A nano-bionic drag reducer and a preparation method and application thereof

Abstract

The application relates to a nano-bionic drag reducer and a preparation method and application thereof, relates to the technical field of drag reducers, and comprises a porous nano core, a smooth liquid precursor solution, a catalyst and a trigger agent; the mass ratio of the porous nano core and the smooth liquid precursor solution is 1: (20-100); the porous nano core is obtained by dispersing polystyrene microspheres in an organic solvent for swelling, and then adding formaldehyde glycol and anhydrous ferric chloride for crosslinking reaction; and the smooth liquid precursor solution is obtained by compounding octamethylcyclotetrasiloxane and a surfactant. Under temperature stimulation, the smooth liquid precursor solution in the nano-bionic drag reducer is combined with the porous nano core on the rock surface to form a porous nano layer similar to a bionic pitcher plant, so that the subsequent injected water generates an interface slip effect on the rock surface when flowing through, the water injection resistance of an oil reservoir is greatly reduced, high-efficiency drag reduction, pressure reduction and injection increase are realized, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of drag reducers, and in particular to a nano bionic drag reducer and a preparation method and application thereof. Background Art

[0002] In the petroleum industry, reservoir waterflooding is a widely used and crucial secondary recovery technology. With the continuous advancement of oilfield development, many reservoirs have entered a high-water-cut development phase, where reservoir heterogeneity becomes increasingly pronounced and the rock pore structure becomes complex and diverse. Waterflooding, particularly in low-permeability reservoirs with permeabilities less than 50 mD, faces a common challenge: as the injected water flows through the tiny rock pores, it generates strong solid-liquid interfacial friction with the rock surface, leading to abnormally high injection pressures. This not only significantly increases waterflooding energy consumption and development costs, but also severely limits water injection sweep efficiency and formation energy replenishment, ultimately impacting oil recovery. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a nano-bionic drag reducer and a preparation method and application thereof.

[0004] In a first aspect, the present invention provides a nano-bionic drag reducer, comprising a porous nano-core, a lubricant precursor solution, a catalyst, and a trigger;

[0005] The mass ratio of the porous nanocore to the smooth liquid precursor solution is 1:(20-100);

[0006] The porous nanocore is obtained by dispersing polystyrene microspheres in an organic solvent for swelling, and then adding formaldehyde glycol and anhydrous ferric chloride for cross-linking reaction;

[0007] The lubricant precursor solution is obtained by compounding octamethylcyclotetrasiloxane and a surfactant;

[0008] In terms of mass percentage, the amount of the triggering agent added accounts for 0.4-2.0% of the total mass of the nano-bionic drag reducer;

[0009] The catalyst comprises at least one of sodium p-toluenesulfonate and sodium dodecylbenzenesulfonate;

[0010] The trigger is a mixture of urotropine and ammonium chloride, and the weight ratio of the urotropine to the ammonium chloride is 1:(1-2).

[0011] Furthermore, the mass ratio of the porous nanocore to the lubricating liquid precursor solution is 1:(40-60), for example, 1:40, 1:42, 1:48, 1:50, 1:55, 1:60, etc.

[0012] Furthermore, the amount of the catalyst added is 0.2-0.5% of the total mass of the nano-bionic drag reducer, for example, 0.2%, 0.3%, 0.4%, 0.5%, etc., in terms of mass percentage;

[0013] Furthermore, the preparation of the porous nanocore includes:

[0014] The polystyrene microspheres are dispersed in 1,2-dichloroethane and allowed to stand for 6 to 10 hours, and then formaldehyde glycol and anhydrous ferric chloride are added and reacted at 75 to 85° C. for 15 to 20 hours. After cooling to room temperature, the mixture is filtered, washed, and dried to obtain the porous nanocore;

[0015] The mass ratio of the polystyrene microspheres, the formaldehyde glycol and the anhydrous ferric chloride is (3-6): (6-8): (10-20).

[0016] Furthermore, the preparation of the polystyrene microspheres includes:

[0017] Adding a mixture of styrene and divinylbenzene dropwise into an aqueous phase containing sodium lauryl sulfate, stirring and emulsifying to form an emulsion;

[0018] Inert gas is introduced into the emulsion to remove dissolved oxygen, and then the temperature is raised to 60-80° C. and a 1% potassium persulfate solution is added to react for 3-6 hours. After the reaction is completed, ethanol is added to the system to break the emulsion, centrifuge, wash, and dry to obtain the polystyrene microspheres.

[0019] The mass ratio of the styrene, the divinylbenzene, the sodium lauryl sulfate and the potassium persulfate solution is (8-11): (0.8-1.2): (2-5): (1-3).

[0020] Furthermore, the preparation of the lubricating liquid precursor solution includes:

[0021] adding octamethylcyclotetrasiloxane to deionized water containing Tween 60 and sodium lauryl sulfate and stirring and mixing to obtain the smooth liquid precursor solution;

[0022] The mass ratio of the octamethylcyclotetrasiloxane, the Tween 60 and the sodium lauryl sulfate is (8-12): (5-10): (3-5).

[0023] In a second aspect, based on the same inventive concept, the present invention provides a method for preparing the nano-bionic drag reducer according to any one of the first aspects, the method for preparing the nano-bionic drag reducer comprising the following steps:

[0024] The porous nano core and the lubricating liquid precursor solution are mixed evenly, and then a catalyst and a trigger are added and dissolved to obtain the nano bionic drag reducer.

[0025] In the third aspect, based on the same inventive concept, the present invention provides a nano-bionic drag reducer as described in any one of the first aspects or a nano-bionic drag reducer prepared by the preparation method as described in any one of the second aspects for use in reducing the water injection pressure of low permeability oil reservoirs with a permeability <50mD.

[0026] Furthermore, the nano-bionic drag reducer and water are mixed in a mass ratio of 1:(10-50) to obtain a nano-bionic drag reducer dispersion; and the nano-bionic drag reducer dispersion is injected into the low permeability oil reservoir to perform a drag reduction operation.

[0027] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0028] The embodiment of the present invention provides a nano-bionic drag reducer and its preparation method and application. Under temperature stimulation, the smooth liquid precursor solution in the nano-bionic drag reducer provided by the present invention combines with the porous nano-core to form a porous nano-layer similar to a bionic pitcher plant on the rock surface, so that the subsequent injected water produces an interfacial slip effect on the rock surface when flowing through, greatly reducing the water injection resistance of the oil reservoir, achieving efficient drag reduction and pressure reduction and increased injection, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0031] Figure 1 Diagram of the action mechanism of the nano-bionic drag reducer prepared by the present invention.

[0032] Figure 2 This is a scanning electron microscope image of the porous nanocores in the nano-bionic drag reducer prepared by the present invention.

[0033] Figure 3 This is the particle size distribution diagram of the porous nanocore in the nano-bionic drag reducer prepared by the present invention.

[0034] Figure 4 This is the nitrogen adsorption-desorption isotherm diagram of the porous nanocore in the nano-bionic drag reducer prepared by the present invention.

[0035] Figure 5 This is the BJH pore size distribution diagram of the porous nanocore in the nano-bionic drag reducer prepared by the present invention. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0037] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0038] The mechanism of action of the nano bionic drag reducer provided by the present invention is as follows:

[0039] like Figure 1 As shown, the nano-bionic drag reducer and water are mixed in a mass ratio of 1: (10-50) to obtain a nano-bionic drag reducer dispersion. The octamethylcyclotetrasiloxane in the nano-bionic drag reducer dispersion is endowed in the microporous structure of the porous nano-core, and the surfactant maintains the dispersion stability of the porous nano-core loaded with octamethylcyclotetrasiloxane in water. When the dispersion is injected into the formation, the trigger reacts under the influence of the formation temperature to slowly release the hydrochloric acid component. At the same time, the hydrochloric acid promotes the conversion of the catalyst sodium p-toluenesulfonate or sodium dodecylbenzenesulfonate into p-toluenesulfonic acid or dodecylbenzenesulfonic acid, thereby achieving octamethylcyclotetrasiloxane through cationic catalysis. The ring-opening polymerization of methylcyclotetrasiloxane. As the polymerization process proceeds, the surfactant gradually cannot maintain the dispersion stability of the porous nanocores loaded with octamethylcyclotetrasiloxane in water. The porous nanocores loaded with octamethylcyclotetrasiloxane begin to adsorb and accumulate on the rock surface. At the same time, octamethylcyclotetrasiloxane gradually generates polydimethylsiloxane and is infused into the pores inside and between the porous nanocores, forming a smooth liquid-injected porous nanolayer on the rock surface that mimics the bionic pitcher plant. The subsequent injected water will produce an interfacial slip effect on the rock surface when flowing through the rock pores containing the porous nanolayer, greatly reducing the water injection resistance of the reservoir and achieving efficient drag reduction.

[0040] Therefore, compared with the prior art, the nano bionic drag reducer provided by the present invention includes at least the following characteristics:

[0041] (1) The nano-bionic drag reducer provided by the present invention has a significant effect, and its drag reduction effect is significantly better than that of conventional drag reducers;

[0042] (2) The nano-bionic drag reducer provided by the application has a long effective period and good erosion resistance, and can maintain the drag reduction effect for a long time;

[0043] (3) The nano-bionic drag reducer provided by the application has good temperature resistance and salt resistance, and can be used for pressure reduction and injection increase operation in high-temperature and high-salt oil reservoirs.

[0044] The application will be further described in combination with specific examples. It should be understood that the examples are only used to illustrate the application and are not used to limit the scope of the application. The experimental methods not specified in the following examples are generally determined according to national standards. If there is no corresponding national standard, the international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0045] The preparation of the porous nano core in the following examples 1 to 7 is carried out by the following method:

[0046] 9g of a mixed solution of styrene and divinylbenzene is added dropwise into 80mL of deionized water containing 3g of sodium dodecyl sulfate, while stirring and emulsifying at 300r / min, after the completion of the dropwise addition of the mixed solution of styrene and divinylbenzene, the emulsification is continued for 0.5 hours, after the emulsification is completed, nitrogen is introduced to remove oxygen for 20 minutes, the emulsion is heated to 70℃, then 2g of 1% potassium persulfate solution is added, and the reaction is carried out for 4 hours, the stirring is maintained at 300r / min during the reaction, after the reaction is completed, ethanol is added to the emulsion for demulsification, then centrifugal separation is carried out to obtain crosslinked polystyrene microspheres, then washing and drying are carried out for multiple times to obtain polystyrene microsphere dry powder;

[0047] 5g of polystyrene microsphere dry powder is dispersed in 100mL of 1,2-dichloroethane and left for 8 hours, then 7.5g of formaldehyde glycol and 15g of anhydrous ferric chloride are added in sequence, then the temperature is raised to 80℃ and the reaction is carried out for 18 hours, after the reaction is completed, the temperature is lowered to room temperature, then washing and drying are carried out to obtain the porous nano core.

[0048] The preparation of the lubricating fluid precursor solution in the following examples 1 to 7 is carried out by the following method:

[0049] 10g of octamethylcyclotetrasiloxane is added into 190mL of deionized water containing 8g of Tween 60 and 4g of sodium dodecyl sulfate, high-speed stirring is carried out at 1000r / min for 10 minutes to obtain the lubricating fluid precursor solution.

[0050] Example 1

[0051] This example provides a nano-bionic drag reducer, and the preparation method of the nano-bionic drag reducer comprises the following processes:

[0052] Mix 1.01g of porous nanocores with 20.2g of the smoothing liquid precursor solution and stir at 1000 rpm for 10 minutes to disperse evenly. Then, add 0.106g of sodium p-toluenesulfonate, 0.042g of hexamethylenetetramine, and 0.042g of ammonium chloride to the mixture and dissolve thoroughly to obtain a nano-bionic drag reducer. Disperse 1g of the nano-bionic drag reducer in 10g of water to obtain a nano-bionic drag reducer dispersion product 1.

[0053] Example 2

[0054] This example provides a nano-bionic drag reducer, and the preparation method of the nano-bionic drag reducer includes the following steps:

[0055] Mix 0.21g of porous nanocores with 21.0g of the smoothing liquid precursor solution and stir at 1000 rpm for 10 minutes to disperse evenly. Then, add 0.042g of sodium dodecylbenzenesulfonate, 0.141g of hexamethylenetetramine, and 0.282g of ammonium chloride to the mixture and dissolve thoroughly to obtain a nano-bionic drag reducer. Disperse 1g of the nano-bionic drag reducer in 50g of water to obtain a nano-bionic drag reducer dispersion product 2.

[0056] Example 3

[0057] This example provides a nano-bionic drag reducer, and the preparation method of the nano-bionic drag reducer includes the following steps:

[0058] Mix 0.8g of the porous nanocore with 20.41g of the smoothing liquid precursor solution and stir at 1000 rpm for 10 minutes to disperse evenly. Then, add 0.084g of sodium p-toluenesulfonate, 0.071g of hexamethylenetetramine, and 0.142g of ammonium chloride to the mixture and dissolve thoroughly to obtain a nano-bionic drag reducer. Disperse 1g of the nano-bionic drag reducer in 30g of water to obtain a nano-bionic drag reducer dispersion product 3.

[0059] Example 4

[0060] This example provides a nano-bionic drag reducer, and the preparation method of the nano-bionic drag reducer includes the following steps:

[0061] Mix 0.21g of the porous nanocores with 21g of the lubricant precursor solution and stir at 1000 rpm for 10 minutes to disperse them evenly. Then, add 0.084g of sodium p-toluenesulfonate, 0.071g of hexamethylenetetramine, and 0.142g of ammonium chloride to the mixture and dissolve them thoroughly to obtain a nano-bionic drag reducer. Disperse 1g of the nano-bionic drag reducer in 30g of water to obtain a nano-bionic drag reducer dispersion, Product 4.

[0062] Example 5

[0063] The example provides a nano-bionic drag reducer, and a preparation method of the nano-bionic drag reducer comprises the following processes:

[0064] 1.01 g of the porous nanometer core is mixed with 20.2 g of the smooth liquid precursor solution, uniformly dispersed at 1000 r / min for 10 minutes, and then 0.084 g of sodium p-toluenesulfonate, 0.071 g of urotropine, and 0.142 g of ammonium chloride are added to the mixture, and the nano-bionic drag reducer is obtained after being fully dissolved. 1 g of the nano-bionic drag reducer is taken and dispersed in 30 g of water to prepare a nano-bionic drag reducer dispersion product 5.

[0065] Example 6

[0066] The example provides a nano-bionic drag reducer, and a preparation method of the nano-bionic drag reducer comprises the following processes:

[0067] 0.8 g of the porous nanometer core is mixed with 20.41 g of the smooth liquid precursor solution, uniformly dispersed at 1000 r / min for 10 minutes, and then 0.106 g of sodium p-toluenesulfonate, 0.071 g of urotropine, and 0.142 g of ammonium chloride are added to the mixture, and the nano-bionic drag reducer is obtained after being fully dissolved. 1 g of the nano-bionic drag reducer is taken and dispersed in 30 g of water to prepare a nano-bionic drag reducer dispersion product 6.

[0068] Example 7

[0069] The example provides a nano-bionic drag reducer, and a preparation method of the nano-bionic drag reducer comprises the following processes:

[0070] 0.8 g of the porous nanometer core is mixed with 20.41 g of the smooth liquid precursor solution, uniformly dispersed at 1000 r / min for 10 minutes, and then 0.084 g of sodium p-toluenesulfonate, 0.028 g of urotropine, and 0.056 g of ammonium chloride are added to the mixture, and the nano-bionic drag reducer is obtained after being fully dissolved. 1 g of the nano-bionic drag reducer is taken and dispersed in 30 g of water to prepare a nano-bionic drag reducer dispersion product 7.

[0071] Example 8

[0072] The example provides a nano-bionic drag reducer, and the difference from the example 3 is only that:

[0073] (1) the preparation of the porous nanometer core is adjusted to be:

[0074] A mixture of 8 g of styrene and 0.8 g of divinylbenzene was added dropwise to 80 mL of deionized water dissolved with 2 g of sodium lauryl sulfate, while stirring and emulsifying at 300 r / min. After the addition of the styrene and divinylbenzene mixture, stirring and emulsification were continued for 0.5 hours. After the emulsification was completed, nitrogen was passed through for deoxygenation for 20 minutes. The emulsion was heated to 70° C., and then 1 g of a 1% potassium persulfate solution was added. The reaction was allowed to proceed for 4 hours. Stirring was maintained at 300 r / min during the reaction. After the reaction was completed, ethanol was added to the emulsion to break the emulsion, and then cross-linked polystyrene microspheres were obtained by centrifugation. The cross-linked polystyrene microspheres were then washed and dried multiple times to obtain a polystyrene microsphere powder.

[0075] 3 g of polystyrene microsphere powder was dispersed in 100 mL of 1,2-dichloroethane and allowed to stand for 6 hours. Subsequently, 6 g of formaldehyde glycol and 10 g of anhydrous ferric chloride were added in sequence. The temperature was then raised to 75°C for reaction for 20 hours. After the reaction was completed, the temperature was lowered to room temperature, and then washed and dried to obtain porous nanocores.

[0076] (2) The preparation of the lubricant precursor solution is adjusted as follows:

[0077] 8 g of octamethylcyclotetrasiloxane was added to 190 mL of deionized water containing 5 g of Tween 60 and 3 g of sodium lauryl sulfate, and stirred at a high speed of 1000 r / min for 10 minutes to obtain a smooth liquid precursor solution.

[0078] In this example, 1 g of the obtained nano-bionic drag reducer was dispersed in 30 g of water to prepare the nano-bionic drag reducer dispersion product 8.

[0079] Example 9

[0080] This example provides a nano-bionic drag reducer, which differs from Example 3 only in that:

[0081] (1) The preparation of porous nanocores is adjusted as follows:

[0082] A mixture of 11 g of styrene and 1.2 g of divinylbenzene was added dropwise to 80 mL of deionized water containing 5 g of sodium lauryl sulfate, while stirring and emulsifying at 300 r / min. After the addition of the styrene and divinylbenzene mixture, stirring and emulsification were continued for 0.5 hours. After the emulsification was completed, nitrogen was passed through for deoxygenation for 20 minutes. The emulsion was heated to 70° C., and then 3 g of a 1% potassium persulfate solution was added. The reaction was allowed to proceed for 4 hours. Stirring was maintained at 300 r / min during the reaction. After the reaction was completed, ethanol was added to the emulsion to break the emulsion, and then cross-linked polystyrene microspheres were obtained by centrifugation. The cross-linked polystyrene microspheres were then washed and dried several times to obtain a polystyrene microsphere powder.

[0083] 6 g of polystyrene microsphere powder was dispersed in 100 mL of 1,2-dichloroethane and allowed to stand for 6 hours. 8 g of formaldehyde glycol and 20 g of anhydrous ferric chloride were then added in sequence. The temperature was then raised to 75°C for reaction for 20 hours. After the reaction was completed, the temperature was lowered to room temperature, and the mixture was washed and dried to obtain a porous nanocore.

[0084] (2) The preparation of the lubricant precursor solution is adjusted as follows:

[0085] 12 g of octamethylcyclotetrasiloxane was added to 190 mL of deionized water containing 10 g of Tween 60 and 5 g of sodium lauryl sulfate, and stirred at a high speed of 1000 r / min for 10 minutes to obtain a smooth liquid precursor solution.

[0086] In this example, 1 g of the obtained nano-bionic drag reducer was dispersed in 30 g of water to prepare the nano-bionic drag reducer dispersion product 9.

[0087] Comparative Example 1

[0088] This example provides a drag reducer, which differs from Example 3 only in that:

[0089] (1) No porous nanocore was added.

[0090] Preparation of the drag reducer: 0.084 g of sodium p-toluenesulfonate, 0.071 g of hexamethylenetetramine, and 0.142 g of ammonium chloride were added to 21.21 g of a lubricant precursor solution (the same as in Example 3) and dissolved fully to obtain the drag reducer.

[0091] 1 g of the drag reducer obtained in this example was dispersed in 30 g of water to prepare comparative example product 1.

[0092] Comparative Example 2

[0093] This example provides a drag reducer, which differs from Example 3 only in that:

[0094] (1) No lubricant precursor solution was added.

[0095] Preparation of the drag reducer: 0.8 g of the porous nanocore (the same as in Example 3) was mixed with 20.41 g of deionized water and stirred at 1000 rpm for 10 minutes to disperse uniformly. 0.084 g of sodium p-toluenesulfonate, 0.071 g of hexamethylenetetramine, and 0.142 g of ammonium chloride were then added to the mixture and fully dissolved to obtain the drag reducer.

[0096] 1 g of the drag reducer obtained in this example was dispersed in 30 g of water to prepare comparative example product 2.

[0097] Comparative Example 3

[0098] This example provides a drag reducer, which differs from Example 3 only in that:

[0099] (1) No catalyst was added.

[0100] Preparation of the above-mentioned drag reducer: 0.8 g of porous nanocores (the same as in Example 3) was mixed with 20.41 g of smooth liquid precursor solution (the same as in Example 3), and the mixture was stirred at a high speed of 1000 rpm for 10 minutes to disperse evenly. Subsequently, 0.071 g of hexamethylenetetramine and 0.142 g of ammonium chloride were added to the mixture and fully dissolved to obtain a nano-bionic drag reducer.

[0101] 1 g of the drag reducer obtained in this example was dispersed in 30 g of water to prepare comparative example product 3.

[0102] Comparative Example 4

[0103] This example provides a drag reducer, which differs from Example 3 only in that:

[0104] (1) No triggering agent was added.

[0105] Preparation of the above-mentioned drag reducer: 0.8 g of porous nanocores (the same as in Example 3) was mixed with 20.41 g of smooth liquid precursor solution (the same as in Example 3), and the mixture was stirred at a high speed of 1000 rpm for 10 minutes to disperse evenly. Subsequently, 0.084 g of sodium p-toluenesulfonate was added to the mixture and fully dissolved to obtain the drag reducer.

[0106] 1 g of the drag reducer obtained in this example was dispersed in 30 g of water to prepare comparative example product 4.

[0107] Comparative Example 5

[0108] This example provides a drag reducer, which differs from Example 3 only in that:

[0109] (1) In the preparation of the lubricant precursor solution, octamethylcyclotetrasiloxane was adjusted to dodecamethylcyclohexasiloxane.

[0110] 1 g of the drag reducer obtained in this example was dispersed in 30 g of water to prepare comparative example product 5.

[0111] Test Example 1

[0112] In this example, the porous nanocore obtained in Example 1 was subjected to microstructural characterization, and the test results are as follows:

[0113] The scanning electron microscope image (SEM image) of the porous nanocore is as follows Figure 2 As shown, the SEM image clearly shows the microscopic morphology of the porous nanocore. The material particles have a highly regular spherical outline, the particle surface is smooth and flat, and there are no obvious depressions, protrusions or other irregular structural features. The morphology is uniform and the overall size distribution is uniform.

[0114] The particle size distribution of porous nanocores is as followsFigure 3 As shown, the volume ratio mainly concentrates on 75-80 nm, reaching 19.04%. The nanoparticles exhibit excellent anti-aggregation performance in liquid phase environment, and no obvious aggregation phenomenon is observed.

[0115] The nitrogen adsorption-desorption isotherm of the porous nanocore is shown in FIG. 3. Figure 4 As shown, the adsorption-desorption isotherm shows typical IV type characteristics, accompanied by obvious H3 type hysteresis loop, indicating that the pore has a "bottle-neck-cavity" configuration, and significant capillary condensation phenomenon can occur. The adsorption amount increases rapidly in the low pressure region, indicating that the porous nanocore material has a certain proportion of microporous structure, which is beneficial to the initial rapid adsorption of molecules.

[0116] The BJH (Barrett-Joyner-Halenda) pore size distribution of the porous nanocore is shown in FIG. 4. Figure 5 As shown, the BJH pore size distribution further proves that the porous nanocore material has a significant microporous-mesoporous hierarchical structure, with pore sizes mainly distributed in the range of 1-10 nm, and a significant peak at 1-2 nm. The pore size is highly matched with the diameter of octamethylcyclotetrasiloxane molecules. This high specific surface area and microporous-mesoporous synergistic structural characteristics not only provide efficient adsorption storage space and diffusion channels for octamethylcyclotetrasiloxane molecules, but also realize the slow release control of the adsorbed octamethylcyclotetrasiloxane molecules through the confinement effect, thereby significantly improving the long-acting and stability of the porous nanocore as a carrier of the octamethylcyclotetrasiloxane-based drag reducer.

[0117] Test Example 2

[0118] In this example, the water dispersion performance of the drag reducers obtained in Examples 1-9 and Comparative Examples 2-5 above was evaluated. The drag reducer dispersion liquids of each example and comparative example were placed in a 20°C and 80°C environment, respectively, and were kept constant for 5 days. The dispersion of different products under different temperature conditions was observed, and the results are shown in Table 1.

[0119] Table 1

[0120] Test sample 20°C test results 80°C test results Example 1 Well dispersed Layered settling Example 2 Well dispersed Layered settling Example 3 Well dispersed Layered settling Example 4 Well dispersed Layered settling Example 5 Well dispersed Layered settling Example 6 Well dispersed Layered settling Example 7 Well dispersed Layered settling Example 8 Well dispersed Layered settling Example 9 Well dispersed Layered settling Comparative Example 2 Layered settling Layered settling Comparative Example 3 Well dispersed Well dispersed Comparative Example 4 Well dispersed Well dispersed Comparative Example 5 Well dispersed Well dispersed

[0121] The results show that all examples maintain good dispersibility at 20°C, while Comparative Example 2 exhibits delamination and sedimentation. Compared to Example 3, Comparative Example 2 does not contain a lubricant precursor solution, indicating that the addition of a surfactant to the lubricant precursor solution is crucial for maintaining the dispersion stability of the porous nanocores. When the temperature rises to 80°C, all examples exhibit delamination and sedimentation, while Comparative Examples 3, 4, and 5 maintain good dispersibility. Compared to Example 3, Comparative Example 3 does not contain a catalyst, and Comparative Example 4 does not contain a trigger. Therefore, Comparative Examples 3 and 4 cannot undergo cationic ring-opening polymerization of octamethylcyclotetrasiloxane to form polydimethylsiloxane at 80°C. Consequently, the porous nanocores are unable to overcome the electrostatic repulsion and steric hindrance generated by the surfactant, resulting in adsorption and sedimentation, thus maintaining good dispersibility. Compared to Example 3, Comparative Example 5 replaces octamethylcyclotetrasiloxane with dodecamethylcyclohexasiloxane. Due to the low reactivity of dodecamethylcyclohexasiloxane, ring-opening polymerization requires high temperature and strong acid conditions. Therefore, it cannot be effectively polymerized at 80°C. As a result, dodecamethylcyclohexasiloxane cannot overcome the electrostatic repulsion and steric hindrance effects of the surfactant and is adsorbed and settled, thus maintaining good dispersion in the system.

[0122] Test Example 3

[0123] In this example, the wetting angle of the drag reducers obtained in Examples 1 to 9 and Comparative Examples 1 to 5 was evaluated. The experimental steps are as follows:

[0124] (1) Place the sandstone core pieces and the nano-bionic drag reducer dispersion prepared in each embodiment and comparative example in a sealed container to ensure that the liquid completely immerses the core pieces. In the blank group, deionized water is used instead of the dispersion;

[0125] (2) Place the sealed container in a constant temperature box at 80°C and let it stand for 2 days;

[0126] (3) Take out the core slice and use the Kruss contact angle meter (DSA) to measure the static contact angle of the deionized water drop on the surface of the core slice.

[0127] The experimental results are shown in Table 2.

[0128] Table 2

[0129] Test sample Contact angle Blank 52.61° Example 1 153.36° Example 2 113.64° Example 3 138.53° Example 4 118.84° Example 5 124.81° Example 6 126.35° Example 7 131.91° Example 8 129.31° Example 9 124.93° Comparative Example 1 63.31° Comparative Example 2 49.36° Comparative Example 3 53.82° Comparative Example 4 51.47° Comparative Example 5 56.32°

[0130] The test results show that:

[0131] The contact angle of the blank group was 52.61°, indicating a hydrophilic core surface. However, after treatment with the nano-bionic drag reducer dispersions prepared in each example, the core surface contact angles were all >118°, indicating a wetting reversal and a hydrophobic appearance. This demonstrates that the nano-bionic drag reducer prepared in this invention can form a hydrophobic layer on the rock surface, altering its wetting properties.

[0132] Compared with Example 3, in Comparative Example 1, no porous nanocores were added, and the contact angle decreased from 138.53° to 63.31°. Although this value was slightly higher than that of the blank group, no wetting reversal occurred on the rock surface. Although octamethylcyclotetrasiloxane in the system can be converted into polydimethylsiloxane at 80°C, due to the lack of porous nanocores, polydimethylsiloxane is immiscible with water and is subject to gravity separation, most of the generated polydimethylsiloxane floats to the upper layer of the aqueous phase, making it difficult to effectively precipitate and adsorb on the rock wall. Only during the removal of the core piece was some polydimethylsiloxane able to adsorb on the rock surface. Therefore, the contact angle only increased slightly, and wetting reversal failed to be achieved.

[0133] Compared to Example 3, the contact angles of the core surfaces treated in Comparative Example 2 (no smoothing liquid precursor), Comparative Example 3 (no catalyst), Comparative Example 4 (no trigger), and Comparative Example 5 (octamethylcyclotetrasiloxane replaced with dodecamethylcyclohexasiloxane) were 49.36°, 53.82°, 51.47°, and 56.32°, respectively. These values ​​did not change significantly compared to the blank control. This indicates that when any key component, such as octamethylcyclotetrasiloxane, the trigger, or the catalyst, is missing from the system, the hydrophobic layer cannot be effectively formed on the rock surface.

[0134] Test Example 4

[0135] This example tests the pressure reduction and injection performance of the drag reducers obtained in Examples 1-9 and Comparative Examples 1-5. The cores used in the tests were all artificial sandstone cores with a permeability of 20 mD and a core size of φ2.5 cm × 5 cm. The test steps are as follows:

[0136] (1) Place the core into the core holder, adjust the temperature of the thermostat to 80°C, and preheat at this temperature for 1 hour;

[0137] (2) Carry out water flooding experiment, inject at a constant flow rate of 0.1 ml / min until the injection pressure stabilizes, and record the stable pressure as P1;

[0138] (3) Inject 2PV of the nano-bionic drag reducer dispersion prepared in each embodiment and comparative example respectively, and then conduct subsequent water flooding experiments until the pressure stabilizes again, and record the stable pressure as P2;

[0139] (4) Calculate the blood pressure reduction rate E (%) according to the formula: E = [(P1-P2) / P1] * 100%.

[0140] The experimental results are shown in Table 3.

[0141] Table 3

[0142] Test sample Pressure drop rate (%) Example 1 26.38% Example 2 9.94% Example 3 19.26% Example 4 16.81% Example 5 14.43% Example 6 17.19% Example 7 11.53% Example 8 13.41% Example 9 11.57% Comparative Example 1 3.61% Comparative Example 2 -2.14% Comparative Example 3 1.05% Comparative Example 4 0.37% Comparative Example 5 0.13%

[0143] The test results show that:

[0144] The nano-bionic drag reducer prepared in each embodiment has a minimum pressure reduction rate of 9.94%, which proves that the nano-bionic drag reducer prepared by the invention can effectively reduce the injection pressure and improve the high-pressure under-injection problem in low-permeability oil reservoirs.

[0145] Compared to Example 3, in Comparative Example 1, no porous nanocore was added, and its decompression rate dropped from 19.26% to 3.61%. Because the system lacks porous nanocores and octamethylcyclotetrasiloxane is insoluble in water, Comparative Example 1 shows a separation phenomenon under static conditions, with octamethylcyclotetrasiloxane floating above the aqueous phase. As a result, during the injection process, octamethylcyclotetrasiloxane and other components of the system are injected as a slug, with octamethylcyclotetrasiloxane being the pre-slug. This results in a reduced efficiency of ring-opening polymerization to generate polydimethylsiloxane in a simulated formation environment, and the polydimethylsiloxane generated simultaneously is difficult to be retained in the formation by adsorption aggregation, resulting in a reduced decompression rate.

[0146] Compared to Example 3, Comparative Example 2, in which no smooth liquid precursor was added, had a negative pressure reduction rate. First, the system lacked the octamethylcyclotetrasiloxane provided by the smooth liquid precursor, resulting in an inability to form a smooth, liquid-injected porous nanolayer on the channel wall in the simulated formation environment, mimicking the pitcher plant's smooth liquid-injection properties, thus failing to achieve the desired pressure reduction. Second, the absence of the smooth liquid precursor also depleted the system of the necessary surfactant component, making it difficult for the porous nanocores to maintain a stable dispersion in the liquid. The porous nanocores easily agglomerated during the injection process, blocking the seepage channel and causing reservoir damage, ultimately leading to an increase in injection pressure.

[0147] Compared to Example 3, the pressure reduction rates for Comparative Example 3 (no catalyst added), Comparative Example 4 (no trigger added), and Comparative Example 5 (octamethylcyclotetrasiloxane replaced with dodecamethylcyclohexasiloxane) were 1.05%, 0.37%, and 0.13%, respectively. This indicates that when the necessary trigger or catalyst is missing from the system, cationic catalysis cannot effectively convert octamethylcyclotetrasiloxane and exert its drag reduction effect in the simulated formation environment, resulting in minimal changes in injection pressure.

[0148] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in a range format is only for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention; therefore, the range description should be considered to have specifically disclosed all possible subranges and single numerical values ​​within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is intended to include any cited numeral (fractional or integer) within the indicated range.

[0149] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A nano bionic drag reducer, characterized in that: The nano bionic drag reducer comprises a porous nano core, a lubricant precursor solution, a catalyst and a trigger; The mass ratio of the porous nanocore to the smooth liquid precursor solution is 1:(20-100); The porous nanocore is obtained by dispersing polystyrene microspheres in an organic solvent for swelling, and then adding formaldehyde glycol and anhydrous ferric chloride for cross-linking reaction; The lubricant precursor solution is obtained by compounding octamethylcyclotetrasiloxane and a surfactant; In terms of mass percentage, the amount of the triggering agent added accounts for 0.4 to 2.0% of the total mass of the nano-bionic drag reducer; The catalyst comprises at least one of sodium p-toluenesulfonate and sodium dodecylbenzenesulfonate; The trigger is a mixture of urotropine and ammonium chloride, and the weight ratio of the urotropine to the ammonium chloride is 1:(1-2); The pore diameter of the porous nanocore is mainly distributed in the range of 1-10 nm.

2. The nano bionic drag reducer according to claim 1, characterized in that: The mass ratio of the porous nanocore to the smooth liquid precursor solution is 1:(40-60).

3. The nano bionic drag reducer according to claim 1, characterized in that: Calculated in mass percentage, the added amount of the catalyst accounts for 0.2-0.5% of the total mass of the nano-bionic drag reducer.

4. The nano bionic drag reducer according to claim 1, characterized in that: The preparation of the porous nanocore comprises: The polystyrene microspheres are dispersed in 1,2-dichloroethane and allowed to stand for 6 to 10 hours, and then formaldehyde glycol and anhydrous ferric chloride are added and reacted at 75 to 85° C. for 15 to 20 hours. After cooling to room temperature, the mixture is filtered, washed, and dried to obtain the porous nanocore; The mass ratio of the polystyrene microspheres, the methylaldehyde glycol and the anhydrous ferric chloride is (3-6): (6-8): (10-20).

5. The nano bionic drag reducer according to claim 4, characterized in that: The preparation of the polystyrene microspheres comprises: Adding a mixture of styrene and divinylbenzene dropwise into an aqueous phase containing sodium lauryl sulfate, stirring and emulsifying to form an emulsion; Inert gas is introduced into the emulsion to remove dissolved oxygen, and then the temperature is raised to 60-80° C. and a 1% potassium persulfate solution is added to react for 3-6 hours. After the reaction is completed, ethanol is added to the system to break the emulsion, centrifuge, wash, and dry to obtain the polystyrene microspheres. The mass ratio of the styrene, the divinylbenzene, the sodium lauryl sulfate and the potassium persulfate solution is (8-11):(0.8-1.2):(2-5):(1-3).

6. The nano bionic drag reducer according to claim 1, characterized in that: The preparation of the smooth liquid precursor solution comprises: adding octamethylcyclotetrasiloxane to deionized water containing Tween 60 and sodium lauryl sulfate and stirring and mixing to obtain the smooth liquid precursor solution; Wherein, the mass ratio of the octamethylcyclotetrasiloxane, the Tween 60 and the sodium lauryl sulfate is (8-12):(5-10):(3-5).

7. A method for preparing the nano-bionic drag reducer according to any one of claims 1 to 6, characterized in that: The preparation method of the nano bionic drag reducer comprises the following steps: The porous nano core and the lubricating liquid precursor solution are mixed evenly, and then a catalyst and a trigger are added and dissolved to obtain the nano bionic drag reducer.

8. Use of the nano-bionic drag reducer according to any one of claims 1 to 6 or the nano-bionic drag reducer prepared by the preparation method according to claim 7 in reducing the water injection pressure of a low permeability oil reservoir with a permeability of less than 50 mD.

9. The use according to claim 8, characterized in that The nano-bionic drag reducer and water are mixed in a mass ratio of 1:(10-50) to obtain a nano-bionic drag reducer dispersion; and the nano-bionic drag reducer dispersion is injected into the low-permeability oil reservoir to perform a drag reduction operation.

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