A graphene oxide temperature-resistant foam stabilizer maintaining amphiphilicity under wide pH conditions and preparation method thereof

Abstract

The present invention relates to the field of oilfield chemical technology, and discloses a graphene oxide temperature-resistant foam stabilizer and a preparation method thereof that maintains amphiphilicity under a wide pH range. Graphene oxide (GO) is first dispersed in an ice-water bath, and then a graphene oxide dispersion, solid paraffin, an emulsifier, and an intercalant are sequentially added using a template method, emulsified and solidified, washed and filtered to obtain GO-coated paraffin microspheres, which are then dispersed in anhydrous ethanol, a hydrolyzed silane coupling agent is added, and after a period of reaction, an amino modifier is added and reacted again. After centrifugal washing, amphiphilic GO-coated paraffin microspheres are obtained, which are finally fully dissolved in chloroform, and subjected to multiple centrifugal washings and freeze-drying to obtain a foam stabilizer. The foam stabilizer has the advantages of increasing the strength of the foam liquid film, extending the drainage time, improving the foam stability, having good surface activity, and having a synergistic foaming effect with a foaming agent under high-temperature and wide pH conditions. It has good application prospects in high-temperature acidic oil and gas reservoir fracturing and chemical flooding.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development engineering, and in particular to a graphene oxide temperature-resistant foam stabilizer capable of maintaining amphiphilicity under a wide pH range and a preparation method thereof. Background Art

[0002] With the rapid development of my country's economy, the demand for energy and resources is growing. In the oil extraction sector, particularly, improving crude oil recovery (ER) has become a focus of industry attention. Chemical flooding and fracturing, as effective technologies for enhancing oil recovery, have been widely adopted. However, conventional foams suffer from insufficient foam stability in practical applications, limiting their effectiveness and widespread adoption.

[0003] Due to the thermodynamic and kinetic instability of foam, it is more susceptible to collapse under high-temperature and high-salinity conditions. Therefore, foam stabilizers play a crucial role in foam flooding technology. Foam stabilizers can improve foam stability, allowing it to maintain a stable state for a longer period of time in complex underground environments, thereby effectively achieving oil displacement. Foam stabilizers are generally classified into polymers, viscoelastic surfactants, and nanoparticles. Foam stabilizers primarily stabilize foam by increasing its viscosity and reducing its fluidity. They are typically composed of high molecular weight polymers and can be further categorized as natural polymer foam stabilizers (such as cellulose, pectin, gum arabic, chitosan, guar gum, and its derivatives) and artificial polymer foam stabilizers (such as polyvinyl alcohol (PVA), polyacrylamide (PAM), polyethylene oxide (PEO), polystyrene sulfonate, and polyvinyl pyrrolidone (PVP)). These foam stabilizers are highly susceptible to decomposition under high-temperature conditions, and residual organic matter can affect the performance of foam fracturing fluids. Viscoelastic surfactant foam stabilizers can form a thick liquid film structure at the interface, suppressing spatial density fluctuations at the air-water interface through intermolecular interactions, resulting in excellent stabilization effects. Typically, these foam stabilizers work synergistically with foaming agents, but their effectiveness is limited under high-temperature, high-salt conditions. Solid particle foam stabilizers demonstrate unique advantages in high-temperature, high-salt environments, as solid particles are less sensitive to temperature. The particles irreversibly and spontaneously adsorb at the gas-liquid interface, balancing interfacial tension and forming a solid-liquid-gas three-phase interface film. This prevents gas-liquid phase transfer and hinders drainage between the gas and liquid phases. Examples of these foam stabilizers include nano-silica, nano-titanium dioxide, nano-calcium carbonate, nano-montmorillonite, and graphene oxide. However, these stabilizers tend to aggregate and sink in aqueous solutions and have difficulty adsorbing at the gas-liquid interface, thus reducing their foaming effectiveness. Therefore, modification of nano-particle foam stabilizers is necessary. These modified particles exhibit improved dispersibility in water, possess moderate wettability, and can stably adsorb at the gas-liquid interface, effectively improving foam stability.

[0004] In recent years, graphene oxide (GO), a two-dimensional nanomaterial with a high specific surface area, good mechanical strength, and excellent chemical stability, has been discovered. Researchers have discovered that GO particles have significant potential for foam stabilization. The oxygen-containing functional groups on the surface of GO particles can interact with gas molecules in the foam, enhancing its stability and making it an ideal candidate for a foam stabilizer.

[0005] As early as 1913, Hoffmann proposed that nanoparticles could stabilize foam. In recent years, many scholars have begun to focus on the research of nanoparticle foam stabilization. CN116148251A discloses a method for testing the foam stabilization performance of nano-CaCO3 / SiO2 core particles. This invention first synthesizes nano-CaCO3 / SiO2 core particles and then modifies them. The resulting hyperbranched nanoparticles have cationic properties, which have a certain affinity with anionic foaming agents and can be firmly adsorbed on the surface of the foam liquid film. Furthermore, the hyperbranched molecules contain a large number of hydrophilic groups, and the cavities of the branching units can encapsulate bound water molecules, controlling their diffusion and effectively stabilizing the foam fluid. However, the preparation process is complex, and CaCO3 dissolves under acidic conditions to form corresponding calcium salts, water, and carbon dioxide gas, making it unsuitable for acidic oil and gas reservoirs and acidified oil and gas reservoirs. CN108410441B discloses a reinforced foam system based on the synergistic stabilization of graphite oxide particles. Hexadecyltrimethylammonium bromide is used as the foaming agent, and the foam stabilizer is graphite oxide particles. The system has good stability and a simple preparation process, but the use concentration and cost are high, and it is difficult to work under a wide pH range. In addition, the foaming agent is a cationic surfactant, and the adsorption loss on the negatively charged rock surface is too large, affecting the foam regeneration effect. CN201910517966.5 discloses a long-lasting foam with a low foam stabilizer dosage and a preparation method. The long-lasting foam prepared by this method has a half-life increased by 550% compared with ordinary foam. The particle foam stabilizers involved in the foam system are graphene oxide and / or amino graphene, and an air-water interface synergist is also added, and the composition is relatively complex. Graphene oxide and / or amino graphene are relatively stable in an alkaline environment, and their stability is greatly reduced under acidic conditions, making them unsuitable for acidic formation environments. Similarly, CN 116143823 A discloses an amphiphilic nanographite high-temperature foam stabilizer, a preparation method, and a temperature-resistant three-phase foam system. Although nanographite can prevent foam drainage to a certain extent, due to the thick layered structure and large particles of nanographite, the gravitational differentiation at the foam-liquid film interface is large, resulting in a decrease in foam stability.

[0006] In summary, a key technology for improving foam performance is how nanomaterials can effectively enhance foam stability through their unique physical and chemical properties. For example, graphene oxide (GO) particles can be modified through physical or chemical methods to further optimize their foam stabilization properties, making them temperature-resistant and tolerant to a wide pH range, environmentally friendly, and better adapted to complex formation environments. This is a pressing challenge for those skilled in the art. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides a graphene oxide heat-resistant foam stabilizer and preparation method that maintains amphiphilicity under a wide pH range. This GO particle-type foam stabilizer can maintain amphiphilicity under a wide pH range (3-12) and can be adsorbed on the foam liquid film to form a solid-liquid-gas three-phase foam, which can improve the strength of the foam liquid film, reduce the liquid film drainage rate and the foam disproportionation rate, thereby improving the stability of the foam. This nano foam stabilizer has a low usage concentration, a low manufacturing cost, and a simple preparation method. The raw material of the present invention, graphene oxide, is stable in nature and has a high specific surface area. The layers easily interact through van der Waals forces, resulting in aggregation. The main reason is that the surface of graphene oxide contains a large number of oxygen-containing functional groups such as hydroxyl and carboxyl groups. These functional groups make graphene oxide highly hydrophilic. In water, the graphene oxide layers will attract each other due to the hydrogen bonds formed by water molecules, promoting the occurrence of aggregation, that is, GO has poor dispersibility. Therefore, it is necessary to modify it to give it foam-stabilizing properties.

[0008] The present invention provides a method for preparing a graphene oxide temperature-resistant foam stabilizer that maintains amphiphilicity under a wide pH range, the preparation process comprising the following steps:

[0009] (1) 1-2 parts of graphene oxide were added to 1000-2000 parts of deionized water, and ultrasonically dispersed in an ice-water bath for 1 hour to prepare a graphene oxide dispersion.

[0010] (2) Weigh 30 to 40 parts of solid paraffin wax and heat it to a liquid state. At 70°C, add liquid paraffin wax, emulsifier OP-10 and intercalant cetyltrimethylammonium bromide (the ratio of the three parts is 55:1:10) to the dispersion obtained in step (1) in sequence, and emulsify it at 10,000 rad / min for 20 minutes using an emulsifier. After emulsification, place the mixture in an ice-water bath to solidify the paraffin microspheres. At this time, the graphene oxide fully wraps the surface of the paraffin microspheres, and the free graphene oxide, cetyltrimethylammonium bromide and OP-10 are removed by filtration and washing to obtain graphene oxide-coated paraffin microspheres.

[0011] (3) Add 1 part of 36.5% concentrated hydrochloric acid to 300 parts of anhydrous ethanol, stir evenly, then add 1 to 3 parts of a silane coupling agent, and hydrolyze for 15 minutes to obtain a silane coupling agent hydrolyzate. Pour the obtained hydrolyzate and the graphene oxide-coated paraffin microspheres obtained in step (2) into a three-necked flask, and react at 30° C. and a stirring speed of 300 rad / min for 48 to 72 hours, so that the hydroxyl groups on the outer side of the graphene oxide sheets coated on the surface of the paraffin microspheres undergo a coupling reaction with the silanol groups of the hydrolyzed silane coupling agent, thereby obtaining a dispersion of silane coupling agent-modified graphene oxide-coated paraffin microspheres, i.e., a dispersion of intermediate 1.

[0012] ((4) adding 3 to 4 parts of an amino modifier to the dispersion of the intermediate 1 obtained in step (3), wherein the primary amine group of the amino modifier reacts with the epoxy group on the graphene oxide modified by the silane coupling agent to undergo a ring-opening reaction, reacting for 3 to 5 hours, cooling to room temperature, and then filtering to obtain amphiphilic graphene oxide-coated paraffin microspheres;

[0013] (5) The amphiphilic graphene oxide-coated paraffin microspheres obtained in step (4) were fully dissolved in 100 parts of chloroform, then centrifuged and washed 6 times with 100 mL of ethanol solution, and freeze-dried for 48 hours to obtain an amphiphilic graphene oxide heat-resistant foam stabilizer.

[0014] The above-mentioned silane coupling agent is KH-560, and its structural formula is: Wherein R is methyl.

[0015] The above-mentioned amino modifier is diethylenetriamine, and its structural formula is:

[0016] The hydrolysis reaction principle of the above-mentioned silane coupling agent KH-560 is:

[0017]

[0018] The silanol groups of the hydrolysis product of KH-560 silane coupling agent reacted with the hydroxyl groups on graphene oxide to obtain intermediate 1, whose structural formula is: In the above structural formula It is the main structure of graphene oxide.

[0019] The epoxy group in intermediate 1 reacts with the primary amine of the amino modifier diethylenetriamine to obtain the target product, an amphiphilic graphene oxide high-temperature resistant foam stabilizer, whose structural formula is:

[0020] The advantages of this patent are as follows:

[0021] (1) The amphiphilic graphene oxide high-temperature resistant foam stabilizer prepared by this invention patent increases the strength of the foam liquid film, prevents bubble aggregation and prolongs the liquid film drainage time, slows down the bubble disproportionation rate, greatly improves the foam stability, and maintains good foam stabilization performance under high temperature (100-160℃) conditions.

[0022] (2) The amphiphilic graphene oxide high-temperature resistant foam stabilizer prepared by this invention patent has a carboxyl group (-COOH) and an amino group (-NH2), is amphiphilic, acid-resistant and alkali-resistant, and can maintain a good foam stabilizing effect under a wide pH range (3 to 12).

[0023] (3) Conventional graphene oxide has weak hydrophilicity and poor dispersion ability in water, which causes the foam stabilizer to easily agglomerate. The amphiphilic graphene oxide high-temperature resistant foam stabilizer prepared by this invention patent avoids the agglomeration of the foam stabilizer, improves the dispersion of the foam stabilizer in water, and improves the foam quality.

[0024] (4) This invention patent adopts a template method to prevent the graphene oxide surface coated with paraffin from chemically reacting, while the surface not coated with wax participates in coupling reaction and ring-opening reaction, effectively realizing the amphiphilicity of graphene oxide and effectively improving the surface and interfacial properties of the amphiphilic graphene oxide high-temperature resistant foam stabilizer.

[0025] (5) The amphiphilic graphene oxide high-temperature resistant foam stabilizer prepared by this invention patent has good surface and interfacial activity, can increase the strength of the foam liquid film, prolong the drainage time, improve the foam stability, and also has a synergistic foaming effect on the foaming agent. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0027] The parts in the specific embodiment are all parts by mass.

[0028] Embodiment 1~9:

[0029] The nine groups of experiments in Examples 1 to 9 were conducted while keeping other experimental parameters and experimental steps unchanged, while changing the amount of solid paraffin, the amount of GO, the amount of deionized water, the amount of coupling agent KH560, the amount of amino modifier DETA, the coupling time and the ring-opening time to obtain amphiphilic graphene oxide foam stabilizers. The changed experimental parameters are shown in Table 1.

[0030] Table 1 Main raw material addition amounts and reaction times corresponding to Examples 1 to 9

[0031]

[0032] Effect of amphiphilic graphene oxide foam stabilizer on foam stabilization and foaming performance:

[0033] 2 parts of the amphiphilic graphene oxide foam stabilizer prepared in Examples 1 to 9 were mixed with 1334 parts of water and ultrasonically dispersed for 25 minutes to obtain an amphiphilic graphene oxide foam stabilizer dispersion. 8 parts of an amphoteric surfactant were added to the foam stabilizer dispersion to obtain a foaming solution. 200 mL of the foaming solution was added to a high-temperature, high-pressure foaming machine and foamed at a constant temperature of 140°C for 15 minutes, with a constant stirring rate of 4000 rad / min and a stirring time of 60 seconds. The foam volumes and half-lives of the foam solutions of Examples 1 to 9 were obtained, respectively, as shown in Table 2. The amphiphilic surfactant was selected from the group consisting of cocamidopropyl betaine, erucamidopropyl betaine, and oleamidopropyl betaine, with cocamidopropyl betaine being preferred.

[0034] Comparative Example 1: 2 parts of unmodified graphene oxide were mixed with 1334 parts of water and ultrasonically dispersed for 25 minutes to obtain a graphene oxide dispersion. 8 parts of an amphoteric surfactant were then added to this dispersion to obtain a foaming solution. 200 mL of this foaming solution was added to a high-temperature, high-pressure foaming machine and foamed at 140°C for 15 minutes, with a constant stirring rate of 4000 rad / min and a stirring time of 60 seconds. The foam volume and half-life of the foam solution of Comparative Example 1 were obtained. The results are shown in Table 2.

[0035] Comparative Example 2: Without adding graphene oxide and amphiphilic graphene oxide, 8 parts of an amphoteric surfactant were directly mixed with 1334 parts of water to produce a foaming solution. 200 mL of this foaming solution was added to a high-temperature, high-pressure foaming machine and foamed at 140°C for 15 minutes, with a constant stirring rate of 4000 rad / min and a stirring time of 60 seconds. The foam volume and half-life of the foam solution of Comparative Example 2 were obtained. The results are also shown in Table 2.

[0036] Table 2 Foam volume and half-life of Examples and Comparative Examples

[0037]

[0038] The foam half-life of comparative example 1 in which unmodified graphene oxide was added as a foam stabilizer and comparative example foam 2 in which no foam stabilizer was added at 140°C were 222min and 208min, respectively, and the foam volumes were 480mL and 485mL, respectively. This shows that the unmodified graphene oxide did not significantly improve the foam stability and the foaming effect was not obvious. However, after using the amphiphilic graphene oxide foam stabilizer provided by the present invention, the foam half-life increased by 1 to 2 times, the stability of the foam was greatly improved, the foam volume increased by about 50%, and the foaming effect was obvious. Among them, the foam half-life using the foam stabilizer of Example 5 reached 614min, and the foam volume reached 630mL, which greatly improved the stability of the foam and significantly improved the foam volume.

[0039] Foam stability and foaming performance under different pH conditions:

[0040] The foaming liquid prepared in Example 5 was prepared using a dilute solution of hydrochloric acid or sodium hydroxide into twelve groups of foaming liquids with pH values ​​of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13 as shown in Table 3. The foaming properties of the foaming liquids under different pH conditions were tested. The experimental conditions and methods of the tests were the same as those in Table 2.

[0041] Table 3 Foam stabilization and foaming performance under different pH conditions

[0042]

[0043] The foam half-life and foam volume of the foaming liquid prepared in Example 5 at different pH values ​​are shown in Table 3. The foam half-life and foam volume vary at different pH values. The improvement in foam stability not only relies on the presence of pH-responsive characteristic groups (-COOH and -NH2) on the modified graphene oxide structural units and the amphiphilicity of the surfactant, but also benefits from the three-phase foam composed of graphene oxide, amphoteric surfactant, and deionized water. Furthermore, graphene oxide has high thermal stability, which gives the graphene oxide prepared in the present invention good temperature resistance. This test is also not tested in other similar patents.

[0044] The modified nano foam stabilizer provided by the present invention has a good foam stabilizing effect on amphoteric surfactant-type foaming agents, and the foam stabilizer with the best foam stabilizing effect is Example 5. Results The amphiphilic graphene oxide heat-resistant foam stabilizer maintained at a wide pH range has a sheet-like structure and has good foam properties at a wide pH range (3-12).

[0045] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A graphene oxide temperature-resistant foam stabilizer that maintains amphiphilicity under a wide pH range, characterized in that: The method for preparing the amphiphilic graphene oxide heat-resistant foam stabilizer, wherein the raw materials used are all calculated by mass, comprises the following steps: (1) 1-2 parts of graphene oxide were added to 1000-2000 parts of deionized water, and ultrasonically dispersed in an ice-water bath for 1 hour to prepare a graphene oxide dispersion; (2) Weigh 30-40 parts of solid paraffin wax, heat it to a liquid state, and add 55 parts of liquid paraffin wax, 1 part of emulsifier OP-10 and 10 parts of intercalant cetyltrimethylammonium bromide to the dispersion obtained in step (1) at 70°C, and emulsify it for 20 minutes at 10,000 rad / min using an emulsifier. After the emulsification is completed, place the mixture in an ice-water bath to solidify the paraffin microspheres, so that the graphene oxide fully wraps the surface of the paraffin microspheres. Remove the free graphene oxide, cetyltrimethylammonium bromide and OP-10 by filtering and washing to obtain graphene oxide-coated paraffin microspheres; (3) adding 1 part of 36.5% concentrated hydrochloric acid to 300 parts of anhydrous ethanol, stirring evenly, adding 1 to 3 parts of a silane coupling agent, and hydrolyzing for 15 minutes to obtain a hydrolyzate of the silane coupling agent. The obtained hydrolyzate and the paraffin microspheres coated with graphene oxide obtained in step (2) are poured into a three-necked flask, and reacted at 30° C. and a stirring speed of 300 rad / min for 48 to 72 hours, so that the hydroxyl groups on the outer side of the graphene oxide sheets coated on the surface of the paraffin microspheres undergo a coupling reaction with the silanol groups of the hydrolyzed silane coupling agent, thereby obtaining an intermediate 1 dispersion; (4) Add 3 to 4 parts of diethylenetriamine as an amino modifier to the intermediate 1 dispersion obtained in step (3); the primary amine group of the amino modifier reacts with the epoxy group on the graphene oxide modified by the silane coupling agent KH-560 to undergo a ring-opening reaction; after reacting for 3 to 5 hours, cool to room temperature, and then filter to obtain amphiphilic graphene oxide-coated paraffin microspheres. The silane coupling agent KH-560 used has the structural formula: Where R is methyl, the hydrolysis product of KH-560 is (5) The amphiphilic graphene oxide-coated paraffin microspheres obtained in step (4) were fully dissolved in 100 parts of chloroform, then centrifuged and washed 6 times with 100 mL of ethanol solution, and freeze-dried for 48 hours to obtain the final product, an amphiphilic graphene oxide heat-resistant foam stabilizer.

2. The amphiphilic graphene oxide temperature-resistant foam stabilizer according to claim 1, wherein The intermediate 1 and the final product are respectively ( is mainly graphene oxide).

3. The amphiphilic graphene oxide temperature-resistant foam stabilizer according to claim 1 can maintain amphiphilicity at high temperatures of 100 to 160°C and a wide pH range of 3 to 12.

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