A foaming agent for carbon dioxide flooding in shale oil and its application

Abstract

This application relates to a foaming agent for carbon dioxide flooding in shale oil and its application, belonging to the field of carbon dioxide flooding technology. The foaming agent for carbon dioxide flooding in shale oil in this application comprises the following components by weight percentage: 4.0-6.0% betaine-type surfactant; 1.0-2.0% hexadecyltrimethylammonium bromide; 3-5% titanate coupling agent-modified silica particles; 0.1-0.5% ethylenediaminetetraacetic acid; 1-2% inorganic salt; and the balance being water. The foaming agent product provided in this application, with its betaine-type surfactant combined with titanate coupling agent-modified silica particles, adsorbs onto the gas-liquid interface, thereby improving the stability of the liquid film. The resulting CO2 foam exhibits improved high-temperature resistance. When applied to shale oil reservoirs with deep burial and formation temperatures around 100℃, it can significantly reduce gas cross-flow and improve sealing performance, ensuring its effectiveness under high-temperature conditions of around 100℃.

Description

Technical Field

[0001] This application relates to a foaming agent for carbon dioxide flooding of shale oil and its application, belonging to the field of carbon dioxide flooding technology. Background Technology

[0002] Carbon dioxide flooding foaming agent is a chemical additive used to improve oil displacement efficiency during carbon dioxide flooding. It reduces reservoir permeability and gas cross-flow by generating foam in the oilfield formation, thereby increasing oil production and ultimately enhancing oil recovery.

[0003] The main applications of carbon dioxide flooding foaming agents are as follows: 1) Reducing gas cross-flow: Foam can effectively block the flow of gas in the reservoir, reduce gas cross-flow, and make carbon dioxide more evenly distributed in the reservoir, thereby improving oil displacement efficiency; 2) Improving oil recovery: By reducing the gas-oil ratio, foam flooding can extract more crude oil from the reservoir, thereby improving the oil recovery rate; 3) Adapting to low-permeability reservoirs: Nano-microbubble flooding technology can significantly improve the oil recovery rate in low-permeability reservoirs, up to 8-20%.

[0004] CO2 foam is a mixed system with CO2 as the dispersed phase and water as the dispersion medium. It is an effective flow control system in CO2 oil displacement processes. CO2 foam improves the sweep efficiency of CO2 by reducing the relative permeability of the gas and increasing the viscosity of the gas flow. The stability of CO2 foam is mainly determined by the stability of the liquid film. To improve foam stability, various types of foaming agents have been developed, such as surfactants, nanoparticles, and polymers.

[0005] Existing patent CN115404068A discloses a foaming agent for carbon dioxide flooding and its preparation method, comprising 15-30 parts of sodium alkylbenzene sulfonate, 3-8 parts of sodium N-dodecylaminocarboxylate, 10-25 parts of betaine-type surfactant, 0.01-0.5 parts of counterionic compound, 1-2 parts of reinforcing agent, 0.1-2 parts of foam stabilizer, 0.2-1 parts of chelating agent, and 80-130 parts of water. After application, the foam significantly reduces the oil-water interfacial tension by improving the mobility ratio, thus expanding the swept volume and improving oil displacement efficiency, increasing oil washing efficiency and formation energy, thereby improving the recovery rate of low-permeability reservoirs. Furthermore, this foaming agent exhibits strong foaming and stabilizing capabilities, and its performance is minimally affected by temperature. However, the foam stabilizer used is polyvinyl alcohol, which still has room for improvement in terms of bubble stability at high temperatures of 60-80℃ compared to solid foam stabilizers.

[0006] Existing patent CN104152132A discloses a modified nano-silica foam stabilizer and its preparation method. This nano-foam stabilizer is obtained by hydrophilic modification of nano-SiO2. When used in combination with organic polymer polyacrylamide, it exhibits excellent foaming and stabilizing properties. However, the modified nano-silica foam stabilizer provided in this solution, when used alone or mainly in combination with polyacrylamide, is difficult to work effectively at the foam-water interface, resulting in a need to improve its stability.

[0007] Shale oil is generally buried at great depths, with formation temperatures and pressures exceeding the critical parameters for CO2 (31.1℃, 7.38 MPa). Therefore, CO2 exists in a supercritical state within shale oil. Although supercritical CO2 foam is more stable than conventional CO2 foam, the lack of a permanent dipole moment and weak van der Waals forces in CO2 molecules result in a generally weak solvation effect of the CO2-loving end of the surfactant in CO2. This makes the surfactant more likely to remain in the liquid phase rather than adsorb at the CO2-water interface. Consequently, the high-temperature stability of existing foaming agents still needs improvement. Therefore, it is necessary to provide a foaming agent with good high-temperature resistance to enhance the stability of foam at high temperatures. Summary of the Invention

[0008] To address the aforementioned issues, this application provides a foaming agent for carbon dioxide flooding in shale oil and its application. The foaming agent product provided in this application uses a betaine-type surfactant combined with a titanate coupling agent to modify silica particles. This allows the particles to be adsorbed onto the gas-liquid interface, thereby improving the liquid film stability of the CO2 foam and significantly enhancing its high-temperature tolerance. When applied to shale oil reservoirs with deep burial and formation temperatures around 100°C, it also significantly reduces gas cross-flow, improves sealing performance, and enhances its effectiveness under high-temperature conditions of around 100°C, thus ensuring the extraction efficiency of carbon dioxide flooding in shale oil.

[0009] This application provides a foaming agent for carbon dioxide flooding of shale oil, comprising the following components by weight percentage:

[0010] Betaine-type surfactants: 4.0~6.0%;

[0011] Cetyltrimethylammonium bromide 1.0~2.0%;

[0012] Titanate coupling agent modified silica particles 3~5%;

[0013] Ethylenediaminetetraacetic acid 0.1-0.5%;

[0014] Inorganic salts 1~2%;

[0015] The remainder is water;

[0016] The betaine-type surfactant is one or more of lauramidopropyl betaine, cocamidopropyl betaine, and perfluorohexyl ethyl sulfonate betaine; the titanate coupling agent in the titanate-modified silica particles is selected from one or more of monoalkoxy unsaturated fatty acid titanates, chelated phosphate titanium coupling agent quaternary ammonium salts, phosphate-type monoalkoxy titanates, and isopropoxytris(dioctyl pyrophosphate) titanates; the inorganic salt is one or more of sodium chloride, magnesium chloride, sodium sulfate, sodium bisulfate, sodium carbonate, potassium chloride, and calcium chloride;

[0017] The titanate coupling agent modified silica particles and the betaine-type surfactant are premixed; the premixing step includes stirring and mixing the titanate coupling agent modified silica particles and the betaine-type surfactant with polyvinylpyrrolidone in an ethanol solvent.

[0018] Optionally, the preparation steps of the titanate coupling agent modified silica particles include:

[0019] 1) Add silica to ethanol solvent, ultrasonically vibrate, and then stir to disperse;

[0020] 2) Add a titanate coupling agent to carry out the reaction;

[0021] 3) After filtration and precipitation, the particles were washed with ethanol and dried to obtain titanate coupling agent modified silica particles.

[0022] Optionally, the amount of the titanate coupling agent is 50 ± 20% of the mass of silica.

[0023] The titanate coupling agent in the titanate-modified silica particles is selected from one or more of LD-105, TC-WT, TC-2 and DLC-K38S.

[0024] Optionally, the titanate coupling agent in the titanate coupling agent modified silica particles is monoalkoxy unsaturated fatty acid titanate LD-105.

[0025] Optionally, the titanate coupling agent in the titanate coupling agent modified silica particles is a chelated phosphate titanium coupling agent quaternary ammonium salt TC-WT.

[0026] Optionally, the titanate coupling agent in the titanate coupling agent modified silica particles is a phosphoric acid type monoalkoxy titanate TC-2.

[0027] Optionally, the titanate coupling agent in the titanate coupling agent modified silica particles is isopropoxytris(dioctylpyrophosphoryloxy)titanate DLC-K38S.

[0028] Optionally, the average particle size of the silica is 200~500nm;

[0029] Optionally, the average particle size of the silica is 200~300nm.

[0030] Optionally, the molecular weight of the polyvinylpyrrolidone is 80,000 to 100,000.

[0031] Optionally, the amount of polyvinylpyrrolidone used is 5 to 10% of the mass of the betaine-type surfactant.

[0032] Optionally, the betaine-type surfactant is perfluorohexyl ethyl betaine.

[0033] Optionally, the inorganic salt is sodium chloride.

[0034] This application provides the application of the aforementioned foaming agent for carbon dioxide flooding in shale oil.

[0035] The beneficial effects of this application include, but are not limited to:

[0036] The foaming agent provided in this application uses a synergistic combination of betaine-type surfactant and titanate coupling agent modified silica particles, which can significantly improve the stability of the foam. The modified silica particles are well compatible with the betaine-type surfactant, and the two work together at the gas-liquid interface to improve the liquid film stability of CO2 foam and significantly improve the high-temperature resistance of CO2 foam.

[0037] Furthermore, by adding polyvinylpyrrolidone (PVP), a synergistic effect can be achieved between betaine-type surfactants and titanate coupling agents modified silica particles. PVP improves the surface wettability of silica particles and enhances the aggregation effect of betaine-type surfactants. By increasing the stability of silica particles at the gas-liquid interface and the distribution of betaine-type surfactants on the gas-liquid surface, the surface tension-improving effect of betaine-type surfactants on liquids and the foam-stabilizing ability of titanate coupling agent-modified silica particles are further enhanced. The combined effect of these two improvements significantly improves the high-temperature resistance of CO2 foam.

[0038] The foaming agent provided in this application, when applied to shale oil reservoirs that are buried at a relatively deep depth and have a formation temperature of around 100°C, can significantly reduce gas cross-flow, improve sealing performance, and enhance its effectiveness under high-temperature conditions of around 100°C, thereby ensuring the extraction efficiency of shale oil carbon dioxide flooding. Attached Figure Description

[0039] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0040] Figure 1 This is a line graph showing the change in foam volume with temperature in Test Example 1 of this application;

[0041] Figure 2 This is a line graph showing the change in the half-life of the foam as a function of temperature in Test Example 1 of this application. Detailed Implementation

[0042] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are all purchased through commercial channels.

[0043] Example 1

[0044] A foaming agent for carbon dioxide flooding is provided, comprising the following components by weight percentage: 5.0 wt% betaine-type surfactant; 1.5 wt% hexadecyltrimethylammonium bromide; 4 wt% titanate coupling agent modified silica particles; 0.3 wt% ethylenediaminetetraacetic acid; 1.5 wt% inorganic salt; and the balance being water.

[0045] The preparation method of this foaming agent includes the following steps:

[0046] S1. Weigh each required raw material according to the weight ratio. The preparation method of the titanate coupling agent modified silica particles is as follows:

[0047] 1.1) Accurately weigh 1.00 g of silica powder (average particle size 254 nm), add it to 100 mL of anhydrous ethanol, place it in a 250 mL beaker, place the beaker in an ultrasonic cleaner, and ultrasonically vibrate at room temperature for 30 min (frequency 40 kHz, power 100 W) to promote particle dispersion. After ultrasonic treatment, transfer the mixture to a magnetic stirrer and stir continuously for 1 h (speed 500 rpm) to form a stable and uniform dispersion.

[0048] 1.2) Take 0.5g of monoalkoxy unsaturated fatty acid titanate LD-105 (50% of the mass of silica), dissolve and dilute it in 5mL of anhydrous ethanol beforehand, and slowly add the diluted coupling agent dropwise to the dispersion while stirring. Keep the reaction at room temperature and continue stirring for 3h to ensure that the coupling agent is in full contact with the silica surface.

[0049] 1.3) After the reaction is completed, the modified silica particles are collected by heating and concentration and then filtered. The precipitate is washed with anhydrous ethanol 1 to 3 times, about 30 mL each time, to remove unreacted coupling agent and impurities. The washed precipitate is placed in a vacuum drying oven and dried at 40°C for 2 hours until it is completely dried to obtain titanate coupling agent modified silica particles.

[0050] 1.4) After SiO2 nanoparticles modified with titanate coupling agent were prepared by tableting, 2 μL of deionized water was dropped on their surface to measure the contact angle. The result was 71.3°, while the contact angle of unmodified SiO2 nanoparticles was 13.3°. It can be seen that the titanate coupling agent successfully modified the silica particles and changed their surface wettability.

[0051] S2, titanate coupling agent modified silica particles, and betaine-type surfactant premix treatment:

[0052] 2.1) Measure 100 mL of anhydrous ethanol into a 250 mL beaker, then weigh polyvinylpyrrolidone (PVP, molecular weight 80,000~100,000, the amount of polyvinylpyrrolidone used is 8 wt% of the mass of betaine-type surfactant), add PVP to ethanol and stir for 3 min until completely dissolved to form a homogeneous solution.

[0053] 2.2) Add the betaine-type surfactant (perfluorohexyl ethyl sulfonate betaine) and the titanate coupling agent modified silica particles prepared above to the above homogeneous solution. After stirring manually for 20 min, place it on a magnetic stirrer and stir at 600 rpm for 1 h to form a stable and uniform suspension.

[0054] 2.3) The obtained suspension was then filtered, and the filtered product was washed with ethanol 2-3 times and then dried under vacuum at 40°C for 2 hours to obtain a premix of betaine-type surfactant and titanate coupling agent modified silica particles.

[0055] S3. Preparation of foaming agent:

[0056] 3.1) Take 50 wt% of deionized water and put it into a 500 mL beaker. Then, slowly add the weighed cationic surfactant cetyltrimethylammonium bromide, the weighed titanate coupling agent modified silica particles and betaine type surfactant premix prepared above into the deionized water while stirring evenly.

[0057] 3.2) First add the inorganic salt (sodium chloride) and stir until completely dissolved; then add ethylenediaminetetraacetic acid and continue stirring for 10 minutes;

[0058] 3.3) Finally, add the remaining deionized water to make up the total mass to 100%, and then stir manually for 10 minutes to make the system evenly dispersed to obtain the foaming agent.

[0059] Example 2

[0060] The example is basically the same as in Example 1, except that the titanate coupling agent is phosphate-type monoalkoxy titanate TC-2.

[0061] Example 3

[0062] The example is essentially the same as in Example 1, except that the titanate coupling agent is isopropoxytris(dioctylpyrophosphate)titanate DLC-K38S.

[0063] Example 4

[0064] The process is basically the same as in Example 1, except that the betaine-type surfactant is lauramidopropyl betaine.

[0065] Example 5

[0066] The process is basically the same as in Example 1, except that the betaine-type surfactant is cocamidopropyl betaine.

[0067] Comparative Example 1

[0068] It is basically the same as Example 1, except that the average particle size of the silica powder is 443 nm.

[0069] Comparative Example 2

[0070] It is basically the same as Example 1, except that the average particle size of the silica powder is 372 nm.

[0071] Comparative Example 3

[0072] It is basically the same as Example 1, except that the titanate coupling agent is replaced with silane coupling agent KH550.

[0073] Comparative Example 4

[0074] The method is basically the same as in Example 1, except that the amount of polyvinylpyrrolidone used is 2 wt% of the mass of the betaine-type surfactant, and the molecular weight of polyvinylpyrrolidone is 140,000 to 180,000.

[0075] Comparative Example 5

[0076] The method is basically the same as in Example 1, except that the amount of polyvinylpyrrolidone used is 15 wt% of the mass of the betaine-type surfactant, and the molecular weight of polyvinylpyrrolidone is 30,000 to 60,000.

[0077] Comparative Example 6

[0078] The process is basically the same as in Example 1, except that the titanate coupling agent modified silica particles are replaced with silica particles of equal weight.

[0079] Comparative Example 7

[0080] The example is basically the same as in Example 1, except that the titanate coupling agent modified silica particles and betaine-type surfactant were not premixed separately and polyvinylpyrrolidone was not added.

[0081] Comparative Example 8

[0082] The process is basically the same as in Example 1, except that the titanate coupling agent modified silica particles and betaine-type surfactant were not premixed in step S2. Instead, in step 3.1), the titanate coupling agent modified silica particles, betaine-type surfactant, polyvinylpyrrolidone and weighed cationic surfactant cetyltrimethylammonium bromide were slowly added to deionized water while stirring evenly.

[0083] Test Example 1

[0084] The performance of the foaming agent prepared above was evaluated using the Waring-Blender method according to GB / T 7462-1994. The foaming volume represents the foaming capacity of the foaming agent. The thermal stability of the foaming agent was measured by measuring the half-life of the foam at 40℃, 60℃, 80℃ and 100℃. Specifically, a constant speed stirrer was used. 100 ml of 1 wt% foaming agent solution was added to the stirring cup, and CO2 gas was introduced. The mixture was stirred at a constant speed of 10000 rpm for 1 min. The foam was then transferred to a measuring cylinder, sealed with plastic film, and the foaming volume (ml) was read. Timing was started simultaneously, and the time when half of the foam volume disappeared was recorded as the foam half-life (min). The test results are shown in Tables 1, 2, 3 and 4 below.

[0085] Table 1. Results of foaming agent foaming capacity and high-temperature foam stability (40℃)

[0086]

[0087] Table 2. Results of foaming agent foaming capacity and high-temperature foam stability (60℃)

[0088]

[0089] Table 3. Results of foaming agent foaming capacity and high-temperature foam stability (80℃)

[0090]

[0091] Table 4. Results of foaming agent foaming capacity and high-temperature foam stability (100℃)

[0092]

[0093] Figure 1 and Figure 2 The foaming capacity and foam half-life of the prepared foaming agent as a function of temperature are shown in the graphs. According to the results, the foaming agent product in Example 1 has excellent comprehensive properties, including large foam volume, long foam half-life, and good high-temperature stability. Although the foam volume is reduced due to the addition of polyvinylpyrrolidone, the reduction is not significant. Its foam half-life under high-temperature conditions can maintain a good level. In particular, its foam half-life under 80~100℃ conditions has a significant advantage over other solutions, demonstrating superior high-temperature stability.

[0094] According to the comparison results of Example 1 with Comparative Examples 1 and 2, it can be seen that when the average particle size of silica is 200~300nm, it can achieve both good foaming ability and foam thermal stability.

[0095] The results of comparing Example 1 and Comparative Example 3 show that the choice of coupling agent has a significant impact on the effect of foaming agent. Among them, titanate coupling agent has a better effect. According to the results of Example 1, Example 2 and Example 3, the effect is best when the titanate coupling agent is LD-105.

[0096] According to the comparison results of Examples 1, 4 and 5, the type of betaine-type surfactant also affects the performance of the foaming agent. Among them, when the betaine-type surfactant is perfluorohexyl ethyl sulfonate betaine, it shows a better synergistic effect with other components.

[0097] Based on the comparison results of Example 1, Comparative Example 4 and Comparative Example 5, it can be seen that the amount of polyvinylpyrrolidone added and its molecular weight have a relatively critical impact on the foaming agent. The best effect is achieved when the molecular weight of polyvinylpyrrolidone is 80,000 to 100,000 and the amount added is appropriate, that is, when the amount of polyvinylpyrrolidone is 5 to 10 wt% of the mass of betaine-type surfactant.

[0098] Based on the comparison results of Example 1 and Comparative Examples 6, 7 and 8, it can be seen that the present application's solution, by modifying silica particles, pretreating them with betaine-type surfactants, and adding polyvinylpyrrolidone, can improve the foam stability of the foaming agent and significantly improve the high-temperature resistance of the foam.

[0099] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A foaming agent for carbon dioxide flooding in shale oil, characterized in that, Includes the following components by weight percentage: Perfluorohexyl ethyl sulfonate betaine 4.0~6.0%; Cetyltrimethylammonium bromide 1.0~2.0%; Titanate coupling agent modified silica particles 3~5%; Ethylenediaminetetraacetic acid 0.1-0.5%; Inorganic salts 1~2%; The remainder is water; The titanate coupling agent modified silica particles are prepared by modifying silica with monoalkoxy unsaturated fatty acid titanate, and the average particle size of the silica is 200~300nm. The titanate coupling agent modified silica particles and the betaine-type surfactant are premixed; the premixing step includes stirring and mixing the titanate coupling agent modified silica particles and the betaine-type surfactant with polyvinylpyrrolidone in an ethanol solvent, wherein the molecular weight of the polyvinylpyrrolidone is 80,000 to 100,000, and the amount of polyvinylpyrrolidone used is 5% to 10% of the mass of the betaine-type surfactant; The inorganic salt is one or more of sodium chloride, magnesium chloride, sodium sulfate, sodium bisulfate, sodium carbonate, potassium chloride, and calcium chloride.

2. The foaming agent for carbon dioxide flooding of shale oil according to claim 1, characterized in that, The preparation steps of the titanate coupling agent modified silica particles include: 1) Add silica to ethanol solvent, ultrasonically vibrate, and then stir to disperse; 2) Add monoalkoxy unsaturated fatty acid titanate to carry out the reaction; 3) After filtration and precipitation, the particles were washed with ethanol and dried to obtain titanate coupling agent modified silica particles.

3. The foaming agent for carbon dioxide flooding of shale oil according to claim 1, characterized in that, The amount of the monoalkoxy unsaturated fatty acid titanate used is 50 ± 20% of the mass of silicon dioxide.

4. The foaming agent for carbon dioxide flooding of shale oil according to claim 1, characterized in that, The inorganic salt is sodium chloride.

5. The application of the foaming agent for carbon dioxide flooding of shale oil as described in any one of claims 1 to 4 in carbon dioxide flooding of shale oil.

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