Multi-core green active microcapsule oil-displacing agent as well as preparation method and application thereof

Abstract

The invention discloses a multi-core green active microcapsule oil-displacing agent and a preparation method and application thereof, the preparation method comprises the following steps: adding myristic acid and cinnamyl aldehyde into absolute ethyl alcohol, stirring at room temperature until the myristic acid and the cinnamyl aldehyde are dissolved to obtain a composite core material solution, and standing for later use; adding sodium alginate into deionized water, stirring at 30-60 DEG C until no floccules exist to obtain a wall material solution, and standing for later use; mixing the composite core material solution with the wall material solution, adding lauryl sodium sulfate, stirring at 75-85 DEG C for 1-3 hours to form a composite electrostatic spraying solution, and standing for later use; performing electrostatic spraying on the composite electrostatic spraying solution to prepare primary microcapsules, curing with a calcium chloride solution, washing with water, and freeze-drying to obtain the microcapsule oil-displacing agent. The microcapsule has a multi-core structure, is high in load rate, is matched with a targeted release characteristic, can enhance the residual oil stripping efficiency and the crude oil recovery efficiency when being used in the field of oil displacement, and can also be used in the field of agriculture.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas exploitation, and particularly relates to a multi-core green active microcapsule oil displacement agent and a preparation method and application thereof. BACKGROUND

[0002] Currently, most of the global oilfields gradually enter the middle and late development stage, and efficiently producing the residual oil in the reservoir pores has become the core challenge in the field of enhanced oil recovery (EOR). As the core oil displacement agent, surfactants become the core support for improving the recovery rate by virtue of the key role of reducing the "oil-water" interfacial tension and regulating the rock surface wettability. However, the traditional surfactants are easily adsorbed and fixed by rock particles during the reservoir migration, and also react with high salinity ions (such as Ca 2 + , Mg 2+ ) in the formation water to lose activity, and the double loss leads to the insufficient utilization rate of the displacement agent of less than 30% and the limited residual oil stripping efficiency. The microcapsule with the core-shell structure provides a train of thought for solving the above problems, which can encapsulate the active ingredients in the inert shell to protect the core material from the external environment and realize the controlled release and slow release of the core material. However, this technology has obvious imbalance in field application: the microcapsule has been widely used in the fields of food and agriculture by virtue of the precise regulation advantage of the structure, but the research and application in the oil displacement field are still in the primary stage. Even the existing small amount of research on the oil displacement microcapsule also has the following problems: 1. Insufficient environmental protection: the core material is mostly synthetic polymer, which often needs to rely on acrylamide comonomer and ammonium persulfate chemical initiator, and the raw material needs to be artificially synthesized; the wall material is mostly synthetic polymer such as polyurea and polyamide, and the preparation process relies on toxic solvents such as toluene and dichloromethane, which has serious environmental risks and is difficult to meet the current development needs of "green and low carbon" in oilfield development; 2. Complex preparation process and harsh conditions: the traditional oil displacement capsule preparation often needs to go through the steps of polymer emulsion synthesis, multiple rounds of coating and cross-linking, and involves harsh conditions such as nitrogen deoxidization, high-temperature reaction, which has high requirements for equipment sealing and temperature control accuracy. Industrialization is difficult, the cost is high, and it cannot meet the economic needs of large-scale injection in oilfields; 3. Single function: the functional design of the existing oil displacement microcapsule is limited to "single oil displacement target", which only focuses on improving the oil stripping efficiency, and does not fully utilize the structural versatility of the microcapsule "core-shell isolation protection + controllable release of active ingredients"; the microcapsule technology has been maturely applied in the fields of medicine, food and agriculture, but the existing oil displacement microcapsule has fixed "core material-wall material" compatibility and lacks adjustable adaptive system, which cannot be expanded to other fields through simple core material replacement or wall material parameter adjustment, and cannot realize the potential of one preparation method covering multiple fields. SUMMARY

[0003] In view of the defects of the prior art, the present application provides a multi-core green active microcapsule oil displacement agent and a preparation method and application thereof, wherein natural degradable myristic acid (MA) and cinnamaldehyde (CA) are used as a composite active core material, sodium alginate (SA) with wide sources and excellent biocompatibility is selected as a green wall material, and a multi-core calcium alginate shell microcapsule is constructed through an "emulsification-electrostatic spraying-crosslinking curing" process. The microcapsule has high core material loading rate, excellent responsiveness, environmental friendliness and universal adaptation potential, and is suitable for enhanced oil recovery in the middle and late stages of oilfield development, and also provides technical support for expanding to agricultural field applications.

[0004] A preparation method of a multi-core green active microcapsule oil displacement agent, comprising the following steps: S1. Preparation of a composite core material solution: myristic acid and cinnamaldehyde are added to anhydrous ethanol, stirred at room temperature until dissolved to obtain a composite core material solution, and then placed for standby; S2. Preparation of a green wall material solution: sodium alginate is added to deionized water, stirred at 30-60°C until no flocculation occurs to obtain a wall material solution, and then placed for standby; S3. Electrostatic spraying solution: the composite core material solution and the wall material solution are mixed, sodium dodecyl sulfate is added thereto, stirred at 75-85°C for 1-3h to form a composite electrostatic spraying solution, and then placed for standby; S4. Microcapsule preparation and curing: the composite electrostatic spraying solution is used to prepare initial microcapsules by electrostatic spraying, and then subjected to calcium chloride solution curing, water washing and freeze-drying to obtain a microcapsule oil displacement agent.

[0005] Preferably, in the composite core material solution, the total mass concentration of myristic acid and cinnamaldehyde is 3-10%, and the mass ratio of myristic acid to cinnamaldehyde is 1:1-3:1.

[0006] Preferably, in the wall material solution, the mass concentration of sodium alginate is 0.5-1%.

[0007] Preferably, in step S3, the volume ratio of the composite core material solution to the wall material solution is 1:3-1:5.

[0008] Preferably, in the composite electrostatic spraying solution, the concentration of sodium dodecyl sulfate is 0.05-0.2wt%.

[0009] Preferably, the parameters of the electrostatic spraying are as follows: applied voltage 15-25kV, nozzle diameter 0.1-0.2mm, distance from nozzle to collection plate 10-12cm, feeding rate 0.1-0.5mL / h, environmental temperature control at 25°C, and relative humidity maintained at 40-50%.

[0010] Preferably, the calcium chloride solution solidification is that the primary microcapsules are immersed in a 0.5-2wt% calcium chloride solution, and the solidification reaction is carried out at room temperature for 0.5-3h.

[0011] Preferably, the stirring speed in step S1 and step S2 is 300-600rpm; and the stirring speed in step S3 is 600rpm.

[0012] Preferably, the freeze-drying is freeze-drying at-50℃ for 24h.

[0013] A multi-core green active microcapsule oil displacement agent prepared by any one of the preparation methods described above.

[0014] Application of the microcapsule oil displacement agent in oil displacement.

[0015] Preferably, the application of the microcapsule oil displacement agent in oil displacement is that the microcapsule oil displacement agent is used for oil displacement under alkaline conditions.

[0016] Application of the microcapsule oil displacement agent in vegetable planting.

[0017] Preferably, the application of the microcapsule oil displacement agent in vegetable planting is that the microcapsule oil displacement agent is added into the soil for planting vegetables, and the addition amount is 0.5-1.5g / kg of soil.

[0018] Advantages of the present application: 1. The composite core material myristic acid (MA) and cinnamaldehyde (CA) are both naturally degradable, the wall material sodium alginate (SA) is widely sourced and has excellent biocompatibility, ethanol and water are used as solvents during preparation, there is no heavy metal and non-degradable component, and there is no harmful discharge throughout the process, which meets the development needs of "green low carbon" of oil fields, and has no damage to the oil reservoir, overcoming the defects of microcapsule synthesis in the prior art using polymers, toxic solvents and chemical initiators; 2. The calcium alginate shell can isolate rock adsorption and high salinity ion interference, and ensure stable migration of the MA / CA composite core material; after the shell is broken in response to the oil reservoir environment, the core material generates an efficient surfactant in situ, which solves the problems of easy loss and inactivation of traditional surfactants from the root; 3. Relying on the advantages of single-step forming by electrostatic spraying, combined with simple operations such as freeze-drying, the cost of equipment and energy consumption is reduced, and low-cost large-scale production is realized; overcoming the defects of the complicated steps of the existing traditional process; 4. The microcapsule prepared by the present application has a multi-core structure, high loading rate, and target release characteristics, which can be used in the oil displacement field to enhance the residual oil stripping efficiency and oil recovery, and also can reduce the subsequent repair cost of the oil reservoir; 5. The microcapsule prepared by the present application can also be used in the agricultural field, breaking the "single oil displacement" limitation. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Preparation flow chart of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 2 Optical microscopic image of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 3 Scanning electron microscopic image of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 4 Yield and loading rate of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 5 Responsiveness test of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 6 Comparison chart of static crude oil stripping performance test of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 7 Efficiency of static crude oil stripping performance test of the multi-core green active microcapsule oil displacement agent provided by the present application; Figure 8 Agricultural application chart of the multi-core green active microcapsule oil displacement agent. DETAILED DESCRIPTION

[0020] Example 1 A preparation method of a multi-core green active microcapsule oil displacement agent, the preparation flow chart is as follows Figure 1 , comprising the following steps: S1. Preparation of composite core material solution: mix myristic acid (MA) and cinnamaldehyde (CA) according to a mass ratio of 3:1, dissolve in anhydrous ethanol, stir at a speed of 400 rpm with a digital temperature-controlled magnetic stirrer at room temperature for 60 min, and the myristic acid and cinnamaldehyde are completely dissolved to obtain a composite core material solution, i.e. MA / CA ethanol solution, which is uniform and transparent; wherein the total mass of myristic acid and cinnamaldehyde is 5%; S2. Preparation of green wall material solution: add sodium alginate (SA) to deionized water, stir at a speed of 500 rpm at a constant temperature of 30℃ for 2h, and the sodium alginate is completely dissolved, and the suspension body has no flocculation, to obtain a wall material solution, i.e. SA aqueous solution; wherein the mass concentration of sodium alginate is 0.75%; S3. Electrostatic spray solution: mix the composite core material solution and the wall material solution according to a volume ratio of 1:5, and add sodium dodecyl sulfate (SDS) to the mixture, stir at a speed of 600 rpm at 80℃ for 2h to form a composite electrostatic spray solution, which is referred to as MC-SA-SDS solution; wherein the mass concentration of sodium dodecyl sulfate is 0.1wt%; S4. Microcapsule preparation and curing: 10 mL of the composite electrostatic spraying solution was taken into the electrostatic spraying device injector, and the initial microcapsule was prepared under the conditions of applied voltage 20 kV, nozzle diameter 0.2 mm, nozzle to collection plate distance 10 cm, feeding rate 0.3 mL / h, ambient temperature 25℃, relative humidity 45%; then the initial microcapsule was immersed in 1wt% calcium chloride solution, cured at room temperature for 30 min, washed with deionized water 4 times, and vacuum freeze-dried at-50℃ for 24h to obtain the microcapsule oil-displacing agent, referred to as MCM microcapsule.

[0021] Example 2 A preparation method of a multi-core green active microcapsule oil-displacing agent, comprising the following steps: S1. Preparation of composite core material solution: Mix myristic acid (MA) and cinnamaldehyde (CA) according to a mass ratio of 1:1, dissolve in anhydrous ethanol, stir at room temperature with a digital temperature-controlled magnetic stirrer at a speed of 300 rpm for 100 min, and the myristic acid and cinnamaldehyde are completely dissolved to obtain a composite core material solution, i.e. MA / CA ethanol solution, which is uniform and transparent; wherein the total mass of myristic acid and cinnamaldehyde is 3%; S2. Preparation of green wall material solution: Add sodium alginate (SA) to deionized water, stir at 30℃ constant temperature at a speed of 300 rpm for 2h, and the sodium alginate is completely dissolved to obtain a wall material solution, i.e. SA aqueous solution; wherein the mass concentration of sodium alginate is 0.5%; S3. Electrostatic spraying solution: Mix the composite core material solution and the wall material solution according to a volume ratio of 1:3, and add sodium dodecyl sulfate (SDS) to form a composite electrostatic spraying solution, referred to as MC-SA-SDS solution; wherein the mass concentration of sodium dodecyl sulfate is 0.05wt%; stir at 75℃ at a speed of 600 rpm for 2h; S4. Microcapsule preparation and curing: 10 mL of the composite electrostatic spraying solution was taken into the electrostatic spraying device injector, and the initial microcapsule was prepared under the conditions of applied voltage 20 kV, nozzle diameter 0.2 mm, nozzle to collection plate distance 10 cm, feeding rate 0.3 mL / h, ambient temperature 25℃, relative humidity 45%; then the initial microcapsule was immersed in 1wt% calcium chloride solution, cured at room temperature for 30 min, washed with deionized water 4 times, and vacuum freeze-dried at-50℃ for 24h to obtain the microcapsule oil-displacing agent, referred to as MCM microcapsule.

[0022] Example 3 A preparation method of a multi-core green active microcapsule oil-displacing agent, the preparation process is shown in Figure 1 , comprising the following steps: S1. Preparation of composite core material solution: Myristic acid (MA) and cinnamaldehyde (CA) were mixed at a mass ratio of 2:1 and dissolved in anhydrous ethanol. The mixture was stirred at 600 rpm for 100 min at room temperature using a digital temperature-controlled magnetic stirrer until the myristic acid and cinnamaldehyde were completely dissolved, resulting in a composite core material solution, namely the MA / CA ethanol solution. The solution was homogeneous and transparent. The total mass percentage of myristic acid and cinnamaldehyde was 10%. S2. Preparation of Green Wall Material Solution: Sodium alginate (SA) was added to deionized water and stirred at 600 rpm for 2 hours at a constant temperature of 60℃ until the sodium alginate was completely dissolved and the suspension was free of flocculent matter, thus obtaining the wall material solution, i.e., an aqueous solution of SA; wherein, the mass concentration of sodium alginate was 1%; S3. Electrostatic spray solution: The composite core material solution and wall material solution are mixed at a volume ratio of 1:4, and sodium dodecyl sulfate (SDS) is added. The mixture is stirred at 600 rpm for 2 hours at 85°C to form a composite electrostatic spray solution, abbreviated as MC-SA-SDS solution; wherein the mass concentration of sodium dodecyl sulfate is 0.2 wt%. S4. Microcapsule preparation and curing: 10 mL of the composite electrostatic spray solution was loaded into the syringe of the electrostatic spray device. Under the conditions of applying a voltage of 25 kV, a nozzle diameter of 0.2 mm, a distance from the nozzle to the collection plate of 12 cm, a feed rate of 0.5 mL / h, an ambient temperature of 25 °C, and a relative humidity of 50%, primary microcapsules were prepared. Then, the primary microcapsules were immersed in a 2 wt% calcium chloride solution and cured at room temperature for 2 h. They were washed 4 times with deionized water and then freeze-dried under vacuum at -50 °C for 24 h to obtain the microcapsule oil displacement agent, referred to as MCM microcapsules.

[0023] Performance testing 1. Morphology inspection Without adding a core material solution, everything else was the same as in Example 1, serving as Comparative Example 1. The microcapsules obtained in Comparative Example 1 and Example 1 were observed using an optical microscope, as shown in the images. Figure 2 As shown, the MA / CA core material was successfully loaded inside the microcapsule and exhibited a multi-core structure. Scanning electron microscopy was performed on the microcapsules of Example 1, such as... Figure 3 As shown, the microcapsules prepared in this embodiment have a diameter of about 100 micrometers and a complete structure.

[0024] 2. Yield and load factor detection Three groups of multi-core green active microcapsule oil displacement agent samples were prepared according to the method in Example 1 for calculating yield and loading rate. The results are as follows: Figure 4As shown, the yields of the three groups of samples ranged from 86% to 88.00%, with small fluctuations, indicating that the preparation method provided by this invention has excellent stability, no significant material loss, and a process basis for industrial scale-up. Furthermore, the MA loading rate and CA loading rate of the three groups of samples both exceeded 51%, with average values ​​reaching 51.92% and 56.80%, respectively, verifying the efficient encapsulation capability of the multi-core structure of this invention for the core material.

[0025] 3. Responsiveness Testing As attached Figure 5 As shown, the responsiveness of the multi-core green active microcapsule oil-displacing agent (MCM) described in Example 1 in an alkaline environment (Na2CO3) solution was verified by four groups of solution systems: Group 1 was deionized water + red oil phase, Group 2 was Na2CO3 solution + red oil phase (both were blank controls), Group 3 was deionized water + MCM + red oil phase, and Group 4 was Na2CO3 solution + MCM + red oil phase. The deionized water consisted of 16g, 2g of light oil stained with Oil Red O, 16g of 1wt% Na2CO3 solution, and 0.1g of MCM. Four systems were observed under the same static conditions. The results showed that Groups 1 and 2 had clear oil-water separation without emulsification, Group 3 had no obvious response from the MCM and the oil phase remained separated, while Group 4 had an emulsified oil phase that appeared turbid. Optical microscopy of Group 4 revealed a large number of uniform oil-in-water droplets with a particle size of 10-50 μm. The reason for this was that the Na2CO3 solution in Group 4 triggered the degradation of the MCM shell, and the released myristic acid and cinnamaldehyde reacted with the aqueous phase ions to generate surfactants, causing the red oil phase to emulsify rapidly and appear turbid. This indicates that the MCM has a specific response in Na2CO3 solution and can achieve targeted release and in-situ emulsification of myristic acid.

[0026] 4. Crude oil stripping performance testing To test the static crude oil stripping performance of the multi-core green active microcapsule oil displacement agent (MCM) described in Example 1 under alkaline conditions, crude oil and quartz sand were first mixed and stirred evenly at a mass ratio of 1:2, and aged in a 60℃ oven for 48 hours to prepare simulated oil sand. Four sets of beakers were each filled with 15g of simulated oil sand, and then 30g of deionized water, 30g of 1wt% Na2CO3 solution, 30g of 1wt% Na2CO3 solution + 1wt% MCM (i.e., the amount of MCM added accounts for 1wt% of the simulated oil sand), and 30g of 1wt% Na2CO3 solution + 2wt% MCM (i.e., the amount of MCM added accounts for 2wt% of the simulated oil sand) were added respectively. After thorough shaking, the mixture was placed in a 60℃ oven and heated for 48 hours. Subsequently, the lower layer of oil sand solids after oil-water separation was treated. Figure 6As shown, in the distilled water and sodium carbonate system without microcapsules, after oil-water separation, only a small amount of oil phase remains in the upper layer, while the bottom oil sand remains solidified into a single, immobile mass. A large oil layer appears on the surface of the bottom oil sand, preventing it from floating. When microcapsules are added and the mixture is fully heated, oil gradually precipitates from the crude oil-encapsulated sand. The amount of oil stripped from the upper layer increases with the increase in the mass fraction of microcapsules. The crude oil stripping efficiency is calculated after washing and drying the lower layer of oil sand solid. Figure 7 As shown, the concentrations were 40.34%, 45.66%, 61.10%, and 71.30%, respectively. The results indicate that the MCM prepared by this invention can significantly improve crude oil stripping efficiency, with higher concentrations resulting in better performance and good oil washing ability, making it suitable for use in oil displacement applications.

[0027] 5. Application in the cultivation of bok choy Bok choy seeds were randomly divided into two groups (each group was planted in a transparent planting box of the same size, with identical soil conditions): a blank control group (no microcapsules were placed in the soil, and only regular watering and maintenance were provided), and a microcapsule group (the multi-core green microcapsules (MCM) prepared in Example 1 of this invention were uniformly buried in the soil, with 1g of microcapsules added per kilogram of soil, followed by regular watering and maintenance), with other culture conditions being the same. After 10 days of culture, the bok choy seedlings in the blank control group showed sparse growth, short plants, few leaves, and a yellowish color; while the bok choy seedlings in the microcapsule group showed vigorous growth, dense plants, bright green leaves, and generally tall stature, exhibiting a significant growth advantage, indicating that the microcapsules provided by this invention have great application potential in the agricultural field.

Claims

1. A method for preparing a multi-core green active microcapsule oil displacement agent, characterized in that: Includes the following steps: S1. Preparation of composite core material solution: Myristic acid and cinnamaldehyde are added to anhydrous ethanol and stirred at room temperature until dissolved to obtain composite core material solution, which is then left to stand for later use; S2. Preparation of green wall material solution: Add sodium alginate to deionized water and stir at 30-60℃ until no flocculent matter is found to obtain the wall material solution, and let it stand for later use; S3. Electrostatic spray solution: Mix the composite core material solution with the wall material solution, add sodium dodecyl sulfate, stir at 75-85℃ for 1-3 hours to form a composite electrostatic spray solution, and let it stand for later use; S4. Microcapsule preparation and curing: The composite electrostatic spray solution is used to prepare primary microcapsules by electrostatic spraying, which are then cured with calcium chloride solution, washed with water and freeze-dried to obtain microcapsule oil displacement agent.

2. The preparation method of the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: In the composite core material solution, the total mass concentration of myristic acid and cinnamaldehyde is 3-10%, and the mass ratio of myristic acid to cinnamaldehyde is 1:1-3:

1.

3. The preparation method of the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: The mass concentration of sodium alginate in the wall material solution is 0.5-1%.

4. The preparation method of the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: In step S3, the volume ratio of the composite core material solution to the wall material solution is 1:3-1:

5.

5. The method for preparing the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: The concentration of sodium dodecyl sulfate in the composite electrostatic spray solution is 0.05-0.2 wt%.

6. The method for preparing the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: The parameters for the electrostatic spraying are as follows: applied voltage 15-25kV, nozzle diameter 0.1-0.2mm, distance from nozzle to collection plate 10-12cm, feed rate 0.1-0.5mL / h, ambient temperature controlled at 25℃, and relative humidity maintained at 40-50%.

7. The method for preparing the multi-core green active microcapsule oil displacement agent according to claim 1, characterized in that: The curing with calcium chloride solution is performed by immersing the microcapsules in a 0.5-2 wt% calcium chloride solution and curing them at room temperature for 0.5-3 hours.

8. A multi-core green active microcapsule oil displacement agent, characterized in that: It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the microcapsule oil displacement agent according to claim 8 in oil displacement.

10. The application of the microcapsule oil-displacing agent according to claim 8 in vegetable cultivation.

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