A polymer oil-displacing agent

Abstract

The present invention relates to a polymer flooding agent, belonging to the technical field of oil and gas reservoir chemicals. The modifier in the polymer flooding agent of the present invention can complex Ca in high brine at room temperature. 2+ Mg 2+ , reducing the influence of high salt on the internal cross-linking of polyacrylamide polymer molecules, and at the same time, the polyacrylamide polymer can jointly accelerate ion diffusion and enhance activation energy. The chelating agent in the modifier can be quickly activated at room temperature, which is conducive to the entry of multivalent metal salts into the polyacrylamide molecular lattice and the rapid formation of intramolecular cross-linking at room temperature. The polymer oil-displacing agent of the present invention can have a high viscosity when used in a low dosage, and at formation temperature, as the degree of hydrolysis of the polyacrylamide polymer increases, the viscosity of the oil-displacing agent increases. Therefore, the oil-displacing agent of the present invention can achieve room temperature cross-linking and have a high apparent viscosity in high-salt water, while having a high viscosity retention rate at high temperature, thereby meeting the use requirements of high-temperature and high-salt oil and gas reservoirs.

Description

Technical Field

[0001] The invention relates to a polymer oil-displacing agent, belonging to the technical field of oil and gas reservoir chemicals. Background Art

[0002] Polymer flooding achieves the purpose of improving oil recovery by improving mobility ratio, increasing flow resistance, and viscoelastic flooding. Scientifically controlling mobility ratio is the key to ensuring the effectiveness of polymer flooding, and the core of controlling mobility ratio is the viscosity of the polymer solution. Studies have shown that conventional acrylamide polymers are greatly affected by temperature and salinity. On the one hand, as temperature and salinity increase, the molecular chain is more likely to break; on the other hand, the carboxyl groups on the molecular chain are more likely to react with Ca 2+ Mg 2+ Complexation and precipitation occur, resulting in a decrease in solution viscosity. Therefore, polymer flooding technology has a good oil recovery effect in Class I-II reservoirs with low temperature and salinity, but its application is limited in Class III-V reservoirs with high temperature and high salinity.

[0003] The current improvement methods are: 1. Introducing a heat-resistant and salt-resistant monomer, such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS), into the polyacrylamide main chain, by regulating the degree of polymerization and the copolymerization unit structure ratio to improve the heat resistance and salt resistance of the product, but the viscosity improvement is limited in high salinity water. For example, Chinese patent document CN102408516B discloses a preparation method of a heat-resistant and salt-resistant polyacrylamide, which introduces three heat-resistant and salt-resistant monomers to copolymerize with acrylamide to synthesize acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / acrylic acid, N-vinyl pyrrolidone / N, N-dimethylacrylamide tetrapolymer. Compared with ordinary polyacrylamide oil-displacing agents, the cost is increased by 30% to 40%, which still cannot meet the application requirements under higher temperature and salinity conditions; 2. Injecting a cross-linking agent into the formation together with the polymer aqueous solution oil-displacing agent to cross-link and thicken the oil-displacing agent during the migration process in the formation. For example, Chinese patent document CN104513654A provides a modifier and an oil-displacing agent composition, an oil-displacing agent, and a preparation method thereof. This patent document uses a modifier to modify a polyacrylamide polymer, enabling the polyacrylamide polymer to meet the requirements of a salinity of less than 30,000 mg / L and a temperature resistance of 95°C. However, the polymer still does not form a gel at room temperature (below 30°C). After entering the formation, it is affected by the complex formation conditions, causing certain difficulties in the cross-linking reaction, and it is impossible to determine whether intramolecular cross-linking is formed underground.

[0004] Therefore, in view of the problem that the current high-temperature and high-salt resistant polymer oil-displacing agents have unstable performance, it is urgent to develop a polymer oil-displacing agent suitable for high-temperature and high-salt conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide a polymer oil-displacing agent that can solve the problem of unstable performance of current polymer oil-displacing agents when used in high-temperature and high-salinity oil and gas reservoirs.

[0006] In order to achieve the above objectives, the technical solution adopted by the polymer oil-displacing agent of the present invention is:

[0007] A polymer oil-displacing agent comprises a polyacrylamide polymer and a modifier, wherein the modifier is composed of a charge-introducing agent, a dialdehyde compound, a chelating agent and a polyvalent metal salt, wherein the charge-introducing agent is a halogenated hydrocarbon compound, and the molar ratio of metal ions in the charge-introducing agent, the dialdehyde compound, the chelating agent and the polyvalent metal salt is (0.1-20):(0.1-5):(0.1-5):1.

[0008] The modifier in the polymer oil displacement agent of the present invention can complex the Ca in the high salt water at room temperature. 2+ Mg 2+ , reducing the influence of high salt on the internal cross-linking of polyacrylamide polymer molecules, while accelerating ion diffusion, reducing activation energy, and rapidly activating the multivalent metal salt in the modifier at room temperature, which is conducive to the multivalent metal salt entering the polyacrylamide molecular lattice and quickly forming intramolecular cross-linking at room temperature. The polymer oil-displacing agent of the present invention can have a high viscosity when used in a low dosage, and at formation temperature, as the degree of hydrolysis of the polyacrylamide polymer increases, the viscosity of the oil-displacing agent increases. Therefore, the oil-displacing agent of the present invention can achieve room temperature cross-linking and have a high apparent viscosity in high-salt water, while having a high viscosity retention rate at high temperature, thereby meeting the use requirements of high-temperature and high-salt oil and gas reservoirs.

[0009] Preferably, the molar ratio of the charge-introducing agent, the dialdehyde compound, the chelating agent, and the metal ions in the multivalent metal salt is (2-15):(1-4):(1-4):1. Limiting the molar ratio of the charge-introducing agent, the dialdehyde compound, the chelating agent, and the metal ions in the multivalent metal salt to the above range has the beneficial effect of fast intramolecular crosslinking of the oil-displacing agent without dehydration.

[0010] Preferably, the halogenated hydrocarbon compound is selected from one or any combination of chlorinated hydrocarbon compounds, brominated hydrocarbon compounds, and fluorinated hydrocarbon compounds.

[0011] In order to reduce toxicity and improve the safety of the polymer oil-displacing agent, preferably, the halogenated hydrocarbon compound is a saturated monohalogenated hydrocarbon compound.

[0012] Preferably, the carbon atoms in the halogenated hydrocarbon compound are 3 to 7. For example, the carbon atoms in the halogenated hydrocarbon compound are 4 or 5. When the carbon atoms in the halogenated hydrocarbon compound are 4, the halogenated hydrocarbon compound is chlorobutane, bromobutane, or fluorobutane; when the carbon atoms in the halogenated hydrocarbon compound are 5, the halogenated hydrocarbon compound is chloropentane, bromopentane, or fluoropentane. In the present invention, the chlorobutane is 1-chlorobutane or 2-chlorobutane; the bromobutane is 1-bromobutane or 2-bromobutane; the fluorobutane is 1-fluorobutane or 2-fluorobutane; the chloropentane is 1-chloropentane, 2-chloropentane, or 3-chloropentane; the bromopentane is 1-bromopentane, 2-bromopentane, or 3-bromopentane; and the fluoropentane is 1-fluoropentane, 2-fluoropentane, or 3-fluoropentane.

[0013] Preferably, the dialdehyde compound is glyoxal. The present invention does not limit the purity of glyoxal, which can be industrial pure or analytical pure.

[0014] All chelating agents used in the field of oil and gas field chemicals are applicable to the present invention. Preferably, the chelating agent is selected from one or any combination of carboxylates, hydroxycarboxylates, sulfosalicylate, alkyldiamine tetracarboxylates, hydroxyalkylalkyldiamine tricarboxylates, and ammonia tricarboxylates.

[0015] Preferably, the carboxylate is a citrate; the hydroxycarboxylate is a glycolate or a hydroxypropionate; the alkyldiaminetetracarboxylate is an ethylenediaminetetraacetate or an ethylenediaminetetrapropionate; the hydroxyalkylalkyldiaminetricarboxylate is a hydroxyethylethylenediaminetriacetate or a hydroxypropylethylenediaminetriacetate; the ammoniatricarboxylate is a nitrilotriacetate or ammoniatripropionate. Preferably, the carboxylate is an alkali metal citrate; the hydroxycarboxylate is an alkali metal glycolate or a hydroxypropionate; the alkyldiaminetetracarboxylate is an alkali metal ethylenediaminetetraacetate or an alkali metal ethylenediaminetetrapropionate; the hydroxyalkylalkyldiaminetricarboxylate is an alkali metal hydroxyethylethylenediaminetriacetate; the ammoniatricarboxylate is an alkali metal nitrilotriacetate or an alkali metal ammoniatripropionate. For example, the carboxylate is sodium citrate; the hydroxycarboxylate is sodium hydroxyacetate and sodium hydroxypropionate; the alkyldiaminetetracarboxylate is disodium ethylenediaminetetraacetate and disodium ethylenediaminetetrapropionate; the hydroxyalkylalkyldiaminetricarboxylate is sodium hydroxyethylethylenediaminetriacetate; and the ammoniatricarboxylate is trisodium nitrilotriacetate and trisodium nitrilotripropionate.

[0016] More preferably, the chelating agent is selected from one or any combination of disodium EDTA, sodium sulfosalicylate, sodium glycolate, and sodium citrate. Using disodium EDTA, sodium sulfosalicylate, sodium glycolate, and sodium citrate as chelating agents can chelate high-valent metal cations in water, reducing or eliminating their effects on the viscosity of the polymer solution and subsequent cross-linking reactions.

[0017] Preferably, the polyvalent metal salt is a water-soluble polyvalent metal salt. Preferably, the polyvalent metal salt is selected from one or any combination of water-soluble aluminum salts, water-soluble chromium salts, water-soluble zirconium salts and water-soluble titanium salts.

[0018] Preferably, the water-soluble multivalent metal salt is selected from one or any combination of aluminum citrate, aluminum chloride, sodium metaaluminate, chromium chloride, zirconium acetate, zirconium chloride and titanium chloride.

[0019] All polyacrylamide polymers used for polymer oil displacement agents are suitable for the present invention. Preferably, the polyacrylamide polymer is a partially hydrolyzed polyacrylamide polymer. Further preferably, the number average molecular weight of the partially hydrolyzed polyacrylamide polymer is not less than 13 million, and the degree of hydrolysis is not more than 24%. At the reservoir temperature, the degree of hydrolysis gradually increases, and the molecular chain of the partially hydrolyzed polyacrylamide polymer stretches, ensuring its viscosity retention rate and reaction with glyoxal under formation conditions. The polyacrylamide polymer in the present invention can adopt commercially available products, for example, acrylamide / 2-acrylamido-2-methylpropanesulfonic acid sodium produced by Dongying Baomo Biochemical Co., Ltd., acrylamide / acrylic acid copolymer 6225 produced by Aisen China Flocculant Co., Ltd., acrylamide / 2-acrylamido-2-methylpropanesulfonic acid sodium copolymer produced by Sinopec Beijing Chemical Research Institute, and polyacrylamide type III produced by Henan Zhengjia Energy and Environmental Protection Co., Ltd. III.

[0020] Preferably, the mass ratio of the polyacrylamide polymer to the modifier is 100:(0.6-10). Preferably, the mass ratio of the polyacrylamide polymer to the modifier is 100:(1-5).

[0021] For the convenience of use, the polymer oil-displacing agent can be directly injected into the well. Preferably, the polymer oil-displacing agent also includes water.

[0022] Preferably, the mineralization of the water is no more than 150,000 mg / L.

[0023] The polymer oil-displacing agent is suitable for oil and gas reservoirs with a formation water salinity of no more than 150,000 mg / L and a formation temperature of no more than 90°C.

[0024] When used, the polymer oil-displacing agent of the present invention can be directly injected into the formation along with water, or the modifier in the polymer oil-displacing agent can be first prepared into a dispersion, and then the polyacrylamide polymer and the dispersion are mixed and then injected into the formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1Schematic diagram of the change curve of apparent viscosity of polyacrylamide polymer solution C1 and oil-displacing agents B1 and B2 at 25° C. over time in the experimental example of the present invention;

[0026] Figure 2 Schematic diagram of the change curve of apparent viscosity of polyacrylamide polymer solution C2 and oil-displacing agents B3 and B4 at 25° C. over time in the experimental example of the present invention;

[0027] Figure 3 Schematic diagram of the apparent viscosity change curve of the polyacrylamide polymer solution C3 at 70°C over time and the apparent viscosity change curve of the oil-displacing agent B3 at 70°C, 80°C, and 90°C over time in the experimental example of the present invention;

[0028] Figure 4 Schematic diagram of the change curve of the viscosity retention rate of the polyacrylamide polymer solution C3 at 70°C over time and the change curve of the viscosity retention rate of the oil-displacing agent B3 at 70°C, 80°C and 90°C over time in the experimental example of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0030] The polymer oil displacement agent of Examples 1-4 comprises a polyacrylamide polymer, a modifier and high saline water, wherein the polyacrylamide polymer is a partially hydrolyzed polyacrylamide polymer, and the modifier is composed of a charge introducing agent, a dialdehyde compound, a chelating agent and a multivalent metal salt.

[0031] The polymer oil-displacing agents of Examples 1-4 are prepared by a method comprising the following steps:

[0032] (1) First, a portion of the high-salt water and the modifier are uniformly dispersed to obtain a modifier dispersion with a concentration of 40 mg / L. Specifically, during the preparation, the charge introduction agent is first added to the high-salt water and stirred for 1 hour, and then the dialdehyde compound, chelating agent and polyvalent metal salt are added and stirred uniformly;

[0033] The modifier dispersions in the polymer oil-displacing agents of Examples 1-4 are numbered A1, A2, A3, and A4, respectively. The salinity of the high-salt water, the chemical name and added molar amount of the charge-introducing agent, the chemical name and added molar amount of the dialdehyde compound, the chemical name and added molar amount of the chelating agent, and the chemical name and added molar amount of the multivalent metal salt used in preparing the modifier dispersions in each Example are shown in Table 1.

[0034] Table 1 The salinity of the high brine used in preparing the modifier dispersion in each embodiment, the chemical name and added molar amount of the charge introducing agent, the chemical name and added molar amount of the dialdehyde compound, the chemical name and added molar amount of the chelating agent, and the chemical name and added molar amount of the multivalent metal salt

[0035]

[0036] (2) At room temperature, a polyacrylamide polymer is prepared into a polyacrylamide polymer solution of a certain concentration using high saline water. The high saline water used in preparing the polyacrylamide polymer solution in each embodiment is the same as the high saline water used in preparing the modifier dispersion. Then, the polyacrylamide polymer solution is added to the modifier dispersion and stirred evenly to obtain an oil-displacing agent. The concentration of the polyacrylamide polymer in the oil-displacing agent is 1500 mg / L. The oil-displacing agents of Examples 1-4 are numbered B1, B2, B3, and B4, respectively. The names of the polyacrylamide polymers used in the polymer oil-displacing agents of Examples 1-4, as well as the weight parts of the modifier dispersion and the polyacrylamide polymer solution used in preparing the oil-displacing agents are shown in Table 2.

[0037] Table 2 Names of polyacrylamide polymers used in the polymer oil-displacing agents of Examples 1-4 and weight parts of modifier dispersion and polyacrylamide polymer solution used in preparing the oil-displacing agents

[0038]

[0039] The manufacturer of acrylamide / sodium 2-acrylamido-2-methylpropanesulfonate used in Examples 1-4 is Dongying Baomo Biochemical Co., Ltd., the manufacturer of acrylamide / acrylic acid copolymer 6225 is Aisen China Flocculant Co., Ltd., the manufacturer of acrylamide / sodium 2-acrylamido-2-methylpropanesulfonate copolymer is Sinopec Beijing Research Institute of Chemical Industry, and the manufacturer of polyacrylamide type III is The manufacturer of III is Henan Zhengjia Energy and Environmental Protection Co., Ltd.

[0040] Experimental example

[0041] In order to evaluate the effect of the modifier in the oil-displacing agent of each embodiment on the polyacrylamide polymer, at room temperature, the polyacrylamide polymer used in Examples 1-4 was prepared into a polyacrylamide polymer solution with a volume of 600 mL and a concentration of 1500 mg / L using high saline water. The polyacrylamide polymer solutions prepared using the polyacrylamide polymer used in Examples 1-4 were numbered C1, C2, C3, and C4, respectively. The high saline water used to prepare the polyacrylamide polymer solutions C1, C2, C3, and C4 was the same as the high saline water used in Examples 1-4. The oil-displacing agent of each embodiment and the polyacrylamide polymer solutions C1, C2, C3, and C4 were then tested for their temperature and salt resistance using a Brookfield DV-III rotational viscometer with a ULA rotor, a speed of 6 RPM, and a shear rate of 7.341 s. -1 Under the conditions of , the apparent viscosity of polyacrylamide polymer solutions C1, C2 and oil displacement agents B1, B2, B3, B4 at 25 ° C was tested with time. The results are as follows Figure 1-2 As shown. Figure 1-2 As can be seen, at room temperature (25°C), oil-displacing agents B1, B2, B3, and B4 began crosslinking after 7 minutes of storage. After 30 minutes, their viscosities remained stable, around 35 mP·s. Furthermore, the viscosity at 30 days differed by no more than 2% from that at 30 minutes. In contrast, the viscosity of polymer solutions C1 and C2 remained unchanged after storage at room temperature (25°C) for a period of time. Therefore, at room temperature, the apparent viscosities of oil-displacing agents B1, B2, B3, and B4 were significantly superior to those of polyacrylamide polymer solutions C1 and C2.

[0042] In addition, the apparent viscosity variation curves of the oil-displacing agent B3 and the polyacrylamide polymer solution C3 at different temperatures were tested. The apparent viscosity variation curves of the polyacrylamide polymer solution C3 at 70°C and the apparent viscosity variation curves of the oil-displacing agent B3 at 70°C, 80°C, and 90°C were summarized in Figure 3 In. By Figure 3As can be seen, the apparent viscosity of oil-displacing agent B3 is significantly superior to that of polyacrylamide polymer solution C3. Furthermore, the apparent viscosity of oil-displacing agent B3 increases with increasing temperature, contrary to the viscosity-temperature characteristics of polyacrylamide polymer solution C3. Furthermore, at a constant temperature, the apparent viscosity of oil-displacing agent B3 increases slightly with storage time, while the apparent viscosity of polyacrylamide polymer solution C3 decreases with storage time. The viscosities of oil-displacing agent B3 after 90 days of storage at 70°C, 80°C, and 90°C are 51, 53, and 55 mP·s, respectively. When the apparent viscosity versus time curves of oil-displacing agents B1, B2, and B4 at different temperatures were measured using the above method, the test results showed that the viscosities of oil-displacing agents B1, B2, and B4 after 90 days of storage at 70°C, 80°C, and 90°C were slightly lower than those of oil-displacing agent B3 under the same conditions, but all ranged from 40 to 50 mP·s.

[0043] In addition, the viscosity retention rate of the oil-displacing agent B3 and the polyacrylamide polymer solution C3 at different temperatures was tested over time. The viscosity retention rate of the polyacrylamide polymer solution C3 at 70°C and the viscosity retention rate of the oil-displacing agent B3 at 70°C, 80°C, and 90°C were summarized in Figure 4 In. By Figure 4 As can be seen, the viscosity retention rate of oil-displacing agent B3 is significantly higher than that of polyacrylamide polymer solution C3. Furthermore, the viscosity retention rate of oil-displacing agent B3 increases with increasing temperature, contrary to the viscosity-temperature characteristics of polyacrylamide polymer solution C3. The viscosity retention rate of a test liquid (oil-displacing agent or polyacrylamide polymer solution) at a given time is the ratio of the viscosity of the test liquid after a certain period of time to the viscosity of the test liquid at the initial test.

Claims

1. A polymer oil-displacing agent, characterized in that: The invention comprises a polyacrylamide polymer and a modifier, wherein the modifier is composed of a charge introducing agent, a dialdehyde compound, a chelating agent and a polyvalent metal salt, wherein the charge introducing agent is a halogenated hydrocarbon compound, and the molar ratio of metal ions in the charge introducing agent, the dialdehyde compound, the chelating agent and the polyvalent metal salt is (0.1-20):(0.1-5):(0.1-5):1; the halogenated hydrocarbon compound is a saturated monohalogenated hydrocarbon compound; and the carbon atoms in the halogenated hydrocarbon compound are 3-7.

2. The polymer oil-displacing agent according to claim 1, wherein The halogenated hydrocarbon compound is selected from one or any combination of chlorinated hydrocarbon compounds, brominated hydrocarbon compounds, and fluorinated hydrocarbon compounds.

3. The polymer oil-displacing agent according to claim 1, wherein The halogenated hydrocarbon compounds are chlorobutane, bromobutane, fluorobutane, chloropentane, bromopentane, and fluoropentane.

4. The polymer oil-displacing agent according to claim 1 or 2, wherein The molar ratio of the charge introducing agent, the dialdehyde compound, the chelating agent and the metal ions in the multivalent metal salt is (2-15):(1-4):(1-4):

1.

5. The polymer oil-displacing agent according to claim 1 or 2, wherein The chelating agent is selected from one or any combination of carboxylates, hydroxycarboxylates, sulfosalicylate, alkyldiamine tetracarboxylates, hydroxyalkylalkyldiamine tricarboxylates, and ammonia tricarboxylates.

6. The polymer oil-displacing agent according to claim 5, wherein The carboxylate is citrate; the hydroxycarboxylate is hydroxyacetate and hydroxypropionate; the alkyldiaminetetracarboxylate is ethylenediaminetetraacetate and ethylenediaminetetrapropionate; the hydroxyalkylalkyldiaminetricarboxylate is hydroxyethylethylenediaminetriacetate and hydroxypropylethylenediaminetriacetate; the ammoniatricarboxylate is ammoniatriacetate and ammoniatripropropionate.

7. The polymer oil-displacing agent according to claim 1 or 2, wherein The multivalent metal salt is a water-soluble multivalent metal salt.

8. The polymer oil-displacing agent according to claim 7, wherein The multivalent metal salt is selected from one or any combination of water-soluble aluminum salts, water-soluble chromium salts, water-soluble zirconium salts and water-soluble titanium salts.

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