Nano oil-water phase permeability regulator and preparation method thereof

Abstract

The invention provides a nano oil-water phase permeability regulator and a preparation method thereof. The nano oil-water phase osmotic adjusting agent is prepared from the following raw materials in percentage by mass: 1.5 to 3 percent of scleroglucan pre-crosslinked particles, 2.5 to 5 percent of nano modified acrylamide, 0.2 to 3 percent of initiator, 0.2 to 2 percent of formaldehyde, 0.3 to 5 percent of diethanol amine, 0.5 to 5 percent of hydrochloric acid and the balance of water. Due to the scleroglucan pre-crosslinked particles, the thermosensitivity and the biological environmental protection property of the gel are improved, and the performances of salt resistance, temperature resistance, durability and the like are improved. Meanwhile, nano-modified acrylamide is obtained by grafting and modifying the surfaces of SiO2 particles and introducing cationic links and hydrophilic groups by adopting a silane coupling method, so that the nano-modified acrylamide has the adsorption and film-forming effects of polymer gel and a nano material, and the effect that 1 + 1 is greater than 2 is achieved. After being heated by the formation temperature, the particles expand to take the effects of occupying space, blocking and controlling water. The oil-water relative permeability of an oil layer is improved, water plugging and oil plugging are achieved, and important significance is achieved for plugging and controlling water in the extra-high water cut period and improving the productivity of an oil well.

Description

Technical Field

[0001] The present invention belongs to the technical field of plugging and water control for medium and high water cut oil wells, and particularly relates to a nano oil-water relative permeability modifier and a preparation method thereof. Background Art

[0002] Due to multiple factors such as hydraulic fracturing production and water injection development in low-permeability oil reservoirs, some oil wells produce water prematurely or even have high water cut, directly affecting the efficient development of oil fields. Especially as old oil fields gradually enter the middle and late stages of development, the number of medium and high water cut oil wells is increasing day by day, and the pressure to maintain stable production is gradually increasing. To control the ineffective water production of oil wells, tap the potential of oil layers, and solve the problems of water control for medium and high water cut oil wells and the recovery or increase of production capacity after water control has important practical significance.

[0003] Relative permeability modifiers (referred to as RPM for short, Relative Permeability Modifiers) usually refer to high molecular weight water-soluble polymers or weak gels, which can reduce the oil-water relative permeability in varying proportions. One of the technologies for plugging and water control of medium and high water cut oil wells is to use oil-water relative permeability modifiers. As a selective water control agent, it has the advantages of simple and convenient construction, low risk, small dosage, and low cost; when injected into the formation generally, it can greatly reduce the water phase permeability while having little effect on reducing the oil phase permeability, and has little damage to the formation, does not block the formation, the polymer can be removed, and has little impact on the environment. Currently, glucose, xanthan gum, multi-polymers, cationic polymers, and polyacrylamide can all be used as the polymers in the relative permeability modifier system, but polyacrylamide polymers are commonly used. However, conventional polyacrylamide polymer-based relative permeability modifiers themselves and the low molecular weight compounds produced by their degradation will cause varying degrees of damage to the formation.

[0004] In recent years, with the gradual progress and maturity of the application and development of nanotechnology in the petroleum industry, it has been found that nanomaterials have surface effects, volume effects, quantum size effects, etc., and the injection of nanomaterials can also play a role in improving relative permeability. Abroad, nanomaterials (mainly nano-SiO2) are mainly used as oil displacement agents, and there is little research on directly using them as selective plugging agents and the relative permeability improvement effect of nanomaterials.

[0005] CN 115368882 A discloses an oilfield relative permeability modifier and a preparation method thereof, which selects specific types of surfactants for compounding to reduce the surface tension of the system, and adds specific synergists. Using the hydroxyl groups contained in the molecular structure of the synergist to form intermolecular hydrogen bonds with the surfactant, expanding the spreading degree of the surfactant, effectively improving the action range of the relative permeability modifier, and exerting a significant synergistic effect; the synergist is of nanoscale size, which can improve the compatibility and dispersibility of other components in the system, contribute to the full and uniform mixing of each component, and further play a synergistic role. Although nanomaterials are used, the effect of improving relative permeability is poor. Nanomaterials have strong adsorption and limited injection depth. Summary of the Invention

[0006] The object of the present invention is to provide a nano oil-water phase permeability regulator, which uses a biopolymer to replace the synthetic polymer polyacrylamide, improves the temperature control of the gel, and enhances the salt tolerance, temperature resistance, persistence, etc.

[0007] Another object of the present invention is to provide a preparation method of the nano oil-water phase permeability regulator.

[0008] For this purpose, the technical solution provided by the present invention is as follows: A nano oil-water phase permeability regulator is prepared from the following raw materials by mass percentage: 1.5 - 3% of pre-crosslinked scleroglucan particles, 2.5 - 5% of nano-modified acrylamide, 0.2 - 3% of initiator, 0.2 - 2% of formaldehyde, 0.3 - 5% of diethanolamine, 0.5 - 5% of hydrochloric acid, and the balance is water. The initiator is ammonium persulfate and / or potassium persulfate.

[0009] A preparation method of the nano oil-water phase permeability regulator includes the following steps: Step 1) Dissolve the formulated amount of pre-crosslinked scleroglucan particles in the formulated amount of water, deoxygenate, then heat to 65 - 75 °C, and then add the formulated amount of initiator and stir evenly; Step 2) Add the formulated amount of nano-modified acrylamide, stir, and then sequentially add the formulated amounts of formaldehyde, diethanolamine, and hydrochloric acid, stir and react at 50 - 65 °C, and finally evaporate and concentrate, cool, and dry to obtain the product.

[0010] The preparation process of the pre-crosslinked scleroglucan particles is as follows: (1) Adjust the pH value of water to 10 - 12, add scleroglucan, stir evenly, and then add a crosslinking agent to obtain an aqueous phase; wherein, by weight percentage, the addition amounts of scleroglucan and the crosslinking agent are 1 - 10% and 0.5 - 2% respectively, and the balance is water; (2) Dissolve an emulsifier in an organic solvent to obtain an oil phase; wherein, by weight percentage, the addition amount of the emulsifier is 3 - 5%, and the balance is the organic solvent; (3) Mix and stir the aqueous phase and the oil phase according to a mass ratio of 2:1 - 5:1 to obtain an emulsion, heat to 60 °C, and react for 8 h; then add a demulsifier, precipitate with ethanol, wash with water, and dry to obtain the product; wherein, by weight percentage, the addition amount of the demulsifier is 1 - 3%.

[0011] The preparation process of the nano-modified acrylamide is as follows: (1) Add the silane coupling agent and nano-SiO2 particles into an ethanol aqueous solution with a mass concentration of 20 - 40%, and stir magnetically to make them evenly dispersed in the ethanol aqueous solution. Then adjust the pH to 3 - 3.5, heat and stir for reaction for 5 - 8 h and then let it stand for reaction; after the reaction is completed, filter, dry in vacuum, and grind to obtain surface-modified nano-SiO2; Among them, by weight percentage, the dosages of the silane coupling agent and nano-SiO2 particles are 0.5 - 3% and 1 - 10% respectively, and the balance is the ethanol aqueous solution; (2) Mix the surface-modified nano-SiO2, initiator, and acrylamide evenly in water, adjust the pH value to 3.5, remove oxygen by passing nitrogen, and then initiate the polymerization reaction in a 70 °C constant temperature water bath for 6 - 8 h to obtain nano-modified acrylamide; among them, by weight percentage, the dosages of the surface-modified nano-SiO2 and acrylamide are both 0.1 - 10%, the dosage of the initiator is 0.1 - 3%, and the balance is water.

[0012] The crosslinking agent in step (1) is zirconium lactate, phenolic resin, dimethyl phthalate imide ester, or maleimide hexane.

[0013] The emulsifier in step (2) is Span 80 and / or Tween 80, and the organic solvent is propylene glycol, liquid paraffin, ethanol, methanol, or ethyl acetate.

[0014] The demulsifier in step (3) is polyoxyethylene polyoxypropylene octadecanol ether or polyoxyethylene polyoxypropylene polyether.

[0015] The silane coupling agent in step (1) is isobutyltriethoxysilane, vinyl silane, amino silane, or methacryloxy silane.

[0016] The initiator in step (2) is ammonium persulfate and / or potassium persulfate.

[0017] The beneficial effects of the present invention are: The nano oil-water phase permeability regulator provided by the present invention uses biopolymer scleroglucan pre-crosslinked particles to replace synthetic polymer (polyacrylamide), improving the thermosensitivity, biological environmental protection, and the properties such as salt tolerance and temperature tolerance persistence of the gel. At the same time, the surface of SiO2 particles is grafted and modified by the silane coupling method, introducing cationic linkages and hydrophilic groups to obtain nano-modified acrylamide, improving the performance of the phase permeability improver, making it have both the functions of polymer gel and nano material adsorption and film formation, and comprehensively achieving the effect of 1 + 1 > 2.

[0018] The aqueous solution of scleroglucan pre-crosslinked particles has pseudoplasticity. Since the viscosity is very low when injected into the well at a large flow rate, it is easy to inject; scleroglucan also has good thermal stability, salt tolerance, and shear resistance, and adding additives to the aqueous solution can further improve its thermal stability.

[0019] The nano oil-water relative permeability regulator of the present invention has thermosensitivity, with low viscosity at normal temperature, which is beneficial to enter the matrix. When heated by formation temperature, the particles expand to occupy space and play a role in plugging water control. Entering the reservoir matrix at the front end of the fracture, it realizes the improvement of the oil-water relative permeability of the oil reservoir, plugs water but not oil, and has important significance for plugging water control in the extra-high water cut period and improving the productivity of oil wells.

[0020] Since the structural unit of polyacrylamide contains amide groups and is easy to form hydrogen bonds, it has good water solubility and high chemical activity. By relying on the hydrophilic groups on the molecular chain of polyacrylamide polymer, the purpose of unequal proportion reduction of oil-water permeability in the reservoir is achieved through water absorption expansion and hydration. The nano relative permeability improvement particles can firmly adsorb on the pore wall of carbonate rock to form a hydrophilic relative permeability improvement layer. The cationic polymer long chains grafted on the surface of the nano particles form a selective barrier in the pore channel. The hydrophilic groups of the molecular chain can freely stretch in water through water absorption expansion and hydration, generating frictional resistance to the flowing water and hindering the flow of water, thereby reducing the effective permeability of formation water. Detailed implementation manners

[0021] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0022] The exemplary implementation manners of the present invention are now introduced. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the relevant technical field. The terms used in the exemplary implementation manners do not limit the present invention.

[0023] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the relevant technical field. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their relevant fields, and should not be understood as idealized or overly formal meanings.

[0024] Example 1 This example provides a nano oil-water relative permeability regulator, which is prepared from the following raw materials by mass percentage: 1.5 - 3% of hard dextran pre-crosslinked particles, 3 - 5% of nano-modified acrylamide, 0.2 - 3% of initiator, 0.2 - 2% of formaldehyde, 0.3 - 5% of diethanolamine, 0.5 - 5% of hydrochloric acid, and the balance is water. The initiator is ammonium persulfate and / or potassium persulfate.

[0025] In the present invention, nano-modified acrylamide and pre-crosslinked hard dextran particles are mixed and then crosslinked, forming a more complex gel network with higher strength and better performance, similar to an interpenetrating network gel system. The aqueous solution of pre-crosslinked hard dextran particles has pseudoplasticity, with very low viscosity when flowing into the well at a large flow rate, being easy to inject, causing low damage to the formation, and having good stability.

[0026] Example 2 Based on Example 1, this example provides a nano oil-water phase permeability regulator, which is prepared from the following raw materials by mass percentage: 1.5% of pre-crosslinked hard dextran particles, 3% of nano-modified acrylamide, 0.2% of initiator, 0.2% of formaldehyde, 0.3% of diethanolamine, 0.5% of hydrochloric acid, and the balance is water. Preparation process: Step 1) Dissolve the formulated amount of pre-crosslinked hard dextran particles in the formulated amount of water, deoxygenate, then heat up to 65 °C, and then add the formulated amount of initiator and stir evenly; Step 2) Add the formulated amount of nano-modified acrylamide, stir, and then sequentially add the formulated amounts of formaldehyde, diethanolamine, and hydrochloric acid, stir and react at 50 °C, and finally evaporate, concentrate, cool, and dry to obtain the product.

[0027] Among them, the initiator is ammonium persulfate. The preparation process of the pre-crosslinked hard dextran particles is as follows: (1) Adjust the pH value of water to 10, add hard dextran, stir evenly and then add the crosslinking agent to obtain the aqueous phase; among them, by weight percentage, the addition amounts of hard dextran and the crosslinking agent are 1% and 0.5% respectively, and water is 98.5%; (2) Dissolve the emulsifier in the organic solvent to obtain the oil phase; among them, by weight percentage, the addition amount of the emulsifier is 3%, and the oil phase is 97%; (3) Mix and stir the aqueous phase and the oil phase according to a mass ratio of 2:1 to obtain an emulsion, heat up to 60 °C, and react for 8 h; then add the demulsifier, precipitate with ethanol, wash with water and dry to obtain the product; among them, by weight percentage, the addition amount of the demulsifier is 1%, and the emulsifier is 99%.

[0028] The preparation process of the nano-modified acrylamide is as follows: (1) Add the silane coupling agent and nano-SiO2 particles to an ethanol aqueous solution with a concentration of 20%, magnetically stir to make them evenly dispersed in the ethanol aqueous solution, then adjust the pH to 3, heat and stir to react for 5 h and then stand for reaction; after the reaction is completed, filter, vacuum dry, and grind to obtain surface-modified nano-SiO2; Among them, by weight percentage, the usage amounts of the silane coupling agent and nano-SiO2 particles are 0.5% and 1% respectively, and the ethanol aqueous solution is 98.5%; (2) Add surface-modified nano-SiO₂, initiator, and acrylamide into water and mix evenly. Adjust the pH value to 3.5. After purging with nitrogen to remove oxygen, initiate the polymerization reaction in a constant temperature water bath at 70 °C for 6 h to obtain nano-modified acrylamide. Among them, by weight percentage, the dosages of surface-modified nano-SiO₂ and acrylamide are both 0.1%, the dosage of the initiator is 0.1%, and water is 99.7%.

[0029] In this example, the crosslinking agent is zirconium lactate; the emulsifier is Span 80; the organic solvent is propylene glycol; the demulsifier is polyoxyethylene polyoxypropylene octadecanol ether; the silane coupling agent is isobutyltriethoxysilane.

[0030] Example 3 On the basis of Example 1, this example provides a nano oil-water phase permeability regulator, which is prepared from the following raw materials by mass percentage: 2% of hard dextran pre-crosslinked particles, 2.5% of nano-modified acrylamide, 1.5% of initiator, 1% of formaldehyde, 2.5% of diethanolamine, 2.5% of hydrochloric acid, and the balance is water. Preparation process: Step 1) Dissolve the formulated amount of hard dextran pre-crosslinked particles in the formulated amount of water. After deoxygenation, heat up to 70 °C, and then add the formulated amount of initiator and stir evenly. Step 2) Add the formulated amount of nano-modified acrylamide. After stirring, sequentially add the formulated amounts of formaldehyde, diethanolamine, and hydrochloric acid, stir and react at 60 °C, and finally evaporate, concentrate, cool, and dry to obtain the product.

[0031] Among them, the initiator is potassium persulfate.

[0032] The preparation process of the hard dextran pre-crosslinked particles is as follows: (1) Adjust the pH value of water to 11, add hard dextran, stir evenly, and then add the crosslinking agent to obtain the aqueous phase. Among them, by weight percentage, the addition amounts of hard dextran and the crosslinking agent are 5% and 1% respectively, and water is 94%. (2) Dissolve the emulsifier in the organic solvent to obtain the oil phase. Among them, by weight percentage, the addition amount of the emulsifier is 4%, and the organic solvent is 96%. (3) Mix and stir the aqueous phase and the oil phase according to a mass ratio of 3:1 to obtain an emulsion. Heat up to 60 °C and react for 8 h; then add the demulsifier, precipitate with ethanol, wash with water, and dry to obtain the product. Among them, by weight percentage, the addition amount of the demulsifier is 2%, and the emulsifier is 98%.

[0033] The preparation process of the nano-modified acrylamide is as follows: (1) Add the silane coupling agent and nano-SiO₂ particles into an ethanol aqueous solution with a mass concentration of 20%, and stir magnetically to make them evenly dispersed in the ethanol aqueous solution. Then adjust the pH to 3.2, heat and stir for 6 h and then let it stand for reaction; after the reaction is completed, filter, dry in vacuum, and grind to obtain surface-modified nano-SiO₂; Among them, by weight percentage, the dosages of the silane coupling agent and nano-SiO₂ particles are 1.5% and 5%, and the ethanol aqueous solution is 93.5%; (2) Mix the surface-modified nano-SiO₂, initiator, and acrylamide evenly in water, adjust the pH value to 3.5, remove oxygen by passing nitrogen, and initiate a polymerization reaction at 70 °C in a constant temperature water bath for 7 h to obtain nano-modified acrylamide; among them, by weight percentage, the dosages of the surface-modified nano-SiO₂ and acrylamide are both 5%, the dosage of the initiator is 1.5%, and water is 88.5%.

[0034] In this example, the crosslinking agent is phenolic resin; the emulsifier is Tween 80; the organic solvent is propylene liquid paraffin; the demulsifier is polyoxyethylene polyoxypropylene polyether; the silane coupling agent is vinyl silane.

[0035] Example 4 On the basis of Example 1, this example provides a nano oil-water phase permeability regulator, which is prepared from the following raw materials by mass percentage: 3% of hard dextran pre-crosslinked particles, 5% of nano-modified acrylamide, 3% of initiator, 2% of formaldehyde, 5% of diethanolamine, 5% of hydrochloric acid, and the balance is water. Preparation process: Step 1) Dissolve the formulated amount of hard dextran pre-crosslinked particles in the formulated amount of water, deoxygenate and then heat to 75 °C, and then add the formulated amount of initiator and stir evenly; Step 2) Add the formulated amount of nano-modified acrylamide, stir and then add the formulated amounts of formaldehyde, diethanolamine, and hydrochloric acid in sequence, stir and react at 65 °C, and finally evaporate and concentrate, cool, and dry to obtain.

[0036] Among them, the initiator is a mixture of ammonium persulfate and potassium persulfate, and the mass ratio is 2:1. The preparation process of the hard dextran pre-crosslinked particles is as follows: (1) Adjust the pH value of water to 12, add hard dextran, stir evenly and then add the crosslinking agent to obtain the aqueous phase; among them, by weight percentage, the addition amounts of hard dextran and the crosslinking agent are 10% and 2% respectively, and water is 88%; (2) Dissolve the emulsifier in the organic solvent to obtain the oil phase; among them, by weight percentage, the addition amount of the emulsifier is 5%, and the organic solvent is 95%; (3) Mix the aqueous phase and the oil phase in a mass ratio of 5:1 and stir to obtain an emulsion. Heat it to 60 °C and react for 8 h; then add a demulsifier, precipitate with ethanol, wash with water, and dry to obtain the product; among them, by weight percentage, the addition amount of the demulsifier is 3%, and the emulsifier is 97%.

[0037] The preparation process of the nano-modified acrylamide is as follows: (1) Add the silane coupling agent and nano-SiO2 particles to an ethanol aqueous solution with a concentration of 20%, and stir magnetically to make them evenly dispersed in the ethanol aqueous solution. Then adjust the pH to 3.5, heat and stir for 8 h, and then let it stand for reaction; after the reaction is completed, filter, dry in vacuum, and grind to obtain surface-modified nano-SiO2; Among them, by weight percentage, the usage amounts of the silane coupling agent and nano-SiO2 particles are 3% and 10%, and the ethanol aqueous solution is 90%; (2) Add the surface-modified nano-SiO2, initiator, and acrylamide to water and mix evenly. Adjust the pH value to 3.5. After purging with nitrogen to remove oxygen, initiate a polymerization reaction at a constant temperature of 70 °C for 8 h to obtain nano-modified acrylamide; among them, by weight percentage, the usage amounts of the surface-modified nano-SiO2 and acrylamide are both 10%, the usage amount of the initiator is 3%, and water is 77%.

[0038] In this example, the cross-linking agent is zirconium lactate, phenolic resin, dimethyl phthalate imide ester, or maleimide hexane.

[0039] In step (2), the emulsifier is Span 80 and / or Tween 80, and the organic solvent is propylene glycol, liquid paraffin, ethanol, methanol, or ethyl acetate.

[0040] In step (3), the demulsifier is polyoxyethylene polyoxypropylene octadecanol ether or polyoxyethylene polyoxypropylene polyether.

[0041] In step (1), the silane coupling agent is isobutyltriethoxysilane, vinylsilane, aminosilane, or methacryloxy silane.

[0042] In step (2), the initiator is ammonium persulfate and / or potassium persulfate.

[0043] In order to further illustrate the effects of the present invention, displacement core experiments were carried out on Examples 2-4 and Comparative Example 1 (the conventional polymer gel is composed of amphoteric polyacrylamide and a cross-linking agent. The amphoteric polyacrylamide is produced by Shanghai Aladdin Biochemical Technology Co., Ltd.; the cross-linking agent is tetraacetylacetone zirconate, self-made in the laboratory), and Comparative Example 2 (the nano material is hydrophilic nano-silica particles, Shanghai Merck Chemical Technology Co., Ltd.). The results are shown in Tables 1 and 2.

[0044] The core displacement experiment was carried out using a high-temperature and high-pressure core displacement experimental device. The specific steps are as follows: (1)Core pretreatment: After the core was evacuated, the core to be measured was placed in an electrothermal constant-temperature oven and dried for 6 hours and then taken out. The length and diameter of the core were measured with a ruler; and its mass was measured with an electronic balance, and the measurement data were recorded.

[0045] (2)Measuring the porosity and water / oil permeability of the core: Under the condition of 90 °C, the core was soaked in brine / simulated crude oil with a saturation salinity of 12,000 mg / L for 24 h. Its mass was measured with an electronic balance, and the injected brine volume was determined; the core porosity was calculated; until no water / oil phase flowed out from the outlet end of the core, the pressure values at both ends of the core were stabilized, and the water / oil permeability K of the core was calculated.

[0046] (3)Back-injecting a certain amount of relative permeability improver system: Under the condition of 90 °C, a certain amount of relative permeability improver system was back-injected and allowed to gel at a constant temperature for 72 h; (100% water saturation) simulating the oil reservoir condition of oil-bearing irreducible water, calculating the oil-phase permeability Ko: Under the experimental temperature of 90 °C, simulated oil was injected into the core using a high-temperature and high-pressure core displacement experimental device until no water flowed out from the outlet end of the core. The pressure values at both ends of the core were measured, the constant pressure value was recorded, and the oil-phase permeability Ko under irreducible water saturation was calculated; (non-100% water saturation) simulating the formation condition containing residual oil, calculating the water-phase permeability Kw: Under the experimental temperature of 90 °C, brine was injected into the core at a constant flow rate of 0.5 mL / min using a high-temperature and high-pressure core displacement experimental device until no oil phase flowed out from the outlet end of the core. The pressure values at both ends of the core were stabilized, the constant pressure value was recorded, and the water-phase permeability Kw was calculated; (4)Back-injecting a certain amount of relative permeability improver system: Under the condition of 90 °C, a certain amount of relative permeability improver system was back-injected and allowed to gel at a constant temperature for 72 h; (5)After back-injecting the relative permeability improver system, calculating the water-phase permeability Kw': After the injected relative permeability improver system gelled, the core was continuously displaced forward with brine, the pressure values at both ends of the core were stabilized, the constant pressure value was recorded, and the water-phase permeability Kw' was calculated; (6)After back-injecting the relative permeability improver system, calculating the oil-phase permeability Ko': The core to be measured was displaced forward with simulated oil until no water phase flowed out from the outlet end of the core, and then continued to be displaced. The pressure values at both ends of the core were stabilized, the constant pressure value was recorded, and the oil-phase permeability Ko' was calculated.

[0047] Table 1 Results of the standard brine displacement test of the relative permeability modifier

[0048] The core is saturated with simulated formation water, and then the original permeability value of the core is tested with standard brine, and then the relative permeability modifier material is injected. After injecting the material of the present invention, the reduction degree of the standard brine permeability is relatively high, while the reduction degree of the prior art is low. This shows that the plugging effect of the present invention on water is high.

[0049] Table 2 Results of the relative permeability modifier kerosene displacement test

[0050] The core is saturated with simulated formation water, and then the original permeability value of the core is tested with decolorized kerosene, and then the relative permeability adjustment material is injected. After injecting the material of the present invention, the reduction degree of the oil-phase permeability is relatively low, while the reduction degree of the prior art is high. This shows that the plugging effect of the present invention on oil is small.

[0051] From Table 1 and Table 2, it can be seen that the oil-water relative permeability modifier of the present invention has an obvious selective plugging effect (the reduction degrees of the water-phase and oil-phase permeabilities are different, with the water-phase reducing more and the oil-phase reducing less), and its performance is superior to that of conventional products on the market.

[0052] The above examples are only illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. Any design identical or similar to the present invention falls within the protection scope of the present invention.

Claims

1. A nano oil-water phase permeability regulator, characterized in that: It is prepared from the following raw materials in mass percentages: 1.5 - 3% of pre-crosslinked dextran particles, 2.5 - 5% of nano-modified acrylamide, 0.2 - 3% of initiator, 0.2 - 2% of formaldehyde, 0.3 - 5% of diethanolamine, 0.5 - 5% of hydrochloric acid, and the balance is water.

2. The nano oil-water phase permeability regulator according to claim 1, wherein: The initiator is ammonium persulfate and / or potassium persulfate.

3. The preparation method of a nano oil-water phase permeability regulator according to claim 1 or 2, characterized in that: It includes the following steps: Step 1): Dissolve the formulated amount of pre-crosslinked dextran particles in the formulated amount of water. After deoxygenation, raise the temperature to 65 - 75 °C, then add the formulated amount of initiator and stir evenly. Step 2): Add the formulated amount of nano-modified acrylamide. After stirring, sequentially add the formulated amounts of formaldehyde, diethanolamine, and hydrochloric acid, and stir and react at 50 - 65 °C. Finally, evaporate and concentrate, cool, and dry to obtain the product. (1) Adjust the pH value of water to 10 - 12, add dextran, stir evenly, and then add a crosslinking agent to obtain an aqueous phase; wherein, by weight percentage, the addition amounts of dextran and the crosslinking agent are 1 - 10% and 0.5 - 2% respectively, and the balance is water. (2) Dissolve an emulsifier in an organic solvent to obtain an oil phase; wherein, by weight percentage, the addition amount of the emulsifier is 3 - 5%, and the balance is the organic solvent. (3) Mix and stir the aqueous phase and the oil phase according to a mass ratio of 2:1 - 5:1 to obtain an emulsion. Raise the temperature to 60 °C and react for 8 h; then add a demulsifier, precipitate with ethanol, wash with water, and dry to obtain the product; wherein, by weight percentage, the addition amount of the demulsifier is 1 - 3%, and the balance is the emulsion.

4. The preparation method of a nano oil-water phase permeability regulator according to claim 3, characterized in that: The preparation process of the nano-modified acrylamide is as follows: (1) Add a silane coupling agent and nano-SiO₂ particles to an ethanol aqueous solution with a mass concentration of 20 - 40%, and magnetically stir to make them evenly dispersed in the ethanol aqueous solution. Then adjust the pH to 3 - 3.5, heat and stir for reaction for 5 - 8 h, and then let it stand for reaction; after the reaction ends, filter, vacuum dry, and grind to obtain surface-modified nano-SiO₂. Among them, by weight percentage, the usage amounts of the silane coupling agent and nano-SiO₂ particles are 0.5 - 3% and 1 - 10% respectively, and the balance is the ethanol aqueous solution. (2) Add the surface-modified nano-SiO₂, initiator, and acrylamide to water and mix evenly. Adjust the pH value to 3.5, purge with nitrogen to remove oxygen, and then initiate a polymerization reaction in a 70 °C constant temperature water bath for 6 - 8 h to obtain nano-modified acrylamide; wherein, by weight percentage, the usage amounts of the surface-modified nano-SiO₂ and acrylamide are both 0.1 - 10%, the usage amount of the initiator is 0.1 - 3%, and the balance is water.

5. The preparation method of a nano oil-water phase permeability regulator according to claim 3, characterized in that: The crosslinking agent in step (1) is zirconium lactate, phenolic resin, dimethyl phthalate imide ester, or maleimide hexane.

6. The preparation method of a nano oil-water phase permeability regulator according to claim 3, characterized in that: The emulsifier in step (2) is Span 80 and / or Tween 80, and the organic solvent is propylene glycol, liquid paraffin, ethanol, methanol, or ethyl acetate.

7. The preparation method of a nano oil-water phase permeability regulator according to claim 3, characterized in that: The demulsifier in step (3) is polyoxyethylene polyoxypropylene octadecanol ether or polyoxyethylene polyoxypropylene polyether.

8. The preparation method of a nano oil-water phase permeability regulator according to claim 4, characterized in that: The silane coupling agent in step (1) is isobutyltriethoxysilane, vinylsilane, aminosilane, or methacryloxy silane.

9. The preparation method of a nano oil-water phase permeability regulator according to claim 4, characterized in that: The initiator in step (2) is ammonium persulfate and / or potassium persulfate.

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