Supercritical carbon dioxide thickener oligomeric glycerol phenyl oleate and application thereof

Abstract

The invention relates to the technical field of supercritical carbon dioxide flooding crude oil extraction, in particular to a supercritical carbon dioxide thickener oligomeric glycerol phenyl oleate and application thereof. The thickening agent comprises oligomeric glycerol phenyl oleate. The low polyglycerol phenyl oleate is used as the supercritical carbon dioxide thickening agent, so that the viscosity of the supercritical carbon dioxide solution can be remarkably improved. The oligomeric glycerol phenyl oleate is easy to prepare, low in production cost, environment-friendly and suitable for large-scale popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of supercritical carbon dioxide enhanced oil recovery, and particularly relates to an oligoglycerol phenyl oleate as a supercritical carbon dioxide thickening agent and its application. Background Art

[0002] In recent years, the technology of carbon dioxide enhanced oil recovery, which has been widely carried out abroad, can not only effectively solve the problem of carbon dioxide sequestration and protect the atmospheric environment, but more importantly, it can meet the needs of oilfield development and improve the "tertiary" oil recovery rate, turning waste into treasure. The principle is that when a large amount of carbon dioxide dissolves in crude oil, it can cause the volume of crude oil to expand and the viscosity to decrease, and can also reduce the interfacial tension between oil and water, thereby improving the oil displacement efficiency. The biggest drawback is that (under formation conditions) the viscosity of carbon dioxide itself is too small (about 0.03 mPa·s to 0.10 mPa·s), which is prone to "viscous fingering" during the injection process and reduces the sweep efficiency of carbon dioxide. Therefore, increasing the viscosity of carbon dioxide and reducing the mobility ratio between carbon dioxide and crude oil have become the key to improving the carbon dioxide enhanced oil recovery technology.

[0003] Foreign countries began to study CO2 thickening agents in the 1980s. In recent years, China has also vigorously developed the research on CO2 thickening agents. It has been found that polyfluorine-based and polysilicon-based ones have good thickening properties and can increase the viscosity of CO2 fluid by 3 to 200 times, but they are expensive and have environmental problems and cannot be actually used. Other cheap and environmentally friendly CO2 thickening agents remain in the stage of laboratory experiments and development, and there has been no application report in oilfield sites.

[0004] Natural polymer thickeners that can thicken aqueous solutions are mainly natural cellulose-based. Their thickening mechanism is mainly the hydrogen bond interaction between cellulose molecules and water molecules. Based on the good water solubility, salt tolerance, and no gel point of hydroxyethyl cellulose (HEC), Shao Ziqiang et al. modified it with halogenated long-chain alkanes such as tetradecyl bromide (MD-14) and dodecyl bromide (MD-12) to improve its thickening property. MD-14 hydroxyethyl cellulose and MD-12 hydroxyethyl cellulose were prepared. The viscosity of MD-14 hydroxyethyl cellulose increased by about 2 times compared with HEC from 250 mPa·s to 500 mPa·s. Synthetic polymer thickeners can also achieve the purpose of thickening aqueous solutions. Polymer thickeners generally form a three-dimensional network structure through electrostatic, hydrogen bond, and hydrophobic interactions of their own macromolecular long-chain structures to achieve thickening. Polymer thickeners generally adsorb on the surface of particles, and the particles adsorb each other and crosslink to form a network structure, increasing the viscosity. Peng Yonggang et al. prepared an inorganic and organic composite electrolyte-resistant thickener using attapulgite and polyacrylic acid. The optimal preparation conditions were: pH = 6.5, T = 75 °C, 0.2% initiator + 0.2% crosslinker + 7.5% acrylamide + 15% modified attapulgite. The electrolyte resistance performance of the obtained composite thickener was improved by 43%.

[0005] The thickening mechanism of supercritical CO2 thickeners is similar to that of thickening water: (1) The long chains of polymer molecules cross and entangle with each other to form irregular fluffy coils, trapping CO2 molecules and preventing them from moving freely; (2) When the polymer concentration reaches a certain value, structural viscosity can be formed, resulting in a sudden jump in viscosity. In 1986, Carbis described the physical properties of CO2 in detail. Heller et al. studied factors such as the molecular structure, properties, and relative molecular mass of polymers. In the solubility test of 53 polymers in liquid CO2, it was found that 18 of them had a certain solubility (0.24% - 1.10%). These polymers have two characteristics: inability to crystallize and irregularity. The poor solubility of these polymers in liquid CO2 leads to poor thickening performance, resulting in the inability to carry out sand-carrying operations, but this research work laid a certain foundation for the subsequent research on CO2 thickeners. It can be divided into the following types according to the types of elements contained in the active ingredients.

[0006] 1. Fluorine-containing CO2 thickeners

[0007] Kilic S et al. studied the effect of the copolymer structure of phenyl acrylate - fluoroacrylate on the viscosity of CO2. Generally, these copolymer structures can be miscible with CO2 under the conditions of P < 15 MPa and T = 295 K, and the viscosity can be increased according to the type and content of aromatic acrylate units in the copolymer. It is known that the association effect of the aromatic ring and the swelling effect of the polymer are the main reasons for the increase in viscosity. The research results show that when the content of phenyl propionate (PHA) units increases, the viscosity of the phenyl acrylate - fluoroacrylate copolymer increases within a certain range. With the increase in the content of aromatic ring acrylate units, the intramolecular association of aromatic rings begins to occur, resulting in a decrease in the amount of viscosity increase. When the relative content of fluoroacrylate (FA) decreases, the affinity of CO2 for the copolymer decreases. Shi C et al. studied the preparation of a carbon dioxide thickener for tight oil reservoirs. The thickener structure contains a CO2 - philic "fluorinated group" to enhance the solubility of the thickener in carbon dioxide, and the intermolecular association can play a role in increasing the viscosity. The research results show that when the concentration of the thickener is in the range of 2% - 4%, the viscosity of liquid carbon dioxide increases by 2 - 3 times; under the condition of not using a cosolvent, by designing a compound with a CO2 - philic group and a hydrophobic associative group that plays a viscosity - increasing interaction, the viscosity of carbon dioxide can be increased; tris(2 - perfluorobutylethyl)tin fluoride is soluble in liquid CO2 under 18 MPa, and the relationship between its cloud point pressure and composition is shown in Figure 2 , tris(3 - perfluoromethylpropyl)tin fluoride is insoluble in liquid CO2 under a high pressure of 48 MPa. Because the excessive fluorinated alkyl chain destroys the weak association effect of the linear polymer, the thickening effect of semi - fluorinated trialkyltin fluoride on liquid carbon dioxide has certain limitations.

[0008] Huang Zhou prepared a class of CO2 thickeners containing fluorourea groups and studied their thermal stability, compatibility with CO2, and compatibility with water and condensate oil. From the thermogravimetric analysis experiment, it can be seen that the thickener DCT starts to thermally degrade at about 200 °C, and the thickener SCT starts to thermally degrade at about 170 °C. Both thickeners have good thermal stability and meet the formation temperature requirements of the oilfield site; under different temperature and pressure conditions, the solubility of the thickeners SCT and DCT in CO2 was tested, and the Chrastil semi - empirical model was used to perform multiple linear fitting on the two thickeners. The calculation results show that the average relative deviations calculated for the thickeners SCT and DCT are 11.14% and 9.52% respectively, and the fitting degree is relatively high. Under different temperature conditions, the solubility of the two thickeners in condensate oil and water was observed by the direct - view method. The research shows that the solubility of the two thickeners is poor, which is convenient for the back - flow and subsequent treatment of the thickener; through single - factor experiments, the optimal dosage of the thickener was screened. The optimal dosages of the thickeners DCT and SCT are both 2%, and the viscosities of CO2 are increased to 1.54 and 1.46 mPa·s respectively, which is about 40 times higher than the original concentration.

[0009] The experimental results of Yu Yifan et al. show that the order of thickening effect is: fluorine-containing compounds > silicone compounds > hydrocarbon (vinyl acetate) compounds. Among them, fluorine-containing polymers have the best thickening effect on supercritical CO2, and the viscosity can reach 2.07-2.79mPa·s. However, fluorine-containing polymers have poor economic efficiency and biological toxicity, and they will also damage the atmospheric environment. As the degree of polymerization of polyvinyl acetate increases, the polarity increases, the solubility in CO2 decreases, but the viscosity is improved to a certain extent. Studies have shown that temperature and pressure have little effect on the thickening effect of hydrocarbon compounds. This is because hydrocarbon compounds (polyvinyl acetate) do not need a cosolvent to be miscible with liquid CO2, and the only factor affecting its viscosity is molecular polarity; when the temperature and pressure rise, the viscosity of silicone compounds decreases linearly. This is because the cosolvent in the system under low temperature and low pressure conditions cannot be completely dissolved with CO2. When the temperature and pressure rise, they gradually dissolve completely, resulting in a decrease in viscosity. For polyvinyl acetate, a suitable molecular weight and cosolvent should be sought to achieve the best thickening effect. This research has laid a good foundation. Due to the high price and biological toxicity of fluorinated CO2 thickeners, this technology is not easy to be widely used. We should avoid further research in this direction and turn our research direction to a diverse combination of hydrocarbon compounds and organosilicon compounds.

[0010] Huang Z et al. obtained the polymer ployFAST by copolymerizing styrene and fluorinated acrylate. The thickening effect on CO2 is good. As the molecular weight of the polymer increases, the solubility of the polymer ployFAST in CO2 decreases. When n(styrene) ∶ n(fluorinated styrene) is about 3:7, the prepared copolymer has the best thickening effect on CO2. However, fluorinated polymers are harmful to the environment and have high costs, so they are not suitable for actual production.

[0011] 2. Siloxane CO2 thickener

[0012] O'Brien et al. prepared a series of aromatic amide-functionalized low molecular weight polydimethylsiloxanes (PDMS) and evaluated their solubility and thickening ability in supercritical CO2. The study showed that the interaction of end groups in amide-capped PDMS oligomers was not sufficient to make them thickeners. The electron-deficient aromatic groups would produce solid polysiloxanes after amidation. For example, 4-nitrobenzamide and biphenylcarboxamide derivatives were waxy solids and had no thickening effect on supercritical CO2. The PDMS derivative with anthraquinone-2-carboxamide (AQCA) end groups could thicken the mixture of gelled hexane and supercritical CO2. The structure of AQCA-capped PDMS contained a large number of alkoxy groups and had great thickening potential. However, the relative content of π-π conjugated groups and C=O in the benzene ring, which provided CO2-philic groups in the structure, was relatively low, and its solubility was limited without using co-solvents, so it could not exert the thickening effect. In future research on supercritical CO2 thickeners, the goal should be to use trace amounts of co-solvents or even no co-solvents.

[0013] Li Q et al. innovatively prepared silicone copolymers using a one-step method. The polymerization process of this polymer was optimized using the response surface method, and the experimental data was consistent with the predicted values. Under the optimal process conditions, the polymer yield was 83.72%. The study showed that after using the silicone copolymer fluid, the relative viscosity of CO2 increased by 5.7 times, which was better than the previously published polymers. Siloxane polymers had good economy and were environmentally friendly. Avoiding the use of fluoropolymers could effectively protect water resources.

[0014] Baej H and Iranic A et al. prepared silicon-containing polymers using siloxane and methane and studied their effects on the viscosity of liquid CO2. The study showed that the viscosity of the mixture of 4% silicon-containing polymer + 20% toluene + 76% CO2 was 1.2 mPa·s, and the liquid viscosity increased by 30 times. The disadvantage was that when thickening liquid CO2, more toluene needed to be added. Excessive use of co-solvents was uneconomical and could only be used as a research result and could not be widely applied.

[0015] 3. Hydrocarbon CO2 thickeners

[0016] Trickett K et al. studied a new method for thickening liquid CO2 using the self-assembly principle of surfactants. The study showed that by controlling the reverse micelle rods formed by surfactants in dense CO2, compared with pure CO2, when the content was 10%, the viscosity increased by 90%.

[0017] Shen Aiguo et al. used azobisisobutyronitrile (AIBN) as a catalyst to synthesize polyvinyl acetate telomer by radical polymerization reaction, and then polymerized it with styrene to generate the reaction mechanism of the binary copolymer. FTIR and HNMR were used to characterize the molecular structure respectively. Styrene-vinyl acetate copolymer itself has a CO2-philic group and a thickening group of styrene, and theoretically can become an environmentally friendly thickener with high efficiency, low cost and little harm.

[0018] Zhang Jian used AIBN as an initiator to synthesize four-arm polyvinyl acetate (PVAc) with different molecular weights by reversible addition-fragmentation chain transfer (RAFT) method. The thickening effect of four-arm PVAc (with ethanol as the co-solvent) on CO2 was investigated. When the concentration of four-arm PVAc was 1.0% and the concentration of ethanol was 5.0%, the viscosity of CO2 increased by 31% - 55%.

[0019] Tang Jun et al. studied the thickening effect of phenyl glycidyl ether polymer on high-pressure CO2. The research shows that in the range of 5 - 30 MPa, under the conditions of constant temperature and pressure, the polyether compound can increase the viscosity of CO2 by 1.5 - 2.5 times. Compared with the reported technologies, phenyl glycidyl ether polymer has good CO2 solubility and can effectively thicken CO2; the polymer structure does not contain expensive fluorinated groups and does not require the use of co-solvents, so it is an environmentally friendly supercritical CO2 thickener. However, due to the too low viscosity increase multiple, this thickener does not have the potential for good sand-carrying performance in supercritical carbon dioxide fracturing technology.

[0020] Cui Weixiang et al. developed a surfactant-type thickener suitable for liquid CO2. Through rheological experiments, the thickening process of liquid CO2 was simulated. The research shows that the surfactant increases the viscosity of liquid CO2 by about 86 - 216 times by forming micelles in liquid CO2. Increasing the pressure or the volume fraction of the thickener has basically no effect on the thickening of liquid CO2. The research did not report the molecular formula and structural formula of the thickener used, and cannot contribute to the design of the supercritical CO2 molecular route, and most of the experiments were carried out at 15℃, which does not have the significance of on-site use.

[0021] Dong Guofeng prepared a thickening agent for carbon dioxide foam fracturing fluid in view of the many problems faced in the construction process of carbon dioxide foam fracturing with guar gum as the liquid phase. Research conclusion: An aqueous solution polymerization method was used to prepare a thickening agent DF with acrylamide (AM), an anionic polymerization monomer (SS-n) with rigid groups and sulfonic acid groups, and cetyl dimethyl allyl ammonium chloride (C16DMAAC) as monomers. When the content of DF was 0.5%, the viscosity of the prepared solution was 130 mPa·s, and DF could be used as a thickening agent for CO2 foam fracturing fluid; the carbon dioxide foam fracturing fluid prepared with DF could still maintain a viscosity of 40 mPa·s after continuous shearing for 100 min (170 s−1) at a temperature of 140–160 °C, ensuring its excellent sand-carrying capacity; under the experimental conditions of formation temperature, the CO2 foam fracturing fluid was completely broken, and DF was a new type of environmentally friendly CO2 foam fracturing thickening agent.

[0022] Tapriyal D et al. studied the solubility of polyvinyl acetate (PVAc), poly((1-O-(vinyloxy)ethyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside)) (P(AcGIcVE)), and amorphous polylactic acid (PLA) in CO2. The research showed that PVAc had the maximum solubility in CO2. The research proved that polymers with flexible -OCH2O- spacers and side-chain glycoacetates in P(AcGIcVE) were more soluble in CO2 than any polymer other than PVAc. PLA required a higher pressure to be miscible with PVAc and CO2. Molecular modeling calculations proved that PVAc had a greater conformational freedom than PLA, and PVAc had a binding mode that was miscible with multiple CO2 molecules. This might be the structural basis for the increased CO2 solubility of PVAc.

[0023] Liave FM et al. studied the effects of using entrainers (cosolvents) with solubility in CO2 on the viscosity and density of the gas phase. The research showed that the use of cosolvents in CO2 effectively increased the solubility of the components of the hydrogen-carbon mixture in the CO2-rich phase. At a given temperature, operating in the pressure region beyond the critical pressure of the mixture and changing the concentration of the cosolvent in the mixture would cause a significant change in the fluid viscosity. For example, at 40 °C and 14 MPa, with octanol as the cosolvent, when the dosage was 44%, the experimental results showed that the viscosity of the CO2 phase only increased to the range of 0.30–0.75 mPa·s. Although adding more of certain cosolvents could increase the density and viscosity of the CO2-rich phase, compared with the economic cost of adding additives (44%), the thickening effect was not ideal compared with the initial viscosity of the CO2 phase and had no practical significance for on-site use. Summary of the Invention

[0024] The main object of the present invention is to provide an oligoglycerol phenyl oleate as a supercritical carbon dioxide thickener and its application. The thickener can significantly increase the viscosity of carbon dioxide, which is beneficial for CO2 flooding under conditions below the minimum miscibility pressure and can greatly improve the crude oil recovery rate.

[0025] To achieve the above object, the present invention adopts the following technical solutions:

[0026] The present invention provides a supercritical carbon dioxide thickener, and the thickener includes oligoglycerol phenyl oleate;

[0027] The oligoglycerol phenyl oleate has a structure shown in the following formula (I):

[0028]

[0029] R1, R2, R3, R4, and R5 each independently selected from or hydrogen; n is an integer.

[0030] Further, the number of selections of R1, R2, R3, R4, and R5 ≥1; n is 2 to 10.

[0031] Further, the thickener further includes an auxiliary agent.

[0032] Further, the mass-volume ratio of the oligoglycerol phenyl oleate to the auxiliary agent is 1:1 to 100 g / mL.

[0033] Still further, the auxiliary agent is one or more of lower alcohols, aromatic hydrocarbons, water, acetone, and petroleum ether.

[0034] The present invention also provides a preparation method of the above-mentioned supercritical carbon dioxide thickener, and the method includes the following steps:

[0035] Mix oligoglycerol and phenyl oleic acid, and react at 180°C to 240°C for 2 to 12 h under the protection of an inert gas. Separate the water generated during the reaction in real time. After the reaction is completed, cool to room temperature to obtain;

[0036] The phenyl oleic acid is

[0037] Further, the molar ratio of oligoglycerol to phenyl oleic acid is 1 to 5:10 to 20.

[0038] Further, mix oligoglycerol and phenyl oleic acid, and react at 220°C to 230°C for 4 to 8 h under the protection of an inert gas.

[0039] The present invention also provides the application of the above-mentioned supercritical carbon dioxide thickener in the exploitation of supercritical carbon dioxide flooding of crude oil.

[0040] Further, the dosage of the thickener accounts for 0.001%-10% of the weight of supercritical carbon dioxide.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] The oligoglycerol phenyl oleate contains ether bonds and hydroxyl groups, which helps to increase its solubility in carbon dioxide; its branched aryl oleate groups can increase steric hindrance and form a network structure in the carbon dioxide solution. The present invention uses oligoglycerol phenyl oleate as a thickener for supercritical carbon dioxide, which can significantly increase the viscosity of the supercritical carbon dioxide solution.

[0043] The oligoglycerol phenyl oleate is easy to prepare, has low production cost and is environmentally friendly, and is suitable for large-scale popularization and application. Description of the Drawings

[0044] Figure 1 It is the infrared spectrum diagram (KBr tablet) of the diglycerol phenyl oleate in Example 1.

[0045] Figure 2 It is the infrared spectrum diagram (KBr tablet) of the decaglycerol phenyl oleate in Example 2. Detailed Embodiments

[0046] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and "including" are used in this specification, they indicate the presence of features, steps, operations, and their combinations.

[0048] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0049] The phenyl oleate in the following examples is

[0050] Example 1

[0051] In a reaction kettle equipped with a stirrer, a thermometer, a condenser and a water separator, 8.3 g of diglycerol (0.05 mol) and 72.0 g of phenyl oleate (0.20 mol) were added. The temperature was raised to 220 °C under stirring conditions for reaction. The water generated during the reaction was continuously separated out, and the reaction time was 6 h. After the reaction was completed, diglycerol phenyl oleate was obtained. The product was subjected to infrared spectroscopy, and the spectrum is shown in Figure 1 。

[0052] The diglycerol phenyl oleate was used as a thickener in supercritical carbon dioxide flooding: the content of the diglycerol phenyl oleate was 0.5 wt%, the auxiliary agent was kerosene, the ratio of diglycerol phenyl oleate to kerosene was 1:10 (g:mL), the test temperature was 120 °C, the pressure was 20 MPa, the viscosity of pure carbon dioxide was 0.033 mPa·s, and the viscosity of the thickened carbon dioxide reached 0.562 mPa·s, with the viscosity increasing by about 16 times.

[0053] Example 2

[0054] In a reaction kettle equipped with a stirrer, a thermometer, a condenser and a water separator, 7.6 g of decaglycerol (0.01 mol) and 43.2 g of phenyl oleate (0.12 mol) were added. The temperature was raised to 230 °C under stirring conditions for reaction. The water generated during the reaction was continuously separated out, and the reaction time was 12 h. After the reaction was completed, decaglycerol phenyl oleate was obtained. The product was subjected to infrared spectroscopy, and the spectrum is shown in Figure 2 。

[0055] The decaglycerol phenyl oleate was used as a thickener in supercritical carbon dioxide flooding: the content of the decaglycerol phenyl oleate was 0.5 wt%, the auxiliary agent was kerosene, the ratio of decaglycerol phenyl oleate to kerosene was 1:15 (g:mL), the test temperature was 120 °C, the pressure was 20 MPa, the viscosity of pure carbon dioxide was 0.033 mPa·s, and the viscosity of the thickened carbon dioxide reached 0.560 mPa·s, with the viscosity increasing by about 16 times.

[0056] Example 3

[0057] In a reaction kettle equipped with a stirrer, a thermometer, a condenser and a water separator, 15.7 g of tetraglycerol (0.05 mol) and 180.0 g of phenyl oleate (0.50 mol) were added. The temperature was raised to 220 °C under stirring conditions for reaction. The water generated during the reaction was continuously separated out, and the reaction time was 8 h. After the reaction was completed, tetraglycerol phenyl oleate was obtained.

[0058] The tetraglycerol phenyl oleate is used as a thickener in supercritical carbon dioxide flooding: the content of the tetraglycerol phenyl oleate is 0.5 wt%, the auxiliary agent is acetone, and the ratio of tetraglycerol phenyl oleate to acetone is 1:30 (g:mL). The test temperature is 120 °C, the pressure is 20 MPa, the viscosity of pure carbon dioxide is 0.033 mPa·s, and the viscosity of the thickened carbon dioxide reaches 0.532 mPa·s, with the viscosity increasing by about 15 times.

[0059] Example 4

[0060] Add 0.01 mol (6.1 g) of octaglycerol and 0.10 mol (36.0 g) of phenyl oleic acid to a reaction kettle equipped with a stirrer, thermometer, condenser and water separator. Heat up to 223 °C under stirring conditions for reaction. The water generated during the reaction is continuously separated out, and the reaction time is 8 h. After the reaction is completed, octaglycerol phenyl oleate is obtained.

[0061] The octaglycerol phenyl oleate is used as a thickener in supercritical carbon dioxide flooding. The content of the octaglycerol phenyl oleate is 0.5 wt%, the auxiliary agent is toluene, and the ratio of octaglycerol phenyl oleate to toluene is 1:30 (g:mL). The test temperature is 120 °C, the pressure is 20 MPa, the viscosity of pure carbon dioxide is 0.033 mPa·s, and the viscosity of the thickened carbon dioxide reaches 0.427 mPa·s, with the viscosity increasing by about 12 times.

[0062] Example 5

[0063] The difference from Example 1 is that the reaction is carried out at 180 °C for 12 h, and other steps are the same as those in Example 1.

[0064] The obtained thickener is used for thickening supercritical carbon dioxide, and the viscosity of the thickened carbon dioxide reaches 0.564 mPa·s, with the viscosity increasing by 16 times.

[0065] Example 6

[0066] The difference from Example 1 is that the reaction is carried out at 240 °C for 2 h, and other steps are the same as those in Example 1.

[0067] The obtained thickener is used for thickening supercritical carbon dioxide, and the viscosity of the thickened carbon dioxide reaches 0.552 mPa·s, with the viscosity increasing by 15.7 times.

[0068] Example 7

[0069] The difference from Example 1 is that the content of the diglycerol phenyl oleate is 0.01 wt%, and other steps are the same as those in Example 1. The viscosity of the thickened carbon dioxide reaches 0.068 mPa·s, with the viscosity increasing by 1 time.

[0070] Example 8

[0071] The difference from Example 1 is that the content of the diglycerol phenyl oleate is 10 wt%, and other steps are the same as those in Example 1. The viscosity of the thickened carbon dioxide reaches 0.96 mPa·s, and the viscosity increases by 28 times.

[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A supercritical carbon dioxide thickener, characterized in that, The thickener includes oligoglycerol phenyl oleate; The oligoglycerol phenyl oleate has the structure shown in the following formula (I): R1, R2, R3, R4, and R5 are each independently selected from or hydrogen; n is an integer.

2. The supercritical carbon dioxide thickener according to claim 1, wherein Selection of R1, R2, R3, R4, R5 The number of them ≥ 1; where n is from 2 to 10.

3. The supercritical carbon dioxide thickener according to claim 1, wherein The thickener further includes an auxiliary agent.

4. The supercritical carbon dioxide thickener according to claim 3, characterized in that, The mass-volume ratio of the oligoglycerol phenyl oleate to the auxiliary agent is 1:1 to 100 g / mL.

5. The supercritical carbon dioxide thickener according to claim 3 or 4, characterized in that, The auxiliary agent is one or more of lower alcohols, aromatic hydrocarbons, water, acetone, and petroleum ether.

6. The preparation method of the supercritical carbon dioxide thickener according to claim 1 or 2, characterized in that, It includes the following steps: Mix oligoglycerol and phenyl oleic acid, react at 180°C to 240°C for 2 to 12 h under the protection of inert gas, and separate the water generated during the reaction in real time. After the reaction is completed, cool to room temperature to obtain it; The phenyl oleic acid is 7. The preparation method according to claim 6, characterized in that, The molar ratio of oligoglycerol to phenyl oleic acid is 1 to 5:10 to 20.

8. The preparation method according to claim 6, characterized in that, Mix oligoglycerol and phenyl oleic acid, and react at 220°C to 230°C for 4 to 8 h under the protection of inert gas.

9. Application of the supercritical carbon dioxide thickener according to any one of claims 1 to 5 in the exploitation of crude oil by supercritical carbon dioxide flooding.

10. The application according to claim 9, wherein The dosage of the thickener accounts for 0.001% - 10% of the weight of supercritical carbon dioxide.

Images