CN110387011B - Nano composite oil displacement agent and preparation method and application thereof - Google Patents

Nano composite oil displacement agent and preparation method and application thereof Download PDF

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CN110387011B
CN110387011B CN201910489311.1A CN201910489311A CN110387011B CN 110387011 B CN110387011 B CN 110387011B CN 201910489311 A CN201910489311 A CN 201910489311A CN 110387011 B CN110387011 B CN 110387011B
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柯扬船
邓青春
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China University of Petroleum Beijing
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Abstract

The invention provides a nano composite oil displacement agent and a preparation method and application thereof. The preparation method comprises the following steps: mixing acrylamide, sodium p-styrene sulfonate and water according to the weight ratio of 10.5-13.5: 4.5-5: mixing the materials in a mass ratio of 90-99 to obtain a mixed solution; adding a surfactant which is 5-7% of the mixed solution in weight into the mixed solution, adjusting the pH value of the mixed solution to 7-7.5, and then adding an inorganic nano intermediate which is 1-3% of the mixed solution in weight into the mixed solution to obtain a reaction solution; adding an initiator into the reaction solution under an inert atmosphere, and reacting for 8-10 hours at 75-80 ℃ to obtain a polymer emulsion; and demulsifying, drying and crushing the polymer emulsion to obtain the nano composite oil displacement agent. The nano composite oil displacement agent provided by the invention has the characteristics of good temperature resistance, salt resistance and reduction of oil-water interfacial tension, and can be used for oil extraction engineering of high-medium low-permeability oil and gas reservoirs and residual oil reservoirs in the later period of tertiary oil recovery.

Description

Nano composite oil displacement agent and preparation method and application thereof
Technical Field
The invention relates to a nano composite oil displacement agent, a preparation method and application thereof, and belongs to the technical field of oil and gas field exploitation.
Background
Petroleum belongs to non-renewable resources, reserves of the petroleum are continuously reduced along with increase of the production amount, new reserves of the petroleum are mainly in unconventional deep and other complex reservoirs, and the key factor for improving the oil and gas production efficiency is caused by the increase of the production difficulty of required production technologies, particularly core materials such as oil displacement agents and the like.
Conventional oil recovery includes primary and secondary oil recovery processes. The primary oil extraction process is to spray oil by using the self pressure of the oil field, and can extract 20% of the original geological reserve. As the formation pressure decreases or the energy decreases, the primary oil recovery yield decreases, and a secondary oil recovery engineering process is required, i.e., additional fluid is injected into the formation to increase the driving pressure or driving energy. About 20% of reserves can be further recovered in the secondary oil recovery engineering process. Thus, conventional oil recovery engineering techniques produce only 40% of the total oil recovered, i.e., about 60% of the oil remains in the subsurface.
At present, the large oil fields in the east, such as Daqing, Shengli, China, North China, big harbor and the like, all enter the middle and later stages of water injection exploitation, the water content of the produced liquid of most oil wells reaches up to 90 percent, and the oil extraction efficiency and the domestic oil yield are difficult to break through. The research of the national development and reform committee reports that the oil demand of China is 4.5 hundred million tons to 6.1 hundred million tons in 2020, and the import dependence reaches 60-70%. For this reason, tertiary oil recovery technology or Enhanced Oil Recovery (EOR) technology is urgently required to improve oil recovery efficiency and oil production.
The tertiary oil recovery technique is a technique of reducing the saturation of residual oil by further increasing the recovery ratio by physical, chemical, biological, or other techniques. Among them, chemical flooding, which enhances the recovery ratio by injecting oil-displacing agents such as conventional surfactants, polymeric surfactants, and alkaline water, is a hot spot of current research. In chemical flooding, the traditional surfactant flooding is to inject a surfactant to reduce the interfacial tension at an oil-water interface, change the wettability of the rock surface and further improve the recovery ratio; polymer flooding is to inject polymer into the stratum to increase the viscosity of the displacement fluid and reduce the mobility ratio of the displacement fluid and the displaced fluid, thereby enlarging swept volume; polymeric surfactants have found widespread use due to the advantages of both surfactants and polymers. However, in the prior art, a large amount of loss of surfactants, polymer surfactants, and the like used as oil displacement agents often occurs during use, which results in a significant increase in interfacial tension and a decrease in performance, and therefore, it is often necessary to increase the oil recovery time and repeat oil displacement to ensure high productivity, but the oil recovery workload, the oil recovery raw material, and the time cost are also increased.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method of a nano composite oil-displacing agent, and the nano composite oil-displacing agent obtained by the preparation method has small interfacial tension change amplitude and small loss amount in actual use, so that the oil production workload, the oil production raw materials and the time cost are reduced.
The invention provides a nano composite oil-displacing agent which is prepared by the preparation method and has small loss and stable performance in actual use.
The invention also provides the application of the nano composite oil displacement agent in oil extraction engineering.
In order to achieve the purpose, the invention provides a preparation method of a nano composite oil displacement agent, which is characterized by comprising the following steps:
acrylamide, sodium p-styrene sulfonate and water are mixed according to the weight ratio of (10.5-13.5): (4.5-5): (90-99) to obtain a mixed solution;
adding a surfactant which is 5-7% of the mixed solution by weight into the mixed solution, adjusting the pH value of the mixed solution to 7-7.5, and then adding an inorganic nano intermediate which is 1-3% of the mixed solution by weight into the mixed solution to obtain a reaction solution;
adding an initiator into the reaction solution under an inert atmosphere, and reacting at the temperature of 75-80 ℃ for 8-10 hours to obtain a polymer emulsion;
demulsifying, drying and crushing the polymer emulsion to obtain a nano composite oil displacement agent;
wherein the surfactant is a solid product which is precipitated after a mixed system of dodecyl benzene sulfonic acid, ethyl acetate and vinyl imidazole is firstly reacted at 45-50 ℃ for at least 24 hours and then sealed and frozen at the temperature of-16 ℃ below zero, wherein the mass ratio of the dodecyl benzene sulfonic acid to the ethyl acetate is 1: (4-5); the mass of the vinyl imidazole is 0.4 to 0.7 percent of the sum of the mass of the dodecyl benzene sulfonic acid and the mass of the ethyl acetate;
the inorganic nano intermediate is synthesized by a method comprising the following steps:
mixing the layered silicate with water and swelling the layered silicate in the water to obtain a swelling system;
heating the swelling system to 60-90 ℃, then adding an intercalation agent which accounts for 1-10% of the mass of the swelling system into the swelling system, reacting for 10-12 hours under the stirring frequency of 30-45 hz, carrying out solid-liquid separation on the obtained product, and drying the solid part to obtain the inorganic nano intermediate.
When the nano composite oil displacement agent provided by the invention is actually used, the problem that the interfacial tension is obviously increased due to a large amount of loss when the traditional oil displacement agents such as surfactants, polymer surfactants and the like are used is solved, so that the displacement efficiency is improved, and the oil extraction cost is reduced.
In addition, the invention utilizes the reaction of dodecyl benzene sulfonic acid and vinyl imidazole to introduce unsaturated double bonds, thus obtaining the surfactant capable of generating polymerization reaction; then the surfactant is copolymerized with acrylamide and sodium p-styrenesulfonate, and the inorganic nano intermediate obtained by using a specific preparation process is added in the process, so that the finally obtained nano composite oil-displacing agent keeps the dual advantages of reducing the interfacial tension of the traditional surfactant and changing the oil-water flow rate ratio of a polymer, and has good temperature resistance, thereby expanding the application range of the nano composite oil-displacing agent.
In addition, the nano composite oil displacement agent contains hydrophilic and hydrophobic molecular chains, changes the wettability distribution of a reservoir in the process of large-pore migration, has the effects of profile control and water shutoff, and has oil drops with permeability, so that the nano composite oil displacement agent can be used for oil displacement engineering to improve the displacement efficiency.
Further, the surfactant in the nano composite oil displacement agent provided by the invention can be synthesized by a method comprising the following steps:
mixing dodecyl benzene sulfonic acid, ethyl acetate and vinyl imidazole according to a proportion to obtain a mixed system;
adopting a condensation reflux process to react the mixed system for 24-48 hours at the temperature of 45-50 ℃ to obtain a reaction product;
hermetically freezing the reaction product at the temperature of below-16 ℃ for at least 24 hours to obtain a freezing system;
washing the freezing system by ethyl acetate, then repeating the steps of sealing, freezing and washing, and collecting the obtained white crystals to obtain the surfactant.
Specifically, in the process of synthesizing the surfactant, dodecyl benzene sulfonic acid and ethyl acetate are firstly mixed, then vinyl imidazole is added in an inert atmosphere, and then the mixture is mixed for 2-2.5 hours under the conditions that the temperature is 0-4 ℃ and the stirring frequency is 30-45 hz, so as to obtain a mixed system.
In the specific implementation process of the invention, firstly, dodecyl benzene sulfonic acid and ethyl acetate are added into a preparation kettle and mixed for 10-15 min; then introducing nitrogen into the preparation kettle to fully discharge oxygen in the preparation kettle and provide an inert atmosphere; and then regulating the temperature in the preparation kettle to about 0 ℃ in an ice-water bath mode, finally adding vinyl imidazole, and violently stirring for 2-2.5 hours under the stirring frequency of 30-45 hz to obtain a mixed system.
And transferring the mixed system into a reaction kettle, connecting a condensation reflux pipe to start condensation reflux, increasing the temperature in the reaction kettle to 45-50 ℃, and reacting for 24-48 h to obtain a reaction product.
And secondly, transferring the reaction product into an ultra-low temperature control chamber, sealing and freezing, wherein the freezing temperature can be controlled to be 16-20 ℃ below zero generally, and standing for 24-48 h to obtain a freezing system.
Taking out the freezing system from the ultralow temperature control chamber, quickly mixing the freezing system with ethyl acetate, extracting the freezing system by using the ethyl acetate as an extracting agent, and removing unreacted substances in the freezing system by washing to improve the reaction purity; and after the mixture is washed by ethyl acetate of a freezing system for multiple times, repeating the steps of sealing and freezing and washing by ethyl acetate for multiple times until white crystals are separated out, namely the surfactant, and refrigerating for later use.
In the present invention, the process of synthesizing the nano-mesophase may specifically include: firstly, the mass ratio of the layered silicate to water is 1: (10-20) adding the mixture into a reaction kettle, mixing, and stirring and swelling for 20-30 min at 30-45 hz to obtain a swelling system; heating the swelling system to 60-90 ℃, such as 80 ℃, then adding an intercalating agent which accounts for 1-10% of the mass of the swelling system into the reaction kettle, such as 5-10% of the mass of the intercalating agent of the swelling system, reacting for 10-12 hours under the stirring frequency of 30-45 hz, then pouring the obtained product into a cooling tank, cooling to below 30 ℃, and obtaining a solid part by solid-liquid separation means such as vacuum filtration and the like; and finally, placing the solid part in an oven, and drying at the temperature of 60-75 ℃ to obtain the inorganic nano intermediate.
The layered silicate of the present invention is not particularly limited, and may be a currently used industrial-grade layered silicate product, such as montmorillonite (MMT). The montmorillonite has a layered crystal structure, and the size of a crystal unit is 1-100 nm. The crystal lamellar structure has natural expansibility and peeling dispersity. By utilizing the cation exchange property between montmorillonite layers, monomer is inserted into the montmorillonite layers to strip MMT layers, and nano-scale layers are dispersed in a polymer matrix to form a nano composite material (namely an inorganic nano intermediate) with excellent performance, so that the temperature resistance of the nano composite oil displacement agent can be improved, the interfacial tension can be reduced, the emulsification performance can be improved, and the like, and the nano composite oil displacement agent can be applied to petroleum tertiary oil recovery engineering to improve the oil gas recovery rate and the yield, and even can be used in the field of drilling and production sewage treatment.
In some embodiments of the invention, the intercalant comprises at least a first portion selected from at least one of cetyltrimethyl ammonium bromide and cetyltrimethyl ammonium chloride. By adopting the organic long-chain compounds (cetyl trimethyl ammonium bromide and cetyl trimethyl ammonium chloride), the ion exchange reaction can be carried out between the organic long-chain compounds and inorganic nano materials such as montmorillonite, so that the organic long-chain compounds smoothly enter the middle of montmorillonite layers, the distance between the montmorillonite layers is further enlarged, and the nano intermediate with good stripping effect is prepared.
Further, the intercalation agent may further include a second component selected from at least one of ethanolamine, phosphoric acid, hydrochloric acid and sulfuric acid; the mass of the second component is not more than that of the first component, and the pH value of the intercalation agent is 6.5-7.5. The first component of the long-chain compound and the second component of the micromolecule are jointly used as the intercalation agent, so that the ion exchange reaction between the organic long-chain compound and the inorganic nano material can be promoted.
In some examples of the invention, the interlayer spacing of the synthesized inorganic nano-intermediate is 1.5-4 nm, such as 1.5-2.5 nm. In the present invention, the interlayer distance refers to the distance between two single sheets of the phyllosilicate, for example, the distance between two single sheets of the nano montmorillonite, that is, the interlayer distance, is generally about 1 nm.
It is understood that the reaction solution is maintainedThe copolymerization of acrylamide, sodium p-styrenesulfonate and surfactant is preferably carried out under an inert atmosphere, and the initiator is preferably added under an inert atmosphere to ensure that the copolymerization reaction is also carried out under an inert atmosphere. Specifically, the prepared reaction solution can be placed in a polymerization kettle, nitrogen is introduced into the polymerization kettle, and the flow rate of the nitrogen is controlled to be 45m3/h～50m3The pressure in the polymerization kettle reaches 0.50-0.55 MPa, the inert atmosphere is achieved after more than 20 minutes and the nitrogen is generally introduced for 20-30 minutes, and then the initiator can be added into the polymerization kettle to initiate the copolymerization reaction.
The flow rate of the nitrogen gas is controlled to be 45-50 m3On one hand, the air in the polymerization kettle, especially the oxygen in the air, can be fully discharged, and a small amount of oxygen in the reaction liquid can be discharged, so that the influence of the oxygen on the subsequent copolymerization is avoided. If the flow of the nitrogen is too small, the oxygen in the reaction liquid is difficult to be removed completely; when the flow rate of nitrogen is too large, bubbling occurs in the polymerization vessel.
The initiator and the amount thereof used in the present invention are not particularly limited, and an appropriate amount of the initiator may be added according to the kind of the initiator, for example, one or more of persulfate initiators may be added. In the specific implementation process of the invention, the initiator used is at least one selected from persulfates, and the amount of the initiator used can be controlled to be 0.6-0.8% of the mass of the reaction liquid. In the specific implementation process of the invention, the initiator used is ammonium persulfate or potassium persulfate.
And after the copolymerization reaction is finished, mixing the obtained polymer emulsion with a demulsifier, demulsifying and mixing to obtain a milky solid, drying, for example, drying in a vacuum drying oven at 76-81 ℃ for about 48 hours, crushing the dried product, and sieving with a 60-mesh sieve (about 0.250mm), thereby obtaining the powdery polymer surfactant product.
In some examples of the invention, the nanocomposite oil-displacing agent product as synthesized has a very uniform particle size distribution when dispersed in water, with an average dispersed particle size in the range of 100nm to 200nm, and a particle size distribution of about 95% (volume fraction) in the range of 100 to 120 nm. The particle size is far smaller than equivalent diameters of the pore canal and the pore, and the nano material in the nano composite oil displacement agent can fully enter the nano-micron pore canal with tiny size and the blind end of the pore of the stratum. Therefore, the nano composite oil displacement agent is particularly suitable for unconventional oil and gas reservoirs such as low permeability, ultra-low permeability, compact oil and gas, and the like, drives oil and gas in the dead end, the micro-pore passage and the peripheral pore passage to flow, and finally realizes effective exploitation of crude oil in the unconventional oil and gas reservoirs. Research shows that the crude oil reserve in an unconventional oil-gas reservoir is far greater than that of a conventional reservoir, so that the nano-composite oil displacement agent provided by the invention can obviously reduce the residual oil in the later period of tertiary oil recovery and improve the recovery ratio.
In addition, the average dispersed particle size of the nano composite oil displacement agent in water is in the range of 100 nm-200 nm, so that the added inorganic nano intermediate can be peeled off and dispersed in water, the characteristics of the nano material are exerted, the interfacial tension of the oil displacement agent is further reduced, and the good oil displacement effect and emulsification effect are realized.
The preparation method of the nano composite oil displacement agent further comprises the step of preparing the surfactant and/or the inorganic nano intermediate, and the preparation process is as described above and is not repeated.
The invention also provides a nano composite oil displacement agent which is prepared by adopting the preparation method.
The nano composite oil displacement agent provided by the invention has the advantages of the traditional surfactant and the polymer surfactant, can change the wettability of reservoir rock, reduce the tension of an oil-water interface, improve the oil transportation performance of a pipeline and the efficiency of oil washing and oil displacement, has the characteristic of high temperature resistance (120 ℃), and further expands the application field of the nano composite oil displacement agent in oil extraction engineering. In addition, the nano composite oil displacement agent is not only suitable for conventional oil and gas reservoirs, but also can be used for unconventional oil and gas reservoirs such as low-permeability, ultra-low-permeability and compact oil and gas reservoirs to drive oil and gas in blind ends, micro-channels and peripheral channels to flow, and finally effective exploitation of crude oil in the unconventional oil and gas reservoirs is realized.
The invention also provides the application of the nano composite oil displacement agent in oil extraction engineering. As mentioned above, the nano composite oil displacement agent is not only suitable for conventional oil and gas reservoirs, but also can be used for unconventional oil and gas reservoirs, so that the nano composite oil displacement agent can be used for tertiary oil recovery engineering of high, medium and low permeability oil fields, and especially under the condition that the residual oil amount is large in the later stage of three-extraction and crude oil cannot be extracted in the traditional oil displacement mode, the nano composite oil displacement agent can enter nano-micron pores and formation pore blind ends with tiny sizes due to the fact that the average dispersed particle size of the nano composite oil displacement agent in water is 100 nm-200 nm, and effective extraction of crude oil in unconventional oil and gas reservoirs is achieved.
According to the preparation method of the nano-composite oil displacement agent, the obtained nano-composite oil displacement agent keeps stable performance in multiple displacement processes, and the loss amount is small, so that the problems of large oil production workload and high cost of the traditional oil displacement agent due to large loss in use are solved, the displacement efficiency is improved, and the oil production cost is reduced.
In addition, the nano composite oil displacement agent also has salt resistance and good temperature resistance, can be used in certain high-salinity stratum environments, can resist the high temperature of more than 130 ℃, and further expands the application range of chemical flooding.
In addition, the nano composite oil displacement agent keeps the dual advantages of reducing interfacial tension by the surfactant and changing oil-water fluidity ratio by the polymer, and particularly, the nano composite oil displacement agent is suitable for unconventional oil and gas layers such as low-permeability, ultra-low-permeability and compact oil and gas layers by adding the inorganic nano intermediate, so that oil and gas in micro-channels and peripheral channels of the micro-channels are driven to flow, and finally, the effective exploitation of crude oil in the unconventional oil and gas layers is realized.
The nano composite oil displacement agent provided by the invention has the advantages that when the nano composite oil displacement agent is used for tertiary oil recovery engineering of high, medium and low permeability oil fields, the wettability of reservoir rock can be changed, the tension of an oil-water interface is reduced, the oil transportation performance of a pipeline and the oil washing and displacement efficiency are improved, especially the stability of the performance is kept in the multiple displacement processes, the loss amount is less, the oil recovery cost is reduced, and the oil recovery efficiency is improved. In addition, the nano composite oil displacement agent has good temperature resistance, so that the nano composite oil displacement agent can be used for some special high-temperature formations.
Drawings
FIG. 1 shows the results of interfacial tension tests (different degrees of mineralization) in Experimental example 4 of the present invention;
FIG. 2 is the results of interfacial tension test (different oil-displacing agent concentrations) in Experimental example 4 of the present invention;
FIG. 3 shows the results of the temperature resistance test in Experimental example 5 of the present invention;
FIG. 4 shows the results of the water absorption test in Experimental example 7;
fig. 5 shows the interfacial tension as a function of the number of displacements in experimental example 8.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The embodiment provides a nano composite oil displacement agent, and the preparation method comprises the following steps:
1. preparation of inorganic nano intermediate
a. By adopting a coprecipitation method, montmorillonite and water are mixed according to the proportion of 1: 15, mixing the materials in a multifunctional reaction kettle of 1 cubic meter, and swelling for 20-30 min at a stirring speed of 30-35 hz to obtain a swelling system;
b. heating the obtained swelling system to 80 ℃, then adding an intercalation agent hexadecyl ammonium bromide which is 10 percent of the mass of the swelling system into the multifunctional reaction kettle, setting the frequency of a stirrer to be 30hz, and reacting for 12 hours;
c. pouring the obtained reaction product into a cooling tank, and carrying out vacuum filtration when the temperature is reduced to 30 ℃;
d. and (3) placing the solid powder obtained by suction filtration in a drying oven, and drying at 65 ℃ to obtain an inorganic nano intermediate for later use.
2. Preparation of surfactants
a. Mixing dodecyl benzene sulfonic acid and ethyl acetate according to the weight ratio of 1: 4.5 adding into a preparation kettle, and mixing for 15 min;
b. introducing nitrogen into a preparation kettle for 20-30 min, adding vinyl imidazole into the preparation kettle, controlling the mass of the vinyl imidazole to be 0.5% of the sum of the mass of dodecylbenzene sulfonic acid and ethyl acetate, carrying out ice-water bath, controlling the temperature to be about 0 ℃, and violently stirring for about 2.3h at 35kHz to obtain a mixed system;
c. transferring the obtained mixed system to a multifunctional reaction kettle, connecting a condensation reflux pipe, adopting a condensation reflux process, raising the temperature of the reaction kettle to 48 ℃, and reacting for 24 hours to obtain a reaction product;
d. transferring the obtained reaction product into an ultralow temperature control chamber, sealing and freezing, controlling the temperature to be 18 ℃ below zero, and standing for 48 hours;
e. taking out the freezing system from the low-temperature control chamber, quickly pouring the freezing system into 250mL of ethyl acetate, and washing for multiple times;
f. repeating the steps d and e until white crystals are separated out, namely the surfactant, and refrigerating for later use.
3. Preparation of nano composite oil displacement agent
a. Mixing acrylamide, sodium p-styrene sulfonate and pure water according to the proportion of 3: 1: 20, adding the mixture into a preparation kettle, and mixing to obtain a mixed solution;
b. and (3) adding the surfactant prepared in the step (2) into the mixed solution, controlling the mass of the surfactant to be 6% of the mass of the mixed solution, stirring for about 35min at the temperature of about 50 ℃ and the stirring frequency of 35kHz, then adjusting the pH value of the mixed solution to be 7-7.5, adding the inorganic nano intermediate obtained in the step (1) into the mixed solution, controlling the mass of the inorganic nano intermediate to be 1% of the total mass of the mixed solution, and uniformly stirring to obtain a reaction solution.
c. Transferring the reaction liquid to a polymerization kettle, introducing nitrogen, and controlling the pressure in the polymerization kettle to be 0.50-0.55 MPa and the flow rate of the nitrogen to be 45-50 m3H, nitrogenThe gas introduction time is about 25 min; adding initiator ammonium persulfate into a polymerization kettle, controlling the mass of the initiator to be 0.7 percent of the mass of the reaction liquid, raising the temperature in the polymerization kettle to 78 +/-1 ℃, and reacting for about 9 hours to obtain the polymer emulsion.
d. Adding a demulsifier into the polymer emulsion for demulsification to obtain a milky solid material, and then sending the milky solid material into a vacuum drying oven for vacuum drying, wherein the drying temperature is controlled to be about 80 ℃, and the drying time is about 48 hours; and crushing the obtained solid product, and sieving the crushed solid product with a 60-mesh sieve to obtain a nano composite oil-displacing agent product.
Tests show that when the nano composite oil displacement agent product is dispersed in water, the particle size distribution of more than 95% (volume fraction) is within the range of 100-120 nm.
Example 2
Embodiment 2 provides a nanocomposite oil displacement agent, which has substantially the same preparation process as embodiment 1, except that: in the step 3-b, the adding mass of the inorganic nano intermediate is controlled to be 2% of the total mass of the mixed solution.
Tests show that when the nano composite oil displacement agent product is dispersed in water, the particle size distribution of more than 95% (volume fraction) is within the range of 100-120 nm.
Example 3
Embodiment 3 provides a nanocomposite oil displacement agent, which has substantially the same preparation process as embodiment 1, except that: in the step 3-c, the adding mass of the inorganic nano intermediate is controlled to be 3% of the total mass of the mixed solution.
Tests show that when the nano composite oil displacement agent product is dispersed in water, the particle size distribution of more than 95% (volume fraction) is within the range of 100-120 nm.
Comparative example 1
Comparative example 1 provides a composite oil-displacing agent, the preparation process of which is substantially the same as that of example 1 except that: in the step 3-b, the mass of the inorganic nano intermediate is controlled to be 0 percent of the total mass of the mixed solution, namely, the nano inorganic phase is not added.
Experimental example 1: effect of different amounts of intercalant on inorganic Nano intermediate size
Inorganic nano-intermediates were prepared according to the method of step 1 in example 1, wherein the mass of the intercalating agent was 10%, 8% and 6% of the mass of the swollen system, respectively, and the inorganic nano-intermediates thus obtained were designated as a1, a2 and A3, and then the sizes of the inorganic nano-intermediates a1 to A3 were measured using XRD, and the results are shown in table 1 below.
TABLE 1
Figure GDA0002415054740000101
Note that: in table 1, the content of the intercalant is the mass percentage of the intercalant in the swelling system.
As can be seen from table 1, in the range of 1% to 10%, especially 5% to 10%, the thickness of the inorganic nano intermediate tends to increase and the interlayer distance tends to decrease as the amount of the intercalating agent decreases. Presumably, as the intercalation agent is reduced, the ion exchange reaction between the intercalation agent and the inorganic nano material (montmorillonite) is slowed down, the interlayer spacing of the inorganic nano intermediate is reduced, and the agglomeration phenomenon of the nano sheet layer is increased.
Further research shows that if the consumption of the intercalation agent is increased continuously, the content of the intercalation agent is higher than 10%, the bubble phenomenon is serious in the reaction process, and the yield and the purity of the product are obviously reduced. This phenomenon also coincides with the above-mentioned presumptive analysis.
Experimental example 2: effect of different amounts of vinylimidazole on surfactant Performance
Surfactants were prepared according to the method of step 2 of example 1, wherein the mass of vinylimidazole was 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7% of the sum of the mass of dodecylbenzenesulfonic acid and ethyl acetate, and the resulting surfactant bodies were identified as B1 to B7. The interfacial tensions of the surfactant bodies B1 to B7 were measured and the yields thereof were calculated, and the results are shown in table 2 below.
TABLE 2
Figure GDA0002415054740000102
Figure GDA0002415054740000111
Note that: in table 2, the vinylimidazole content is: mass of vinylimidazole ÷ (mass of dodecylbenzenesulfonic acid + ethyl acetate) × 100%;
the yield calculation method comprises the following steps: product mass ÷ (dodecylbenzenesulfonic acid + ethyl acetate + vinylimidazole). times.100%.
As can be seen from Table 2, as the dosage of vinyl imidazole is increased from 0.1% to 0.7%, the yield of the surfactant is increased, and the yield is slightly reduced but not greatly reduced in the later period, and is basically kept at about 93%; the interfacial tension of the surfactant is reduced and is basically maintained at 1.50 x 10-3The mN/m is nearby.
Experimental example 3: effect of different surfactant amounts on Compound oil-displacing Agents
The composite oil-displacing agent was prepared by referring to the process in comparative example 1, wherein the mass of the surfactant was 5%, 6% and 7% of the mass of the mixed solution, respectively, and the numbers of the composite oil-displacing agents obtained accordingly were designated as C1, C2 and C3.
The compound oil displacement agents C1, C2 and C3 are dissolved in deionized water to prepare 3g/L solution for detection, and the results are shown in Table 3.
TABLE 3
Numbering Surfactant content Yield (%) Interfacial tension (mN/m)
C1 5％ 78.9 3.21
C2 6％ 96.3 1.56
C3 7％ 95.9 1.38
Note that: in table 3, the surfactant content is the percentage of the mass of the surfactant to the mass of the mixed solution; the yield was calculated as: product mass ÷ (acrylamide + sodium p-styrene sulfonate + surfactant mass) × 100%.
As can be seen from Table 3, the yield was the highest at a surfactant content of 6%, reaching 96.3%.
Experimental example 4
The results of the interfacial tension test on the nanocomposite oil-displacing agent of examples 1-3 and the composite oil-displacing agent of comparative example 1 are shown in fig. 1 and fig. 2, where fig. 1 is an interfacial tension curve at different degrees of mineralization (NaCl concentration), and fig. 2 is a corresponding interfacial tension curve at different concentrations of the oil-displacing agent (examples 1-3 are nanocomposite oil-displacing agents, comparative example 1 is a composite oil-displacing agent).
As can be seen from fig. 1, the interfacial tension of the nanocomposite oil-displacing agent in examples 1 to 3 and the composite oil-displacing agent in comparative example 1 both decreased with increasing NaCl concentration, and remained almost unchanged or increased slightly until the NaCl concentration reached 0.008 g/mL.
As can be seen from fig. 2, the interfacial tension of the nanocomposite oil-displacing agent of examples 1 to 3 and the composite oil-displacing agent of comparative example 1 both showed a significantly decreasing trend as the concentration of the oil-displacing agent increased, and the interfacial tension remained substantially unchanged until the concentration of the oil-displacing agent reached about 0.8 g/L.
It can be seen that under the same conditions, the nanocomposite oil-displacing agents in examples 1-3 have significantly lower interfacial tension than the composite oil-displacing agent in comparative example 1, and especially when the addition amount of the inorganic nano-intermediate is 2% (example 2), the interfacial tension is the lowest.
In addition, the nanocomposite oil displacement agent provided in embodiments 1 to 3 has significantly lower interfacial tension under the condition of high salinity, and thus can be used for oil and gas field exploitation under the condition of high salinity.
Experimental example 5
The thermal resistance tests were performed on the nanocomposite oil-displacing agents of examples 1 to 3 and the composite oil-displacing agent of comparative example 1, and the thermal weight loss curves thereof are shown in fig. 3.
As can be seen from fig. 3, the temperature at which the composite oil-displacing agent in comparative example 1 starts to lose weight is about 125 ℃, and the weight-loss temperature of the nanocomposite oil-displacing agent obtained by adding the inorganic nano intermediate is significantly increased, for example, when the addition amounts of the inorganic nano intermediate are 1%, 2% and 3%, the weight-loss temperatures reach about 135 ℃, 150 ℃ and 170 ℃, respectively, which are significantly increased as compared with comparative example 1. And the temperature resistance of the obtained nano composite oil displacement agent is improved along with the increase of the addition amount of the inorganic nano intermediate.
Experimental example 6
Taking 4 cores with the numbers of 1-4, respectively injecting crude oil into the cores, firstly, respectively displacing the cores 1-4 by adopting water with the mineralization degree of 80000ppm, and calculating the water-flooding efficiency according to the mass of the displaced crude oil; then on the basis of water flooding, the core 1 is displaced by using the composite oil displacement agent in the comparative example 1, the cores 2 to 4 are respectively displaced by using the nano composite oil displacement agents in the examples 1 to 3, the oil displacement efficiency (recorded as the agent displacement) of the nano composite oil displacement agent in each example and the oil displacement efficiency (recorded as the agent displacement) of the composite oil displacement agent in the comparative example 1 on the respective cores is calculated according to the mass of the displaced crude oil, and specific results are shown in the following table 4.
TABLE 4
Figure GDA0002415054740000131
As can be seen from table 4, the oil displacement efficiency of the nano composite oil displacement agent in examples 1 to 3 to each core is significantly higher than that of the composite oil displacement agent in comparative example 1. In addition, in examples 1 to 3, as the amount of the inorganic nano intermediate increases, the oil displacement efficiency of the nano composite oil displacement agent tends to increase first and then decrease, which indicates that the inorganic nano intermediate is peeled off in the material, and in example 2, the peeling effect is the best, and the advantages (nano effect) of the nano material can be exerted, so that the nano composite oil displacement agent has the best interfacial tension and oil displacement effect.
Experimental example 7
Taking the nano composite oil displacement agent sample in the embodiment 2, and carrying out crude oil displacement on the sample by using a low-permeability core and a compact core, wherein the method specifically comprises the following steps: taking two rock cores, numbering the rock core 5 and the rock core 6 respectively, and injecting crude oil into the rock core 5 and the rock core 6 respectively; firstly, displacing rock cores 5-6 by respectively adopting water with the mineralization degree of 60000ppm, and calculating the water displacement efficiency according to the mass of the displaced crude oil; then, on the basis of water flooding, the cores 5-6 are respectively displaced by using the composite oil displacement agent prepared in the example 2, and the oil displacement efficiency of the composite oil displacement agent on the respective cores (denoted as the present agent flooding) is calculated according to the mass of the displaced crude oil, and specific results are shown in the following table 5.
TABLE 5
Figure GDA0002415054740000132
As can be seen from Table 5, the nanocomposite oil displacement agent prepared by the method provided by the invention has a good displacement effect on crude oil in low permeability rock cores and compact rock cores. The nano composite oil displacement agent can be used for the low-permeability and compact oil and gas exploitation process, and has a good effect on residual oil in the later period of three-extraction.
Experimental example 7
The nano composite oil-displacing agent samples in examples 1 to 3 and the composite oil-displacing agent sample in comparative example 1 were taken and dissolved in a NaCl solution having a concentration of 0.008g/mL, respectively, to prepare a sample having a concentration of 0.8g/L, to obtain a test sample.
Placing 7mL of test sample in a graduated flask, adding 3mL of crude oil at normal temperature, then violently shaking to fully mix the crude oil and the test sample, standing, starting timing, measuring the water precipitation per minute to calculate the water absorption (the water precipitation is the percentage of the water precipitation to the total water), and the result is shown in FIG. 4.
The emulsification effect is used for representing the interfacial tension characteristic of the material, the smaller the water precipitation rate is, the better the emulsification effect is, and the larger the water precipitation rate is, the worse the emulsification effect is. As can be seen from fig. 3, the water evolution rates of the nanocomposite oil-displacing agent samples in examples 1 to 3 and the composite oil-displacing agent sample in comparative example 1 were not more than 16%, which is consistent with the interfacial tension data shown in fig. 1 and 2.
However, it is clear that the water-bleeding rate of the nanocomposite oil-displacing agent samples in examples 1 to 3 is significantly lower, the emulsification effect is better, and the interfacial tension is lower, compared to the composite oil-displacing agent sample in comparative example 1. Especially when the amount of the inorganic nano intermediate MMT added was 2% (example 2), the water-bleeding rate was the lowest, the emulsification effect was the best, and the interfacial tension was the lowest, because it is likely that the inorganic nano intermediate would be peeled off, and when the amount of the inorganic nano intermediate was 2%, the peeling effect was the best, and the nano effect was the best.
Experimental example 8
Taking the sample of the nanocomposite oil displacement agent in the embodiment 2, displacing the core, collecting the displacement fluid after the displacement is completed, measuring the interfacial tension of the displacement fluid, re-displacing the core with the displacement fluid this time, measuring the interfacial tension of the newly collected displacement fluid, repeating the operation for 6 times within 30 days, wherein the change curve of the interfacial tension of the displacement fluid obtained each time is shown in fig. 5, so as to measure the loss of the nanocomposite oil displacement agent.
The traditional surfactant flooding method is to reduce the oil-water interfacial tension to displace oil, but because the rock is various carbonates or silicates and is easy to be electrostatically adsorbed with salt surfactants, and because the pore channels of the reservoir are too tiny, the pore channel distribution is in the micron and submicron level, even in the near nanometer level, the capillary force of the reservoir is very large, and the adsorption effect on the surfactants is large. For the reasons, the traditional surfactant is adsorbed by rocks in the migration process of the reservoir pore canal, so that the loss of the surfactant is caused, and the interfacial tension is visually expressed to be increased, thereby reducing the recovery rate and improving the production cost. On the other hand, if the loss amount of the surfactant is small, the interfacial tension does not change much. Therefore, the experimental example uses the interfacial tension change in the multiple displacement processes to characterize the loss condition of the surfactant.
As shown in fig. 5, after a plurality of times of displacement, although the interfacial tension value of the displacement fluid is increased, the increase amplitude is not large, and the difference between the interfacial tensions of the displacement fluid obtained in the first and last displacement is within 0.01mN/m, which indicates that the nano composite oil displacement agent has stable performance and the oil displacement agent has less loss in use in the process of a plurality of times of displacement.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A preparation method of a nano composite oil displacement agent is characterized by comprising the following steps:
mixing acrylamide, sodium p-styrene sulfonate and water according to the weight ratio of 10.5-13.5: 4.5-5: mixing the materials in a mass ratio of 90-99 to obtain a mixed solution;
adding a surfactant which is 5-7% of the mixed solution in weight into the mixed solution, adjusting the pH value of the mixed solution to 7-7.5, and then adding an inorganic nano intermediate which is 1-3% of the mixed solution in weight into the mixed solution to obtain a reaction solution;
adding an initiator into the reaction liquid under an inert atmosphere, and reacting for 8-10 hours at 75-80 ℃ to obtain a polymer emulsion;
demulsifying, drying and crushing the polymer emulsion to obtain a nano composite oil displacement agent;
the surfactant is a solid product which is obtained by firstly reacting a mixed system of dodecylbenzene sulfonic acid, ethyl acetate and vinyl imidazole at 45-50 ℃ for at least 24 hours, and then hermetically freezing at the temperature of below-16 ℃ to separate out, wherein the mass ratio of the dodecylbenzene sulfonic acid to the ethyl acetate is 1: 4-5; the mass of the vinyl imidazole is 0.4-0.7% of the sum of the mass of the dodecyl benzene sulfonic acid and the mass of the ethyl acetate;
the inorganic nano intermediate is synthesized by a method comprising the following steps:
mixing the layered silicate with water and swelling the layered silicate in the water to obtain a swelling system;
heating the swelling system to 60-90 ℃, adding an intercalation agent which accounts for 1-10% of the mass of the swelling system into the swelling system, reacting for 10-12 hours under the stirring frequency of 30-45 hz, performing solid-liquid separation on the obtained product, and drying the solid part to obtain the inorganic nano intermediate.
2. The method for preparing a surfactant according to claim 1, comprising the step of preparing the surfactant by:
mixing dodecyl benzene sulfonic acid, ethyl acetate and vinyl imidazole according to a proportion to obtain a mixed system;
adopting a condensation reflux process to react the mixed system for 24-48 hours at the temperature of 45-50 ℃ to obtain a reaction product;
hermetically freezing the reaction product at the temperature of below-16 ℃ for at least 24 hours to obtain a freezing system;
washing the freezing system by using ethyl acetate, then repeating the steps of sealing, freezing and washing, and collecting the obtained white crystals to obtain the surfactant.
3. The preparation method according to claim 1 or 2, wherein in the process of synthesizing the surfactant, dodecylbenzene sulfonic acid and ethyl acetate are first mixed, then vinyl imidazole is added in an inert atmosphere, and then the mixture is mixed for 2 to 2.5 hours under the conditions that the temperature is 0 to 4 ℃ and the stirring frequency is 30 to 35hz, so as to obtain the mixed system.
4. The preparation method according to claim 1, wherein the reaction solution is placed in a polymerization kettle, nitrogen is introduced into the polymerization kettle, and the flow rate of the nitrogen is controlled to be 45-50 m3And h, enabling the pressure in the polymerization kettle to reach 0.50-0.55 MPa, and achieving the inert atmosphere after more than 20 min.
5. The preparation method according to claim 1, wherein the initiator is at least one selected from persulfates, and the initiator is 0.6-0.8% of the mass of the reaction solution.
6. The method of claim 1, wherein the intercalant during the synthesis of the inorganic nano-intermediate comprises at least a first component selected from at least one of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride.
7. The method of claim 6, wherein the intercalant further comprises a second component selected from at least one of ethanolamine, phosphoric acid, hydrochloric acid, and sulfuric acid;
the mass of the second component is not more than that of the first component, and the pH value of the intercalating agent is 6.5-7.5.
8. The preparation method according to claim 5 or 6, wherein the interlayer distance of the inorganic nano intermediate is 1.5-4 nm.
9. A nanocomposite oil-displacing agent characterized by being produced by the production method according to any one of claims 1 to 8.
10. Use of the nanocomposite oil displacement agent of claim 9 in oil recovery engineering.
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