rpm according to the mass ratio of the phase change component to the water-based dispersed stable component of 1:2 to obtain the triple-response wide temperature range in-situ phase change self-supporting fracturing fluid IPSSF-1.

[0043] Example 2 This embodiment provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid IPSSF-2, the raw material composition and preparation method of which are as follows: Preparation of the phase change component: 50.0 g of bisphenol F epoxy resin and 27.0 g of diallyl phthalate were added to a reaction vessel, and high-purity nitrogen gas was introduced. The mixture was stirred continuously at 400 rpm at 50 ℃ until completely dissolved to form a homogeneous system. Under stirring conditions, 5.0 g of glycidyl methacrylate, 3.0 g of triallyl isocyanurate, 2.0 g of benzoyl peroxide, 2.5 g of dicumyl peroxide, and 2.5 g of hydrophobically modified hydroxyethyl cellulose were added sequentially, and the mixture was stirred for 30 min to ensure that the components were fully mixed. The mixture was cooled to 30 ℃, and 8.0 g of salt-sensitive curing agent microcapsules (core material is m-phenylenediamine, shell layer is alginate-chitosan complex, average particle size 25 μm) were added. The mixture was dispersed by low-speed stirring at 300 rpm for 10 min to obtain the phase change component.

[0044] Preparation of the water-based dispersion stabilizer: 95.0 g of simulated formation water with a salinity of 20000 mg / L (composition: NaCl 15000 mg / L, CaCl2 3000 mg / L, MgCl2 2000 mg / L) was added to a preparation vessel and heated to 50°C. Under stirring, 3.4 g of polyethylene glycol (PEG-4000), 1.0 g of sorbitan monooleate (Span 80), and 0.6 g of guar gum were added sequentially, and stirring was continued for 30 min until all components were completely dissolved, forming a homogeneous and stable aqueous phase system; the mixture was cooled to room temperature to obtain the water-based dispersion stabilizer.

[0045] Preparation of in-situ phase change self-supporting fracturing fluid: The two components prepared above were mixed evenly at 300 rpm with a mass ratio of 1:2.5 between the phase change component and the water-based dispersed stable component to obtain the triple-response wide temperature range in-situ phase change self-supporting fracturing fluid IPSSF-2.

[0046] Example 3 This embodiment provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid IPSSF-3, the raw material composition and preparation method of which are as follows.

[0047] Preparation of the phase change component: 60.0 g of phenolic epoxy resin and 15.0 g of methyl methacrylate were added to a reaction vessel, and high-purity nitrogen was introduced. The mixture was stirred continuously at 400 rpm at 60 ℃ until completely dissolved to form a homogeneous system. Under stirring conditions, 6.0 g of vinyltriethoxysilane, 1.0 g of benzoyl peroxide, 4.0 g of dicumyl peroxide, and 1.5 g of cationic polyelectrolyte (polydiallyldimethylammonium chloride) were added sequentially. The mixture was stirred for 30 min to ensure that the components were fully mixed and homogeneous. The temperature was lowered to 30 ℃, and 12.0 g of salt-sensitive curing agent microcapsules (core material is m-phenylenediamine, shell is alginate-chitosan complex, average particle size is 30 μm) were added. The mixture was dispersed by low-speed stirring at 300 rpm for 10 min to obtain the phase change component.

[0048] Preparation of water-based dispersion stabilizer: 93.2 g of simulated formation water with a salinity of 50000 mg / L (composition: NaCl 35000 mg / L, CaCl2 10000 mg / L, MgCl2 5000 mg / L, including 500 mg / L calcium ions and 1500 mg / L magnesium ions) was added to a preparation tank and heated to 50 ℃. Under stirring, 4.0 g of polycarboxylate dispersant (PC-101), 2.0 g of cetyltrimethylammonium bromide (CTAB), and 0.8 g of carboxymethyl cellulose were added sequentially, and stirring was continued for 30 min until all components were completely dissolved, forming a homogeneous and stable aqueous phase system; the mixture was cooled to room temperature to obtain the water-based dispersion stabilizer.

[0049] Preparation of in-situ phase change self-supporting fracturing fluid: The two components prepared above were mixed evenly at 300 rpm according to the mass ratio of the phase change component to the water-based dispersed stable component of 1:3, so as to obtain the triple-response wide temperature range in-situ phase change self-supporting fracturing fluid IPSSF-3.

[0050] Example 4 This embodiment provides a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid IPSSF-4, the raw material composition and preparation method of which are as follows.

[0051] Preparation of phase change components: Same as in Example 2.

[0052] Preparation of water-based dispersion stabilized component: 93.0 g of simulated seawater with a salinity of 35000 mg / L (composition: NaCl2 8000 mg / L, MgCl2 3500 mg / L, CaCl2 2000 mg / L, KCl 800 mg / L, Na2SO4 700 mg / L) was added to a preparation tank and heated to 50 ℃; under stirring, 4.0 g of polyethylene glycol (PEG-4000), 2.0 g of sodium dodecylbenzenesulfonate (SDBS), and 1.0 g of xanthan gum were added sequentially, and stirring was continued for 30 min until all components were completely dissolved to form a homogeneous and stable aqueous phase system; cooled to room temperature, the water-based dispersion stabilized component was obtained.

[0053] Preparation of in-situ phase change self-supporting fracturing fluid: The two components prepared above were mixed evenly at 300 rpm according to the mass ratio of the phase change component to the water-based dispersed stable component of 1:2.5 to obtain the triple-response wide temperature range in-situ phase change self-supporting fracturing fluid IPSSF-4.

[0054] V. Comparative Examples To verify the beneficial effects of the technical solution of the present invention, the following comparative examples are provided.

[0055] Comparative Example 1 (DBF-1) The only difference between this comparative example and Example 1 is that: instead of adding salinity-sensitive curing agent microcapsules, 10.0g of an equal amount of m-phenylenediamine was added directly; hydrophobically modified polyacrylamide and benzoyl peroxide were not added; the microcapsule step of cooling and low-speed stirring was not performed during the preparation of the phase change component; the other components and preparation methods were the same as in Example 1, and fracturing fluid DBF-1 was obtained.

[0056] Comparative Example 2 (DBF-2) The only difference between this comparative example and Example 2 is that hydrophobically modified hydroxyethyl cellulose (shear-responsive rheology modifier) ​​was not added; all other components and preparation methods are the same as in Example 2. Fracturing fluid DBF-2 was obtained.

[0057] Comparative Example 3 (DBF-3) The only difference between this comparative example and Example 1 is that the thermal initiator composite system is replaced with benzoyl peroxide (5.5 g, the same as the total amount of the two initiators in Example 1), while the other components and preparation methods are the same as in Example 1, to obtain fracturing fluid DBF-3.

[0058] VI. Performance Test Results and Analysis According to the above performance testing methods, the fracturing fluids IPSSF-1~4 prepared in Examples 1~4 and DBF-1~3 prepared in Comparative Examples 1~3 were subjected to comprehensive performance tests, and the test results are summarized in Table 1.

[0059] Table 1: Results of Comprehensive Performance Tests of Fracturing Fluid

[0060] As shown in Table 1, the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluids IPSSF-1~4 prepared in Examples 1~4 all exhibit excellent comprehensive performance. Specifically: (1) Shear response performance: The fracturing fluids of Examples 1-4 showed a shear response performance of 1000 s. -1 The viscosity decreased significantly after high shear (from 38~48 mPa·s to 14~21 mPa·s), which is beneficial for reducing friction during pumping; at 10 s -1 The viscosity recovered significantly after low shear (to 52-61 mPa·s), which is beneficial for suspending the proppant after entering the crack and preventing settlement. However, Comparative Example 2, lacking a shear-responsive rheology modifier, had a viscosity of only 14 mPa·s after low shear, failing to recover effectively, resulting in a significant decrease in the mid-to-far end proppant coverage to 52% (see Comparative Example 2). Figure 2 ).

[0061] (2) Phase change initiation temperature and curing time: The phase change initiation temperature of Examples 1-4 covers a wide temperature range of 30 ℃ to 150 ℃, and the curing time can be adjusted within the range of 5 min to 150 min. By adjusting the compound ratio of thermal initiator (BPO:DCP=2.67:1 in Example 1, phase change initiation temperature 30 ℃, curing time 5 min; BPO:DCP=0.25:1 in Example 3, phase change initiation temperature 150 ℃, curing time 150 min), continuous adjustment from fast curing to slow curing was achieved. However, Comparative Example 3 only uses a single low activation energy initiator BPO, which starts curing at 45 ℃ and completes curing in 8 min. The curing time window is extremely narrow, and it is sensitive to temperature fluctuations. Moreover, the compressive strength of the proppant is only 35 N, and the breakage rate is as high as 15.6% at 69 MPa, which cannot meet the requirements of high temperature deep reservoirs (see Figure 3 ).

[0062] (3) Salinity Delayed Response Performance: Examples 1-4 all exhibited excellent salinity delayed release characteristics. Taking Example 2 (simulated formation water with a salinity of 20,000 mg / L) and Example 4 (simulated seawater with a salinity of 35,000 mg / L) as examples, their phase change initiation temperatures (72 ℃, 68 ℃) and solidification times (65 min, 57 min) were relatively moderate, indicating that the microcapsule shell underwent moderate swelling or dissolution in a high salinity environment, and the curing agent was released reasonably. However, Comparative Example 1 did not use microcapsule encapsulation, and the curing agent participated in the reaction too early, resulting in a mid-to-far end support coverage of only 41% and a conductivity of only 46 D·cm, which was far lower than the 86% and 72 D·cm of Example 1 (see Comparative Example 1). Figure 4 ).

[0063] (4) Mechanical properties of the proppant: The proppant formed in Examples 1-4 had a breakage rate of only 4.2%-6.5% under 69 MPa pressure, significantly lower than 9.2% in Comparative Example 1, 7.5% in Comparative Example 2, and 15.6% in Comparative Example 3. The compressive strength of the proppant in Example 3 reached 78 N (at 52 MPa), much higher than that of the comparative examples. This is due to the synergistic effect of the triple response mechanism, which ensures that the fracturing fluid is fully solidified at the appropriate time and location, forming a dense, high-strength solid proppant (see...). Figure 5 ).

[0064] (5) Mid-to-distal support coverage and conductivity: The mid-to-distal support coverage of Examples 1-4 reached 78%-92%, and the conductivity reached 72 D·cm-92 D·cm. In particular, Example 3 achieved a mid-to-distal support coverage of 92% and a conductivity of 92 D·cm, indicating that the fracturing fluid could be effectively delivered to the mid-to-distal end of the fracture and solidify in situ into a high-strength proppant, establishing an efficient oil and gas flow channel. In contrast, the mid-to-distal support coverage of Comparative Examples 1 and 2 was only 41% and 52%, and the conductivity was only 46 D·cm and 58 D·cm, respectively, which further verified the importance of salinity-sensitive microcapsules and shear-responsive rheology modifiers (see Figure 6 ).

[0065] In summary, this invention, by simultaneously introducing thermosetting resin prepolymer, gradient thermal initiation composite system, salinity-sensitive curing agent microcapsules, and shear-responsive rheology modifier, prepares a triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid. This achieves the synergistic effect of the triple response mechanism of "temperature gradient response - salinity delayed response - shear intelligent response," enabling curing within a wide temperature range of 30 ℃ to 150 ℃, with an adjustable curing time range of 5 min to 150 min. The cured proppant exhibits a fragmentation rate of less than 6.5% at 69 MPa, a mid-to-far end support coverage rate of over 86%, and a conductivity of over 72 D·cm. This effectively solves the technical problems of narrow phase change temperature window, limited adjustable curing time range, and difficulty in adapting to complex reservoir conditions in existing technologies.

[0066] VII. Industrial Application Examples Taking the fracturing fluid IPSSF-3 prepared in Example 3 as an example, it was applied to the fracturing operation of a deep shale gas well (well depth 4500 m, reservoir temperature 145 ℃, formation water salinity 48000 mg / L). A conventional fracturing pump truck with a displacement of 12m³ / L was used. 3 The fracturing fluid was pumped into the wellbore at a rate of [per unit speed] / min. During pumping, the pump pressure remained stable with low friction. Under formation temperature (145℃) and salinity (48000 mg / L), the fracturing fluid solidified in situ within approximately 130 minutes, forming a high-strength solid proppant. Post-fracturing flowback was effective, with a daily natural gas production of 8.5 × 10⁻⁶ mg / L. 4 m 3 Compared with adjacent wells using traditional proppant fracturing, the production increased by about 35%, demonstrating the excellent adaptability of the fracturing fluid of this invention in deep, highly salinized, and complex reservoirs.

[0067] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid, characterized in that, The raw materials include phase change components and water-based dispersion stabilizers, in parts by mass. The phase changeable component includes: 50-60 parts of thermosetting resin prepolymer, 15-27 parts of diluent, 4.5-5.5 parts of thermal initiator composite system, 8-12 parts of salinity-sensitive curing agent microcapsules, 1.5-2.5 parts of shear-responsive rheology modifier, and 5-8 parts of functional monomer. The water-based dispersing and stabilizing component comprises: 93-95 parts water, 3-4 parts dispersant, 1-2 parts surfactant, and 0.5-1 part thickening and stabilizing agent; the functional monomer is selected from one or more of triallyl isocyanurate, glycidyl methacrylate, and vinyltriethoxysilane. The thermosetting resin prepolymer is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin. The thermal initiator composite system is composed of a low activation energy initiator benzoyl peroxide and a high activation energy initiator dicumyl peroxide, with a mass ratio of benzoyl peroxide to dicumyl peroxide of (0.5~3):(1~5); the salt-sensitive curing agent microcapsules use polyamide or m-phenylenediamine as the core material and a salt-sensitive polyelectrolyte as the shell, wherein the salt-sensitive polyelectrolyte is one or more of alginate-chitosan composite, polyacrylic acid-chitosan composite, and sodium polystyrene sulfonate-polydiallyl dimethylammonium chloride composite; the shear-responsive rheology modifier is selected from one or more of hydrophobically modified polyacrylamide, hydrophobically modified hydroxyethyl cellulose, and cationic polyelectrolytes.

2. The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to claim 1, characterized in that, The diluent is selected from one or more of styrene, methyl methacrylate, and diallyl phthalate.

3. The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to claim 1, characterized in that, The shear-responsive rheology modifier is a shear-time dual-responsive rheology modifier.

4. The triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to claim 1, characterized in that, The dispersant is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and polycarboxylic acid dispersants; the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, and sorbitan monooleate; and the thickening stabilizer is selected from one or more of xanthan gum, guar gum, and carboxymethyl cellulose.

5. The preparation method of the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to any one of claims 1 to 4, characterized in that, include: Thermosetting resin prepolymer and diluent are added to a reaction vessel, inert gas is introduced, and the mixture is stirred until dissolved. Then, functional monomers, thermal initiator composite system, and shear-responsive rheology modifier are added. Stirring is continued, the temperature is lowered, and salt-sensitive curing agent microcapsules are added. The mixture is stirred and dispersed to obtain a phase change component. After heating water from different sources, dispersants, surfactants, and thickeners / stabilizers are added, stirred to dissolve, and cooled to room temperature to obtain a water-based dispersion and stabilization component. A triple-response, wide-temperature-range in-situ phase change self-supporting fracturing fluid is obtained by uniformly mixing a phase change-prone component with a water-based dispersion stabilizer.

6. The preparation method of the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to claim 5, characterized in that, The inert gas is nitrogen or argon. After the inert gas is introduced and stirred at 50 ℃~60 ℃ until dissolved, the functional monomer, thermal initiator composite system, and shear-responsive rheology modifier are added.

7. The preparation method of the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to claim 5, characterized in that, The mass ratio of the phase change component to the water-based dispersed stable component is 1:(2~3).

8. The application of the triple-response wide-temperature-range in-situ phase change self-supporting fracturing fluid according to any one of claims 1 to 4 in hydraulic fracturing of deep, ultra-deep or complex-salinity reservoirs.

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