CN109233780B - Nano-emulsion oil displacement agent and preparation method thereof - Google Patents
Nano-emulsion oil displacement agent and preparation method thereof Download PDFInfo
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Abstract
The invention provides a nano-emulsion oil displacement agent and a preparation method thereof, wherein the nano-emulsion oil displacement agent is prepared from the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent. The invention mixes the raw materials orderly and stirs them to form water-in-oil system emulsion, the molecular weight of the prepared nano-emulsion oil displacement agent is more than 200 ten thousand, the median diameter of the particles is less than 40nm, the interfacial tension is 9.0 x 10‑5～8.6×10‑4mN/m, stable storage period is more than 240 days, and delamination is not easy to occur. The nanoemulsion oil displacement agent can reach any corner of oil reservoir communication, changes the surface wettability of rocks, improves swept volume, and is beneficial to stripping and recovery of crude oil.
Description
Technical Field
The invention relates to the technical field of polymer synthesis, in particular to a nanoemulsion oil displacement agent and a preparation method thereof.
Background
Most of the oil fields with medium and high permeability developed by water injection in China enter the exploitation period with high water content and high extraction degree, most oil layers on the oil fields are flooded by water, and the rest oil is sporadically distributed seriously; in addition, many low permeability oil fields have small porosity, low permeability, extremely low water-flooding oil washing efficiency, small swept volume, high injection pressure and difficult development. In order to improve the oil extraction efficiency, a series of methods are continuously explored and formed at home and abroad, for example, polymer flooding, alkali water flooding, surfactant flooding and the like are adopted, the methods achieve some performances, and a series of problems are encountered in application.
The method of adding low carbon alcohol to prepare the surfactant flooding oil is simple in system and good in emulsifying property, but the oil flooding capability of the surfactant flooding oil is reduced due to chromatographic separation of the stratum; the lignin is used as sacrificial agent, urea and hexametaphosphate are mixed into the oil displacement system to improve the salt resistance of the oil displacement system, but only partial adsorption loss can be reduced. Some oil fields add a large amount of alkali when adding the oil displacement agent in tertiary oil recovery, can reduce oil-water interfacial tension by a wide margin like this, but the oil field injects the stratum into and is easy to harden after adding alkali, blocks off the oil outlet, is unfavorable for the further exploitation of surplus oil, and the alkali that also leads to the ground injection system scale deposit seriously. In the current oil extraction profile control technology, no matter polymer flooding, alkali flooding, surfactant flooding, ASP, microorganism flooding and the like, each tiny pore is difficult to reach, so that the oil extraction amount of an oil field still has limited rising space.
In the research and development direction of nano oil displacement, experts and scholars conduct continuous research and development. The oil displacement agent prepared by adopting the nano silicon dioxide modified sulfonate surfactant, which is proposed by the Kinghua of the Shengli oil field Shengli engineering and the like, has the advantages of strong surface activity, good compatibility with oil reservoirs, low interfacial tension and easy biodegradation, but also has the advantages of higher production cost, low efficiency of the oil displacement agent and difficult meeting the requirement of ultra-low interfacial tension of stratum in some oil fields. And like the nanometer oil displacement agent for the thermal oil recovery process proposed by Fushun group holdings Limited company Lizhong, the nanometer oil displacement agent can be used with high-temperature fluid in a synergistic way or co-injected, can microcrystallize the structures of asphaltene, colloid and wax crystals, can effectively solve the problem of oil layer emulsification and blockage, can be used in the field of thermal oil recovery, but still has poor product adaptability, insufficient viscosity reduction capability and higher cost in other areas, and does not accord with the current concept of cost reduction and efficiency improvement. In the schemes, optimization cannot be realized on the oil displacement sweep volume and the oil displacement efficiency, namely, maximization of oil displacement is difficult to realize on unit cost, and the prior art cannot be completely adapted to the current low-cost development situation. Therefore, in view of the above-mentioned defects, it is necessary to develop a nanoemulsion oil displacement agent again to meet the requirements of cost reduction and efficiency improvement, and how to improve the sweep efficiency of an oil reservoir while reducing the production cost becomes a problem to be solved urgently.
Disclosure of Invention
In view of the above, the present invention aims to provide a nanoemulsion oil displacement agent and a preparation method thereof, and the nanoemulsion oil displacement agent provided by the present invention has the advantages of low cost, simple preparation method and high oil displacement efficiency.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a nanoemulsion oil displacement agent which is prepared from the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent.
Preferably, the composition comprises the following components in parts by weight: 45 parts of mineral oil, 6 parts of emulsifier, 48 parts of monomer alkali-water mixed solution, 0.2 part of cross-linking agent, 0.3 part of oxidant and 0.5 part of reducing agent.
Preferably, the monomer alkaline water mixed solution is a mixed solution obtained by neutralizing a monomer and a sodium hydroxide aqueous solution, the neutralization temperature is 70 ℃, the neutralization degree of the monomer is 60-80%, and the mass concentration of a monomer sodium salt in the mixed solution is 60%.
Preferably, the monomer is any one of an acrylic acid monomer, a methacrylic acid monomer, an allylsulfonic acid monomer, and a methallylsulfonic acid monomer.
Preferably, the emulsifier comprises span 80 and tween 60; the mass ratio of span 80 to tween 60 in the emulsifier is 1: 2-2: 1.
Preferably, the crosslinking agent comprises one or more of N, N-methylenebisacrylamide, polyvinyl alcohol, ethylene glycol, diethylene glycol, and glycerol.
Preferably, the oxidizing agent comprises one or more of sodium persulfate, potassium persulfate, ammonium persulfate, and hydrogen peroxide.
Preferably, the reducing agent comprises one or more of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, L-ascorbic acid, and ferrous chloride.
The invention also provides a preparation method of the nano emulsion oil displacement agent in the technical scheme, which comprises the following steps:
(1) under the condition of nitrogen protection, mixing a cross-linking agent and the monomer alkali water mixed solution to obtain a monomer aqueous phase solution;
(2) mixing mineral oil with emulsifier to obtain oil phase;
(3) adding the oil phase obtained in the step (2) into the monomer water phase solution obtained in the step (1) for emulsification to obtain an emulsion;
(4) under the condition of nitrogen protection, mixing an oxidant, a reducing agent and the emulsion obtained in the step (3) for polymerization reaction to obtain a nano emulsion oil displacement agent;
there is no sequential limitation to the steps (1) and (2).
Preferably, the temperature of the polymerization reaction in the step (4) is 70 ℃; the polymerization reaction time is 8-10 h.
Has the advantages that: the nano-emulsion oil displacement agent provided by the invention comprises the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent. The nano emulsion oil displacement agent provided by the invention has simple raw material components, reduces the cost on one hand, ensures the advantage of strong surface activity of the system on the other hand, and the formed surfactant system has high oil displacement efficiency.
The preparation method of the nano-emulsion oil displacement agent provided by the invention has simple steps, and the nano-emulsion oil displacement agent with the molecular weight more than 200 ten thousand and the particle size less than 40nm in emulsion particles is obtained by orderly mixing the raw materials to obtain the monomer aqueous phase solution and the oil phase, then mixing the monomer aqueous phase solution and the oil phase to form the emulsion, and heating and polymerizing under the action of the oxidant and the reducer.
The nano emulsion oil displacement agent provided by the invention is a water-in-oil nano system, and is adsorbed and deposited on the surface of oil reservoir oleophilic rock to form a nano film, so that the wettability of the surface of the rock is changed, the interface tension with ultralow order of magnitude is formed, the adhesion work of an oil phase is reduced, the surface of the rock is changed to be hydrophilic, the peeling of residual oil is facilitated, and the swept volume is increased; the nano emulsion oil displacement agent provided by the invention can reach any corner of oil reservoir communication, intelligently and dynamically expands swept volume along the way, improves the oil washing efficiency, and completely displaces the trapped crude oil, thereby improving the oil field recovery ratio.
The embodiment result shows that compared with the product in the prior art, the nano emulsion oil displacement agent prepared by the invention realizes cost reduction and efficiency improvement, the cost is reduced by 10-20%, and the preparation method is simpler; the nano emulsion oil displacement agent prepared by the invention has the molecular weight of more than 200 ten thousand and the interfacial tension of 9.0 multiplied by 10-5～8.6×10-4mN/m, the median particle size of emulsion particles is less than 40nm, the stable storage period is more than 240 days, and delamination is not easy to occur; when the oil field recovery agent is used for oil field recovery, the swept volume can be increased by 10-15%, and the crude oil recovery rate is increased by 10-15%.
Detailed Description
The invention provides a nanoemulsion oil displacement agent which is prepared from the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent.
The preparation raw materials of the nano-emulsion oil displacement agent comprise, by weight, 30-45 parts of mineral oil, preferably 37-45 parts of mineral oil, and more preferably 45 parts of mineral oil. The mineral oil of the invention is preferably industrial white oil which has the marks of No. 3, No. 5, No. 7 and the like, is a non-fluorescent light yellow or transparent oily liquid and does not contain water and mechanical impurities. The invention takes the mineral oil as the oil phase of the nano emulsion oil displacement agent system, has good fluidity and can be adsorbed on the surface of oleophilic rock. The source of the mineral oil is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
The preparation raw materials of the nano-emulsion oil displacement agent comprise 3-8 parts of an emulsifier, preferably 5-7 parts of the emulsifier, and more preferably 6 parts of the emulsifier by weight. The emulsifier preferably comprises span 80 and tween 60, and the mass ratio of span 80 to tween 60 in the emulsifier is preferably 1: 2-2: 1, and more preferably 1: 1. Span 80 is a high-grade lipophilic emulsifier, HLB is 4.3; tween 60, also called polysorbate 60, is insoluble in mineral oil and vegetable oil, and can be used as an emulsifier and a stabilizer. The sources of span 80 and tween 60 in the present invention are not particularly limited, and commercially available products known to those skilled in the art may be used.
Based on the weight parts of the mineral oil, the preparation raw material of the nano emulsion oil displacement agent comprises 30-50 parts of monomer alkaline water mixed solution, preferably 40-50 parts, and more preferably 48 parts. In the present invention, the monomer aqueous alkali mixture is preferably a mixture obtained by neutralizing a monomer and an aqueous sodium hydroxide solution, the temperature of the neutralization is preferably 70 ℃, and the degree of neutralization of the monomer is preferably 60% to 80%, and more preferably 70%; in the present invention, after completion of the heat neutralization, the resulting mixed solution is a mixed aqueous solution of a monomer having a certain acidity and a sodium salt of the monomer, wherein the mass concentration of the sodium salt of the monomer is preferably 60%.
In the present invention, the monomer is preferably any one of an acrylic acid monomer, a methacrylic acid monomer, an allylsulfonic acid monomer, and a methallylsulfonic acid monomer; the organic acid monomer used in the invention has low price and good performance, and can be neutralized with sodium hydroxide aqueous solution to obtain monomer alkali water mixed solution with low molecular weight. The sources of the monomers and sodium hydroxide are not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
Based on the weight part of the mineral oil, the preparation raw material of the nano emulsion oil displacement agent comprises 0.01-0.5 part of cross-linking agent, preferably 0.1-0.3 part, and more preferably 0.2 part. In the present invention, the crosslinking agent is preferably one or more of N, N-methylenebisacrylamide, polyvinyl alcohol, ethylene glycol, diethylene glycol, or glycerin. In the invention, the crosslinking agent contains a plurality of unsaturated double bonds in the molecule, has good water solubility, can be well dissolved in aqueous solution together with the monomer and the monomer sodium salt, and does not generate crosslinking reaction when not heated. The source of the crosslinking agent is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
The preparation raw materials of the nano-emulsion oil displacement agent comprise 0.05-0.5 part of oxidant, preferably 0.2-0.4 part of oxidant, and more preferably 0.3 part of oxidant by weight part of mineral oil. In the present invention, the oxidizing agent preferably includes one or more of sodium persulfate, potassium persulfate, ammonium persulfate, and hydrogen peroxide.
The preparation raw materials of the nano emulsion oil displacement agent comprise 0.04-0.7 part of reducing agent, preferably 0.3-0.6 part, and more preferably 0.5 part by weight of mineral oil. In the present invention, the reducing agent preferably includes one or more of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, L-ascorbic acid, and ferrous chloride. The invention uses the oxidant and the reducer as the initiator to promote the polymerization of the monomer, and the invention ensures that the polymerization reaction is safely and stably carried out by strictly controlling the types and the proportion of the oxidant and the reducer, thereby obtaining the nanoemulsion oil displacement agent with high polymerization degree. The source of the oxidizing agent and the reducing agent is not particularly required in the present invention, and commercially available products known to those skilled in the art may be used.
The invention provides a preparation method of the nanoemulsion oil displacement agent, which comprises the following steps:
(1) under the condition of nitrogen protection, mixing a cross-linking agent and the monomer alkali water mixed solution to obtain a monomer aqueous phase solution;
(2) mixing mineral oil with emulsifier to obtain oil phase;
(3) adding the oil phase obtained in the step (2) into the monomer water phase solution obtained in the step (1) for emulsification to obtain an emulsion;
(4) under the condition of nitrogen protection, mixing an oxidant, a reducing agent and the emulsion obtained in the step (3) for polymerization reaction to obtain a nano emulsion oil displacement agent;
there is no sequential limitation to the steps (1) and (2).
Under the condition of nitrogen protection, the cross-linking agent and the monomer alkaline water mixed solution are mixed to obtain the monomer aqueous phase solution. In the present invention, the monomer alkali-water mixture solution is preferably prepared by:
adding the monomer into sodium hydroxide aqueous solution, heating and neutralizing to obtain monomer alkaline water mixed solution.
In the present invention, the temperature for heating and neutralizing is preferably 70 ℃, and the degree of neutralization of the monomer is preferably 60% to 80%, and more preferably 70%; in the present invention, after completion of the heat neutralization, the resulting mixed solution is a mixed aqueous solution of a monomer having a certain acidity and a sodium salt of the monomer, wherein the mass concentration of the sodium salt of the monomer is preferably 60%. The invention neutralizes the monomer and the sodium hydroxide water solution, aims to reduce the molecular weight of the organic acid monomer, has good monomer dispersibility in the formed emulsion and ensures the smooth proceeding of the later polymerization reaction.
In the embodiment of the present invention, it is preferable to put the monomer aqueous alkali mixture into the reaction kettle, then introduce nitrogen into the monomer aqueous alkali mixture for 30 minutes in order to replace air to reduce the oxygen content of the aqueous phase, and then add the cross-linking agent and stir until completely dissolved to obtain the monomer aqueous phase solution.
The invention mixes mineral oil with emulsifier to obtain oil phase. The invention has no requirement on the sequence of preparing the aqueous phase solution and the oil phase of the monomer, the stirring aims at uniformly mixing all materials, no special requirement on the stirring speed exists, and the monomer does not generate crosslinking reaction in the period.
After the monomer aqueous phase solution and the oil phase are obtained, the oil phase is added into the monomer aqueous phase solution for emulsification to obtain the emulsion. In the invention, the oil phase and the monomer aqueous phase solution are preferably mixed and then stirred at a high speed, wherein the high speed stirring speed is preferably 800-2000 rpm, more preferably 1200-1800 rpm, and further preferably 1600 rpm; stirring at high speed to form milky emulsion.
After the emulsion is obtained, the invention mixes the oxidant, the reducer and the emulsion for polymerization under the condition of nitrogen protection to obtain the nano emulsion oil displacement agent. In the invention, preferably, the temperature of the emulsion is raised to 50 ℃, then the oxidant and the reductant are slowly and sequentially added into the emulsion, the reductant is added at an interval of ten minutes after the oxidant is added, stirring is continuously carried out in the interval, the stirring speed is preferably 200-500 rpm, more preferably 350rpm, the temperature of the system is raised to 70 ℃ after polymerization is initiated, and the nano-emulsion oil displacement agent is prepared by carrying out heat preservation polymerization for 8-10 hours at 70 ℃. In the invention, the polymerization reaction belongs to an exothermic reaction, the exothermic rate is related to the dosage of the initiator, the heat preservation polymerization refers to maintaining the reaction system at a constant temperature of 70 ℃ by external heating or cooling and stirring in a reaction kettle, and the invention preferably introduces nitrogen for protection in the whole polymerization reaction.
The raw materials for preparing the nano emulsion oil-displacing agent by the preparation method comprise the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent. The nano emulsion oil displacement agent provided by the invention has simple preparation raw material components, reduces the cost on one hand, ensures the advantage of strong surface activity of the system on the other hand, and forms the surfactant system with high oil displacement efficiency. The nano emulsion oil-displacing agent provided by the invention is a water-in-oil nano system, and is heated and polymerized to obtain the nano emulsion oil-displacing agent with the molecular weight of more than 200 ten thousand and the particle size of emulsion particles of 10-500 nm. The nano-emulsion oil displacement agent provided by the invention can be adsorbed and deposited on the surface of an oil reservoir oleophilic rock to form a layer of nano-scale film, so that the wettability of the rock surface is changed, the interface tension with ultralow order of magnitude is formed, the adhesion work of an oil phase is reduced, the rock surface is changed to be hydrophilic, the peeling of residual oil is facilitated, and the swept volume is increased; the nano emulsion oil displacement agent provided by the invention can reach any corner of oil reservoir communication, intelligently and dynamically expands swept volume along the way, improves the oil washing efficiency, and completely displaces the trapped crude oil, thereby improving the oil field recovery ratio.
The nano emulsion oil displacement agent and the preparation method thereof provided by the invention are described in detail below with reference to the examples, but the nano emulsion oil displacement agent and the preparation method thereof are not to be construed as limiting the scope of the invention.
The same raw materials are adopted in the embodiments 1-3, and the difference is that the mass proportion relation among the components is different;
raw materials of examples 1 to 3: the mineral oil is industrial white oil, the emulsifier is a mixture of span 80 and tween 60 in a mass ratio of 1:1, the monomer alkaline water mixed solution is a sodium acrylate aqueous solution with a mass concentration of 60% obtained by neutralizing acrylic acid and sodium hydroxide, the cross-linking agent is N, N-methylene bisacrylamide, the oxidant is potassium persulfate, and the reducing agent is sodium sulfite.
Example 1
The nanoemulsion oil displacement agent is prepared from the following raw materials in parts by weight: 45 parts of mineral oil, 6 parts of emulsifier, 48 parts of monomer alkali-water mixed solution, 0.2 part of cross-linking agent, 0.3 part of oxidant and 0.5 part of reducing agent;
the preparation method of the nano-emulsion oil displacement agent comprises the following steps:
weighing the raw materials according to the weight, placing a sodium acrylate aqueous solution with the mass concentration of 60% in a reaction kettle, introducing nitrogen to remove air, adding N, N-methylene bisacrylamide, and uniformly stirring to obtain a sodium acrylate aqueous phase solution; adding the mixture of span 80 and tween 60 into the industrial white oil and uniformly stirring to obtain an oil phase; adding the oil phase into a reaction kettle, mixing with the sodium acrylate aqueous phase solution, and stirring at the speed of 1600rpm to form milky emulsion; heating the emulsion to 50 ℃, introducing nitrogen for protection, stirring at the speed of 350rpm, slowly adding an oxidant, continuously stirring for 10 minutes after the oxidant is added, slowly adding a reducing agent, continuously stirring to initiate polymerization reaction, and then keeping the constant temperature of 70 ℃ for polymerization reaction to obtain the nano emulsion oil-displacing agent.
Example 2
The nanoemulsion oil displacement agent is prepared from the following raw materials in parts by weight: 37 parts of mineral oil, 4 parts of emulsifier, 30 parts of monomer alkaline water mixed solution, 0.5 part of cross-linking agent, 0.05 part of oxidant and 0.04 part of reducing agent; the preparation method is the same as that of example 1.
Example 3
The nanoemulsion oil displacement agent is prepared from the following raw materials in parts by weight: 45 parts of mineral oil, 8 parts of emulsifier, 40 parts of monomer alkaline water mixed solution, 0.01 part of cross-linking agent, 0.5 part of oxidant and 0.2 part of reducing agent; the preparation method is the same as that of example 1.
Examples 4 to 7 adopt the same raw material mass ratio relationship and preparation method as those of example 1, except that the types of part of raw materials were changed.
Example 4
This example uses the raw material mass ratio relationship and the preparation method of example 1, the only difference being that the monomer alkali-water mixed solution is replaced by an aqueous solution of sodium methacrylate having a mass concentration of 60% obtained by neutralizing methacrylic acid and sodium hydroxide.
Example 5
In this example, the raw material mass ratio relationship and the preparation method of example 1 were used, and the only difference was that the monomer alkali-water mixed solution was replaced with an aqueous solution of sodium allylsulfonate having a mass concentration of 60% obtained by neutralizing allylsulfonic acid and sodium hydroxide.
Example 6
In this example, the raw material mass ratio relationship and the preparation method of example 1 were used, and the only difference was that the monomer aqueous alkali mixture was replaced with a 60% sodium methallylsulfonate aqueous solution neutralized with methallylsulfonic acid and sodium hydroxide.
Example 7
In this example, the raw material mass ratio relationship and the preparation method of example 1 were used to replace the relevant additives: the cross-linking agent is a mixture of polyvinyl alcohol and ethylene glycol in a mass ratio of 1:1, the oxidizing agent is a mixture of a reducing agent and ammonium persulfate in a mass ratio of 1:1, and the reducing agent is a mixture of sodium bisulfite and L-ascorbic acid in a mass ratio of 1: 1.
Specific parameters of the nanoemulsion oil-displacing agent prepared in examples 1-7 are shown in table 1.
TABLE 1 nanoemulsion oil-displacing agent parameters
As can be seen from Table 1, in examples 1 to 3, the same raw materials were used, and the masses between the raw material components were adjustedThe proportioning relation shows that the molecular weight distribution of the prepared nano emulsion oil displacement agent is 220-270 ten thousand, and the interfacial tension is 4.8 multiplied by 10-4～8.6×10-4The stable storage period is more than 8 months between mN/m; examples 4 to 7, in which the monomer aqueous alkali mixture and the auxiliary agent were replaced, the molecular weight distribution of the prepared nanoemulsion oil-displacing agent was 240 to 300 ten thousand, and the interfacial tension was 9 × 10-5～8.6×10-4The stable storage period is more than 9 months between mN/m.
Example 8
According to the invention, the nano-emulsion oil displacement agent prepared in the embodiments 1-7 and the commercially available oil displacement commodities PJ-4 and FMS are respectively subjected to oil displacement efficiency measurement by adopting an indoor simulation test method.
The indoor simulation test method adopts a sand-filled pipe model to carry out a simulation experiment of crude oil recovery ratio, and the experiment parameters are as follows:
displacement of the brine medium: artificially simulating formation water with the mineralization degree of 35456mg/L and the sodium bicarbonate water type;
crude oil medium: crude oil on site, viscosity 22.6mPa.s at 60 ℃;
thirdly, sand filling pipe model parameters: the pipe diameter is 2.54cm and the length is 30.0 cm.
The indoor simulation test method comprises the following specific steps:
at room temperature, evacuating the sand filling pipe model for 4 hours, saturating the simulated formation water, and measuring the porosity pv value of the sand filling pipe model;
placing the saturated saline water model in a constant temperature box at 60 ℃ for 6 hours, establishing internal and external temperature balance, and then performing the steps of three-five displacement;
thirdly, displacing the formation water in the sand-packed pipe by using crude oil at a constant speed of 12mL/min (constant speed method) until the oil content percentage of the outlet end face of the model is kept constant, recording the pressure difference, the total liquid amount and the oil output amount, and establishing the original oil saturation and the irreducible water saturation;
fourthly, injecting a nano oil displacement agent slug at a constant speed of 12mL/min, and displacing 1000pv numbers (pore volume times);
and fifthly, displacing with simulated formation water until the oil content of the outlet end face is constant, and calculating the oil displacement recovery ratio after the experiment is finished.
TABLE 2 oil displacement simulation experiment results of nanoemulsion oil displacement agent
As can be seen from table 2, the results of the evaluation of the nano-emulsion oil displacement agent prepared in the embodiments 1 to 7 of the present invention by the indoor physical modeling experiment show that, compared with the commercially available oil displacement commodity PJ-4 and the commercially available oil displacement commodity FMS, the interfacial tension value of the nano-emulsion oil displacement agent prepared in the present invention is reduced by more than 40%, and the crude oil recovery ratio is increased by 10% to 15%.
The nano emulsion oil displacement agent provided by the invention has the advantages that the preparation method is simple, the cost of used raw materials is lower, and the cost is reduced by 10% -20% compared with the cost of a commercially available oil displacement commodity PJ-4 and an oil displacement commodity FMS.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. The nanoemulsion oil displacement agent is characterized by being prepared from the following components in parts by weight: 30-45 parts of mineral oil, 3-8 parts of emulsifier, 30-50 parts of monomer alkaline water mixed solution, 0.01-0.5 part of cross-linking agent, 0.05-0.5 part of oxidant and 0.04-0.7 part of reducing agent;
the monomer alkaline water mixed solution is a mixed solution obtained by neutralizing a monomer and a sodium hydroxide aqueous solution, the neutralization temperature is 70 ℃, the neutralization degree of the monomer is 60-80%, and the mass concentration of a monomer sodium salt in the mixed solution is 60%;
the monomer is any one of an acrylic acid monomer, a methacrylic acid monomer, an allylsulfonic acid monomer and a methallylsulfonic acid monomer;
the cross-linking agent comprises one or more of N, N-methylene bisacrylamide, polyvinyl alcohol, ethylene glycol, diethylene glycol and glycerol;
the molecular weight of the nano emulsion oil displacement agent is more than 200 ten thousand, the particle size of emulsion particles is 10-500 nm, and the median particle size of the emulsion particles is less than 40 nm.
2. The nanoemulsion oil displacement agent according to claim 1, which is characterized by comprising the following components in parts by weight: 45 parts of mineral oil, 6 parts of emulsifier, 48 parts of monomer alkali-water mixed solution, 0.2 part of cross-linking agent, 0.3 part of oxidant and 0.5 part of reducing agent.
3. The nanoemulsion oil displacement agent according to claim 1 or 2, wherein the emulsifier comprises span 80 and tween 60; the mass ratio of span 80 to tween 60 in the emulsifier is 1: 2-2: 1.
4. the nanoemulsion oil displacement agent of claim 1 or 2, wherein the oxidant comprises one or more of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide.
5. The nanoemulsion oil displacement agent of claim 1 or 2, wherein the reducing agent comprises one or more of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, L-ascorbic acid and ferrous chloride.
6. The preparation method of the nano emulsion oil-displacing agent according to any one of claims 1 to 5, characterized by comprising the following steps:
(1) under the condition of nitrogen protection, mixing a cross-linking agent and the monomer alkali water mixed solution to obtain a monomer aqueous phase solution;
(2) mixing mineral oil with emulsifier to obtain oil phase;
(3) adding the oil phase obtained in the step (2) into the monomer water phase solution obtained in the step (1) for emulsification to obtain an emulsion;
(4) under the condition of nitrogen protection, mixing an oxidant, a reducing agent and the emulsion obtained in the step (3) for polymerization reaction to obtain a nano emulsion oil displacement agent;
there is no sequential limitation to the steps (1) and (2).
7. The method according to claim 6, wherein the temperature of the polymerization reaction in the step (4) is 70 ℃; the polymerization reaction time is 8-10 h.
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| CN112094379A (en) * | 2020-08-31 | 2020-12-18 | 新疆新易通石油科技有限公司 | Preparation method of nano-emulsion oil displacement agent and intelligent control system |
| CN112940701B (en) * | 2021-01-27 | 2024-06-07 | 河北光大石化有限公司 | High-rheological continuous phase profile control agent and preparation method thereof |
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