CN116948622A - A nano-microemulsion oil displacing agent and its preparation method - Google Patents

Abstract

The invention provides a nano-microemulsion oil-displacing agent, which includes: oil and water. The volume ratio of the oil and water is 0.9:1. Based on the total mass of the oil and water, the nano-microemulsion oil-displacing agent Also includes: first surfactant, 1.0-1.5%; second surfactant, 1.0-1.5%; third surfactant, 0.4-0.8%; alkyl alcohol, 5%-10%; and chlorination Sodium, 3 to 6%; the first surfactant is an anionic surfactant, the second surfactant is a nonionic surfactant, and the third surfactant is an anionic polymer surfactant; Compared with the prior art, the nano-microemulsion oil displacing agent provided by the present invention has better stability.

Description

A nano-microemulsion oil displacing agent and its preparation method

Technical field

The present application relates to the field of crude oil extraction, and in particular to a nano-microemulsion oil displacing agent and a preparation method.

Background technique

Low permeability oil reservoirs have the characteristics of dense rock burial and poor permeability. After volume fracturing, as the production time prolongs, the energy of the oil and gas layer itself continues to be consumed and the pressure continues to decrease, resulting in a significant reduction in production or even shutdown of production, resulting in reservoir There is a lot of residual oil in it. How to extract the remaining oil is the bottleneck to further improve the recovery rate. The use of oil displacing agents is an important method to improve oil recovery;

In recent years, microemulsion oil flooding, as a relatively new oil displacement method, can maximize the displacement efficiency and sweep coefficient. It has achieved breakthrough results in tertiary oil recovery of low permeability reservoirs, and the oil recovery rate has been significantly improved. Microemulsion is a thermodynamically stable, isotropic, low-viscosity transparent or translucent dispersion system formed spontaneously by oil and water under certain conditions under the action of surfactants and co-surfactants. The particle size of microemulsion is generally 10 to 100nm, and the particle size is much smaller than the pore throat radius of low-permeability reservoirs, so the throat blockage will not occur. Microemulsion solutions can be miscible with oil and water, and significantly reduce the oil-water interfacial tension. Compared with the upper phase microemulsion and the lower phase microemulsion, the ability of the middle phase microemulsion to reduce the oil-water interfacial tension is more significant, and the interfacial tension can reach 10 ^-2 ~ 10 ^-5 mN/m. Microemulsion has important application value in tertiary oil recovery, and the crude oil recovery rate generally increases by more than 10 percentage points.

Contents of the invention

The invention provides a nano-microemulsion oil-displacing agent, which includes: oil and water. The volume ratio of the oil and water is 0.9:1. Based on the total mass of the oil and water, the nano-microemulsion oil-displacing agent Also includes:

First surfactant, 1.0-1.5%;

Second surfactant, 1.0~1.5%;

Third surfactant, 0.4~0.8%;

Alkyl alcohol, 5% to 10%; and,

Sodium chloride, 3 to 6%;

The first surfactant is an anionic surfactant, the second surfactant is a nonionic surfactant, and the third surfactant is an anionic polymer surfactant.

Optionally, the first surfactant is a polyoxyethylene ether nonionic surfactant.

Optionally, the first surfactant is selected from one or more of Tween-80, Span-80, and TritonX-100.

Optionally, the second surfactant is an alkyl phosphate surfactant.

Optionally, the second surfactant is sodium dodecyl phosphate.

Optionally, the third surfactant is a ternary copolymer surfactant of styrene, itaconic acid and hydroxypropyl methacrylate.

Optionally, the number average molecular weight of the third surfactant is 3500-4000.

Optionally, the alkyl group may be one or more selected from the group consisting of isopropanol, n-butanol and isobutanol.

Optionally, the oil is a long-chain alkane.

The invention also provides a method for preparing a nano-microemulsion oil-displacing agent. The nano-microemulsion oil-displacing agent is the nano-microemulsion oil-displacing agent described in any one of the above, including:

The reaction kettle is heated to the first temperature;

According to the measurement ratio, add oil and water into the reaction kettle and stir;

According to the metering ratio, mix the first surfactant, the second surfactant and the third surfactant to form a mixed surfactant, then add the mixed surfactant into the reaction kettle, and then add sodium chloride into the reaction kettle according to the metering ratio. medium and stir to obtain an emulsion;

According to the measurement ratio, add alkyl alcohol and stir while adding to obtain a homogeneous microemulsion.

Compared with the existing technology, the nano-microemulsion oil displacing agent provided by the present invention has better stability, can be stored for a long time, and can maintain the microemulsion temperature in a relatively high-temperature environment in the formation.

Description of the drawings

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

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those of ordinary skill in the art, It is said that other drawings can be obtained based on these drawings without exerting creative labor.

Figure 1 is a flow chart of the preparation method of the nano-microemulsion oil displacing agent provided by the present invention.

Figure 2 is the experimental situation of Example 3 provided by the present invention after being placed at 70°C for 15 days.

Figure 3 is the experimental situation of Example 8 provided by the present invention after being placed at 70°C for 15 days.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments These are part of the embodiments of this application, but not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

It should be noted that in this article, relational terms such as “first” and “second” are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these There is no such actual relationship or sequence between entities or operations. Furthermore, the terms "comprises," "comprises," or any other variations thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also those not expressly listed other elements, or elements inherent to the process, method, article or equipment. Without further limitation, elements qualified by the statement "includes a..." are not excluded from the package.

Low permeability oil reservoirs have the characteristics of dense rock burial and poor permeability. After volume fracturing, as the production time prolongs, the energy of the oil and gas layer itself continues to be consumed and the pressure continues to decrease, resulting in a significant reduction in production or even shutdown of production, resulting in reservoir There is a lot of residual oil in it. How to extract the remaining oil is the bottleneck to further improve the recovery rate. The use of oil displacing agents is an important method to improve oil recovery;

In recent years, microemulsion oil flooding, as a relatively new oil displacement method, can maximize the displacement efficiency and sweep coefficient. It has achieved breakthrough results in tertiary oil recovery of low permeability reservoirs, and the oil recovery rate has been significantly improved. Microemulsion is a thermodynamically stable, isotropic, low-viscosity transparent or translucent dispersion system formed spontaneously by oil and water under certain conditions under the action of surfactants and co-surfactants. The particle size of microemulsion is generally 10 to 100nm, and the particle size is much smaller than the pore throat radius of low-permeability reservoirs, so the throat blockage will not occur. Microemulsion solutions can be miscible with oil and water, and significantly reduce the oil-water interfacial tension. Compared with the upper phase microemulsion and the lower phase microemulsion, the ability of the middle phase microemulsion to reduce the oil-water interfacial tension is more significant, and the interfacial tension can reach 10 ^-2 ~ 10 ^-5 mN/m. Microemulsion has important application value in tertiary oil recovery, and the crude oil recovery rate generally increases by more than 10 percentage points.

The biggest problem of nano-oil displacing agents is their storage stability. The storage temperature refers to the ability of the system to maintain stability under long-term storage; the droplets in nano-oil displacing agents are close to each other or collide with each other due to Brownian motion. The interface film is thinned and disturbed, which leads to the rupture of the liquid film and the merger and coalescence of droplets.

In order to improve the stability of the nano-oil displacing agent, the present invention provides a nano-microemulsion oil-displacing agent, including: oil and water. The volume ratio of the oil and water is 0.9:1. According to the volume ratio of the oil and water, In terms of total mass, the nano-microemulsion oil displacing agent also includes:

First surfactant, 1.0-1.5%;

Second surfactant, 1.0~1.5%;

Third surfactant, 0.4~0.8%;

Alkyl alcohol, 5% to 10%; and,

Sodium chloride, 3 to 6%;

The first surfactant is an anionic surfactant, the second surfactant is a nonionic surfactant, and the third surfactant is an anionic polymer surfactant.

Optionally, the first surfactant is a polyoxyethylene ether nonionic surfactant.

Optionally, the first surfactant is selected from one or more of Tween-80, Span-80, and TritonX-100.

Optionally, the second surfactant is an alkyl phosphate surfactant.

Optionally, the second surfactant is sodium dodecyl phosphate.

Optionally, the third surfactant is a ternary copolymer surfactant of styrene, itaconic acid and hydroxypropyl methacrylate.

Optionally, the number average molecular weight of the third surfactant is 3500-4000.

Optionally, the alkyl group may be one or more selected from the group consisting of isopropanol, n-butanol and isobutanol.

Optionally, the oil is a long-chain alkane.

The invention also provides a method for preparing a nano-microemulsion oil-displacing agent. The nano-microemulsion oil-displacing agent is the nano-microemulsion oil-displacing agent described in any one of the above, including:

The reaction kettle is heated to the first temperature;

According to the measurement ratio, add oil and water into the reaction kettle and stir;

According to the metering ratio, mix the first surfactant, the second surfactant and the third surfactant to form a mixed surfactant, then add the mixed surfactant into the reaction kettle, and then add sodium chloride into the reaction kettle according to the metering ratio. medium and stir to obtain an emulsion;

According to the measurement ratio, add alkyl alcohol and stir while adding to obtain a homogeneous microemulsion.

Example 1:

Preparation of terpolymerized surfactant:

Add 2000 parts of deionized water to the reaction kettle;

Add sodium bisulfite and isopropyl alcohol to deionized water at a molar ratio of 1:1 to form a mixed solution, and then add 20 parts of the above mixed solution into the above reaction kettle;

Raise the temperature of the reaction kettle to 65~70°C; then add 400 parts of styrene, 1000 parts of itaconic acid, 500 parts of hydroxypropyl methacrylate and 60 parts of initiator into the reaction kettle; control the speed of the liquid pump to Complete the dropwise addition within 2.5h; then react at 65℃~70℃ for 2h;

After the reaction is completed, the reaction kettle is lowered to room temperature, and NaOH in an amount of 50% of the moles of carboxyl groups is used to neutralize the hydroxy acid in the system; the ternary copolymerized surfactant is obtained.

The synthesis route of Example 1 is shown in the figure below:

Example 2:

Synthesis of Sodium Dilauryl Phosphate:

The reaction kettle was purged with N2 and irradiated with an infrared lamp for 2 h.

Add solvent toluene into the reaction kettle, and then add 1000 parts of dodecyl alcohol in mole fraction into the reaction kettle;

Slowly add 250 mole parts of pyrophosphoric acid into the reaction kettle under strong stirring, and control the temperature of the reaction kettle to be below 30°C.

After the addition is completed, the reaction temperature is raised to 60-65°C, and the crude alkyl phosphate ester is obtained after a 10-hour heat preservation reaction.

Diethyl ether was added to dilute the crude reaction product. Add an equal volume of deionized water, raise the temperature to 70°C, and hydrolyze for 1.5 hours. Wash three times with deionized water to remove unreacted pyrophosphoric acid and by-product phosphoric acid in the product. The organic solvent was evaporated to obtain dodecyl phosphate.

Add NaOH aqueous solution to the reaction kettle, stir and evaporate the solvent in the reaction kettle to obtain the sodium disodecyl phosphate.

The synthesis route of Example 2 is shown in the figure below:

Example 3:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water at a volume ratio of 0.9:1 into the reaction kettle, and stir; add 5g Tween-80; 5g sodium dodecyl phosphate and 2g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 1.5g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 2.5g isopropyl alcohol into the reaction kettle while adding Stir to obtain a homogeneous microemulsion.

Example 4:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1 into the reaction kettle, and stir; add 6g Span-80; 5g sodium dodecyl phosphate and 2g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 2g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 4g isopropyl alcohol into the reaction kettle and stir while adding. A homogeneous microemulsion was obtained.

Example 5:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 6g TritonX-100; 6g sodium dodecyl phosphate and 3g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 2g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 4g isopropyl alcohol into the reaction kettle and stir while adding. A homogeneous microemulsion was obtained.

Example 6:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 7g of TritonX-100; 7g of sodium dodecyl phosphate and 3g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 2g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 4g isopropyl alcohol into the reaction kettle and stir while adding. A homogeneous microemulsion was obtained.

Example 7:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 7g of TritonX-100; 7g of sodium monolauryl phosphate and 3g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 2g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 4g isopropyl alcohol into the reaction kettle and stir while adding. A homogeneous microemulsion was obtained.

Example 8:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 6.5g Tween-80; 6g sodium dodecyl phosphate; and then mix the surface Add the active agent to the reaction kettle; then add 2g of sodium chloride to the reaction kettle and stir to obtain an emulsion; add 4g of isopropyl alcohol to the reaction kettle and stir while adding to obtain a homogeneous microemulsion.

Example 9:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 5.5g Tween-80; 5.5g sodium dodecyl phosphate and 2.5g of Mix the above terpolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 1.5g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 2.5g isopropyl alcohol into the reaction kettle, Stir while adding to obtain a homogeneous microemulsion.

Example 10:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 6g Tween-80; 6g sodium dodecyl phosphate and 3g of the ternary Mix the copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 1.5g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 2.5g isopropyl alcohol into the reaction kettle while adding Stir to obtain a homogeneous microemulsion.

Example 11:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 7g of Tween-80; 7g of sodium dodecyl phosphate and 3.5g of the trisulfide Mix meta-copolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 1.5g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 2.5g isopropyl alcohol into the reaction kettle while adding While stirring, a homogeneous microemulsion was obtained.

Example 12:

Heat the reaction kettle to 65°C, add 500g of a mixed solvent of oil and water in a volume ratio of 0.9:1, and stir; add 7.5g Tween-80; 7.5g sodium dodecyl phosphate and 4g of the above Mix the terpolymerized surfactant; then add the mixed surfactant into the reaction kettle; then add 1.5g sodium chloride into the reaction kettle and stir to obtain an emulsion; add 2.5g isopropyl alcohol into the reaction kettle while stirring. Add while stirring to obtain a homogeneous microemulsion.

Performance experiment 1:

Particle size test: Observe the microemulsion particle size through JEM2000EX electron microscope and analyze its particle size range.

Stability test: Place the prepared microemulsion in a transparent container at 25°C and 70°C for 15 days, and observe the stability changes of the microemulsion.

The performance test results are shown in the following table:

Experimental results show that compared to Example 8, the microemulsions formed in Examples 3 to 6 have better stability. This is due to the ternary copolymer surfactant, which has a longer molecular chain and an inter-molecular chain. It is easy to entangle with each other, thereby increasing the viscosity of the solution and improving the stability of the microemulsion; and the ternary copolymer surfactant is an anionic polymer surfactant, which increases the electrostatic force on the surface of the microemulsion droplets and makes the microemulsions interact with each other. Repellent, thus forming smaller droplets and making the microemulsion more stable.

Performance test 2:

Measurement of crude oil recovery capacity: Take a core sample, fill the core sample in the pipeline, evacuate the core sample, saturate it with water, and then saturate it with crude oil; then inject two samples, one sample with water; the other sample, add nano-microemulsion The oil-displacing agent is diluted with water to a 0.5% aqueous solution, and then a 0.3PV slug of the nano-microemulsion oil-displacing agent aqueous solution is injected into the sample; the test is stopped when the continuous water content is above 98%, and the water flooding recovery rate is recorded and the nano-microemulsion is injected. The oil recovery achieved by the oil displacing agent.

The liquid recovery rate of Example 7 is low, which is due to the larger average particle size of the liquid droplets of Example 8. The test results also show that the thermal stability of the disodium dodecyl phosphate system is higher than that of the monosodium dodecyl phosphate system. This may be due to the higher degree of molecular entanglement of the disodium dodecyl phosphate system, making it Microemulsion droplets are more stable. The recovery rate of Example 8 is significantly different from that of other Examples. This may be because this system is difficult to form an emulsion, is extremely unstable, and is prone to delamination at high temperatures in the formation. Judging from the experimental data, nano-microemulsions have very good oil recovery rates under the action of capillary force; and it can be found that as the total content of surfactants increases, the oil recovery rate tends to increase, but when the surface activity When the agent content reaches a certain value, the oil recovery rate will not be significantly improved.

The above descriptions are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims (10)

1. A nano-microemulsion oil displacing agent, characterized in that it includes: oil and water. The volume ratio of the oil and water is 0.9:1. According to the total mass of the oil and water, the nano-microemulsion Oil displacing agents also include: First surfactant, 1.0-1.5%; Second surfactant, 1.0~1.5%; Third surfactant, 0.4~0.8%; Alkyl alcohol, 5% to 10%; and, Sodium chloride, 3 to 6%; The first surfactant is an anionic surfactant, the second surfactant is a nonionic surfactant, and the third surfactant is an anionic polymer surfactant. 2. The nano-microemulsion oil displacing agent according to claim 1, characterized in that the first surfactant is a polyoxyethylene ether type nonionic surfactant. 3. The nano-microemulsion oil displacing agent according to claim 2, characterized in that the first surfactant is selected from one or more of Tween-80, Span-80 and TritonX-100. 4. The nano-microemulsion oil displacing agent according to claim 1, characterized in that the second surfactant is an alkyl phosphate surfactant. 5. The nano-microemulsion oil displacing agent according to claim 4, characterized in that the second surfactant is sodium dodecyl phosphate. 6. The nano-microemulsion oil displacing agent according to claim 1, characterized in that the third surfactant is a ternary copolymer surfactant of styrene, itaconic acid and hydroxypropyl methacrylate. 7. The nano-microemulsion oil displacing agent according to claim 6, characterized in that the number average molecular weight of the third surfactant is 3500-4000. 8. The nano-microemulsion oil displacing agent according to claim 1, characterized in that the alkyl group is selected from one or more of isopropanol, n-butanol and isobutanol. 9. The nano-microemulsion oil displacing agent according to claim 1, characterized in that the oil is a long-chain alkane. 10. A method for preparing a nano-microemulsion oil-displacing agent. The nano-micro-emulsion oil-displacing agent is the nano-microemulsion oil-displacing agent according to any one of claims 1 to 9, which is characterized in that it includes: The reaction kettle is heated to the first temperature; According to the measurement ratio, add oil and water into the reaction kettle and stir; According to the metering ratio, mix the first surfactant, the second surfactant and the third surfactant to form a mixed surfactant, then add the mixed surfactant into the reaction kettle, and then add sodium chloride into the reaction kettle according to the metering ratio. medium and stir to obtain an emulsion; According to the measurement ratio, add alkyl alcohol and stir while adding to obtain a homogeneous microemulsion.