CN110439517A - A kind of flooding method suitable for heavy crude reservoir - Google Patents

Abstract

The invention relates to the technical field of crude oil collection, and discloses an oil displacement method suitable for heavy oil reservoirs. The Pickering emulsion system and the foam system were alternately flooded by slug combination for 2-4 times, and the total slug injection volume of the Pickering emulsion system and the foam system was 0.4-0.8PV; the emulsifier of the foam system included magnetic nano-Fe ₃ O ₄ @ _SiO2 particles and foaming agent; the emulsifier of the Pickering emulsion system includes magnetic nano-Fe3O4@SiO2 particles, surfactants and polymers. The suitable oil displacement method of the present invention is suitable for crude oil with a viscosity lower than 5000mPa·s, has a wide range of suitable crude oil viscosity, and greatly improves the recovery factor for high-viscosity heavy oil reservoirs.

Description

A flooding method suitable for heavy oil reservoirs

technical field

The invention relates to the technical field of crude oil collection, in particular to an oil displacement method suitable for heavy oil reservoirs.

Background technique

With the development of industry, the contradiction between the social demand for oil and the serious shortage of oil resources has become increasingly serious. How to extract more oil from the developed oil fields has become the focus of research. With the advancement of science and technology, some special reservoirs are being developed more and more, such as low permeability reservoirs, ultra-low permeability reservoirs, high temperature and high salinity reservoirs and so on. The viscosity of flowable heavy oil is usually as high as thousands to tens of thousands of mPa·s. Due to the large difference in the mobility ratio of water and heavy oil, it is easy to cause water fingering, resulting in ineffective displacement and low recovery. Exxon Company first proposed the Pickering emulsion oil recovery method, and was used to develop heavy oil with a viscosity in the range of 20-3000mPa·s. Indoor and field tests have proved that the Pickering emulsion can be injected for a long time, and can remain stable during the flow process, significantly improving the recovery factor. Son et al. also used Pickering emulsion for oil displacement, and at the same time proposed that the alternating injection of emulsion and water has a better oil displacement effect. However, these methods have the disadvantage of low oil recovery for high-concentration crude oil. Chinese Patent Publication No. CN101949282 discloses a residual oil bitumen emulsion flooding method. The residual oil or bitumen is heated to a flow state, and a certain concentration of surfactant aqueous solution is prepared and heated to 80° C., and then the flow state residual oil or Asphalt is added to the hot surfactant solution according to the proportion, stirred to emulsify it, and the oil is flooded with water on site to a water content above 98%, and then the residual oil or bitumen emulsion is injected for displacement, followed by water flooding, but the residual oil Asphalt emulsion is only suitable for ordinary heavy oil reservoirs (crude oil viscosity is less than 300mPa.s), and the viscosity range of heavy oil is narrow, and the oil recovery rate for high viscosity heavy oil reservoirs will be greatly reduced.

Contents of the invention

The present invention aims to overcome the problem of low recovery of high-concentration heavy oil in the prior art, and provides an oil displacement method suitable for heavy oil reservoirs, suitable for crude oil with a viscosity lower than 5000mPa·s, and suitable for a wide range of crude oil viscosity , and the recovery factor for high-viscosity heavy oil reservoirs has been greatly improved.

In order to achieve the above object, the present invention adopts the following technical solutions: an oil displacement method suitable for heavy oil reservoirs, in which the Pickering emulsion system and the foam system are alternately displaced 2-4 times in the form of slug combination.

The invention adopts the Pickering emulsion system and the foam system to alternately inject the rock core in a slug combination mode, and the emulsion system and the foam system can be dispersed into the high-viscosity heavy oil. On the one hand, this dispersion effect inhibits the fingering of the low-viscosity oil displacement system, making the sweeping effect better; The viscosity of the heavy oil in contact with each other increases the fluidity of the heavy oil. In addition, there are surfactants in the continuous phase of the emulsion. Under the disturbance of the flow, the heavy oil can form an obvious stringing phenomenon. Through this mechanism, the heavy oil can be emulsified into oil-in-water emulsion droplets, thereby improving the washing effect. oil efficiency. The polymer in the system can reduce the fluidity of the subsequent water flow and increase the swept volume of the subsequent water flow. The recovery factor of crude oil whose viscosity is lower than 5000mPa·s is greatly improved.

Preferably, the total slug injection volume of the Pickering emulsion system and the foam system is 0.4-0.8 PV.

Preferably, the emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and a foaming agent.

Preferably, the preparation method of the foam system includes the following steps: adding foaming agent and foam stabilizer magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, and stirring at a high speed of 2000-5000r/min for 1-3min, that is have to.

Preferably, the emulsifier of the Pickering emulsion system includes magnetic nano-Fe3O4@SiO2 particles, surfactants and polymers.

Preferably, the polymer is selected from any one of polyacrylamide, xanthan gum, polyethylene glycol, sodium alginate, sclerodextran, and carboxymethyl cellulose.

Preferably, the surfactant is selected from any one of petroleum carboxylate, petroleum sulfonate, heavy alkylbenzene sulfonate, lignin sulfonate, and biological surfactants.

Preferably, the oil phase is selected from any one of kerosene, vegetable oil, white oil, gasoline and diesel oil.

Preferably, the preparation method of the magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: Dissolve sodium hydroxide in water to form a sodium hydroxide solution; mix equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed solution of iron salt; heat the sodium hydroxide solution to 60 -80°C, add the iron salt mixed solution dropwise into the sodium hydroxide solution, stop heating when the solution turns black, cool to room temperature, separate the black product generated by the reaction, wash with water, and dry to obtain _Fe3O4 nanoparticles _;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to form a colloidal solution, heat to 40-60°C, add Na ₂ SiO ₃ solution and H ₂ dropwise to the colloidal solution Control the pH of the SiO ₄ solution to 9-10, react for 3-4 hours, raise the temperature to 80-95°C and react for 1-2 hours, wash with deionized water under the action of a magnet, add the cleaned particles to boiling water and boil, and deionize water under the action of a magnet Washing and vacuum drying to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: Add aminosilane coupling agent to ethanol aqueous solution for hydrolysis, then add Fe ₃ O ₄ @SiO ₂ particles to the hydrolyzed solution, stir and react, wash with absolute ethanol under the action of a magnet, and dry to obtain alkanes Base Fe ₃ O ₄ @SiO ₂ particles;

4) Grafting: Mix the mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, stir and emulsify at 70-80°C to obtain an emulsion, cool until the paraffin solidifies, and deionize the water under the action of a magnet Washing and drying to obtain paraffin emulsion; mixing paraffin emulsion with perfluorooctanoic acid solution, reacting at room temperature, washing with ethanol under the action of a magnet, and drying to obtain.

As preferably, the preparation method of described Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form a water phase solution, and disperse evenly by ultrasonic; take the oil phase and add the water phase solution to form an oil-water system with upper and lower layers, and homogenize in a homogenizer A homogeneously mixed oil-water system is obtained, let it stand at room temperature, and then separate the precipitated oil phase and water phase.

In the present invention, Fe ₃ O ₄ nanoparticles are firstly prepared by a redox method, and the Fe ₃ O ₄ nanoparticles are used as an emulsifier, which can have a better emulsifying effect on the solution. In addition, the present invention uses Fe ₃ O ₄ nanoparticles as a carrier to cover a layer of silicon dioxide on the surface of Fe ₃ O ₄ nanoparticles through Na ₂ SiO ₃ hydrolysis to obtain Fe ₃ O ₄ @SiO ₂ particles, and then to Fe ₃ O ₄ @SiO ₂ particles were subjected to alkylation treatment, so that the surface of the inorganic Fe ₃ O ₄ @SiO ₂ particles was loaded with amino active groups, and the amino active groups were used to react with paraffin and perfluorooctanoic acid respectively, and the paraffin and perfluorooctanoic acid were grafted onto Fe ₃ O ₄ @SiO _{2 On} the surface of the particles, hydrophilic and lipophilic magnetic nanoparticles are formed. The emulsion formed by the configuration of the magnetic nanoparticles has good stability under high temperature and high salt conditions, and maintains the oil displacement effect of the emulsion system.

Therefore, the present invention has the following beneficial effects: (1) suitable for crude oil with a viscosity lower than 5000mPa·s, suitable for a wide range of crude oil viscosity, and greatly improved recovery for high-viscosity heavy oil reservoirs; (2) milky The liquid system has strong stability and can be applied to high-temperature and high-salt environments.

Detailed ways

The technical solutions of the present invention will be further described below through specific examples.

In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or commonly used in the field. The methods in the examples, unless otherwise specified, are conventional methods in the field.

Example 1

The preparation method of magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: dissolving sodium hydroxide in water to form a sodium hydroxide solution with a concentration of 80g/L; mixing equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed iron salt solution, FeCl ₃ solution It is a mixed aqueous solution of FeCl ₃ and HCl, the concentration of FeCl ₃ is 2mol/L, and the concentration of HCl is 0.5mol/L; the FeSO ₄ solution is a mixed aqueous solution of FeSO ₄ and HCl; the concentration of FeSO ₄ is 1mol/L; the concentration of HCl is 0.5mol /L; heat the sodium hydroxide solution to 70°C, dropwise add the iron salt mixed solution to the sodium hydroxide solution, the amount of the iron salt mixed solution added is 15wt% of the sodium hydroxide solution, and stop heating when the solution turns black , cooled to room temperature, separated the black product generated by the reaction, washed with water and dried to obtain Fe ₃ O ₄ nanoparticles;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to form a colloidal solution with a concentration of 25g/L, heat to 50°C, and drop Na ₂ SiO with a concentration of 2mol/L into the colloidal solution ₃ solution and at the same time dropwise add a concentration of 0.4mol/L H ₂ SiO ₄ solution to control the pH to 9.5, the mass ratio of Na ₂ SiO ₃ to Fe ₃ O ₄ nanoparticles is 1:0.5, react for 3h, heat up to 90°C and react for 1h , wash with deionized water under the action of a magnet, add the cleaned particles into boiling water to boil, wash with deionized water under the action of a magnet, and dry in vacuum to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: add aminosilane coupling agent KH-550 into ethanol aqueous solution for hydrolysis, the volume ratio of aminosilane coupling agent KH _- 550 to absolute ethanol is 1:30, and then add Fe3 to the hydrolyzate O ₄ @SiO ₂ particles, the initial concentration of Fe ₃ O ₄ @SiO ₂ particles in the hydrolyzed solution is 10g/L, stirred and reacted, washed with absolute ethanol under the action of a magnet, and dried to obtain alkylated Fe ₃ O ₄ @SiO ₂ pellets;

4) Grafting: a mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, the concentration of alkylated Fe ₃ O ₄ @SiO ₂ particles in the mixed solution is 30g/L, The concentration of paraffin in the mixed liquid is 100g/L. Stir and emulsify at 75°C to obtain an emulsion, cool until the paraffin is solidified, wash with deionized water under the action of a magnet, and dry to obtain paraffin emulsion; mix the paraffin emulsion with PFOA solution, paraffin wax The mass ratio of emulsion droplets to perfluorooctanoic acid is 1:0.1, react at room temperature, wash with ethanol under the action of a magnet, and dry to obtain the product.

The emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and foaming agent sodium lauryl sulfate; the preparation method of foam system comprises the following steps: mixing the foaming agent sodium lauryl sulfate and foam stabilizer Add magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, the concentration of surfactant is 0.2g/L, the concentration of magnetic nano-Fe ₃ O ₄ @SiO ₂ particles is 2g/L, stir at 3000r/min for 2min, Instantly.

The emulsifiers of the Pickering emulsion system include magnetic nano-Fe3O4@SiO2 particles, surfactant petroleum carboxylate and polymer polyacrylamide. The preparation method of Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form an aqueous phase solution. The concentration of magnetic nano _{- Fe3O4} @ _SiO2 particles in the aqueous phase solution is 2g/L, and the concentration of surfactant is 0.2g/L, the concentration of the polymer is 1000mg/L; ultrasonic dispersion is uniform; kerosene is added to the water phase solution to form a layered oil-water system, the volume ratio of the water phase and the oil phase is 1:4, as for the homogenizer Homogenize to obtain a uniformly mixed oil-water system, let it stand at room temperature, and then separate the precipitated oil phase and water phase to obtain the product.

The oil displacement method suitable for heavy oil reservoirs, the Pickering emulsion system and the foam system are alternately displaced by slug combination three times (Pickering emulsion system flooding first, then foam system flooding, then Pickering emulsion system flooding); The total slug injection volume of Pickering emulsion system and foam system is 0.6PV; the slug injection volume of Pickering emulsion system is 0.4PV, and the slug injection volume of foam system is 0.2PV.

Example 2

The preparation method of magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: dissolving sodium hydroxide in water to form a sodium hydroxide solution with a concentration of 80g/L; mixing equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed iron salt solution, FeCl ₃ solution It is a mixed aqueous solution of FeCl ₃ and HCl, the concentration of FeCl ₃ is 2mol/L, and the concentration of HCl is 0.5mol/L; the FeSO ₄ solution is a mixed aqueous solution of FeSO ₄ and HCl; the concentration of FeSO ₄ is 1mol/L; the concentration of HCl is 0.5mol /L; heat the sodium hydroxide solution to 75°C, dropwise add the iron salt mixed solution to the sodium hydroxide solution, the amount of the iron salt mixed solution added is 15wt% of the sodium hydroxide solution, stop heating until the solution turns black , cooled to room temperature, separated the black product generated by the reaction, washed with water and dried to obtain Fe ₃ O ₄ nanoparticles;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to prepare a colloidal solution with a concentration of 25g/L, heat to 55°C, and drop Na ₂ SiO with a concentration of 2mol/L into the colloidal solution ₃ solution and at the same time dropwise add a concentration of 0.4mol/L H ₂ SiO ₄ solution to control the pH to 10, the mass ratio of Na ₂ SiO ₃ to Fe ₃ O ₄ nanoparticles is 1:0.5, react for 4h, heat up to 95°C and react for 1h , wash with deionized water under the action of a magnet, add the cleaned particles into boiling water to boil, wash with deionized water under the action of a magnet, and dry in vacuum to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: add aminosilane coupling agent KH-550 into ethanol aqueous solution for hydrolysis, the volume ratio of aminosilane coupling agent KH _- 550 to absolute ethanol is 1:30, and then add Fe3 to the hydrolyzate O ₄ @SiO ₂ particles, the initial concentration of Fe ₃ O ₄ @SiO ₂ particles in the hydrolyzed solution is 10g/L, stirred and reacted, washed with absolute ethanol under the action of a magnet, and dried to obtain alkylated Fe ₃ O ₄ @SiO ₂ pellets;

4) Grafting: a mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, the concentration of alkylated Fe ₃ O ₄ @SiO ₂ particles in the mixed solution is 30g/L, The concentration of paraffin in the mixed solution is 100g/L. Stir and emulsify at 80°C to obtain an emulsion, cool until the paraffin solidifies, wash with deionized water under the action of a magnet, and dry to obtain paraffin emulsion; mix the paraffin emulsion with PFOA solution, and the paraffin wax The mass ratio of emulsion droplets to perfluorooctanoic acid is 1:0.1, react at room temperature, wash with ethanol under the action of a magnet, and dry to obtain the product.

The emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and foaming agent sodium lauryl sulfate; the preparation method of foam system comprises the following steps: mixing the foaming agent sodium lauryl sulfate and foam stabilizer Add magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, the concentration of surfactant is 0.3g/L, the concentration of magnetic nano-Fe ₃ O ₄ @SiO ₂ particles is 2g/L, stir at 4000r/min for 3min, Instantly.

The emulsifiers of the Pickering emulsion system include magnetic nano-Fe3O4@SiO2 particles, surfactant petroleum sulfonate and polymer xanthan gum. The preparation method of Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form an aqueous phase solution. The concentration of magnetic nano _{- Fe3O4} @ _SiO2 particles in the aqueous phase solution is 2.5g/L, and the concentration of surfactant The concentration of the polymer is 0.3g/L, the concentration of the polymer is 1200mg/L; the ultrasonic dispersion is uniform; the vegetable oil is added to the water phase solution to form a layered oil-water system, the volume ratio of the water phase and the oil phase is 1:4, as for the homogenizer Homogenize in a medium to obtain a uniformly mixed oil-water system, let it stand at room temperature, and then separate the precipitated oil phase and water phase to obtain.

The oil displacement method suitable for heavy oil reservoirs, the Pickering emulsion system and the foam system are alternately displaced by slug combination four times (Pickering emulsion system flooding-foam system flooding-Pickering emulsion system flooding-foam system flooding) The total slug injection volume of Pickering emulsion system and foam system is 0.8PV; the slug injection volume of Pickering emulsion system is 0.4PV, and the slug injection volume of foam system is 0.4PV.

Example 3

The preparation method of magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: dissolving sodium hydroxide in water to form a sodium hydroxide solution with a concentration of 80g/L; mixing equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed iron salt solution, FeCl ₃ solution It is a mixed aqueous solution of FeCl ₃ and HCl, the concentration of FeCl ₃ is 2mol/L, and the concentration of HCl is 0.5mol/L; the FeSO ₄ solution is a mixed aqueous solution of FeSO ₄ and HCl; the concentration of FeSO ₄ is 1mol/L; the concentration of HCl is 0.5mol /L; heat the sodium hydroxide solution to 65°C, dropwise add the iron salt mixed solution to the sodium hydroxide solution, the amount of the iron salt mixed solution added is 15wt% of the sodium hydroxide solution, stop heating until the solution turns black , cooled to room temperature, separated the black product generated by the reaction, washed with water and dried to obtain Fe ₃ O ₄ nanoparticles;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to prepare a colloidal solution with a concentration of 25g/L, heat to 45°C, and drop Na ₂ SiO with a concentration of 2mol/L into the colloidal solution ₃ solution and at the same time dropwise add the concentration of 0.4mol/L H ₂ SiO ₄ solution to control the pH to 9, the mass ratio of Na ₂ SiO ₃ to Fe ₃ O ₄ nanoparticles is 1:0.5, react for 3h, heat up to 85°C and react for 1h , wash with deionized water under the action of a magnet, add the cleaned particles into boiling water to boil, wash with deionized water under the action of a magnet, and dry in vacuum to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: add aminosilane coupling agent KH-550 into ethanol aqueous solution for hydrolysis, the volume ratio of aminosilane coupling agent KH _- 550 to absolute ethanol is 1:30, and then add Fe3 to the hydrolyzate O ₄ @SiO ₂ particles, the initial concentration of Fe ₃ O ₄ @SiO ₂ particles in the hydrolyzed solution is 10g/L, stirred and reacted, washed with absolute ethanol under the action of a magnet, and dried to obtain alkylated Fe ₃ O ₄ @SiO ₂ pellets;

4) Grafting: a mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, the concentration of alkylated Fe ₃ O ₄ @SiO ₂ particles in the mixed solution is 30g/L, The concentration of paraffin in the mixed solution is 100g/L. Stir and emulsify at 70°C to obtain an emulsion, cool until the paraffin is solidified, wash with deionized water under the action of a magnet, and dry to obtain paraffin emulsion; mix the paraffin emulsion with PFOA solution, paraffin wax The mass ratio of emulsion droplets to perfluorooctanoic acid is 1:0.1, react at room temperature, wash with ethanol under the action of a magnet, and dry to obtain the product.

The emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and foaming agent sodium lauryl sulfate; the preparation method of foam system comprises the following steps: mixing the foaming agent sodium lauryl sulfate and foam stabilizer Add magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, the concentration of surfactant is 0.15g/L, the concentration of magnetic nano-Fe ₃ O ₄ @SiO ₂ particles is 1g/L, stir at 3000r/min for 2min, Instantly.

The emulsifiers of the Pickering emulsion system include magnetic nano-Fe3O4@SiO2 particles, surfactant heavy alkylbenzene sulfonate and polymer polyethylene glycol. The preparation method of Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form an aqueous phase solution. The concentration of magnetic nano _{- Fe3O4} @ _SiO2 particles in the aqueous phase solution is 1g/L, and the concentration of surfactant is 0.15g/L, the concentration of the polymer is 800mg/L; ultrasonic dispersion is uniform; take white oil and add water phase solution to form an oil-water system with upper and lower layers. The volume ratio of water phase and oil phase is 1:3. As for the homogenizer Homogenize in a medium to obtain a uniformly mixed oil-water system, let it stand at room temperature, and then separate the precipitated oil phase and water phase to obtain.

The oil displacement method suitable for heavy oil reservoirs, the Pickering emulsion system and the foam system are alternately displaced twice in a slug combination (first the Pickering emulsion system drives oil, then the foam system drives oil); the Pickering emulsion system and the foam system drive oil twice; The total slug injection volume of the foam system is 0.4PV; the slug injection volume of the Pickering emulsion system is 0.2PV, and the slug injection volume of the foam system is 0.2PV.

Example 4

The preparation method of magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: dissolving sodium hydroxide in water to form a sodium hydroxide solution with a concentration of 80g/L; mixing equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed iron salt solution, FeCl ₃ solution It is a mixed aqueous solution of FeCl ₃ and HCl, the concentration of FeCl ₃ is 2mol/L, and the concentration of HCl is 0.5mol/L; the FeSO ₄ solution is a mixed aqueous solution of FeSO ₄ and HCl; the concentration of FeSO ₄ is 1mol/L; the concentration of HCl is 0.5mol /L; heat the sodium hydroxide solution to 80°C, dropwise add the iron salt mixed solution to the sodium hydroxide solution, the amount of the iron salt mixed solution added is 15wt% of the sodium hydroxide solution, stop heating until the solution turns black , cooled to room temperature, separated the black product generated by the reaction, washed with water and dried to obtain Fe ₃ O ₄ nanoparticles;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to prepare a colloidal solution with a concentration of 25g/L, heat to 60°C, and add Na ₂ SiO with a concentration of 2mol/L to the colloidal solution dropwise ₃ solution and at the same time dropwise add a concentration of 0.4mol/L H ₂ SiO ₄ solution to control the pH to 10, the mass ratio of Na ₂ SiO ₃ to Fe ₃ O ₄ nanoparticles is 1:0.5, react for 4h, heat up to 95°C and react for 1h , wash with deionized water under the action of a magnet, add the cleaned particles into boiling water to boil, wash with deionized water under the action of a magnet, and dry in vacuum to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: add aminosilane coupling agent KH-550 into ethanol aqueous solution for hydrolysis, the volume ratio of aminosilane coupling agent KH _- 550 to absolute ethanol is 1:30, and then add Fe3 to the hydrolyzate O ₄ @SiO ₂ particles, the initial concentration of Fe ₃ O ₄ @SiO ₂ particles in the hydrolyzed solution is 10g/L, stirred and reacted, washed with absolute ethanol under the action of a magnet, and dried to obtain alkylated Fe ₃ O ₄ @SiO ₂ pellets;

4) Grafting: a mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, the concentration of alkylated Fe ₃ O ₄ @SiO ₂ particles in the mixed solution is 30g/L, The concentration of paraffin in the mixed solution is 100g/L. Stir and emulsify at 80°C to obtain an emulsion, cool until the paraffin solidifies, wash with deionized water under the action of a magnet, and dry to obtain paraffin emulsion; mix the paraffin emulsion with PFOA solution, and the paraffin wax The mass ratio of emulsion droplets to perfluorooctanoic acid is 1:0.1, react at room temperature, wash with ethanol under the action of a magnet, and dry to obtain the product.

The emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and foaming agent sodium lauryl sulfate; the preparation method of foam system comprises the following steps: mixing the foaming agent sodium lauryl sulfate and foam stabilizer Add magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, the concentration of surfactant is 0.3g/L, the concentration of magnetic nano-Fe ₃ O ₄ @SiO ₂ particles is 3g/L, stir at 5000r/min for 1min, Instantly.

The emulsifiers of the Pickering emulsion system include magnetic nano-Fe3O4@SiO2 particles, surfactant lignosulfonate and polymer sodium alginate. The preparation method of Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form an aqueous phase solution. The concentration of magnetic nano _{- Fe3O4} @ _SiO2 particles in the aqueous phase solution is 3g/L, and the concentration of surfactant is 0.3g/L, the concentration of the polymer is 1500mg/L; the ultrasonic dispersion is uniform; take gasoline and add the water phase solution to form a layered oil-water system, the volume ratio of the water phase and the oil phase is 1:5, as for the homogenizer Homogenize to obtain a uniformly mixed oil-water system, let it stand at room temperature, and then separate the precipitated oil phase and water phase to obtain the product.

The oil displacement method suitable for heavy oil reservoirs, the Pickering emulsion system and the foam system are alternately displaced by slug combination four times (Pickering emulsion system flooding-foam system flooding-Pickering emulsion system flooding-foam system flooding) The total slug injection volume of Pickering emulsion system and foam system is 0.8PV; the slug injection volume of Pickering emulsion system is 0.4PV, and the slug injection volume of foam system is 0.4PV.

Example 5

The preparation method of magnetic nano Fe3O4@SiO2 particles comprises the following steps:

1) Preparation of Fe ₃ O ₄ nanoparticles: dissolving sodium hydroxide in water to form a sodium hydroxide solution with a concentration of 80g/L; mixing equal volumes of FeCl ₃ solution and FeSO ₄ solution to obtain a mixed iron salt solution, FeCl ₃ solution It is a mixed aqueous solution of FeCl ₃ and HCl, the concentration of FeCl ₃ is 2mol/L, and the concentration of HCl is 0.5mol/L; the FeSO ₄ solution is a mixed aqueous solution of FeSO ₄ and HCl; the concentration of FeSO ₄ is 1mol/L; the concentration of HCl is 0.5mol /L; heat the sodium hydroxide solution to 60°C, add the iron salt mixed solution dropwise to the sodium hydroxide solution, the amount of the iron salt mixed solution added is 15wt% of the sodium hydroxide solution, and stop heating when the solution turns black , cooled to room temperature, separated the black product generated by the reaction, washed with water and dried to obtain Fe ₃ O ₄ nanoparticles;

2) Preparation of Fe ₃ O ₄ @SiO ₂ particles: Add Fe ₃ O ₄ nanoparticles into water to form a colloidal solution with a concentration of 25g/L, heat to 40°C, and add Na ₂ SiO with a concentration of 2mol/L to the colloidal solution dropwise ₃ solution and at the same time drop the concentration of 0.4mol/L H ₂ SiO ₄ solution to control the pH to 9, the mass ratio of Na ₂ SiO ₃ and Fe ₃ O ₄ nanoparticles is 1:0.5, react for 3h, heat up to 80°C and react for 2h , wash with deionized water under the action of a magnet, add the cleaned particles into boiling water to boil, wash with deionized water under the action of a magnet, and dry in vacuum to obtain Fe ₃ O ₄ @SiO ₂ particles;

3) Alkylation treatment: add aminosilane coupling agent KH-550 into ethanol aqueous solution for hydrolysis, the volume ratio of aminosilane coupling agent KH _- 550 to absolute ethanol is 1:30, and then add Fe3 to the hydrolyzate O ₄ @SiO ₂ particles, the initial concentration of Fe ₃ O ₄ @SiO ₂ particles in the hydrolyzed solution is 10g/L, stirred and reacted, washed with absolute ethanol under the action of a magnet, and dried to obtain alkylated Fe ₃ O ₄ @SiO ₂ pellets;

4) Grafting: a mixture of alkylated Fe ₃ O ₄ @SiO ₂ particles, paraffin and deionized water, the concentration of alkylated Fe ₃ O ₄ @SiO ₂ particles in the mixed solution is 30g/L, The concentration of paraffin in the mixed solution is 100g/L. Stir and emulsify at 70°C to obtain an emulsion, cool until the paraffin is solidified, wash with deionized water under the action of a magnet, and dry to obtain paraffin emulsion; mix the paraffin emulsion with PFOA solution, paraffin wax The mass ratio of emulsion droplets to perfluorooctanoic acid is 1:0.1, react at room temperature, wash with ethanol under the action of a magnet, and dry to obtain the product.

The emulsifier of the foam system includes magnetic nano Fe ₃ O ₄ @SiO ₂ particles and foaming agent sodium lauryl sulfate; the preparation method of foam system comprises the following steps: mixing the foaming agent sodium lauryl sulfate and foam stabilizer Add magnetic nano-Fe ₃ O ₄ @SiO ₂ particles into deionized water, the concentration of surfactant is 0.1g/L, the concentration of magnetic nano-Fe ₃ O ₄ @SiO ₂ particles is 0.5g/L, stir at 2000r/min for 3min , that is.

The emulsifiers of the Pickering emulsion system include magnetic nano-Fe3O4@SiO2 particles, surfactant biosurfactant and polymer scleroglucan. The preparation method of Pickering emulsion system comprises the following steps:

Mix magnetic nano-Fe3O4@SiO2 particles, surfactants, polymers and deionized water to form an aqueous phase solution. The concentration of magnetic nano _{- Fe3O4} @ _SiO2 particles in the aqueous phase solution is 0.5g/L, and the concentration of surfactant The concentration of the polymer is 0.1g/L, the concentration of the polymer is 500mg/L; the ultrasonic dispersion is uniform; the diesel oil is added to the water phase solution to form a layered oil-water system, the volume ratio of the water phase and the oil phase is 1:3, as for the homogenizer Homogenize in a medium to obtain a uniformly mixed oil-water system, let it stand at room temperature, and then separate the precipitated oil phase and water phase to obtain.

The oil displacement method suitable for heavy oil reservoirs, the Pickering emulsion system and the foam system are alternately displaced twice in a slug combination (first the Pickering emulsion system drives oil, then the foam system drives oil); the Pickering emulsion system and the foam system drive oil twice; The total slug injection volume of the foam system is 0.4PV; the slug injection volume of the Pickering emulsion system is 0.3PV, and the slug injection volume of the foam system is 0.1PV.

Experimental test:

Select a core with a permeability of about 1000mD, vacuumize, saturate the formation water, weigh the wet weight, and calculate the porosity of the core; put the core into a holder, connect the pipeline, displace crude oil, create bound water, and age for 30 hours. Use formation water to displace the crude oil in the rock core until no oil comes out at the outlet, record the oil output at the outlet, and calculate the water flooding recovery; transfer a certain slug size of magnetic Pickering emulsion, after the injection is completed, transfer a certain slug Then inject formation water into the core of the rock until there is no oil at the outlet, stop the injection, record the oil output at the outlet, and calculate the enhanced oil recovery of the magnetic Pickering emulsion.

From the experimental data, it can be obtained that the present invention can drive oil with a viscosity as high as 4000mPa·s, and the enhanced oil recovery rate can be kept above 20%. High viscosity crude oil recovery.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the technical content disclosed above to make some changes or modify them into equivalent embodiments with equivalent changes, but as long as they do not depart from the technical solution of the present invention, the Technical Essence Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solution of the present invention.

Claims (10)

1. a kind of flooding method suitable for heavy crude reservoir, which is characterized in that by Pickering emulsion system and foam system With Segment combination models alternating the displacement of reservoir oil 2-4 times.

2. a kind of flooding method suitable for heavy crude reservoir according to claim 1, which is characterized in that described Pickering emulsion system and the total slug injection rate of foam system are 0.4-0.8PV.

3. a kind of flooding method suitable for heavy crude reservoir according to claim 1, which is characterized in that the foams The emulsifier of system includes magnetic Nano Fe₃O₄@SiO₂Particle and foaming agent.

4. a kind of flooding method suitable for heavy crude reservoir according to claim 1 or 3, which is characterized in that the foam The preparation method of system is the following steps are included: by foaming agent and foam stabilizer magnetic Nano Fe₃O₄@SiO₂Deionized water is added in particle In, with 2000-5000r/min high-speed stirred 1-3min to get.

5. a kind of flooding method suitable for heavy crude reservoir according to claim 1, which is characterized in that described The emulsifier of Pickering emulsion system includes magnetic Nano Fe3O4@SiO2 particle, surfactant and polymer.

6. a kind of flooding method suitable for heavy crude reservoir according to claim 5, which is characterized in that the polymer choosing From any one of polyacrylamide, xanthan gum, polyethylene glycol, sodium alginate, scleroglucan, carboxymethyl cellulose.

7. a kind of flooding method suitable for heavy crude reservoir according to claim 5, which is characterized in that the surface-active Agent appointing in petroleum carboxylate, petroleum sulfonate, heavy alkylbenzene sulfonate, lignosulfonates, biosurfactant It is a kind of.

8. a kind of flooding method suitable for heavy crude reservoir according to claim 1 or 5, which is characterized in that described The preparation method of Pickering emulsion system the following steps are included:

Magnetic Nano Fe3O4@SiO2 particle, surfactant, polymer and deionized water are mixed into composition aqueous phase solution, ultrasound It is uniformly dispersed；It takes oil to be added to the grease system that aqueous phase solution forms upper lower leaf, must be mixed as homogeneous is carried out in homogenizer Uniform grease system, is stored at room temperature, then divide isolated oil mutually and water phase to get.

9. a kind of flooding method suitable for heavy crude reservoir according to claim 8, which is characterized in that the oil is mutually selected from Any one of kerosene, vegetable oil, white oil, gasoline, diesel oil.

10. a kind of flooding method suitable for heavy crude reservoir according to claim 3 or 5, which is characterized in that the magnetism The preparation method of nanometer Fe_3O_4@SiO2 particle the following steps are included:

1) Fe₃O₄Nano particle preparation: sodium hydroxide solution is configured to by sodium hydroxide is soluble in water；By isometric FeCl₃It is molten Liquid and FeSO₄Solution mixes to obtain molysite mixed solution；Sodium hydroxide solution is heated to 60-80 DEG C, is dropwise mixed molysite molten Drop is added in sodium hydroxide solution, is stopped heating to solution blackening, is cooled to room temperature, the black product that separation reaction generates, By washing, drying and obtaining Fe₃O₄Nano particle；

2) Fe₃O₄@SiO₂Particle preparation: by Fe₃O₄Nano particle, which is added to the water, is configured to colloidal solution, is heated to 40-60 DEG C, to Na is added dropwise in colloidal solution₂SiO₃Simultaneously H is added dropwise in solution simultaneously₂SiO₄It is 9-10 that solution, which controls pH, reacts 3-4h, is warming up to 80-95 DEG C 1-2h is reacted again, in magnet effect deionised water cleaning, the particle after cleaning, which is added in boiling water, to be boiled, under magnet effect Deionized water cleaning, vacuum drying obtain Fe₃O₄@SiO₂Particle；

3) alkylation is handled: amino silicane coupling agent being added in ethanol water and is hydrolyzed, is then added into hydrolyzate Fe₃O₄@SiO₂Particle is stirred to react, the washes of absolute alcohol under magnet effect, so dry that be alkylated Fe₃O₄@SiO₂Particle；

4) it is grafted: Fe will be alkylated₃O₄@SiO₂The mixed liquor of particle, paraffin and deionized water mixing, stirs cream at 70-80 DEG C Change to obtain emulsion, be cooled to paraffin solidification, magnet acts on deionised water cleaning, dry paraffin emulsion droplet；By paraffin emulsion droplet with The mixing of perfluoro caprylic acid solution, room temperature reaction, magnet act on lower ethyl alcohol cleaning, it is dry to get.