Emulsion polymer, emulsion gelling system and preparation method and application of emulsion polymer and emulsion gelling system

Abstract

The invention belongs to the technical field of oilfield exploitation, and relates to an emulsion polymer, an emulsion gelling system and a preparation method and application thereof, in particular to a novel high-temperature-resistant and high-salt-resistant emulsion polymer, an emulsion gelling system and a preparation method and application thereof. The preparation method of the emulsion polymer comprises the following steps: (1) dissolving an emulsifier in solvent oil, and uniformly stirring to obtain an oil phase; (2) completely dissolving a monomer in water to obtain a water phase, and then adjusting the pH value of the water phase with alkali; (3) dropwise adding the oil phase into the water phase to form an oil-in-water emulsion, and stirring after emulsification is finished; and (4) introducing nitrogen to remove oxygen, adding an initiator to initiate a polymerization reaction, then preserving heat, and obtaining an emulsion polymer after the reaction is finished. The emulsion polymer disclosed by the invention is low in initial viscosity and high in temperature resistance and salt resistance, and has the capability of realizing reservoir plugging and profile adjustment in high-temperature and high-salt oil reservoir profile control measures.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield exploitation, and relates to an emulsion polymer, an emulsion gelling system, and a preparation method and application thereof, and in particular to a novel high-temperature and high-salt resistant emulsion polymer, an emulsion gelling system, and a preparation method and application thereof. Background Art

[0002] As one of the most effective and widely used profile control systems, polymer gel can effectively block water flow channels, improve water drive flow profiles, and significantly reduce the water production rate of oil wells. It is widely used in offshore oil fields. However, due to the small operating space of offshore oil field platforms, conventional dry powder polymer gels have a large footprint, which greatly affects the efficiency of on-site implementation. Through optimization research on emulsion polymer gel systems and supporting equipment, technicians have realized the miniaturization and integration of online injection processes and equipment, greatly promoting the scale implementation of offshore oil field profile control. As deep, high-temperature, and high-salinity reservoirs gradually begin to implement profile control measures, higher requirements are placed on the emulsion polymer gel profile control system. Summary of the invention

[0003] In view of the defects of the prior art, the present invention provides an emulsion polymer, an emulsion gelling system and a preparation method and application thereof.

[0004] Specifically, the preparation method of the emulsion polymer of the present invention comprises:

[0005] (1) dissolving the emulsifier in solvent oil and stirring evenly to obtain an oil phase;

[0006] (2) completely dissolving the monomer in water to obtain an aqueous phase, and then adjusting the pH of the aqueous phase with a base;

[0007] (3) adding the oil phase dropwise to the water phase to form an oil-in-water emulsion, and stirring after the emulsification is completed;

[0008] (4) nitrogen is introduced to remove oxygen, an initiator is added to initiate a polymerization reaction, and then the temperature is kept high to obtain an emulsion polymer after the reaction is completed.

[0009] In the above-mentioned method for preparing the emulsion polymer, the emulsifier is one or more of Tween series surfactants, polyoxyethylene ether type surfactants, and span series surfactants.

[0010] In the above-mentioned method for preparing the emulsion polymer, the emulsifier is Span-80 / OP-10, Span-80 / Tween-60 or Span-80 / Tween-80 with a molar ratio of (0.05-0.2):(0.5-1.5).

[0011] In the above-mentioned method for preparing emulsion polymer, the solvent oil is white oil.

[0012] In the preparation method of the emulsion polymer, the emulsifier is 2-10 parts and the solvent oil is 90-98 parts by weight.

[0013] In the above-mentioned method for preparing the emulsion polymer, the monomer is one or more of AM and AMPS; and the water is ultrapure water.

[0014] In the preparation method of the emulsion polymer, the monomer is 20-40 parts and the water is 60-80 parts by weight.

[0015] In the above-mentioned method for preparing the emulsion polymer, the base is one or more of NaOH and KOH, and the pH of the aqueous phase after adding the base is 7-8.

[0016] In the above-mentioned method for preparing the emulsion polymer, in step (3), the volume ratio of the oil phase to the water phase is (0.6-0.9): (0.9-1.2).

[0017] In the above-mentioned method for preparing the emulsion polymer, the initiator is (NH4)2S2O8-NaHSO3.

[0018] In the above-mentioned method for preparing the emulsion polymer, the temperature for initiating the polymerization reaction is 40-70° C.; the temperature for heat preservation is 40-50° C., and the heat preservation time is 2-4 hours.

[0019] On the other hand, the present invention also provides an emulsion polymer, which is prepared by the above-mentioned preparation method of the emulsion polymer.

[0020] In another aspect, the present invention further provides a method for preparing an emulsion gelling system, comprising: dissolving the emulsion polymer, crosslinking agent and auxiliary agent in simulated water in sequence under stirring to obtain an emulsion gelling system.

[0021] In the preparation method of the emulsion gelling system, the crosslinking agent is an organic phenolic crosslinking agent; the auxiliary agent is one or more of a stabilizer, a pH regulator, a complexing agent, and an inorganic crosslinking agent.

[0022] In the preparation method of the above-mentioned emulsion gelling system, the organic phenolic crosslinking agent is hydroquinone / hexamethylenetetramine, hydroquinone / glyoxal, resorcinol / hexamethylenetetramine, resorcinol / glyoxal, aspirin / hexamethylenetetramine, aspirin / glyoxal or a water-soluble phenolic resin.

[0023] In the preparation method of the emulsion gelling system, the stabilizer is one or more of thiourea, urea, sodium isoascorbate and bentonite; the pH regulator is one or more of sodium bicarbonate, citric acid and sodium hydroxide; the complexing agent is one or more of sodium tripolyphosphate, sodium ethylenediaminetetramethylenephosphonate, tetrasodium hydroxyethylenediphosphonate, trisodium methylglycine diacetate and tetrasodium ethylenediaminetetraacetate; and the inorganic crosslinking agent is one or more of chromium acetate and sodium silicate.

[0024] In another aspect, the present invention provides an emulsion gelling system, which is prepared by the above-mentioned preparation method.

[0025] The above-mentioned emulsion gelling system comprises, by weight percentage, 0.5%-1.5% of emulsion polymer, 0.5%-1.5% of composite cross-linking agent, 1%-3.5% of composite auxiliary agent, and the balance is simulated water.

[0026] In another aspect, the present invention also provides the use of the above-mentioned emulsion polymer or the above-mentioned emulsion gel system as a profile control agent in the process of oil reservoir exploitation.

[0027] In the above application, the reservoir temperature of the oil reservoir is ≤140°C, and the mineralization is ≤45550mg / L.

[0028] The technical solution of the present invention has the following beneficial effects:

[0029] (1) The emulsion polymer of the present invention has good solubility in 45550 mg / L mineralized water. When heated at 140° C. for 24 hours, the viscosity retention rate of the polymer solution can reach 66.8%;

[0030] (2) The emulsion polymer of the present invention has low initial viscosity, high temperature and salt resistance, and has the ability to achieve reservoir plugging and profile adjustment in high-temperature and high-salinity oil reservoir profile control measures;

[0031] (3) The new high temperature resistant gel profile control agent prepared by using the emulsion polymer of the present invention and optimizing the system formula can achieve a 90-day dehydration rate of less than 10% under high temperature (140°C) and high salt (mineralization 45550 mg / L, divalent metal ion 2000 mg / L) conditions;

[0032] (4) The emulsion gel system of the present invention has significant application effects in the field of oil field profile control and flooding control. The system has good injectability and plugging properties (>85%), and has good reservoir profile adjustment capabilities in the formation, which can significantly improve the recovery rate (>10%). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0034] Figure 1 is the infrared spectrum of the emulsion polymer;

[0035] Figure 2 The viscosity-concentration relationship curves of different emulsion polymers;

[0036] Figure 3 is the temperature resistance of different emulsion polymer solutions;

[0037] Figure 4 is the salt resistance of emulsion polymer solution at different sodium chloride concentrations;

[0038] Figure 5 is the salt resistance of emulsion polymer solution at different calcium chloride concentrations;

[0039] Figure 6-Figure 7 are the rheological properties of different polymer gels;

[0040] Figure 8-Figure 9 The effect of polymer and cross-linker concentration on the system;

[0041] Figure 10-11 The influence of mineralization on the system;

[0042] Fig.12 is the effect of temperature on the system;

[0043] Fig.13 It is the injection pressure variation curve of the gel system;

[0044] Fig.14 This is the relationship curve between pressure and injection multiple. DETAILED DESCRIPTION

[0045] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process method of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0046] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0047] Specifically, in a first aspect, the present invention provides a method for preparing an emulsion polymer, comprising:

[0048] (1) dissolving the emulsifier in solvent oil and stirring evenly to obtain an oil phase;

[0049] (2) completely dissolving the monomer in water to obtain an aqueous phase, and then adjusting the pH of the aqueous phase with a base;

[0050] (3) adding the oil phase dropwise to the water phase to form an oil-in-water emulsion, and stirring after the emulsification is completed;

[0051] (4) nitrogen is introduced to remove oxygen, an initiator is added to initiate a polymerization reaction, and then the temperature is kept high to obtain an emulsion polymer after the reaction is completed.

[0052] In the present invention, the emulsifier added in step (1) can reduce the interfacial tension, solubilize the monomer, and form a protective film to stabilize the emulsion system. Step (2) evenly disperses the monomer in the aqueous solution. Water, as a reaction medium, has a high specific heat, which helps to dissipate heat, reduce the viscosity of the system, and make the reaction heat easy to remove. Step (3) forms a uniform and stable water-in-oil emulsion, which is convenient for subsequent initiation of polymerization. In step (4), the initiator decomposes under certain conditions to produce free radicals, thereby initiating a polymerization reaction, so that the monomer molecules are connected to each other to form a high molecular weight polymer. Nitrogen deoxygenation is to prevent polymer oxidation, make the synthesis reaction purer and more accurate, and ensure the quality and purity of the synthesized polymer.

[0053] In some preferred embodiments, the emulsifier is one or more of Tween series surfactants, polyoxyethylene ether type surfactants, and span series surfactants.

[0054] The emulsifier of the present invention may specifically include Span-80 / OP-10, Span-80 / Tween-60 or Span-80 / Tween-80 in a molar ratio of (0.05-0.2):(0.5-1.5). The emulsifier system compounded in a specific ratio of the present invention has better stability than the emulsion system formed by a single emulsifier system and the selected dispersion medium.

[0055] More preferably, the molar ratio of Span-80 to OP-10 or Tween-60 or Tween-80 in the emulsifier is 0.1:1, thereby achieving a better effect.

[0056] In some preferred embodiments, the solvent oil is white oil.

[0057] Wherein, by weight, the emulsifier in the oil phase is 2-10 parts, and the solvent oil is 90-98 parts. More preferably, the emulsifier is 5 parts, and the solvent oil is 95 parts.

[0058] In some preferred embodiments, the monomers used in step (2) are one or more of AM and AMPS. AMPS is a salt-tolerant monomer, and its content is 13-20 parts (preferably 20 parts), and the content of AM monomer is 80-87 parts (preferably 80 parts). The present invention can effectively improve the salt tolerance of the polymer by adding AMPS monomer.

[0059] Preferably, the water used to prepare the aqueous phase in the present invention is ultrapure water, thereby ensuring the purity of the polymerization environment and avoiding the influence of ions in the water on the polymerization reaction.

[0060] Wherein, by weight, in the aqueous phase of the present invention, the monomer is 20-40 parts and the water is 60-80 parts. More preferably, the aqueous phase includes 30 parts of monomer and 70 parts of ultrapure water.

[0061] In step (2), the base is one or more of NaOH and KOH. After adding the base, the pH of the aqueous phase is 7-8, and the stability of the formed emulsion is enhanced by means of a weak alkaline environment.

[0062] In step (3), the volume ratio of the oil phase to the water phase is (0.6-0.9): (0.9-1.2), and more preferably 0.8: 1. In practice, when the volume ratio of the oil phase to the water phase exceeds this ratio, the formed oil-in-water emulsion has poor stability in the subsequent polymerization process and low yield of the synthesized polymer.

[0063] In some preferred embodiments, the initiator is (NH4)2S2O8-NaHSO3. The polymerization initiation temperature is 40-70°C; the heat preservation reaction temperature is 40-50°C, and the reaction time is 2-4 hours.

[0064] The preparation method of the emulsion polymer of the present invention is an emulsion polymerization method. In the emulsion polymerization process, an initiator first generates free radicals in water to initiate a polymerization reaction between AM and AMPS monomers to form a high molecular weight long-chain polymer.

[0065] In a second aspect, the present invention further provides an emulsion polymer, which is prepared by the above-mentioned preparation method.

[0066] The polymer prepared according to the method of the present invention is an emulsion polymer, which has good high temperature resistance, salt resistance and high viscoelasticity.

[0067] The AMPS molecule used in the emulsion polymer of the present invention contains a sulfonic acid group, which is beneficial to enhancing the water solubility, hydration ability and thermal stability of the polymer, so that the synthetic polymer has strong temperature and salt resistance. In addition, AMPS has a large side chain, which improves the rigidity of the main chain of the synthetic polymer and further enhances the high temperature resistance of the polymer.

[0068] The reservoir characteristics of high-temperature, high-salinity and strong water-breakthrough oil reservoirs in offshore oil fields are high temperature (≥140℃), high mineralization (≥5×10 4 The present invention takes an organic phenolic cross-linked polymer gel system as a research object, provides a high temperature and high salt emulsion polymer, evaluates the effects of different organic cross-linking agents and additives on gelling properties (gelling time, gel strength and thermal stability, etc.), analyzes the dehydration rate of the gel at different temperatures, mineralization degrees and aging times, and determines the injectability, plugging property and erosion resistance of the gel system, clarifies the effect of the system on improving the recovery rate, and thus develops an emulsion polymer gel system suitable for profile control of high temperature and high salt reservoirs.

[0069] The inventors found in the research process that the inorganic metal cross-linking agent has a short gelation time, poor gel stability at high temperature, and is easy to dehydrate and degrade; the PEI cross-linking agent has high thermal stability at high temperature, but the required polymer concentration is very high (usually 7%) and the gelation time is too short (about 3 hours), which cannot meet the requirements of on-site construction; the phenolic cross-linking agent and the conventional dry powder polymer form a spatial network structure through covalent bonds, and the heat resistance and salt resistance are improved, but the stability is greatly reduced after the temperature exceeds 120°C, which cannot meet the requirements of safe, effective and long-term plugging. When the mineralization of the local formation is high, the polymer molecules in the solution tend to curl from stretching, the effective volume of the molecules is reduced, the coils are tight, and the cross-linking reaction is not easy to occur. These unfavorable factors limit the application of conventional polymer gel systems in high-temperature and high-salt oil reservoirs.

[0070] Specifically, in the third aspect, the present invention provides a method for preparing an emulsion gelling system, comprising: dissolving the emulsion polymer, crosslinking agent and auxiliary agent in simulated water in sequence under stirring to obtain an emulsion gelling system.

[0071] Preferably, the emulsion polymer is added into a beaker filled with simulated water and stirred at 300 rpm to fully dissolve the polymer solution until it is uniform and free of insoluble matter.

[0072] In the present invention, the emulsion polymer solution is fully dissolved, which can prevent the uneven concentration from causing local gelation during the subsequent addition of the composite crosslinking agent and composite auxiliary agent. The added crosslinking agent can undergo a crosslinking reaction with the emulsion polymer under a specific environment, linking the emulsion polymer chain to form a high-strength gel space network structure. The added composite auxiliary agent has the functions of controlling the time of the crosslinking reaction, adjusting the gel strength and long-term stability, etc.

[0073] Preferably, the emulsion gelling system comprises, by weight percentage, 0.5%-1.5% of emulsion polymer, 0.5%-1.5% of composite cross-linking agent, 1%-3.5% of composite auxiliary agent, and the balance is simulated water.

[0074] In some preferred embodiments, the crosslinking agent used in the present invention is an organic phenolic crosslinking agent, preferably: hydroquinone / hexamethylenetetramine, hydroquinone / glyoxal, resorcinol / hexamethylenetetramine, resorcinol / glyoxal, aspirin / hexamethylenetetramine, aspirin / glyoxal or a water-soluble phenolic resin. Further preferably, the crosslinking agent is hydroquinone / hexamethylenetetramine.

[0075] Among them, the masses of the two components in the organic phenolic cross-linking agent are the same, and the mass ratio is 1:1.

[0076] The crosslinking agent used in the present invention is a composite organic crosslinking agent, which can complement the conventional single crosslinking agent, effectively improve the gelling strength of the emulsion gel, and facilitate the adjustment of the gelling properties of the emulsion gel by adjusting the ratio.

[0077] The auxiliary agent used in the present invention is one or more of a stabilizer, a pH regulator, a complexing agent, and an inorganic cross-linking agent.

[0078] Further preferably, the stabilizer is one or more of thiourea, urea, sodium isoascorbate, and bentonite; the pH adjuster is one or more of sodium bicarbonate, citric acid, and sodium hydroxide; the complexing agent is one or more of sodium tripolyphosphate, sodium ethylenediaminetetramethylenephosphonate, tetrasodium hydroxyethylenediphosphonate, trisodium methylglycine diacetate, and tetrasodium ethylenediaminetetraacetic acid; and the inorganic cross-linking agent is one or more of chromium acetate and sodium silicate.

[0079] The auxiliary agent used in the present invention is a composite auxiliary agent, which is used to adjust the time of the cross-linking reaction, the gel strength and the long-term stability.

[0080] The present invention develops new emulsion polymers, crosslinking agents and additives and optimizes the system formula combination ratio to prepare a gel profile control agent with a 90-day dehydration rate of less than 10% under high temperature (120-140°C) and high salt (mineralization 20000-45550 mg / L, divalent metal ions 1000-2000 mg / L) conditions.

[0081] In a fourth aspect, the present invention further provides an emulsion gelling system, which is prepared by the above-mentioned preparation method.

[0082] The emulsion gel system prepared according to the method of the present invention has good injectability, a plugging rate of more than 85%, an increased recovery rate of more than 10%, and good profile adjustment capability in the formation.

[0083] In a fifth aspect, the present invention also provides the use of the above-mentioned emulsion polymer or emulsion gel system as a profile control agent in the process of oil reservoir exploitation.

[0084] Specifically, the emulsion polymer or emulsion gel system is used to improve the recovery rate and adjust the water absorption profile of high-temperature and high-salinity oil reservoirs. The high temperature can reach up to 140° C., and the high salt can reach up to 45550 mg / L.

[0085] Through practice, the new type of high-temperature and high-salt resistant emulsion polymer or emulsion gel system has excellent heat and salt resistance, and can still maintain the system's action strength in high-temperature and high-salt formations, block water channeling channels, adjust water absorption profiles, improve water injection swept area, and effectively improve oil field recovery rates.

[0086] Example

[0087] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions. The raw materials used in the following examples are all conventionally purchased.

[0088] Example 1

[0089] This embodiment provides a series of novel high temperature and high salt resistant emulsion polymers and preparation methods thereof, which specifically include the following steps:

[0090] Weigh 5 parts of emulsifier with a total mass of m(Span-80) / m(Tween-80)=0.1:1 and dissolve it in 95 parts of white oil as the oil phase. Use a high-speed emulsifier to stir the solvent oil and emulsifier evenly at a speed of 1000r / min. Then dissolve 30 parts of the monomer combination (AM+salt-resistant monomer AMPS) in 70 parts of ultrapure water, use a magnetic stirrer to accelerate the dissolution, wait for the monomer to be completely dissolved, and add NaOH solution to adjust the pH value of the water phase to 7.5. During the high-speed emulsification process of the emulsifier, the oil phase solution is added dropwise to the water phase system, and the monomer droplets are dispersed in the water phase to form an oil-in-water (O / W) emulsion with an oil-water volume ratio of 0.8:1. After the emulsification is completed, the total system is stirred. After nitrogen was passed to drive out oxygen for half an hour, the initiator (NH4)2S2O8-NaHSO3 was added to 0.4 parts of the monomer mass, and the polymerization was initiated in an environment of 10°C. After the initiation was completed, the reaction was kept at 50°C for 5 hours, and the reaction system was removed from the reactor to obtain a milky white liquid product. By controlling the content of the salt-tolerant monomer AMPS, a series of three emulsion polymers with AMPS contents of 13%, 15%, and 18% were synthesized, and the synthetic products were characterized by infrared spectroscopy tests to clarify their functional groups.

[0091] The experimental results are as follows Figure 1 As shown, wave number 3327cm -1 NH asymmetric stretching vibration peak, 3176cm -1 NH symmetric stretching vibration peak, 2923cm -1 The CH2 antisymmetric stretching vibration peak is 1648 cm -1 is the C=O stretching vibration peak in amide, 1602 cm -1 NH bending vibration peak in amide, 1548 cm -1 -COO - The C=O stretching vibration peak in the -1 The peak of CH2 asymmetric in-plane bending vibration is 1401 cm -1 -SO3 - The stretching vibration absorption peak, 1314 cm -1 The above results can infer that the synthesized high temperature and high salt resistant emulsion polymer contains unique functional groups -COOH, CONH2 and -SO3 - , these groups come from monomers AM and AMPS.

[0092] Example 2

[0093] At room temperature, the emulsion polymer solutions prepared in Example 1 with mass fractions of 0.4%, 0.6%, 0.8%, 1.0%, and 1.2% were prepared using saline with a mineralization of 45550 mg / L (40000 mg / L sodium chloride and 5550 mg / L calcium chloride), and stirred at 500 rpm for 4 h to observe the solubility of different polymers and the shear rate of 7.34 s -1 The viscosity was measured under the following conditions. The experimental results are shown in Figure 2 In saline with a salinity of 45550 mg / L, the three polymers provided by the present invention can all be dissolved, and as the polymer concentration increases, the polymer viscosity increases exponentially, but the viscosity after dissolution is lower than 25 mPa·s.

[0094] Three emulsion polymer solutions of R13 with an AMPS monomer content of 13%, R15 with an AMPS monomer content of 15%, and R18 with an AMPS monomer content of 18% were prepared using saline with a mineralization degree of 45550 mg / L. The polymer solutions were injected into ampoules and heated at 140°C for 24 hours. The viscosity of the polymer solutions was measured at regular intervals, with a shear rate of 7.34 s -1 The experimental results are as follows Figure 3 In a 140℃ environment, the viscosity of the polymer decreases fastest within 12 hours of heating. The viscosity retention rate of the R18 emulsion polymer solution is the highest, reaching 66.8%, while the retention rate of the R13 emulsion polymer solution is the lowest, at 51.7%.

[0095] Three emulsion polymer solutions of R13, R15 and R18 with a mass fraction of 1.2% were prepared using saline with different mineralization degrees (5000 mg / L calcium chloride + different concentrations of sodium chloride, 40000 mg / L sodium chloride + different concentrations of calcium chloride). After aging for 24 hours, the -1 The viscosity was measured at the shear rate. The experimental results are as follows Figure 4 and Figure 5 As shown. When the calcium chloride concentration is 5000mg / L, the polymer viscosity increases slightly with the increase of sodium chloride concentration; when the sodium chloride concentration is 40000mg / L, as the calcium chloride concentration increases, calcium ions compress the polymer molecular coils, which is manifested as a slight decrease in viscosity. In summary, R18 has stronger temperature and salt resistance.

[0096] Example 3

[0097] 1% of the three polymers R13, R15, and R18 were prepared in saline with a mineralization degree of 45550 mg / L and mixed with 1% crosslinker (0.5% hydroquinone + 0.5% hexamethylenetetramine), and then heated at 140°C for 48 hours. The storage modulus and loss modulus were measured at a frequency of 0.1 to 100 Hz using a Physica MCR 301 rotational rheometer, with a constant shear rate of 7.34 s -1 Determine the gel viscosity, the experimental results are as follows Figure 6 and Figure 7 As shown. The storage modulus of R18 and R15 polymer gels can reach 10Pa, and the loss modulus can reach more than 2Pa, while the storage modulus and loss modulus of R13 polymer gel are smaller, so the gel formed by R18 and R15 can form a strong plugging underground. From the perspective of gel strength, the gel constructed by R18 polymer with good temperature and salt resistance has the highest viscosity and the best gelling effect.

[0098] Example 4

[0099] 1% R18 polymer solution was prepared using saline with a mineralization degree of 45550 mg / L, mixed with different types of 1% cross-linking agents, and heated at 140°C for 48 hours. The gel formation is shown in Table 1. After the R18 polymer was mixed with the cross-linking agent hydroquinone / hexamethylenetetramine, the gel strength was the highest. Among them, the gel using the cross-linking agent PEI began to dehydrate after 12 hours, so hydroquinone / hexamethylenetetramine was preferred as the cross-linking agent.

[0100] 1% R18 polymer solution was prepared using saline water with a mineralization degree of 45550 mg / L, the total concentration of the crosslinker was controlled to be 1%, hydroquinone and hexamethylenetetramine were added in different proportions, and heated at 140°C for 48 hours. The experimental results are shown in Table 2. The gelation time of the polymer gel was about 20 hours. When the ratio of hydroquinone to hexamethylenetetramine was 1:1, the gelation time was appropriate, the gel strength was high, and it did not dehydrate for 48 hours.

[0101] Table 1 The gelation of 1% R18 polymer and 1% different types of crosslinking agents

[0102]

[0103] Table 2 Effect of the ratio of phenols and aldehydes in crosslinking agents on the gelling effect

[0104]

[0105] Example 5

[0106] A 1% R18 polymer solution was prepared using saline with a mineralization degree of 45550 mg / L, and mixed with 1% cross-linking agent (0.5% hydroquinone + 0.5% hexamethylenetetramine) to prepare a gel. Different combinations of additives were added and heated at 140°C for 48 hours. The experimental results are shown in Table 3.

[0107] After adding thiourea and urea as single additives, the gel stability was improved. Among them, the four combinations of ethylenediaminetetra (methylene phosphonic acid) sodium and thiourea, chromium acetate and urea, sodium silicate and urea, and tetrasodium hydroxyethylene diphosphonic acid and thiourea can significantly reduce the dehydration rate of the gel, but the gel strength of adding chromium acetate and urea dropped to Class C within 15 days, which was a significant decrease. In summary, the three additive combinations of ethylenediaminetetra (methylene phosphonic acid) sodium and thiourea, sodium silicate and urea, and tetrasodium hydroxyethylene diphosphonic acid and thiourea have a better effect on improving the gel stability.

[0108] Table 3 Effects of different additive combinations on gel

[0109]

[0110] Example 6

[0111] At room temperature, a gel system was prepared using 45550 mg / L mineralization water: 1% R18 + 0.5% hydroquinone + 0.5% hexamethylenetetramine + 1.8% sodium ethylenediaminetetra (methylenephosphonate) + 0.5% thiourea. The concentrations of other agents were kept constant. (1) The concentrations of polymer and crosslinker were changed and heated at 140°C for 48 hours. The experimental results are shown in the following table. Figure 8 and Fig. 9 (2) When the calcium chloride concentration is 5000 mg / L, the sodium chloride concentration is changed to 10000-60000 mg / L. When the sodium chloride concentration is 40000 mg / L, the calcium chloride concentration is changed to 1000-6000 mg / L. The mixture is placed in a 140°C environment and heated for 48 hours. The experimental results are as follows: Fig.10 and Fig.11 (3) Place it in an environment with different temperatures and heat it for 48 hours. The temperature is set to 130℃, 140℃ and 150℃. Record the gelation time and gel strength. Use a rheometer to measure the gel viscosity. The experimental results are shown in Fig.12 shown.

[0112] With the increase of polymer and cross-linking agent concentration, the viscosity of the gel system increases and the gelation time shortens. The effect of cross-linking agent concentration on gelation time is more significant, and the effect of polymer concentration on gel viscosity is relatively greater. In summary, the gelation time is controllable within 19-40h; the viscosity of the gel system is 7255-23015mPa·s after heating at 140℃ for 48h, and the gel strength is HI level.

[0113] As the concentration of sodium chloride and calcium chloride increases, the compression shielding ability of the double electric layer force of polymer molecules is enhanced, and the contact ability between polymer molecules and between polymer molecules and crosslinking agent molecules is enhanced, resulting in a shortened gelation time, but a slight decrease in gel strength. The size and charge strength of the divalent ions in calcium chloride are larger, which has a more significant effect on the gelation time. Under this condition, the gelation time can be adjusted from 17 to 50 hours, the gel viscosity is between 18395 and 25651 mPa·s, and the strength is HI level;

[0114] As the temperature increases, the gelation time of the gel system shortens. Within 140°C, the strength of the gel system remains basically stable, but when the temperature rises to 150°C, the strength of the gel system decreases slightly. The gel system does not dehydrate after 48 hours of heating.

[0115] Example 7

[0116] The gel system was selected as follows: 1% R18 + 0.5% hydroquinone + 0.5% hexamethylenetetramine + 1.8% sodium ethylenediaminetetra(methylenephosphonate) + 0.5% thiourea; the experimental conditions were injection multiple 1.0PV, injection speed 0.25mL / min, and permeability 500mD. The injection performance, plugging performance, and erosion resistance of the system were evaluated. The experimental results are as follows Fig.13 , Table 4, Fig.14 shown.

[0117] The injection pressure of the gel system is relatively small, and the injection pressure after stabilization is 0.3MPa, with good injection performance, indicating that the gel system can be well injected into the formation and play a role in plugging the formation. In addition, the plugging rate of the gel system for 5 cores with different permeabilities is above 99%, and after being flushed with 10PV salt water, the pressure can still be stabilized at around 8.6MPa, with a small change range, indicating that the system has good plugging and flushing resistance.

[0118] Table 4 Gel system II core plugging performance

[0119]

[0120]

[0121] Example 8

[0122] The experimental conditions are a single core experimental model, the injection rate is 0.25ml / min, and the injection time is 98% water content. The gel system is selected: 1% R18 + 0.5% hydroquinone + 0.5% hexamethylenetetramine + 1.8% sodium ethylenediaminetetramethylenephosphonate + 0.5% thiourea, and the effect of different injection volumes on the effect of improving the recovery rate is observed. The experimental results are shown in Table 5. With the increase of the injection multiple, the recovery rate increase gradually increases, and the maximum recovery rate increase is 16.39%. Among them, when the injection volume is greater than 0.8PV, the recovery rate increase does not change much, indicating that the optimal injection volume is 0.8PV.

[0123] Table 5 Effect of injection rate on recovery factor

[0124]

[0125] The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be deemed to be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined in the claims.

Claims

1. A method for preparing an emulsion polymer, characterized in that: include: (1) dissolving the emulsifier in solvent oil and stirring evenly to obtain an oil phase; (2) completely dissolving the monomer in water to obtain an aqueous phase, and then adjusting the pH of the aqueous phase with a base; (3) adding the oil phase dropwise to the water phase to form an oil-in-water emulsion, and stirring after the emulsification is completed; (4) nitrogen is introduced to remove oxygen, an initiator is added to initiate a polymerization reaction, and then the temperature is kept high to obtain an emulsion polymer after the reaction is completed.

2. The method for preparing an emulsion polymer according to claim 1, characterized in that: The emulsifier is one or more of Tween series surfactants, polyoxyethylene ether type surfactants, and span series surfactants.

3. The method for preparing an emulsion polymer according to claim 2, characterized in that: The emulsifier is Span-80 / OP-10, Span-80 / Tween-60 or Span-80 / Tween-80 in a molar ratio of (0.05-0.2):(0.5-1.5).

4. The method for preparing an emulsion polymer according to claim 1, characterized in that: The solvent oil is white oil.

5. The method for preparing an emulsion polymer according to claim 1, characterized in that: In terms of weight, the emulsifier is 2-10 parts, and the solvent oil is 90-98 parts.

6. The method for preparing an emulsion polymer according to claim 1, characterized in that: The monomer is one or more of AM and AMPS; the water is ultrapure water.

7. The method for preparing an emulsion polymer according to claim 1, characterized in that: In terms of weight, the monomer is 20-40 parts, and the water is 60-80 parts.

8. The method for preparing an emulsion polymer according to claim 1, characterized in that: The alkali is one or more of NaOH and KOH, and the pH of the aqueous phase is 7-8 after adding the alkali.

9. The method for preparing an emulsion polymer according to claim 1, characterized in that: In step (3), the volume ratio of the oil phase to the water phase is (0.6-0.9):(0.9-1.2).

10. The method for preparing an emulsion polymer according to claim 1, characterized in that: The initiator is (NH4)2S2O8-NaHSO3.

11. The method for preparing an emulsion polymer according to claim 1, characterized in that: The polymerization initiation temperature is 40-70° C.; the heat preservation temperature is 40-50° C., and the heat preservation time is 2-4 hours.

12. An emulsion polymer, characterized in that The preparation method is described in any one of claims 1 to 11.

13. A method for preparing an emulsion gelling system, characterized in that: include: Under stirring, the emulsion polymer, crosslinking agent and auxiliary agent are fully dissolved in simulated water in turn to obtain an emulsion gel system.

14. The method for preparing the emulsion gelling system according to claim 13, characterized in that: The cross-linking agent is an organic phenolic cross-linking agent; the auxiliary agent is one or more of a stabilizer, a pH regulator, a complexing agent, and an inorganic cross-linking agent.

15. The method for preparing the emulsion gelling system according to claim 14, characterized in that: The organic phenolic crosslinking agent is hydroquinone / hexamethylenetetramine, hydroquinone / glyoxal, resorcinol / hexamethylenetetramine, resorcinol / glyoxal, aspirin / hexamethylenetetramine, aspirin / glyoxal or a water-soluble phenolic resin.

16. The method for preparing the emulsion gelling system according to claim 14, characterized in that: The stabilizer is one or more of thiourea, urea, sodium isoascorbate, and bentonite; the pH adjuster is one or more of sodium bicarbonate, citric acid, and sodium hydroxide; the complexing agent is one or more of sodium tripolyphosphate, sodium ethylenediaminetetramethylenephosphonate, tetrasodium hydroxyethylenediphosphonate, trisodium methylglycine diacetate, and tetrasodium ethylenediaminetetraacetate; and the inorganic crosslinking agent is one or more of chromium acetate and sodium silicate.

17. An emulsion gelling system, characterized in that: The preparation method is described in any one of claims 13 to 16.

18. The emulsion gelling system according to claim 17, comprising, by weight percentage: 0.5%-1.5% emulsion polymer, 0.5%-1.5% composite cross-linking agent, 1%-3.5% composite auxiliary agent, and the balance is simulated water.

19. Use of the emulsion polymer according to claim 12 or the emulsion gelling system according to any one of claims 17 to 18 as a profile control agent in an oil reservoir exploitation process.

20. The use according to claim 19, characterized in that The reservoir temperature of the oil reservoir is ≤140°C, and the mineralization is ≤45550mg / L.

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