A fracturing reservoir protectant with anti-expansion and anti-collapse functions, its preparation method and application

Abstract

This invention discloses a fracturing reservoir protectant with anti-swelling and anti-collapse functions, its preparation method, and its application, belonging to the field of fracturing technology. The fracturing reservoir protectant comprises: amphiphilic modified graphene oxide, an amine-based clay stabilizer, a cationic surfactant, a nonionic surfactant, and deionized water. The fracturing reservoir protectant of this invention achieves synergistic anti-swelling and anti-collapse effects. Through the combination of the amine-based clay stabilizer and the cationic surfactant, it exerts a highly efficient clay hydration inhibition effect, with an anti-swelling rate greater than 95% and excellent water wash resistance, effectively inhibiting the hydration and swelling of clay minerals for a long time. The core component, amphiphilic modified graphene oxide, can physically adsorb onto the surface of rock fractures and nanopores, forming a dense hydrophobic barrier that effectively prevents water phase intrusion. Simultaneously, it synergistically alters rock wettability with the surfactant. This invention fundamentally solves the problem of skeletal instability and collapse in weakly cemented reservoirs caused by hydration swelling and capillary percolation.

Description

Technical Field

[0001] This invention belongs to the field of fracturing technology, specifically relating to a reservoir protection agent for fracturing with anti-expansion and anti-collapse functions, its preparation method, and its application. Background Technology

[0002] In the development of tight oil and gas reservoirs, hydraulic fracturing is a key engineering method for improving oil recovery. The compatibility of the injection fluid with the reservoir rock minerals is one of the key factors affecting its effectiveness. For special reservoirs with high clay mineral content (clay content > 30%, montmorillonite content > 80%), strong water sensitivity, weak cementation, and easily loosened structures, conventional water-based injection fluids are prone to causing significant reservoir damage during operation, resulting in post-fracturing fluid production failing to meet the expected fracturing effect. Specifically, the problems include the following two aspects:

[0003] (1) High-content clay minerals undergo strong hydration and expansion upon contact with water. In reservoirs with low porosity, well-developed microfractures, and strong heterogeneity, the expansion will directly lead to the narrowing or even complete blockage of effective seepage channels (pore throats and microfractures), causing irreversible water-sensitive damage and severely affecting post-compression conductivity;

[0004] (2) Rock skeleton instability caused by weak cementation. In this type of reservoir, the cementation between the matrix and the skeleton particles is weak, the rock structure is loose, and the stress sensitivity is high. When external fluids intrude, even slight expansion of the clay is enough to destroy the fragile interparticle bonds, induce skeleton collapse, sand production and fracture network structure damage, and then block artificial fractures, resulting in production capacity far below expectations.

[0005] Currently, existing literature mainly focuses on research into clay hydration expansion inhibitors for fracturing and anti-collapse plugging agents for drilling fluids. There are few reports in the literature on how to simultaneously achieve the dual goals of inhibiting expansion and preventing rock structure collapse during fracturing. Although drilling fluid systems involve wellbore stabilization technology, their mechanisms of action and operating conditions are fundamentally different from those of the fracturing process, and therefore cannot be directly applied.

[0006] Chinese patents CN114656647A and CN117003967A disclose a "Terminal Amino Hyperbranched Polymer Grafted Graphene Oxide Plugging Agent and Drilling Fluid," respectively. CN117003967A discloses a "Preparation of a Modified Graphene Oxide Plugging Agent for Shale and a Water-Based Drilling Fluid." Both disclose that using modified graphene oxide plugging agents in drilling fluids can effectively seal nano- and micron-sized pores in shale wellbores, thereby effectively stabilizing the wellbore and preventing collapse. CN118813217A discloses a "Drilling Fluid Anti-Collapse Agent and its Preparation Method." This anti-collapse agent is a mixture of boron-containing quaternary ammonium salt modified phenolic resin, ester-based epoxy resin modified polyacrylamide, natural asphalt, and calcium chloride. Its strong plugging power prevents irreversible damage to low-permeability reservoirs.

[0007] The modified graphene oxide plugging agents for drilling fluids mentioned above are mainly aimed at wellbore stability. Their design concept focuses on inhibiting fluid intrusion and maintaining the integrity of the wellbore structure by sealing pores during the drilling process. However, during fracturing, the reservoir faces the scouring of high-pressure, high-volume fluids and the long-term contact between the fracturing fluid and reservoir minerals. This places different requirements on the anti-swelling performance of the protective agent, its compatibility with the fracturing fluid system, and its effectiveness under dynamic conditions. Therefore, these drilling fluid plugging agents cannot be directly applied to reservoir protection for fracturing.

[0008] Chinese patent CN114181683 A discloses "A hydrophobic surface-modified nano-plugging agent and a fracturing fluid containing the same". The nano-plugging agent is composed of hydrophobic modified silica, fluorocarbon surfactant, urea, ethylene glycol, etc. It is designed for tight sandstone reservoirs in western Sichuan with small porosity, low permeability and strong heterogeneity. It mainly reduces fluid intrusion by physically sealing the pore throats. However, it does not address the problems of hydration expansion of clay minerals and stability of the rock skeleton, and it is difficult to meet the dual requirements of preventing swelling and collapse of reservoirs with high clay content and weak cementation.

[0009] Chinese patent CN 117343720A discloses a "Low-damage fracturing fluid system for preventing core collapse and its preparation method." The key material in this system, the anti-collapse agent, consists of quaternary ammonium clay stabilizers, amine-based clay stabilizers, and surfactant-based interface modifiers. It primarily utilizes the compounding of different types of clay stabilizers to efficiently inhibit the hydration and swelling of clay minerals, and the interface modifiers to reduce interfacial tension and regulate wetting, thereby reducing water-locking damage and inhibiting water infiltration into the reservoir to prevent collapse. However, the system suffers from insufficient long-term effectiveness in preventing collapse, and the changes in rock mechanical strength after soaking have not yet been systematically evaluated.

[0010] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0011] The purpose of this invention is to provide a fracturing reservoir protectant with anti-swelling and anti-collapse functions, its preparation method, and its application. This invention solves the problem that existing fracturing reservoir protectants cannot simultaneously meet the dual requirements of anti-swelling and anti-collapse in reservoirs with high clay content and weak cementation. The fracturing reservoir protectant of this invention can enhance the bonding strength between rock skeleton particles, improve the compressive strength and anti-collapse ability of reservoir rocks, thereby achieving effective protection of the reservoir during fracturing, reducing reservoir damage, and improving fracturing efficiency.

[0012] To achieve the above objectives, this invention provides a fracturing reservoir protectant with anti-swelling and anti-collapse functions. The fracturing reservoir protectant comprises: amphiphilic modified graphene oxide, an amine-based clay stabilizer, a cationic surfactant, a nonionic surfactant, and deionized water. The amphiphilic modified graphene oxide is obtained by reacting graphene oxide sequentially with 3-amino-1,2-propanediol and a silane coupling agent.

[0013] The structure of the amphiphilic modified graphene oxide is shown in Formula I: ;

[0014] In Formula I, the connection positions of R1 and R2 are only used to illustrate certain sites of reaction between 3-amino-1,2-propanediol and the silane coupling agent and graphene oxide; similar structural sites can all undergo the reaction; R1 is R2 is R3 is selected from alkane chains of C12 to C16.

[0015] Preferably, the amine clay stabilizer is selected from at least one of diethylenetriamine hydrochloride and triethylenetetramine hydrochloride; or / and, the cationic surfactant is selected from at least one of lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, stearyltrimethylammonium chloride, benzyltrimethylammonium chloride and benzalkonium chloride; or / and, the nonionic surfactant is selected from polyoxyethylene ether, wherein the number of ethylene oxide units (EO) in the polyoxyethylene ether is 5 to 40; or / and, the silane coupling agent is selected from silane coupling agents containing C12 to C16 alkyl chains.

[0016] More preferably, the polyoxyethylene ether is selected from at least one of isomeric decaol polyoxyethylene ether, fatty amine polyoxyethylene ether, castor oil polyoxyethylene ether, and whale stearyl alcohol polyoxyethylene ether.

[0017] More preferably, the polyoxyethylene ether is selected from at least one of isomeric decaol polyoxyethylene ether with EO=6, fatty amine polyoxyethylene ether with EO=5, castor oil polyoxyethylene ether with EO=40, and whale stearyl alcohol polyoxyethylene ether with EO=6.

[0018] More preferably, the silane coupling agent is selected from trimethoxysilane coupling agents or triethoxysilane coupling agents containing a C12-C16 alkyl chain.

[0019] Preferably, the reservoir protectant for fracturing comprises the following components in parts by weight: 0.3 to 0.75 parts amphiphilic modified graphene oxide, 10 to 20 parts amine clay stabilizer, 2 to 5 parts cationic surfactant, 4 to 8 parts nonionic surfactant, and 100 parts deionized water.

[0020] A second objective of this invention is to provide a method for preparing the aforementioned reservoir protection agent with anti-swelling and anti-collapse functions, the method comprising:

[0021] 3-amino-1,2-propanediol-modified graphene oxide nanoparticles and a silane coupling agent were reacted in a mixture of ethanol and water at 60-70°C. After the reaction was completed, the solid and liquid were separated, and the solid was washed to obtain amphiphilic modified graphene oxide.

[0022] The nonionic surfactant is dissolved in water, and the amphiphilic modified graphene oxide is added. The mixture is heated to 30-50°C and ultrasonically dispersed at a frequency of 15-20 kHz (to ensure the stability of the reservoir protectant) to form a stable dispersion. Finally, an amine clay stabilizer and a cationic surfactant are added and mixed evenly to obtain the fracturing reservoir protectant with anti-swelling and anti-collapse functions.

[0023] Preferably, the mass ratio of the 3-amino-1,2-propanediol-modified graphene oxide nanoparticles to the silane coupling agent is 1:(1~3); or / and, the mass ratio of the 3-amino-1,2-propanediol-modified graphene oxide nanoparticles to the ethanol and water mixture is (0.1~0.2):20; or / and, in the ethanol and water mixture, the mass ratio of ethanol to water is 1:1.

[0024] Preferably, the preparation method of the 3-amino-1,2-propanediol modified graphene oxide nanoparticles includes:

[0025] Graphene oxide was ultrasonically dispersed in water to form a GO dispersion. 3-Amino-1,2-propanediol was added to the GO dispersion under stirring, and the reaction was continued at 50-80℃. Sodium chloride was added to the mixture after the reaction, and the mixture was stirred and dispersed. The solid and liquid were separated, and the solid was washed with a mixture of ethanol and water to obtain 3-amino-1,2-propanediol modified graphene oxide nanoparticles.

[0026] More preferably, the mass ratio of graphene oxide to water is 0.5:100; or / and, the mass ratio of graphene oxide to 3-amino-1,2-propanediol is 1:(1~4); or / and, the mass ratio of graphene oxide to sodium chloride is 1:(1~4); or / and, in the preparation method of 3-amino-1,2-propanediol modified graphene oxide nanoparticles, the volume ratio of ethanol to water in the ethanol and water mixture is 1:1; or / and, in the preparation method of 3-amino-1,2-propanediol modified graphene oxide nanoparticles, solid-liquid separation is performed by centrifugation at a speed of 1000~2000 r / min.

[0027] A third objective of this invention is to provide the application of the aforementioned reservoir protectant with anti-expansion and anti-collapse functions in the fracturing process.

[0028] Specifically, the fracturing reservoir protectant can effectively protect the reservoir during the fracturing process. It can also enhance the bonding strength between rock skeleton particles, thereby improving the reservoir rock's resistance to pressure and collapse.

[0029] The present invention relates to a fracturing reservoir protectant with anti-swelling and anti-collapse functions, its preparation method, and its application. This invention solves the problem that existing fracturing reservoir protectants cannot simultaneously meet the dual requirements of anti-swelling and anti-collapse in reservoirs with high clay content and weak cementation, and has the following advantages:

[0030] (1) This invention addresses the problem of clay hydration expansion, core collapse, and damage to fracturing fractures caused by the interaction of water-based in-well fluids with high clay mineral content, weak cementation, and easy loosening in special water-sensitive and stress-sensitive reservoirs. It provides a fracturing reservoir protectant with anti-expansion and anti-collapse functions and its preparation method. This reservoir protectant can effectively reduce the damage to the reservoir caused by water-based in-well fluids, help unconventional oil and gas extraction, and improve recovery rate.

[0031] (2) The reservoir protectant for fracturing of the present invention achieves synergistic anti-swelling and anti-collapse. This protectant, through the compounding of amine clay stabilizer (such as diethylenetriamine hydrochloride) and cationic surfactant, exerts a highly efficient clay hydration inhibition effect, with an anti-swelling rate of more than 95%, and excellent water washing resistance, and can effectively inhibit the hydration swelling of clay minerals for a long time. The core component, amphiphilic modified graphene oxide, can form a dense hydrophobic barrier by physical adsorption on the surface of rock fractures and nanopores, effectively preventing the intrusion of water phase. At the same time, it synergistically changes the wettability of the rock with the surfactant. This triple synergistic mechanism of "chemical inhibition + physical blocking + wettability reversal" fundamentally solves the problem of skeleton instability and collapse caused by hydration swelling and capillary permeation in weakly cemented reservoirs;

[0032] (3) The reservoir protectant for fracturing of the present invention can protect the reservoir throughout the entire cycle and is suitable for the fracturing operation process. The protectant is designed to meet the needs of each stage of fracturing operation. In the pre-flush stage, it can quickly inhibit the initial hydration of clay on the fracture surface and form a hydrophobic film; in the long-term proppant-carrying fluid stage, it provides long-term stabilizing effect, maintains the strength of the fracture wall, reduces proppant embedding, and ensures conductivity; in the shut-in and flowback stages, its static protection effect can resist drastic pressure changes, reduce sand production, ensure efficient flowback of fracturing fluid, and open up clean seepage channels for oil and gas. Core damage tests show that its permeability damage rate to the core matrix is ​​extremely low (as low as 6.75%), which is significantly better than traditional treatment agents;

[0033] (4) The reservoir protectant for fracturing of the present invention has superior performance, is green and efficient, and is easy to apply. The protectant formulation consists entirely of liquid components, making on-site compounding simple. Its core functional component, amphiphilic modified graphene oxide, is nanoscale (200~500nm), has good dispersibility, and can effectively enter microfractures. The system does not contain restrictive components such as fluorocarbons, making it green and environmentally friendly. The product solution has excellent stability (no stratification after 60 days), outstanding anti-collapse performance (no collapse of rock samples after 30 days and can maintain rock sample strength), and long-lasting effect. At the same time, the system is a low-residue cleaning system with good compatibility with reservoirs. It can be prepared using backflow water, has low overall application cost, and has good prospects for promotion. Attached Figure Description

[0034] Figure 1 The infrared spectrum is shown for the amphiphilic modified graphene (KRM-GO) prepared in Example 1 of this invention.

[0035] Figure 2 This is a particle size distribution diagram of the fracturing reservoir protectant with anti-swelling and anti-collapse functions prepared in Example 1 of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that: Unless otherwise specified in the examples, conditions should be followed according to standard conditions or the manufacturer's recommendations. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0038] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0039] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0040] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] The main sources of experimental materials in the following examples are as follows:

[0042] Graphene oxide (purchased from Juguang Evonik), 3-amino-1,2-propanediol (purchased from TCI Chemical), n-dodecyltrimethoxysilane, n-hexadecyltrimethoxysilane (purchased from Shandong Huachen), ethylenetriamine hydrochloride, triethylenetetramine hydrochloride (purchased from Huntsman), lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride (purchased from Sinco Chemical), benzalkonium chloride (purchased from Wanli Chemical), deca-ol polyoxyethylene ether EL-1006 (purchased from Jiangsu Haian Petrochemical), and whale stearyl alcohol polyoxyethylene ether Emulgade A6 (purchased from Huimin Pharmaceutical).

[0043] Example 1

[0044] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared by the following steps:

[0045] (1) Preparation of modified graphene oxide nanoparticles AP-GO

[0046] 0.5 g of graphene oxide (GO) was ultrasonically dispersed in 100 g of deionized water for 1 h to form a GO dispersion. 0.5 g of 3-amino-1,2-propanediol (AP) was added to the GO dispersion at a rate of 5 mL / min under stirring, and the reaction was continued at 50 °C for 6 h. 0.5 g of sodium chloride was added to the mixture after reaction and stirred to disperse. The mixture was then centrifuged at 1000 r / min for 20 min. The supernatant was discarded, and the lower solid was washed with ethanol / deionized water at a volume ratio of 1:1. This process was repeated twice to obtain 3-amino-1,2-propanediol modified graphene oxide nanoparticles (AP-GO).

[0047] (2) Preparation of amphiphilic modified graphene oxide KRM-GO

[0048] 0.55 g AP-GO intermediate, 0.58 g n-dodecyltrimethoxysilane, 100 g ethanol / water mixture (m 乙醇:m 水 After mixing (1:1), the mixture was reacted at 60℃ for 7 h; then centrifuged at 4500 r / min for 20 min, the supernatant was discarded, and the mixture was reacted with an ethanol / water mixture (m... 乙醇 :m 水 After washing the lower solid layer twice with deionized water (ratio 1:1), it was dried at 75°C to obtain amphiphilic modified graphene oxide (KRM-GO).

[0049] like Figure 1 The image shows the infrared spectrum of the amphiphilic modified graphene oxide prepared in Example 1 of this invention. The infrared spectrum is located at 3290 cm⁻¹. -1 The peak is the -OH stretching vibration peak, at 2924 cm⁻¹. -1 2838 cm -1 The peaks at 1105 cm⁻¹ represent both asymmetric and symmetric stretching vibrations of CH in -CH₂-, indicating the introduction of a long alkyl carbon chain; -1 and 1027 cm -1 The peak at 903 cm⁻¹ is the stretching vibration peak of Si-OC or Si-O-Si. -1 and 790 cm -1 This may be a CO vibration or Si-C vibration peak following the ring-opening of the epoxy group; at 688 cm⁻¹ -1 716cm -1 These are peaks associated with out-of-plane bending vibrations of long-chain alkyl groups (CH) or deformation vibrations of Si-O-Si.

[0050] (3) Preparation of fracturing reservoir protectant with anti-swelling and anti-collapse function

[0051] Weigh 4 g of isomeric decaethylene alcohol polyoxyethylene ether (the number of ethylene oxide units EO = 6) and dissolve it in 100 mL of deionized water. Then add 0.3 g of amphiphilic modified graphene oxide KRM-GO, heat it to 30 ℃ in a constant temperature water bath, and disperse it for 30 min (frequency 20 kHz) using an ultrasonic disperser to form a stable dispersion. Finally, add 10 g of diethylenetriamine hydrochloride and 2 g of lauryltrimethylammonium chloride in sequence, and stir gently until uniform to obtain a fracturing reservoir protectant with anti-swelling and anti-collapse functions.

[0052] Example 2

[0053] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared in a manner that is basically the same as that in Example 1, except that:

[0054] In step (1), the amount of 3-amino-1,2-propanediol used is 0.75 g;

[0055] In step (2), n-hexadecyltrimethoxysilane is used instead of n-dodecyltrimethoxysilane;

[0056] In step (3), hexadecyltrimethylammonium chloride is used to replace lauryltrimethylammonium chloride.

[0057] Example 3

[0058] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared in a manner that is basically the same as that in Example 1, except that:

[0059] In step (1), the GO dispersion was formed by ultrasonic dispersion for 1.5 h; the stirring speed was 10 mL / min; the amount of 3-amino-1,2-propanediol was 1.0 g; the reaction was continued at 60 °C for 5 h; 1.0 g of sodium chloride was added and stirred to disperse; the lower solid was washed with ethanol / deionized water three times.

[0060] In step (2), the amount of n-dodecyltrimethoxysilane used is 1.15 g; the reaction is carried out at 65 °C for 7 h;

[0061] In step (3), 6g of whale stearyl alcohol polyoxyethylene ether (EO=6) was used to replace isomeric decayl alcohol polyoxyethylene ether; the amount of amphiphilic modified graphene oxide KRM-GO was 0.5g; the temperature was heated to 40℃; the amount of diethylenetriamine hydrochloride was 15g and the amount of lauryltrimethylammonium chloride was 4g.

[0062] Example 4

[0063] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared in a manner that is basically the same as that in Example 3, except that:

[0064] In step (1), the amount of 3-amino-1,2-propanediol used is 1.25 g; the reaction is continued at 70 °C for 5 h; 1.5 g of sodium chloride is added to the reaction mixture and stirred to disperse, and then centrifuged at 2000 r / min for 15 min;

[0065] In step (2), n-hexadecyltrimethoxysilane is used to replace n-dodecyltrimethoxysilane; ethanol / water mixed solution (m 乙醇 :m 水 =1:1), wash the lower solid layer three times with deionized water;

[0066] In step (3), hexadecyltrimethylammonium chloride is used to replace lauryltrimethylammonium chloride.

[0067] Example 5

[0068] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared in a manner that is basically the same as that in Example 1, except that:

[0069] In step (1), the mixture was ultrasonically dispersed for 2 h to form a GO dispersion; the amount of 3-amino-1,2-propanediol used was 1.5 g; the reaction was continued at 80 °C for 4 h; 2.0 g of sodium chloride was added to the mixture after the reaction and stirred to disperse it, and then centrifuged at 2000 r / min for 10 min; the lower solid was washed with ethanol / deionized water three times.

[0070] In step (2), the amount of n-dodecyltrimethoxysilane used was 1.60 g; the reaction was carried out at 70 °C for 6 h; and the solution was prepared using an ethanol / water mixture (m 乙醇 :m 水 =1:1), wash the lower solid layer three times with deionized water;

[0071] In step (3), 4g of isomeric decayl alcohol polyoxyethylene ether (EO=6) and 4g of whale stearyl alcohol polyoxyethylene ether (EO=6) were dissolved in 100 mL of deionized water, and then 0.75g of amphiphilic modified graphene oxide KRM-GO was added; the mixture was heated to 50 °C; and finally 20g of diethylenetriamine hydrochloride, 2g of lauryltrimethylammonium chloride and 3g of benzalkonium chloride were added in sequence.

[0072] Example 6

[0073] A fracturing reservoir protectant with anti-expansion and anti-collapse functions is prepared in a manner that is basically the same as that in Example 5, except that:

[0074] In step (1), 2.0 g of 3-amino-1,2-propanediol (AP) was added to the GO dispersion at a rate of 10 mL / min under stirring conditions.

[0075] In step (2), n-hexadecyltrimethoxysilane is used instead of n-dodecyltrimethoxysilane;

[0076] In step (3), the amount of isomeric decayl alcohol polyoxyethylene ether is 2g, the amount of whale stearyl alcohol polyoxyethylene ether is 6g, and hexadecyl trimethylammonium chloride is used to replace lauryl trimethylammonium chloride.

[0077] Comparative Example 1

[0078] Compared to Example 5, the system does not contain amphiphilic modified graphene oxide KRM-GO. Specifically: Weigh 4g of isomeric decayl alcohol polyoxyethylene ether (EO=6), 4g of whale stearyl alcohol polyoxyethylene ether (EO=6), 20g of diethylenetriamine hydrochloride, 2g of lauryltrimethylammonium chloride, and 3g of benzalkonium chloride, dissolve them in 100 mL of deionized water, heat to 50 ℃ in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min until a homogeneous liquid is obtained.

[0079] Comparative Example 2

[0080] Compared to Example 5, the system does not contain the amine clay stabilizer diethylenetriamine hydrochloride. Specifically: Weigh 4g of isomeric decayl alcohol polyoxyethylene ether (EO=6) and 4g of whale stearyl alcohol polyoxyethylene ether (EO=6) and dissolve them in 100 mL of deionized water. Then add 0.75g of amphiphilic modified graphene oxide KRM-GO, heat to 50 ℃ in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min to form a stable dispersion. Finally, add 2g of lauryltrimethylammonium chloride and 3g of benzalkonium chloride sequentially, and gently stir until homogeneous.

[0081] Comparative Example 3

[0082] Compared to Example 5, the system does not contain the cationic surfactants lauryltrimethylammonium chloride and benzalkonium chloride. Specifically: Weigh 4g of isomeric decayl alcohol polyoxyethylene ether (EO=6) and 4g of whale stearyl alcohol polyoxyethylene ether (EO=6) and dissolve them in 100 mL of deionized water. Then add 0.75 g of amphiphilic modified graphene oxide KRM-GO, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min to form a stable dispersion. Finally, add 20 g of diethylenetriamine hydrochloride and gently stir until homogeneous.

[0083] Comparative Example 4

[0084] Compared to Example 5, the system does not contain amine clay stabilizer (diethylenetriamine hydrochloride) and cationic surfactants (lauryltrimethylammonium chloride and benzalkonium chloride). Weigh 4g of isomeric deca-ol polyoxyethylene ether (EO=6) and 4g of whale stearyl alcohol polyoxyethylene ether (EO=6) and dissolve them in 100 mL of deionized water. Then add 0.75 g of amphiphilic modified graphene oxide KRM-GO, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min until a homogeneous liquid is obtained.

[0085] Comparative Example 5

[0086] Compared to Example 5, the system does not contain amphiphilic modified graphene oxide KRM-GO and cationic surfactants (lauryltrimethylammonium chloride and benzalkonium chloride). Specifically: Weigh 4g of isomeric decayl alcohol polyoxyethylene ether (EO=6), 4g of whale stearyl alcohol polyoxyethylene ether (EO=6), and 20g of diethylenetriamine hydrochloride, dissolve them in 100 mL of deionized water, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min until a homogeneous liquid is obtained.

[0087] Comparative Example 6

[0088] Compared to Example 5, this system does not contain amphiphilic modified graphene oxide KRM-GO or amine clay stabilizer (diethylenetriamine hydrochloride). Specifically: Weigh 4g of isomeric decaol polyoxyethylene ether (EO=6), 4g of whale stearyl alcohol polyoxyethylene ether (EO=6), 2g of lauryl trimethylammonium chloride, and 3g of benzalkonium chloride, dissolve them in 100 mL of deionized water, heat to 50°C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min until a homogeneous liquid is obtained.

[0089] Comparative Example 7

[0090] Compared to Example 5, the system does not contain nonionic surfactants (isomeric decayl alcohol polyoxyethylene ether (EO=6) and whale stearyl alcohol polyoxyethylene ether (EO=6)) and amphiphilic modified graphene oxide KRM-GO. Specifically: 20 g of diethylenetriamine hydrochloride, 2 g of lauryltrimethylammonium chloride, and 3 g of benzalkonium chloride were weighed and dissolved in 100 mL of deionized water, heated to 50 °C in a constant temperature water bath, and dispersed using an ultrasonic disperser for 30 min until a homogeneous liquid was obtained.

[0091] Comparative Example 8

[0092] Compared to Example 5, this system does not contain nonionic surfactants (isomeric decayl alcohol polyoxyethylene ether (EO=6) and whale stearyl alcohol polyoxyethylene ether (EO=6)) and amino clay stabilizers (diethylenetriamine hydrochloride). Specifically: Weigh 2 g of lauryltrimethylammonium chloride and 3 g of benzalkonium chloride, dissolve them in 100 mL of deionized water, add 0.75 g of amphiphilic modified graphene oxide KRM-GO, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min until homogeneous.

[0093] Comparative Example 9

[0094] Compared to Example 5, the system does not contain nonionic surfactants (isomeric decayl alcohol polyoxyethylene ether (EO=6) and whale stearyl alcohol polyoxyethylene ether (EO=6)) and cationic surfactants (lauryltrimethylammonium chloride and benzalkonium chloride). Specifically: Weigh 20 g of diethylenetriamine hydrochloride and dissolve it in 100 mL of deionized water, then add 0.75 g of amphiphilic modified graphene oxide KRM-GO, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min.

[0095] Comparative Example 10

[0096] Compared to Example 5, this system does not contain nonionic surfactants (isodecyl alcohol polyoxyethylene ether (EO=6) and cetearyl alcohol polyoxyethylene ether (EO=6)), cationic surfactants (lauryltrimethylammonium chloride and benzalkonium chloride), or amino clay stabilizers (diethylenetriamine hydrochloride). Weigh 0.75 g of amphiphilic modified graphene oxide KRM-GO into 100 mL of deionized water, heat to 50 °C in a constant temperature water bath, and disperse using an ultrasonic disperser for 30 min.

[0097] Comparative Example 11

[0098] Compared to Example 5, the system does not contain nonionic surfactants (isodecyl alcohol polyoxyethylene ether (EO=6) and whale stearyl alcohol polyoxyethylene ether (EO=6)), cationic surfactants (lauryl trimethylammonium chloride and benzalkonium chloride), or amphiphilic modified graphene oxide KRM-GO. Specifically: 20 g of diethylenetriamine hydrochloride was weighed and dissolved in 100 mL of deionized water, and stirred to form a homogeneous liquid.

[0099] Comparative Example 12

[0100] Compared to Example 5, the system does not contain nonionic surfactants (isodecyl alcohol polyoxyethylene ether (EO=6) and whale stearyl alcohol polyoxyethylene ether (EO=6)), amino clay stabilizer (diethylenetriamine hydrochloride), and amphiphilic modified graphene oxide KRM-GO. Specifically, 2 g of lauryltrimethylammonium chloride and 3 g of benzalkonium chloride are weighed and dissolved in 100 mL of deionized water, and stirred to form a homogeneous liquid.

[0101] The fracturing reservoir protectants in Examples 1-6 and Comparative Examples 1-12, as well as a commercially available product (benzyltrimethylammonium chloride), were compared in efficacy experiments. The mass concentration of all agents was 0.5%. Evaluation included product stability (30°C, static setting), anti-swelling performance (swelling rate and long-term erosion resistance), core permeability damage rate, rock sample collapse resistance, and compressive strength. Details are as follows:

[0102] 1. Evaluation method for anti-swelling performance

[0103] The anti-swelling rate test method was performed in accordance with the industry standard SY / T 5971—2016 "Performance Evaluation Method of Clay Stabilizers for Fracturing, Acidizing and Water Injection in Oil and Gas Fields". The anti-swelling rate was tested after no flushing, one wash, two washes and three washes.

[0104] The results are shown in Table 1. The test data indicate that the reservoir protectant formulations in Examples 1-6 all achieved long-term stability (no stratification after 60 days) and high-efficiency anti-swelling (anti-swelling rate >92%), and exhibited excellent water wash resistance (the anti-swelling rate typically decreased by no more than 2% after three water washes). In contrast, the comparative examples revealed the design challenge of balancing stability and anti-swelling performance: some formulations (such as Comparative Example 9) had high initial anti-swelling rates but failed due to rapid stratification; other formulations (such as Comparative Examples 6 and 12) were stable but had very low anti-swelling rates and insufficient functionality. This highlights the crucial importance of achieving performance balance through component synergy.

[0105] Table 1. Test results of stability and anti-swelling performance of reservoir protective agents used in fracturing.

[0106] ;

[0107] 2. Test methods for collapse resistance and compressive strength

[0108] (1) Collapse resistance test

[0109] Take a 250 mL wide-mouth bottle, add 100 g of the test solution (0.5% reservoir protection agent solution) to the wide-mouth bottle, and then add about 30 g of weakly cemented rock sample. Observe the degree of collapse of the rock sample (slight spalling, moderate collapse, severe collapse) at different times (1d, 3d, 9d, 30d) at room temperature.

[0110] (2) Compressive strength test

[0111] The main objective was to evaluate the effect of prolonged water-rock interaction between the test solution and the rock sample on the mechanical properties of the rock sample. Since standard-sized cores are difficult to obtain for weakly cemented rock samples, some experiments used non-standard core-sized rock samples as the research object. The uniaxial compressive strength of the rock samples after immersion in the test solution for 30 days was tested according to DZ / T 0276.23-2015 "Test Procedure for Physical and Mechanical Properties of Rocks Part 23: Rock Point Load Strength Test". The specific test methods are as follows:

[0112] ① Sample preparation: The test rock blocks were prepared into flat rectangular shapes and immersed in different test solutions for 30 days. After that, the rock samples were removed, dried at 105℃ for 12 hours, cooled to room temperature, and placed in a desiccator for later use. At least three rock blocks of the same type were prepared. The dimensions of irregular samples should meet the following requirements: the shortest side length is 30~50mm, and the ratio of the distance between loading points to the shortest side is 0.3~1.2.

[0113] ② Point load strength test:

[0114] a) Check whether the upper and lower loading heads of the sample tester are accurately aligned, and use the scale on the frame column to read the zero displacement value between the two cones;

[0115] b) Place the specimen in the testing apparatus, ensuring that the loading cone is in close contact with the shortest side of the specimen, and that the contact point is as close as possible to the center of the specimen. If the strength of a weak surface is being measured, ensure that the line connecting the loading points is in the same weak surface.

[0116] c) Apply a uniform load at an acceleration that will cause the test specimen to break within 10s to 60s until the specimen breaks, and record the pressure gauge reading. F If the failure surface passes through only one loading point, local failure will occur, and the sample will be invalid.

[0117] d) Measure the distance between two loading points on the sample surface. D The average width of the line perpendicular to the loading point W f The error should not exceed ±0.2mm.

[0118] The calculation formula is as follows:

[0119] (Equation 1);

[0120] (Equation 2);

[0121] (Equation 3);

[0122] (Equation 4);

[0123] (Equation 5);

[0124] In the above formula, A f The area of ​​the damaged surface of the specimen is in mm. 2 ; D The distance between two loading points measured on the fracture surface of the specimen, in mm; W f The average width of the continuous fracture surface of the specimen perpendicular to the loading point, in mm; De The equivalent core diameter is in mm. P The total load at which the specimen fails is in N; I s The point load strength of the specimen is expressed in MPa. Is (50) This refers to the standard point load strength after dimensional correction; F This is a correction factor; m The correction index was determined based on empirical values ​​of similar rocks, ranging from 0.4 to 0.45; 0.45 was used in this experiment. When the distance between the two loading points is not equal to 50 mm and the experimental data is limited, the rock point load strength value should be corrected according to GB / T 50266-99 "Standard for Engineering Rock Mass Specimen Testing Methods".

[0125] Table 2 Test results of anti-collapse performance and compressive strength

[0126] ;

[0127] Analysis of the anti-collapse properties and compressive strength of the reservoir protectants showed that the 0.5% solutions in Examples 1-6 maintained the rock samples without collapse for 30 days, and the average compressive strength after 30 days of soaking remained at 13.6-15.0 MPa (the average point load strength of the rock samples before soaking was 15.8 MPa), demonstrating good long-term anti-collapse effect and rock sample strength maintenance ability. In contrast, Comparative Examples 1-7, 11 and the traditional treatment agent benzyltrimethylammonium chloride all showed varying degrees of collapse (from slight spalling to severe collapse) during the observation period, and the compressive strength of most of them could not be effectively measured, indicating that their anti-collapse properties and rock sample strength protection effects were significantly weaker than those of the formulations in the examples.

[0128] 3. Core matrix permeability damage rate test

[0129] The test method for the damage rate of fracturing fluid to the core matrix permeability was performed in accordance with the recommended standard of China's petroleum and natural gas industry, "SY / T 5107—2016 Performance Evaluation Method of Water-based Fracturing Fluid". Artificial cores were prepared indoors to simulate the weakly cemented cores in Block A of the field. The compression parameters for the artificial cores were: natural cores from Block A were crushed to 200-220 mesh, with a gravel content of 35% and a gravel particle size of 4-7 mm; the compression pressure was 120 MPa, and the compression time was 12 h. A reservoir protectant solution with a concentration of 0.5% (Examples 1-6), comparative examples (1, 3, 5, 7, 11), and 0.5% benzyltrimethylammonium chloride were prepared with tap water, and the permeability damage rate of the artificial cores was tested. The temperature was 80℃, the aging time was 24 h, and the injection rate was 0.2 mL / min.

[0130] Table 3 Test results of permeability damage rate of artificial cores

[0131] ;

[0132] In the core matrix permeability damage rate test, the 0.5% solutions of Examples 1-6 all showed low damage rates to the simulated core, ranging from 6.75% to 14.63%, demonstrating good permeability protection effects. In contrast, the damage rates of Comparative Examples 1, 3, 5, 7, 11 and the traditional treatment agent benzyltrimethylammonium chloride were significantly higher, reaching 34.91% to 55.88%, indicating that their damage to core permeability was much greater than that of the formulations in the examples.

[0133] In summary, the reservoir protectants (0.5% concentration) of Examples 1-6 of this invention exhibit comprehensive and excellent reservoir protection performance. Their solutions are long-term stable (no stratification after 60 days) and possess highly efficient and erosion-resistant anti-swelling capabilities (anti-swelling rate >92%, with minimal decrease after three water washes). They can completely prevent the collapse of weakly cemented rock samples within 30 days and effectively maintain rock sample strength (average compressive strength 13.6-15.0 MPa), while causing extremely low damage to the core matrix (6.75%-14.63%). However, the absence of any one of the components—amphiphilic modified graphene oxide, amine clay stabilizer, cationic surfactant, or nonionic surfactant—significantly reduces their storage stability, anti-swelling performance (anti-swelling rate and long-term erosion resistance), rock sample collapse resistance, and compressive strength. In contrast, the comparative examples and commercially available products, benzyltrimethylammonium chloride, exhibit one or more significant defects in terms of stability, long-lasting anti-swelling effect, anti-collapse effect, or protection of reservoir permeability. This demonstrates that the anti-swelling and anti-collapse fracturing reservoir protectant of the present invention has excellent protective effects on special reservoirs with high clay mineral content, weak cementation, and easy loosening, which are highly water-sensitive and stress-sensitive. This provides strong technical support for the development of fracturing benefits for such reservoirs.

[0134] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A reservoir protection agent for fracturing with anti-expansion and anti-collapse functions, characterized in that, The reservoir protectant for fracturing comprises: amphiphilic modified graphene oxide, amine clay stabilizer, cationic surfactant, nonionic surfactant, and deionized water; The amphiphilic modified graphene oxide was obtained by reacting graphene oxide sequentially with 3-amino-1,2-propanediol and a silane coupling agent. The amine-based clay stabilizer is selected from at least one of diethylenetriamine hydrochloride and triethylenetetramine hydrochloride; The cationic surfactant is selected from at least one of lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, stearyltrimethylammonium chloride, benzyltrimethylammonium chloride, and benzalkonium chloride; The nonionic surfactant is selected from polyoxyethylene ether; The silane coupling agent is selected from silane coupling agents containing C12~C16 alkyl chains; The reservoir protectant for fracturing contains the following components in parts by weight: 0.3 to 0.75 parts amphiphilic modified graphene oxide, 10 to 20 parts amine clay stabilizer, 2 to 5 parts cationic surfactant, 4 to 8 parts nonionic surfactant, and 100 parts deionized water.

2. The fracturing reservoir protectant with anti-expansion and anti-collapse functions according to claim 1, characterized in that, The number of ethylene oxide (EO) units in the polyoxyethylene ether is 5 to 40.

3. The fracturing reservoir protectant with anti-expansion and anti-collapse functions according to claim 2, characterized in that, The polyoxyethylene ether is selected from at least one of isomeric deca-ol polyoxyethylene ether, fatty amine polyoxyethylene ether, castor oil polyoxyethylene ether, and cetearyl alcohol polyoxyethylene ether.

4. The fracturing reservoir protectant with anti-bulging and anti-collapse functions according to claim 3, characterized in that, The polyoxyethylene ether is selected from at least one of the following: isomeric decaol polyoxyethylene ether with EO=6, fatty amine polyoxyethylene ether with EO=5, castor oil polyoxyethylene ether with EO=40, and cetearyl alcohol polyoxyethylene ether with EO=6.

5. The method for preparing the fracturing reservoir protectant with anti-swelling and anti-collapse function as described in any one of claims 1 to 4, characterized in that, The preparation method includes: 3-amino-1,2-propanediol-modified graphene oxide nanoparticles and a silane coupling agent were reacted in a mixture of ethanol and water at 60-70°C. After the reaction was completed, the solid and liquid were separated, and the solid was washed to obtain amphiphilic modified graphene oxide. The nonionic surfactant is dissolved in water, and the amphiphilic modified graphene oxide is added. The mixture is heated to 30-50°C and ultrasonically dispersed at a frequency of 15-20 kHz to form a stable dispersion. Finally, an amine clay stabilizer and a cationic surfactant are added and mixed evenly to obtain the fracturing reservoir protection agent with anti-swelling and anti-collapse functions.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the 3-amino-1,2-propanediol-modified graphene oxide nanoparticles to the silane coupling agent is 1:(1~3). Or / and, the mass ratio of the 3-amino-1,2-propanediol-modified graphene oxide nanoparticles to the ethanol and water mixture is (0.1~0.2):20; Or / and, in the ethanol and water mixture, the mass ratio of ethanol to water is 1:

1.

7. The preparation method according to claim 5, characterized in that, The preparation method of the 3-amino-1,2-propanediol modified graphene oxide nanoparticles includes: Graphene oxide was ultrasonically dispersed in water to form a GO dispersion. 3-Amino-1,2-propanediol was added to the GO dispersion under stirring, and the reaction was continued at 50-80℃. Sodium chloride was added to the mixture after the reaction, and the mixture was stirred and dispersed. The solid and liquid were separated, and the solid was washed with a mixture of ethanol and water to obtain 3-amino-1,2-propanediol modified graphene oxide nanoparticles.

8. The preparation method according to claim 7, characterized in that, The mass ratio of graphene oxide to water is 0.5:100; Or / and, the mass ratio of the graphene oxide to 3-amino-1,2-propanediol is 1:(1~4). Or / and, the mass ratio of the graphene oxide to sodium chloride is 1:(1~4); Or / and, in the preparation method of the 3-amino-1,2-propanediol modified graphene oxide nanoparticles, the volume ratio of ethanol to water in the ethanol and water mixture is 1:1; Or / and, in the preparation method of the 3-amino-1,2-propanediol modified graphene oxide nanoparticles, the solid-liquid separation is carried out by centrifugation at a speed of 1000~2000 r / min.

9. The application of the fracturing reservoir protectant with anti-expansion and anti-collapse function as described in any one of claims 1 to 4 in the fracturing process.

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