A super-stable foam system, its preparation method and application

Abstract

This invention discloses an ultra-stable foam system, its preparation method, and its applications. By mass percentage, the foam system comprises 0.4-0.6% amphoteric surfactant, 0.03-0.2% carbonized polymer molecular clusters, and the balance being water. This invention introduces carbonized polymer molecular clusters into the foam system, achieving not only control over foam stabilization performance but also avoiding the problem of excessive damage to micropore throats caused by existing foam stabilizers' solid particles and large polymer molecules. It can be used as a foaming agent in oil displacement and other applications during the development of low-permeability oilfields, which is of great significance for improving the development of low-permeability oilfields.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, specifically relating to an ultra-stable foam system, its preparation method, and its application. Background Technology

[0002] Foam flooding technology is an effective method for enhancing oil recovery in low-permeability oilfields, especially suitable for reservoirs with low permeability that are difficult to develop effectively using conventional methods. By injecting a special foam system into the reservoir, foam flooding technology can improve the oil-water mobility ratio and increase the swept volume, thereby improving crude oil recovery. In practical applications, the low-permeability reservoirs in the SN well area of ​​Xinjiang Oilfield have achieved significant results after using nitrogen foam flooding technology. In a pilot field test, the cumulative injection of nitrogen foam slugs with a pore volume of 0.43 times the pore volume resulted in an increase in oil production of over 8 tons per day, a decrease in water cut of 6.6 percentage points, and an input-output ratio of 1.0:1.6. In addition, CO2-driven foam sealing technology is another technique applied in low-permeability oilfields. This technology improves the development efficiency of low-permeability oilfields by injecting foam formed from CO2 and surfactants. Foam flooding technology has significant application value and potential in the development of low-permeability oilfields, and can significantly improve reservoir development effects and economic benefits. However, foam flooding technology still faces some challenges and limitations in low-permeability oilfields. For example, foam systems have poor stability and limited regulation and flooding performance; currently used polymer and solid particulate foam stabilizers are prone to retention in micropore throats, leading to serious reservoir damage. Therefore, developing foam systems with high stability and low pore throat damage is of great significance for improving the development effect of low-permeability reservoirs.

[0003] Using foam stabilizers is a common method to improve the stability of foam systems. Polymers, due to their large molecular long-chain or branched structure, significantly increase the viscosity of the liquid phase in the foam system after dissolving in water, thereby reducing the drainage rate of the liquid film and making it less prone to liquid loss from the foam film. They are often used as foam stabilizers. However, while the addition of both organic polymers and biomolecules increases solution viscosity, it also leads to a decrease in foam generation capacity and makes it difficult to inject into low-permeability reservoirs due to excessive viscosity. Furthermore, polymer residues at the pore throats cause serious damage to the formation. Another commonly used foam stabilizer is solid-phase particles, which assist the foam system in constructing a rigid liquid film structure, thereby improving the mechanical strength of the foam. However, conventional nanoparticle foam stabilizers have two problems: first, they require large quantities, resulting in high costs; second, the particle size of conventional nanoparticles is generally above 10 nm, and their adsorption and retention on the surface of reservoir pore throats can damage low-permeability oil and gas layers to some extent.

[0004] Therefore, there is an urgent need to develop a polymer-free, ultra-stable foam system suitable for low-permeability reservoirs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an ultra-stable foam system, its preparation method, and its application, thereby solving the problems of poor foam stability and significant damage to micropore throats caused by the polymers and solid particles contained in traditional foam systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On the one hand, the present invention provides an ultra-stable foam system, comprising, by mass percentage, 0.4-0.6% amphoteric surfactant, 0.03-0.2% carbonized polymer molecular clusters, and the balance being water.

[0008] Preferably, by mass percentage, the above-mentioned ultra-stable foam system comprises 0.4-0.6% amphoteric surfactant, 0.05-0.1% carbonized polymer molecular clusters, and the balance being water.

[0009] Preferably, the carbonized polymer molecular clusters are obtained by hydrothermal reaction of citric acid, taurine and hexylamine.

[0010] Preferably, the hydrothermal reaction temperature is 140~180℃ and the reaction time is 8~12 h.

[0011] Preferably, the mass ratio of citric acid to taurine is (0.1:1) to (1:0.1); the mass ratio of hexylamine to the total mass of citric acid and taurine is (2~6):1.

[0012] Preferably, the amphoteric surfactant is at least one of cocamidopropyl betaine, lauramidopropyl hydroxysulfonate betaine, lauramidopropyl betaine, and cocamidopropyl hydroxysulfonate betaine.

[0013] On the other hand, the present invention also provides a method for preparing an ultra-stable foam system, comprising the following steps:

[0014] (1) The carbonized polymer molecular clusters were mixed with water and ultrasonically dispersed to obtain a carbonized polymer molecular cluster dispersion;

[0015] (2) Add an amphoteric surfactant to the carbonized polymer molecular cluster dispersion, and dissolve by ultrasonication to obtain a compound solution;

[0016] (3) Stir the compound solution in a gas atmosphere to generate bubbles and obtain an ultra-stable foam system.

[0017] Preferably, in steps (1) and (2), the ultrasonic power is 100~150W and the ultrasonic time is 5~10min.

[0018] Preferably, in step (3), the gas atmosphere is one or more of the following: air, nitrogen, carbon dioxide, natural gas, and flue gas.

[0019] Preferably, in step (3), the stirring speed is 2000~2500 rpm and the stirring time is 3 min.

[0020] The present invention also provides an application of the ultra-stable foam system described above, including crude oil development in low-permeability reservoirs. The permeability of the low-permeability reservoir is less than 50 mD.

[0021] The beneficial effects of this invention are:

[0022] This invention introduces carbonized polymer molecular clusters into the foam system, which not only enables the regulation of foam stabilization performance, but also avoids the problem of existing foam stabilizers' solid particles and macromolecular polymers causing significant damage to micropore throats.

[0023] The foam system provided by this invention has good performance of each component material, appropriate addition ratio, no polymer and low solid content, its liquid half-life can reach more than 2 hours, and it still has good foaming performance in 20000 mg / L brine. It can be used as a foaming agent in oil displacement and other fields in the development of low-permeability oilfields. Attached Figure Description

[0024] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation thereof. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of the carbonized polymer molecular cluster in Example 1 of the present invention;

[0026] Figure 2 This is a graph showing the change in the microstructure of the ultra-stable foam system over time in Example 2 of the present invention;

[0027] Figure 3 This is a graph showing the change of the microstructure of a conventional foam system over time. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides an ultra-stable foam system, comprising, by mass percentage, 0.4-0.6% amphoteric surfactant, 0.03-0.2% carbonized polymer molecular clusters, and the balance being water.

[0030] In some preferred embodiments, the amount of carbonized polymer molecular clusters is 0.05~0.1%, preferably 0.05%.

[0031] In some preferred embodiments, the carbonized polymer molecular clusters are obtained by a hydrothermal reaction of citric acid, taurine, and hexylamine, specifically including the following steps: dispersing citric acid, taurine, and hexylamine in a solvent, and hydrothermally reacting at 140-180°C for 8-12 h; after the reaction, cooling and removing the solvent to obtain the carbonized polymer molecular clusters. The preferred reaction temperature is 160-170°C; the mass ratio of citric acid to taurine is (0.1:1) to (1:0.1), preferably 1:1; the mass ratio of hexylamine to the total mass of citric acid and taurine is (2-6):1. By controlling the ratio of hexylamine to citric acid and taurine, the proportion of hydrophilic and lipophilic groups in the carbonized polymer molecular clusters is controlled, thereby regulating the foam-stabilizing properties of the carbonized polymer molecular clusters.

[0032] On the other hand, the present invention also provides a method for preparing an ultra-stable foam system, comprising the following steps:

[0033] (1) Mix carbonized polymer molecular clusters with water and sonicate at 100~150W ultrasonic power for 5~10min to obtain a carbonized polymer molecular cluster dispersion;

[0034] (2) Add an amphoteric surfactant to the carbonized polymer molecular cluster dispersion and sonicate at 100-150W for 5-10 minutes to obtain a compound solution;

[0035] (3) The compound solution is stirred in a Wu Yin mixer at a speed of 2000~2500 rpm in a gas atmosphere for 3 minutes until foaming occurs, to obtain an ultra-stable foam system. The gas atmosphere is one or more of the following: air, nitrogen, carbon dioxide, natural gas, and flue gas.

[0036] Example 1

[0037] An ultra-stable foam system is prepared by the following steps:

[0038] S1: Weigh 5g of citric acid, 5g of taurine and 10g of hexylamine, and add them to 100mL of ethanol; after dispersing evenly, pour the mixture into a 150mL hydrothermal reactor and react at 160℃ for 8 hours; after the reaction is complete, remove the solvent by rotary evaporation at 50℃ to obtain carbonized polymer molecular clusters.

[0039] S2: Add 0.06g of carbonized polymer molecular clusters to 200g of simulated formation water with a mineralization of 24300mg / L, and ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a light yellow dispersion.

[0040] S3: Add 1.0g of cocamidopropyl betaine to the carbonized polymer molecular cluster dispersion obtained in S2, and then ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a compound foam solution.

[0041] S4: Take 100mL of the compound foam solution prepared in S3 and pour it into the high-speed stirring cup of the Wu Yin mixer. Stir it in the air at a speed of 2000rpm for 3 minutes to obtain a polymer-free, low-solid-phase, ultra-stable foam system.

[0042] Figure 1 This is a schematic diagram of the structure of a carbonized polymer molecular cluster. The prepared carbonized polymer molecular cluster carries amino, sulfonic acid, and hydroxyl groups on its surface and has a large specific surface area and an amphiphilic structure, exhibiting a strong adsorption effect on amphoteric surfactants. After compounding, the surfactant molecules in the adsorption layer are more easily arranged more tightly through the interaction of positive and negative charges, thereby increasing the viscosity and elasticity of the adsorption layer, enhancing the stability of the adsorption film, and improving the foaming and foam-stabilizing properties of the surfactant.

[0043] Example 2

[0044] An ultra-stable foam system is prepared by the following steps:

[0045] S1: Weigh 5g of citric acid, 5g of taurine and 10g of hexylamine, and add them to 100mL of ethanol; after dispersing evenly, pour the mixture into a 150mL hydrothermal reactor and react at 160℃ for 8 hours; after the reaction is complete, remove the solvent by rotary evaporation at 50℃ to obtain carbonized polymer molecular clusters.

[0046] S2: Add 0.1g of carbonized polymer molecular clusters to 200g of simulated formation water with a mineralization of 24300mg / L, and ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a light yellow dispersion.

[0047] S3: Add 1.0g of cocamidopropyl betaine to the carbonized polymer molecular cluster dispersion obtained in S2, and then ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a compound foam solution.

[0048] S4: Take 100mL of the compound foam solution prepared in S3 and pour it into the high-speed stirring cup of the Wu Yin mixer. Stir it in the air at a speed of 2000rpm for 3 minutes to obtain a polymer-free, low-solid-phase, ultra-stable foam system.

[0049] Figure 2 and Figure 3The images show the microscopic changes over time for an ultra-stable foam system (0.05% carbonized polymer molecular clusters) and a conventional AOS foam system (0.5% AOS). It can be seen that compared with the commonly used AOS system, the foam system described in this invention has a more stable liquid film and a slower coalescence rate between bubbles, which can form a more stable foam system and better modulating performance.

[0050] Example 3

[0051] An ultra-stable foam system is prepared by the following steps:

[0052] S1: Weigh 5g of citric acid, 5g of taurine and 10g of hexylamine, and add them to 100mL of ethanol; after dispersing evenly, pour the mixture into a 150mL hydrothermal reactor and react at 160℃ for 8 hours; after the reaction is complete, remove the solvent by rotary evaporation at 50℃ to obtain carbonized polymer molecular clusters.

[0053] S2: Add 0.2g of carbonized polymer molecular clusters to 200g of simulated formation water with a mineralization of 24300mg / L, and ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a light yellow dispersion.

[0054] S3: Add 1.0g of cocamidopropyl betaine to the carbonized polymer molecular cluster dispersion obtained in S2, and then ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a compound foam solution.

[0055] S4: Take 100mL of the compound foam solution prepared in S3 and pour it into the high-speed stirring cup of the Wu Yin mixer. Stir it in the air at a speed of 2000rpm for 3 minutes to obtain a polymer-free, low-solid-phase, ultra-stable foam system.

[0056] Example 4

[0057] The foam system was prepared using essentially the same method as in Example 1, except that the mass fraction of the solid-phase particulate carbonized polymer molecular clusters was 0.15%.

[0058] Example 5

[0059] The foam system was prepared using essentially the same method as in Example 1, except that the mass fraction of the solid-phase particulate carbonized polymer molecular clusters was 0.2%.

[0060] Comparative Example 1

[0061] The foam system was prepared using essentially the same method as in Example 1, except that the mass fraction of the solid-phase particulate carbonized polymer molecular clusters was 0%.

[0062] Comparative Example 2

[0063] A polymer foam system, prepared by the following method:

[0064] S1: Add 0.6g of polyacrylamide (HPAM) to 199.4g of simulated formation water with a salinity of 24300 mg / L, and ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a polymer solution;

[0065] S2: Add 1.0g of cocamidopropyl betaine to the polymer solution obtained in S1, and then disperse it by ultrasonication (150W, 5min) to obtain the HPAM polymer-stabilized foam system solution.

[0066] S3: Take 100mL of the compound foam system solution prepared in S2 and pour it into the high-speed stirring cup of the Wu Yin mixer. Stir it in air at a speed of 2000rpm for 3 minutes to obtain the HPAM stable foam system.

[0067] Comparative Example 3

[0068] A nano-silica stabilized foam system is prepared by the following method:

[0069] S1: Add 0.1g of nano-silica to 200g of simulated formation water with a mineralization of 24300 mg / L, and ultrasonically disperse it in an ultrasonic cleaner at 150W power for 5min to obtain a nanoparticle dispersion.

[0070] S2: Add 1.0g of cocamidopropyl betaine to the nano silica dispersion obtained in S1, and then ultrasonically disperse (150W, 5min) to obtain the nano silica stabilized foam system solution.

[0071] S3: Take 100mL of the compound foam system solution prepared in S2 and pour it into the high-speed stirring cup of the Wu Yin mixer. Stir it in the air at a speed of 2000rpm for 3 minutes to obtain the nano-silica stabilized foam system.

[0072] After stirring, the foam systems prepared in Examples 1-5 and Comparative Example 1 were quickly poured into a 500 mL graduated cylinder, and the foam volume and liquid separation half-life were recorded. The foam volume and liquid separation half-life of the carbonized polymer molecular cluster-stabilized foam system under different solid phase contents are shown in Table 1.

[0073] Table 1. Effect of solid content on the performance of foam system

[0074]

[0075] As shown in Table 1, in simulated formation water of 24300 mg / L, the half-life of foam generated by a simple amphoteric surfactant is only 11 min. The stability of the foam is greatly improved after adding carbonized polymer molecular clusters. The preferred amount of carbonized polymer molecular clusters is 0.05%.

[0076] After stirring, the foam systems prepared in Comparative Examples 2 and 3 were quickly poured into a 500 mL graduated cylinder, and the foam volume and liquid separation half-life were recorded. The foam volume and liquid separation half-life of the conventional polymer and nanoparticle stabilized foam systems are shown in Table 2.

[0077] Table 2 Performance of conventional polymer and nanoparticle stabilized foam systems

[0078]

[0079] Table 2 shows that 0.3% HPAM by mass has a certain foam-stabilizing effect, but it has a significant impact on the foam volume. Meanwhile, 0.05% nano-silica by mass has a slight effect on increasing the stability of the foam system. Therefore, the polymer-free, low-solids foam system provided by this invention has superior stability and is suitable for the development of low-permeability reservoirs.

[0080] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0081] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A super-stable foaming liquid, characterized in that, By mass percentage, it includes 0.4-0.6% amphoteric surfactants, 0.03-0.2% carbonized polymer molecular clusters, and the balance being water; The carbonized polymer molecular clusters were prepared by a hydrothermal reaction of citric acid, taurine, and hexylamine. The mass ratio of citric acid to taurine is (0.1:1) to (1:0.1); the mass ratio of hexylamine to the total mass of citric acid and taurine is (2~6):

1.

2. The ultra-stable foam liquid according to claim 1, characterized in that, The ultra-stable foam liquid comprises, by mass percentage, 0.4-0.6% amphoteric surfactant, 0.05-0.1% carbonized polymer molecular clusters, and the balance being water.

3. The ultra-stable foam liquid according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 140~180℃ for 8~12 h.

4. The ultra-stable foam liquid according to claim 1, characterized in that, The amphoteric surfactant is at least one of cocamidopropyl betaine, lauramidopropyl hydroxysulfonate betaine, lauramidopropyl betaine, and cocamidopropyl hydroxysulfonate betaine.

5. The method for preparing the ultra-stable foam liquid according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) The carbonized polymer molecular clusters were mixed with water and ultrasonically dispersed to obtain a carbonized polymer molecular cluster dispersion; (2) Add an amphoteric surfactant to the carbonized polymer molecular cluster dispersion and dissolve by ultrasonication to obtain a compound solution; (3) Stir the compound solution in a gas atmosphere until it foams to obtain the ultra-stable foam liquid.

6. The method for preparing the ultra-stable foam liquid according to claim 5, characterized in that, In steps (1) and (2), the ultrasonic power is 100~150W and the ultrasonic time is 5~10min.

7. The method for preparing the ultra-stable foam liquid according to claim 5, characterized in that, In step (3), the gas atmosphere is one or more of the following: air, nitrogen, carbon dioxide, natural gas, and flue gas; the stirring speed is 2000~2500 rpm and the stirring time is 3 min.

8. An application of the ultra-stable foam liquid as described in any one of claims 1 to 4 in crude oil development in low-permeability reservoirs.

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