CN118703186A - A nano-imbibition oil displacement agent for improving oil recovery - Google Patents

Abstract

The invention belongs to the technical field of oil displacement agents for oil exploitation, and discloses a nano imbibition oil displacement agent for improving recovery ratio, which comprises 100 parts by weight of cationic acrylamide copolymer and 5-25 parts by weight of sodium carboxylate modified nano silicon dioxide; after organically modifying, the nano silicon dioxide is uniformly dispersed in the oil displacement agent solution of the cationic acrylamide copolymer, and the solution shows rheological property of nano fluid, has a certain viscosity increasing effect, and is beneficial to improving the apparent viscosity of the oil displacement agent solution. The nano silicon dioxide contains a large amount of carboxylate, can form acid-base interaction with quaternary ammonium salt in the cationic acrylamide copolymer to generate a betaine group, and has good shearing resistance. The total recovery ratio of the nano imbibition oil displacement agent reaches 47.6-53.5%, and the nano imbibition oil displacement agent has excellent oil displacement efficiency.

Description

A nano-imbibition oil displacement agent for improving oil recovery

Technical Field

The invention belongs to the technical field of oil reservoir exploitation oil displacement agent, in particular to a nano-imbibition oil displacement agent for improving oil recovery.

Background Art

At present, low-permeability reservoirs account for a large proportion of my country's oil reservoirs. The method of exploiting low-permeability reservoirs is water phase displacement, which increases the formation pressure by injecting water, thereby increasing the oil recovery rate. However, with the continuous increase in the degree of exploitation, the oil layer pressure drops rapidly, and the water content of the produced fluid increases rapidly, which seriously affects the oil recovery rate.

Enhanced oil recovery using chemical flooding is an effective method to improve crude oil recovery. Among them, polymer flooding has the advantages of high recovery efficiency and low cost, and has great development and application prospects. Polyacrylamide oil displacement agents are the most widely used; copolymerization of acrylamide with monomers such as acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, and N-allylmorpholine is conducive to improving the temperature resistance and shear resistance of polyacrylamide oil displacement agents, so that the oil displacement agents can meet the actual application in complex oil reservoir environments such as high temperature and high salt.

The nanofluid oil displacement agent system has the properties of temperature resistance, salt resistance, improved polymer swelling, etc., and the nanofluid oil displacement agent system can control the rheology of the injected fluid, which is beneficial to improve the recovery rate. Chinese invention patent CN113717709B discloses a nanofluid imbibition agent and its preparation method and application, with amphiphilic grafted modified nano silica particles, betaine type surfactant, non-ionic surfactant, etc. as the main components of the nanofluid imbibition agent, which can change the oil-water interface properties and increase the imbibition replacement rate of the gel-breaking liquid to the tight oil, but the nanofluid imbibition agent does not show good high temperature resistance and shear resistance.

Summary of the invention

(I) Technical problems to be solved: The present invention provides a nano-imbibition oil-displacing agent for improving oil recovery, which solves the problems of poor high temperature resistance, poor shear resistance and low oil recovery of polyacrylamide-based oil-displacing agents.

(II) Technical solution: A nano-imbibition oil displacement agent for improving oil recovery, comprising 100 parts by weight of a cationic acrylamide copolymer and 5-25 parts by weight of sodium carboxylate-modified nano-silica.

The preparation method of the cationic acrylamide copolymer is as follows: water, acrylamide, acrylic acid, 4-(dimethylalkylammonium chloride)phenylacrylamide, and emulsifier OP10 are added to a reaction container, and then the temperature is raised to the reaction temperature, and ammonium persulfate and sodium bisulfite are added in a nitrogen atmosphere, and after the reaction, the mixture is cooled, ethanol is added to precipitate, and the mixture is extracted, dried, and crushed to obtain the cationic acrylamide copolymer.

4-(Dimethylalkylammonium chloride)phenylacrylamide has the structural formula (I) as follows:

Formula (I).

The preparation method of sodium carboxylate modified nano-silica is as follows: hexamethylene diisocyanate is used to modify the surface of nano-silica to obtain HDI modified silica; then the HDI modified silica is added to a reaction container, a toluene solvent is added, stirred and dispersed, and DL-glutamic acid is added. After the reaction, sodium hydroxide is added to adjust the pH to 9-10, centrifugation is performed, washing is performed with water and ethanol, and drying is performed to obtain sodium carboxylate modified nano-silica.

Preferably, in the preparation method of the cationic acrylamide copolymer, the mass ratio of acrylamide, acrylic acid, and 4-(dimethylalkylammonium chloride)phenylacrylamide is 100:(70-100):(3-10).

Preferably, in the preparation method of the cationic acrylamide copolymer, the reaction temperature is 50-60° C. and the reaction time is 5-7 h.

Preferably, in the preparation method of sodium carboxylate-modified nano-silica, the mass ratio of HDI-modified silica to DL-glutamic acid is 100:(150-400).

Preferably, in the method for preparing sodium carboxylate-modified nano-silicon dioxide, the reaction temperature is 60-80° C. and the reaction time is 4-8 hours.

Preferably, the preparation method of 4-(dimethylalkylammonium chloride)phenylacrylamide is as follows:

Step (1), in an ice bath, add dichloromethane, 4-(dimethylaminomethyl)aniline, triethylamine, and acryloyl chloride to a reaction vessel, stir and react at room temperature for 4-6 hours, and distill under reduced pressure. The product is washed with saturated sodium chloride and then recrystallized from ethanol to obtain 4-(dimethylaminomethyl)phenylacrylamide.

Step (2), add acetonitrile, 4-(dimethylaminomethyl)phenylacrylamide and benzyl chloride in a mass ratio of 100:(60-82) to a reaction vessel equipped with a condenser reflux tube, raise the temperature to 75-85°C, react for 24-36 hours, distill under reduced pressure, wash the product with petroleum ether, and then recrystallize in ethanol to obtain 4-(dimethylalkylammonium chloride)phenylacrylamide.

Preferably, in step (1), the mass ratio of 4-(dimethylaminomethyl)aniline, triethylamine and acryloyl chloride is 100:(66-75):(60-70).

(III) Technical effect: The present invention uses cationic acrylamide copolymer and sodium carboxylate-modified nano-silica as components of the oil displacement agent, wherein 4-(dimethylalkylammonium chloride)phenylacrylamide is used as a functional monomer to undergo polymerization reaction with acrylamide and acrylic acid, and multiple benzene ring structures are introduced into the molecular chain of the acrylamide copolymer, which can improve the structural stability of the polymer at high temperatures, improve the temperature resistance of the oil displacement system, and still have a high apparent viscosity at high temperatures. In addition, 4-(dimethylalkylammonium chloride)phenylacrylamide contains an amide group and has good hydrophilicity. After polymerization, the hydrophilicity and water solubility of the acrylamide copolymer will not be affected by the introduction of the benzene ring structure.

After being organically modified, the nano silicon dioxide of the present invention is uniformly dispersed in the oil displacement agent solution of the cationic acrylamide copolymer, and exhibits the rheological properties of nanofluids in the solution, has a certain viscosity-increasing effect, and is conducive to improving the apparent viscosity of the oil displacement agent solution. In addition, the nano silicon dioxide contains a large amount of carboxylate, and its carboxylate anion (COO ^- ) forms an acid-base interaction with the quaternary ammonium salt N ⁺ cation in the cationic acrylamide copolymer to generate a betaine group, which has good shear resistance. At a high shear rate, it still has a high apparent viscosity.

The present invention uses cationic acrylamide copolymer and sodium carboxylate modified nano silicon dioxide as components of the nano-infiltration oil displacement agent, and the total recovery rate after the secondary oil displacement agent solution is flooded reaches 47.6-53.5%, showing excellent oil displacement efficiency. It has good practical application in the field of chemical flooding enhanced oil recovery and oil reservoir exploitation.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with specific embodiments and comparative examples to help those skilled in the art have a more complete, accurate and in-depth understanding of the technical solution of the present invention.

Preparation method of HDI modified silica: add 30 mL toluene, 1 g nano-silica, and 2.4 g hexamethylene diisocyanate into a reaction container, heat to 80°C, react for 12 hours, centrifuge, wash with toluene, and dry to obtain HDI modified silica; the reaction formula is as follows:

Example 1

(1) Add 40 mL of toluene solvent and 1 g of HDI-modified silica to a reaction vessel, stir and disperse, then add 4 g of DL-glutamic acid, heat to 60°C, stir and react for 8 hours, add sodium hydroxide to adjust the pH to 9, centrifuge, wash with water and ethanol, and dry to obtain sodium carboxylate-modified nano-silica. The reaction formula is as follows:

(2) In an ice bath, add 40 mL of dichloromethane, 4 g of 4-(dimethylaminomethyl)aniline, 2.64 g of triethylamine, and 2.8 g of acryloyl chloride to the reaction vessel, stir and react at room temperature for 4 h, distill under reduced pressure, wash the product with saturated sodium chloride, and then recrystallize in ethanol to obtain 4-(dimethylaminomethyl)phenylacrylamide. The reaction formula is as follows:

(3) Add 80 mL of acetonitrile, 5 g of 4-(dimethylaminomethyl)phenylacrylamide, and 4.1 g of benzyl chloride to a reaction vessel equipped with a condenser reflux tube, heat to 75°C, stir and react for 24 hours, distill under reduced pressure, wash the product with petroleum ether, and then recrystallize in ethanol to obtain 4-(dimethylalkylammonium chloride)phenylacrylamide. The reaction formula is as follows:

(4) Add 90 mL of water, 10 g of acrylamide, 7 g of acrylic acid, 0.5 g of 4-(dimethylalkylammonium chloride)phenylacrylamide, and 0.3 g of emulsifier OP10 to a reaction container, then heat to 60°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 5 h, cool, add ethanol to precipitate, extract, dry, and pulverize to obtain a cationic acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of cationic acrylamide copolymer and 0.05g of sodium carboxylate-modified nano-silica.

Example 2

(1) Add 30 mL of toluene solvent and 1 g of HDI-modified silica into a reaction container, stir and disperse, then add 3.2 g of DL-glutamic acid, heat to 70°C, stir and react for 5 h, add sodium hydroxide to adjust the pH to 9, centrifuge, wash with water and ethanol, and dry to obtain sodium carboxylate-modified nano-silica.

(2) In an ice bath, add 50 mL of dichloromethane, 4 g of 4-(dimethylaminomethyl)aniline, 2.64 g of triethylamine, and 2.4 g of acryloyl chloride to a reaction vessel, stir and react at room temperature for 6 h, and distill under reduced pressure. The product is washed with saturated sodium chloride and then recrystallized from ethanol to obtain 4-(dimethylaminomethyl)phenylacrylamide.

(3) Add 60 mL of acetonitrile, 5 g of 4-(dimethylaminomethyl)phenylacrylamide, and 3 g of benzyl chloride to a reaction vessel equipped with a condenser reflux tube, raise the temperature to 85°C, stir and react for 24 hours, and distill under reduced pressure. The product is washed with petroleum ether and then recrystallized in ethanol to obtain 4-(dimethylalkylammonium chloride)phenylacrylamide.

(4) Add 90 mL of water, 10 g of acrylamide, 8 g of acrylic acid, 0.3 g of 4-(dimethylalkylammonium chloride)phenylacrylamide, and 0.28 g of emulsifier OP10 to a reaction container, then heat to 60°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 5 h, cool, add ethanol to precipitate, extract, dry, and pulverize to obtain a cationic acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of cationic acrylamide copolymer and 0.12g of sodium carboxylate-modified nano-silica.

Example 3

(1) Add 30 mL of toluene solvent and 1 g of HDI-modified silica into a reaction container, stir and disperse, then add 2.4 g of DL-glutamic acid, heat to 60°C, stir and react for 6 hours, add sodium hydroxide to adjust the pH to 10, centrifuge, wash with water and ethanol, and dry to obtain sodium carboxylate-modified nano-silica.

(2) Prepare 4-(dimethylalkylammonium chloride)phenylacrylamide according to the method of Example 1.

(3) Add 100 mL of water, 10 g of acrylamide, 8 g of acrylic acid, 1 g of 4-(dimethylalkylammonium chloride)phenylacrylamide, and 0.3 g of emulsifier OP10 to a reaction container, then heat to 60°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 6 h, cool, add ethanol to precipitate, extract, dry, and pulverize to obtain a cationic acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of cationic acrylamide copolymer and 0.18g of sodium carboxylate-modified nano-silica.

Example 4

(1) Add 30 mL of toluene solvent and 1 g of HDI-modified silica into a reaction container, stir and disperse, then add 1.5 g of DL-glutamic acid, heat to 80°C, stir and react for 4 h, add sodium hydroxide to adjust the pH to 9, centrifuge, wash with water and ethanol, and dry to obtain sodium carboxylate-modified nano-silica.

(2) Prepare 4-(dimethylalkylammonium chloride)phenylacrylamide according to the method of Example 1.

(3) Add 90 mL of water, 10 g of acrylamide, 7 g of acrylic acid, 0.5 g of 4-(dimethylalkylammonium chloride)phenylacrylamide, and 0.28 g of emulsifier OP10 to a reaction vessel, then heat to 50°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 7 h, cool, add ethanol to precipitate, extract, dry, and pulverize to obtain a cationic acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of cationic acrylamide copolymer and 0.25g of sodium carboxylate-modified nano-silica.

Comparative Example 1

(1) Prepare a cationic acrylamide copolymer according to the method of Example 1.

The imbibition oil displacement agent for enhancing oil recovery is composed of 1g of cationic acrylamide copolymer.

Comparative Example 2

(1) Prepare a cationic acrylamide copolymer according to the method of Example 1.

The nano-imbibition oil displacement agent for enhancing oil recovery is composed of 1 g of cationic acrylamide copolymer and 0.05 g of HDI-modified silica.

Comparative Example 3

(1) Add 90 mL of water, 10 g of acrylamide, 7 g of acrylic acid, and 0.3 g of emulsifier OP10 to a reaction container, then heat to 60°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 5 h, cool, add ethanol to precipitate, extract, dry, and crush to obtain an acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of acrylamide copolymer and 0.05g of sodium carboxylate-modified nano-silica.

Comparative Example 4

(1) Add 90 mL of water, 10 g of acrylamide, 7 g of acrylic acid, 0.5 g of dimethyldiallylammonium chloride, and 0.3 g of emulsifier OP10 to a reaction container, then heat to 60°C, add 30 mg of ammonium persulfate and 30 mg of sodium bisulfite in a nitrogen atmosphere, react for 5 h, cool, add ethanol to precipitate, extract, dry, and crush to obtain a cationic acrylamide copolymer.

The nano-imbibition oil displacement agent for improving oil recovery is composed of 1g of cationic acrylamide copolymer and 0.05g of sodium carboxylate-modified nano-silica.

The nano-imbibition oil displacement agent for enhanced oil recovery was added to 2L of formation water (mineralization of 14692mg/L) to prepare an oil displacement agent solution, which was heated to 25-85°C and the apparent viscosity of the oil displacement agent solution was tested using a rheometer at a shear rate of 170s ^-1 . The test results are shown in Table 1.

Table 1 Temperature resistance test of nano-imbibition oil displacement agent

The apparent viscosity of the oil displacement agent solution was tested by a rheometer at a temperature of 25°C and a shear rate of 400-1000s ^-1 . The test results are shown in Table 2.

Table 2 Shear resistance test of nano-imbibition oil displacement agent

As shown in Table 1 and Table 2, embodiment 1-4 is with cationic acrylamide copolymer, sodium carboxylate modified nano silicon dioxide as the composition of oil displacement agent, has the characteristics of high apparent viscosity, and at high temperature, and under high shear rate, still has higher apparent viscosity, shows good temperature resistance and shear resistance. This is attributed to using 4-(dimethyl alkyl ammonium chloride) phenyl acrylamide as functional monomer, with acrylamide, acrylic acid carries out polymerization reaction, multiple benzene ring structures are introduced in the molecular chain of copolymer, can improve the structural stability of polymer at high temperature, improve the temperature resistance of oil displacement system. And 4-(dimethyl alkyl ammonium chloride) phenyl acrylamide contains amide group, has good hydrophilicity, can not affect the hydrophilicity and water solubility of acrylamide copolymer after polymerization because of introducing benzene ring structure.

At the same time, after organic modification, nano-silica is evenly dispersed in the oil displacement agent solution of cationic acrylamide copolymer, showing the rheological properties of nanofluids in the solution, with a certain viscosity-increasing effect, which is beneficial to improve the apparent viscosity of the oil displacement agent solution. In addition, its nano-silica contains a large amount of carboxylates, and its carboxylate anions ( ^COO- ) form acid-base interactions with quaternary ammonium salt N ⁺ cations in cationic acrylamide copolymers to generate betaine groups, which have good shear resistance.

The imbibition oil displacement agent of Comparative Example 1 does not contain nano-silicon dioxide and has a relatively low apparent viscosity.

The HDI-modified silica in Comparative Example 2 does not contain sodium carboxylate groups, cannot form acid-base interaction with the cationic acrylamide copolymer, and does not generate betaine groups. The shear resistance of the oil displacement agent is poor, and at high shear rates, the apparent viscosity of the oil displacement agent solution decreases significantly.

In Comparative Example 3, acrylamide copolymer was prepared without adding 4-(dimethylalkylammonium chloride)phenylacrylamide. The polymer did not contain a heat-resistant benzene ring structure, and the temperature resistance of the oil-displacing agent solution was poor. The apparent viscosity decreased significantly at high temperatures. The polymer did not contain quaternary ammonium salt cations and could not form acid-base interactions with the cationic acrylamide copolymer. No betaine groups were generated, which absorbed the shear resistance of the oil-displacing agent. At high shear rates, the apparent viscosity of the oil-displacing agent solution decreased significantly.

Comparative Example 4 uses dimethyldiallylammonium chloride as a cationic monomer to polymerize a cationic acrylamide copolymer. The polymer does not contain a heat-resistant benzene ring structure, the oil displacement agent solution has poor temperature resistance, and the apparent viscosity decreases significantly at high temperatures.

Core displacement and crude oil recovery test: Add nano-imbibition oil-displacing agent for enhanced oil recovery to 2L formation water (mineralization of 14692mg/L) to prepare oil-displacing agent solution; saturate the sand-filling pipe with formation water (mineralization of 14692mg/L) with crude oil for 72h, the inner diameter of the sand-filling pipe is 3cm, the length is 40cm, and the porosity is about 23.1%; then use formation water to displace oil to a water content of 95%, the injection rate is 0.2mL/mL, and the injection volume is 1PV; finally, use oil-displacing agent solution to displace oil to a water content of 95%, the injection rate is 0.2mL/mL, and the injection volume is 1PV. The test results are shown in Table 3.

Table 3 Core displacement and crude oil recovery test of nano-imbibition oil displacement agent

As shown in Table 3, in Examples 1-4, cationic acrylamide copolymer and sodium carboxylate-modified nano-silica are used as components of the oil displacement agent, and the total recovery rate after oil displacement by the secondary oil displacement agent solution reaches 47.6-53.5%, showing excellent oil displacement efficiency.

This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims (9)

1. A nano-infiltration oil displacement agent for improving oil recovery, characterized in that the nano-infiltration oil displacement agent comprises 100 parts by weight of cationic acrylamide copolymer and 5-25 parts by weight of sodium carboxylate modified nano-silica; The preparation method of the cationic acrylamide copolymer is as follows: water, acrylamide, acrylic acid, 4-(dimethylalkylammonium chloride)phenylacrylamide, and emulsifier OP10 are added to a reaction container; then the temperature is raised to the reaction temperature, and ammonium persulfate and sodium bisulfite are added in a nitrogen atmosphere, and after the reaction, the mixture is cooled, ethanol is added to precipitate, and the mixture is extracted, dried, and crushed to obtain the cationic acrylamide copolymer; The 4-(dimethylalkylammonium chloride)phenylacrylamide has the following structural formula (I): Formula (I); The preparation method of the sodium carboxylate modified nano-silica is as follows: hexamethylene diisocyanate is used to modify the surface of nano-silica to obtain HDI modified silica; then the HDI modified silica is added to a reaction container, a toluene solvent is added, stirred and dispersed, and DL-glutamic acid is added. After the reaction, sodium hydroxide is added to adjust the pH to 9-10, centrifugation is performed, washing is performed, and drying is performed to obtain the sodium carboxylate modified nano-silica. 2. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 1, characterized in that in the preparation method of the cationic acrylamide copolymer, the mass ratio of acrylamide, acrylic acid, and 4-(dimethylalkylammonium chloride)phenylacrylamide is 100:(70-100):(3-10). 3. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 1, characterized in that in the preparation method of the cationic acrylamide copolymer, the reaction temperature is 50-60°C and the reaction time is 5-7h. 4. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 1, characterized in that in the preparation method of the sodium carboxylate-modified nano-silica, the mass ratio of HDI-modified silica to DL-glutamic acid is 100:(150-400). 5. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 1, characterized in that in the preparation method of the sodium carboxylate-modified nano-silica, the reaction temperature is 60-80°C and the reaction time is 4-8h. 6. The nano-infiltration oil displacement agent for enhancing oil recovery according to claim 2, characterized in that the preparation method of the 4-(dimethylalkylammonium chloride)phenylacrylamide is as follows: Step (1), in an ice bath, add dichloromethane, 4-(dimethylaminomethyl)aniline, triethylamine, and acryloyl chloride to a reaction vessel, stir and react at room temperature for 4-6 hours, distill under reduced pressure, wash, and recrystallize to obtain 4-(dimethylaminomethyl)phenylacrylamide; Step (2), adding acetonitrile, 4-(dimethylaminomethyl)phenylacrylamide and benzyl chloride into a reaction vessel equipped with a condenser reflux tube, distilling under reduced pressure after the reaction, washing and recrystallizing to obtain 4-(dimethylalkylammonium chloride)phenylacrylamide. 7. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 6, characterized in that in the step (1), the mass ratio of 4-(dimethylaminomethyl)aniline, triethylamine and acryloyl chloride is 100:(66-75):(60-70). 8. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 6, characterized in that in the step (2), the mass ratio of 4-(dimethylaminomethyl)phenylacrylamide to benzyl chloride is 100:(60-82). 9. The nano-imbibition oil displacement agent for enhancing oil recovery according to claim 6, characterized in that in the step (2), the reaction temperature is 75-85°C and the reaction time is 24-36h.