Graphene oxide temperature-resistant foam stabilizer capable of maintaining amphipathy under wide pH range and preparation method of graphene oxide temperature-resistant foam stabilizer

Abstract

The invention relates to the technical field of oilfield chemistry, and discloses a graphene oxide temperature-resistant foam stabilizer capable of maintaining amphipathy under a wide pH range and a preparation method of the graphene oxide temperature-resistant foam stabilizer. The preparation method comprises the following steps: dispersing graphene oxide (GO) in an ice-water bath, sequentially adding a graphene oxide dispersion liquid, solid paraffin, an emulsifier and an intercalator by using a template method, carrying out emulsification and curing treatment, washing and filtering to obtain GO-coated paraffin microspheres, dispersing the GO-coated paraffin microspheres in absolute ethyl alcohol, adding a hydrolyzed silane coupling agent, and carrying out ultrasonic dispersion to obtain the graphene-coated paraffin microspheres. The preparation method comprises the following steps: adding GO into a reaction kettle, reacting for a period of time, adding an amino modifier, reacting again, centrifugally washing to obtain amphipathic GO coated paraffin microspheres, finally fully dissolving the amphipathic GO coated paraffin microspheres in trichloromethane, and sequentially carrying out multiple times of centrifugal washing and freeze drying to obtain the foam stabilizer. The foam stabilizer has the effects of increasing the strength of a foam liquid film, prolonging the drainage time, improving the foam stability and having good surface and interface activity under the conditions of high temperature and wide pH, has a synergistic foam increasing effect with a foaming agent, and has a good application prospect in fracturing and chemical flooding of high-temperature acidic oil and gas reservoirs.

Description

Technical Field

[0001] The 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 increasing, especially in the field of oil extraction, and improving crude oil recovery has become the focus of the industry. Chemical flooding and fracturing, as an effective technology to improve crude oil recovery, have been widely used. However, traditional foams have the problem of insufficient foam stability in practical applications, which limits the effect and promotion of foam flooding technology and foam fracturing technology.

[0003] Due to the thermodynamic and kinetic instability of foam, foam is more likely to break under high temperature and high salt conditions, so foam stabilizers play a vital role in foam flooding technology. Foam stabilizers can improve the stability of foam, so that it can maintain a stable state for a long time in a complex underground environment, so as to better play the role of oil displacement. Foam stabilizers are usually divided into polymers, viscoelastic surfactants and nanoparticles. Foam stabilizers mainly stabilize foam by increasing the viscosity of foam and reducing foam fluidity. They are usually composed of high molecular polymers and can be subdivided into natural polymer foam stabilizers (such as cellulose, pectin, gum arabic, chitosan, guar gum and its derivatives, etc.) and artificial polymer foam stabilizers (such as polyvinyl alcohol (PVA), polyacrylamide (PAM), polyethylene oxide (PEO), polystyrene sulfonate, polyvinyl pyrrolidone (PVP), etc.). This type of foam stabilizer is very easy to decompose under high temperature conditions, and the residual organic matter will affect the performance of foam fracturing fluid. Viscoelastic surfactant foam stabilizers can form a thicker liquid film structure on the interface, and suppress the spatial density fluctuation on the gas-water interface through intermolecular interactions, thereby having a good stabilizing effect. Usually this type of foam stabilizer has a synergistic effect with the foaming agent, but its effect is limited under high temperature and high salt conditions. Solid particle foam stabilizers show their unique advantages in high temperature and high salt environments, and solid particles are less sensitive to temperature. The particles are irreversibly and spontaneously adsorbed on the gas-liquid interface, balancing the tension of the interface, forming a solid-liquid-gas three-phase interface film, preventing gas-liquid phase transfer, and hindering the drainage effect between the gas and liquid phases. This type of foam stabilizer mainly includes nano-silicon dioxide, nano-titanium dioxide, nano-calcium carbonate, nano-montmorillonite and graphene oxide. However, they are easy to agglomerate and sink in aqueous solution, and are difficult to adsorb on the gas-liquid interface, thereby reducing the foaming effect. Therefore, it is necessary to modify the nano-blue solid particle foam stabilizer. The modified particles have better dispersibility in water, have moderate wettability, and can be stably adsorbed on the gas-liquid interface, thereby effectively improving the stability of the foam.

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

[0005] As early as 1913, Hoffmann proposed that nano solid particles can stabilize foam. In recent years, many scholars have begun to pay attention to the research on nano particle foam stabilization. CN116148251A discloses nano CaCO 3 / SiO 2 The invention first synthesizes nano-CaCO 3 / SiO 2 Core particles, and then nano-CaCO 3 / SiO 2 The core particles are modified to obtain hyperbranched nanoparticles with cationic properties, which have a certain affinity with anionic foaming agents and can be firmly adsorbed on the surface of the foam liquid film; on the other hand, the hyperbranched molecules contain a large number of hydrophilic groups, and the branch unit cavities can wrap bound water molecules, control the diffusion of water molecules, and effectively stabilize the foam fluid. However, the preparation process is complicated, and CaCO 3 Under acidic conditions, it will dissolve to generate corresponding calcium salts, water and carbon dioxide gas, which cannot be applied to 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. Hexadecyl trimethylammonium bromide is used as a 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 act under a wide pH. In addition, the foaming agent is a cationic surfactant, and the adsorption loss on the surface of negatively charged rocks 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 the method has a half-life increased by 550% compared with ordinary foam. The particle foam stabilizer involved in the foam system is graphene oxide and / or amino graphene, and a gas-water interface synergist is also added, and the composition is relatively complex. And graphene oxide and / or amino graphene are relatively stable in an alkaline environment, and the stability is greatly reduced under acidic conditions, and it cannot be applied to an acidic formation environment. Similarly, CN 116143823 A discloses an amphiphilic nanographite high-temperature foam stabilizer and 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 of nanographite and the large particles, the gravity differentiation at the foam liquid film interface is large, resulting in a decrease in foam stability.

[0006] In summary, how nanomaterials can effectively improve the stability of foams through their unique physical and chemical properties is a key technology to improve foam performance. For example, graphene oxide GO particles can be modified by physical or chemical methods to further optimize their foam stabilization performance, making them temperature-resistant and pH-tolerant, environmentally friendly, and better adaptable to the complex environment of the formation. This is an urgent problem to be solved by technicians in this field. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a graphene oxide temperature-resistant foam stabilizer and a preparation method thereof that maintains amphiphilicity under a wide pH range. The 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 speed and the foam disproportionation rate, thereby improving the stability of the foam. The nano foam stabilizer has a low concentration, a low manufacturing price and a simple preparation method.

[0008] The raw material graphite oxide of the present invention is stable in nature and has a high specific surface area. The sheets are easily interacted through van der Waals forces, resulting in aggregation. The main reason is that the surface of graphite oxide contains a large number of oxygen-containing functional groups such as hydroxyl and carboxyl groups, which make graphene oxide highly hydrophilic. In water, the graphene oxide sheets will attract each other due to the hydrogen bonds formed by water molecules, which promotes the occurrence of aggregation, that is, GO has poor dispersibility. Therefore, it needs to be modified to give it foam-stabilizing properties. Its preparation process includes the following steps:

[0009] (1) Take 1-2 parts of graphene oxide, add it to 1000-2000 parts of deionized water, and disperse it in an ice-water bath by ultrasonication for 1 hour to prepare a graphene oxide dispersion.

[0010] (2) Weigh 30 to 40 parts of solid paraffin and heat it to a liquid state. At 70°C, add liquid paraffin, emulsifier OP-10 and intercalant hexadecyltrimethylammonium chloride (the ratio of the three parts is 55:1:10) to the dispersion obtained in step (1) in sequence, and emulsify 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. At this time, the graphene oxide fully wraps the surface of the paraffin microspheres, and the free graphene oxide, hexadecyltrimethylammonium bromide and OP-10 are removed by filtering 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 silane coupling agent, and perform hydrolysis reaction for 15 minutes to obtain a hydrolysis product of the silane coupling agent. Pour the obtained hydrolysis product and the paraffin microspheres coated with graphene oxide obtained in step (2) into a three-necked flask, and react for 48 to 72 hours at 30° C. and a stirring speed of 300 rad / min, so that the hydroxyl groups on the outer side of the graphene oxide sheets coated on the surface of the paraffin microspheres undergo coupling reaction with the silanol groups of the hydrolyzed silane coupling agent, and obtain a dispersion of paraffin microspheres coated with graphene oxide modified by a silane coupling agent, i.e., a dispersion of intermediate 1.

[0012] (4) Add 3 to 4 parts of an amino modifier to the dispersion of the intermediate 1 obtained in step (3), and 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. After reacting for 3 to 5 hours, the mixture is cooled to room temperature and filtered 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 silane coupling agent is one of KH-550 silane coupling agent, KH-560 silane coupling agent and KH-570 silane coupling agent. Preferably, the silane coupling agent is KH-560 silane coupling agent, and the structural formula is: Wherein R is methyl.

[0015] The amino modifier is one of diethylenetriamine and triethylenetetramine. Preferably, the amino modifier is diethylenetriamine, and the structural formula is:

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

[0017] The silanol groups of the hydrolyzed 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 body of graphene oxide structure.

[0018] The epoxy group in the 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:

[0019] The advantages of this patent are as follows:

[0020] (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°C) conditions.

[0021] (2) The amphiphilic graphene oxide high temperature resistant foam stabilizer prepared by this invention patent has carboxyl and amine groups, is amphiphilic, is acid and alkali resistant, and can maintain a good foam stabilizing effect under a wide pH range (3 to 12).

[0022] (3) Conventional graphene oxide has weak hydrophilicity and poor dispersion in water, which makes the foam stabilizer easy to 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.

[0023] (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 amphiphilic graphene oxide high temperature resistant foam stabilizer.

[0024] (5) The amphiphilic graphene oxide high temperature resistant foam stabilizer prepared by this invention patent has good surface activity and can also be used as a foaming agent. It can synergistically increase foaming with the foaming agent and improve the foaming ability of the foam system. DETAILED DESCRIPTION

[0025] 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 implementation methods.

[0026] The parts in the specific implementation manner are all parts by mass.

[0027] Embodiment 1~9:

[0028] The nine groups of experiments in Examples 1 to 9 are amphiphilic graphene oxide foam stabilizers obtained by changing the amount of solid paraffin, GO, deionized water, coupling agent KH550, amino modifier DETA, coupling time and ring-opening time while keeping other experimental parameters and experimental steps unchanged. The changed experimental parameters are shown in Table 1.

[0034] Table 1 Main raw material addition amounts and reaction times corresponding to Examples 1 to 9

[0029] Effect of amphiphilic graphene oxide foam stabilizer on foam stabilization and foaming properties:

[0030] 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 amphoteric surfactants were added to the foam stabilizer dispersion to obtain a foaming liquid. 200 mL of the foaming liquid was added to a high-temperature and high-pressure foaming machine, and foaming was performed at a constant temperature of 140°C for 15 minutes, a constant stirring rate of 4000 rad / min, and a stirring time of 60 seconds to obtain the foam volume and half-life of the foam liquid of Examples 1 to 9, respectively, as shown in Table 2. Among them, the amphiphilic surfactant is one of cocamidopropyl betaine, erucic acid amide propyl betaine, and oleic acid amide propyl betaine, and cocamidopropyl betaine is preferred here.

[0031] Comparative Example 1: 2 parts of unmodified graphene oxide were mixed with 1334 parts of liquid preparation water, and ultrasonically dispersed for 25 minutes to obtain a graphene oxide dispersion; 8 parts of amphoteric surfactant were added to the dispersion to obtain a foaming liquid: 200 mL of the foaming liquid was added to a high-temperature and high-pressure foaming machine, and foaming was performed at a constant temperature of 140°C for 15 minutes, a constant stirring rate of 4000 rad / min, and a stirring time of 60 seconds to obtain the foam volume and half-life of the foam liquid of Comparative Example 1; the results are shown in Table 2.

[0032] Comparative Example 2: Without adding graphene oxide and amphiphilic graphene oxide, 8 parts of amphoteric surfactant were directly mixed with 1334 parts of liquid preparation water to obtain a foaming liquid. 200 mL of the foaming liquid was added to a high-temperature and high-pressure foaming machine, and foaming was performed at a constant temperature of 140°C for 15 minutes, a constant stirring rate of 4000 rad / min, and a stirring time of 60 seconds to obtain the foam volume and half-life of the foam liquid of Comparative Example 2; the results are also shown in Table 2.

[0033] Table 2 Foam volume and half-life of Examples and Comparative Examples

[0034] The foam half-life of comparative example 1 in which unmodified graphene oxide is added as a foam stabilizer and comparative example foam 2 in which no foam stabilizer is added at 140°C are 222min and 208min, respectively, and the foaming volumes are 480mL and 485mL, respectively. It is shown that the unmodified graphene oxide does not significantly improve the foam stability, and the foaming effect is 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 foaming volume increased by about 50%, and the foaming effect was obvious. Among them, the foam half-life of the foam stabilizer using Example 5 reached 614min, and the foaming volume reached 630mL, the stability of the foam was greatly improved, and the foaming volume was also significantly improved.

[0035] Foam stability and foaming performance under different pH conditions:

[0036] The foaming liquid prepared in Example 5 was prepared into twelve groups of foaming liquids with pH values ​​of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13 as described in Table 3 using a dilute solution of hydrochloric acid or sodium hydroxide. 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.

[0037] Table 3 Foam stability and foaming performance under different pH conditions

[0038] The foam half-life and foaming volume of the foaming liquid prepared in Example 5 at different pH values ​​are shown in Table 3. The foam half-life and foaming volume are different at different pH values. The improvement of foam stability depends not only on the presence of pH-responsive characteristic groups (-COOH and -NH 2 ) and the amphiphilicity of the surfactant, and at the same time, thanks to the three-phase foam composed of graphene oxide-amphoteric surfactant-deionized water, and the high thermal stability of graphene oxide, the graphene oxide prepared by the present invention has good temperature resistance. At the same time, this test is also not tested in other patents of the same type.

[0039] The modified nano foam stabilizer provided by the present invention has a good foam stabilizing effect on amphoteric surfactant 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 value is a sheet-like structure and has good foam properties at a wide pH value (3 to 12).

[0040] 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 amphiphilic graphene oxide has a structural formula shown in formula (1):

2. The graphene oxide temperature-resistant foam stabilizer maintaining amphiphilicity under a wide pH range according to claim 1, characterized in that: The method for preparing the amphiphilic graphene oxide temperature-resistant foam stabilizer comprises the following steps: (1) taking 1-2 parts of graphene oxide, adding it to 1000-2000 parts of deionized water, and ultrasonically dispersing it in an ice-water bath for 1 hour to obtain a graphene oxide dispersion; (2) Weigh 30-40 parts of solid paraffin and heat it to a liquid state. At 70°C, add liquid paraffin, emulsifier OP-10 and intercalant hexadecyltrimethylammonium chloride (the ratio of the three parts is 55:1:10) to the dispersion obtained in step (1) in sequence, and emulsify for 20 minutes at 10000rad / min using an emulsifier. After the emulsification is completed, 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, hexadecyltrimethylammonium bromide and OP-10 are removed by filtering and washing to obtain graphene oxide-coated paraffin microspheres; (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 silane coupling agent, and hydrolyze for 15 minutes to obtain a hydrolyzate of the silane coupling agent. Pour the obtained hydrolyzate and the paraffin microspheres coated with graphene oxide obtained in step (2) into a three-necked flask, and react for 48 to 72 hours at 30° C. and a stirring speed of 300 rad / min, 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, to obtain a dispersion of intermediate 1; (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; (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.

3. The method for preparing the amphiphilic graphene oxide temperature-resistant foam stabilizer according to claim 2, wherein: The silane coupling agent is one of KH-550 silane coupling agent, KH-560 silane coupling agent and KH-570 silane coupling agent. Preferably, the silane coupling agent is KH-560 silane coupling agent, and the structural formula is Where R is methyl, the hydrolysis product of KH-560 is 4. The method for preparing the amphiphilic graphene oxide temperature-resistant foam stabilizer according to claim 2, wherein: The amino modifier is one of diethylenetriamine and triethylenetetramine. Preferably, the amino modifier is diethylenetriamine.

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

6. The amphiphilic graphene oxide heat-resistant foam stabilizer according to claim 1 can maintain amphiphilicity at high temperature (100-160° C.) and wide pH (3-12), has the advantages of increasing the strength of the foam liquid film, prolonging the drainage time, improving the foam stability, and having good surface activity, and has a synergistic foaming effect on the foaming agent.

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