Polymer oil displacement agent

Abstract

The invention relates to a polymer oil-displacing agent, and belongs to the technical field of oil and gas reservoir chemicals. The modifier in the polymer oil-displacing agent disclosed by the invention can be complexed with Ca < 2 + > and Mg < 2 + > in heavy salt water at normal temperature, so that the internal crosslinking influence of high salt on polyacrylamide polymer molecules is reduced, and meanwhile, the modifier and the polyacrylamide polymer can jointly accelerate ion diffusion and enhance activation energy, so that a chelating agent in the modifier can be quickly activated at normal temperature; the polymer oil-displacing agent provided by the invention has the advantages that polyvalent metal salt can enter polyacrylamide molecular lattices easily, intramolecular crosslinking can be quickly formed at normal temperature, the polymer oil-displacing agent can have higher viscosity under the condition of lower dosage, and the viscosity of the oil-displacing agent is increased along with the increase of the hydrolysis degree of the polyacrylamide polymer at the formation temperature. Therefore, the oil-displacing agent disclosed by the invention can realize normal-temperature crosslinking, has relatively high apparent viscosity in high-salinity water, and also has relatively high viscosity retention rate at high temperature, so that the use requirements of high-temperature and high-salinity oil and gas reservoirs are met.

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 oil displacement. Scientifically controlling mobility ratio is the key to ensuring the effect of polymer flooding, and the core of controlling mobility ratio is the viscosity of 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 easily 2+ Mg 2+ Complexation occurs and precipitation occurs, 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 is limited in its application in Class III-V reservoirs with high temperature and high salinity.

[0003] The current improvement method is: ① Introducing a heat-resistant and salt-resistant monomer, such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS), into the main chain of polyacrylamide, by regulating the degree of polymerization and the proportion of copolymerization unit structure, to improve the heat resistance and salt resistance of the product, but the viscosity is limited in high-mineralization water. For example, Chinese patent document CN102408516B discloses a method for preparing a heat-resistant and salt-resistant polyacrylamide, introducing three heat-resistant and salt-resistant monomers to copolymerize with acrylamide, synthesizing acrylamide / 2-acrylamide-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%, and still cannot meet the application requirements under higher temperature and mineralization conditions; ② Injecting a cross-linking agent into the formation together with the polymer aqueous solution oil-displacing agent, so that the oil-displacing agent is cross-linked and thickened during the migration process of the formation. For example, Chinese patent document CN104513654A provides a modifier and oil displacement agent composition and oil displacement agent and preparation method thereof, which uses a modifier to modify polyacrylamide polymers, so that the polyacrylamide polymers can meet the use requirements of mineralization below 30000 mg / L and temperature resistance of 95°C. However, it still does not gel at room temperature (below 30°C), and after entering the formation, it is affected by the complex formation conditions, and the cross-linking reaction has certain difficulties, and it is impossible to determine whether intramolecular cross-linking is formed underground.

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

[0005] The purpose of the present invention is to provide a polymer oil-displacing agent, which 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 multivalent 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 multivalent 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, 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 higher viscosity when used in a lower 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 higher apparent viscosity in high-salinity water, and at the same time have a higher viscosity retention rate at high temperature, thereby meeting the use requirements of high-temperature and high-salinity oil and gas reservoirs.

[0009] Preferably, the molar ratio of metal ions in the charge-introducing agent, dialdehyde compound, chelating agent and polyvalent metal salt is (2-15): (1-4): (1-4): 1. Limiting the molar ratio of metal ions in the charge-introducing agent, dialdehyde compound, chelating agent and polyvalent metal salt to the above range has the beneficial effect of fast intramolecular crosslinking of the oil-displacing agent and no 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, and fluorobutane; when the carbon atoms in the halogenated hydrocarbon compound are 5, the halogenated hydrocarbon compound is chloropentane, bromopentane, and fluoropentane. In the present invention, the chlorobutane is 1-chlorobutane and 2-chlorobutane; the bromobutane is 1-bromobutane and 2-bromobutane; the fluorobutane is 1-fluorobutane and 2-fluorobutane; the chloropentane is 1-chloropentane, 2-chloropentane, and 3-chloropentane; the bromopentane is 1-bromopentane, 2-bromopentane, and 3-bromopentane; the fluoropentane is 1-fluoropentane, 2-fluoropentane, and 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 technical field of oil and gas field chemicals are suitable for the present invention. Preferably, the chelating agent is selected from one or any combination of carboxylates, hydroxycarboxylates, sulfosalicylate, alkyldiaminetetracarboxylates, hydroxyalkylalkyldiaminetricarboxylates and ammoniatricarboxylates.

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

[0016] Further preferably, the chelating agent is selected from one or any combination of disodium ethylenediaminetetraacetate, sodium sulfosalicylate, sodium hydroxyacetate, and sodium citrate. Disodium ethylenediaminetetraacetate, sodium sulfosalicylate, sodium hydroxyacetate, and sodium citrate are used as chelating agents to chelate high-valent metal cations in water, thereby reducing or eliminating their effects on the viscosity of the polymer aqueous solution and its subsequent cross-linking reaction.

[0017] Preferably, the multivalent metal salt is a water-soluble multivalent metal salt. Preferably, 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.

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

[0019] Polyacrylamide polymers used for polymer oil displacement agents are all suitable for the present invention. Preferably, the polyacrylamide polymers are partially hydrolyzed polyacrylamide polymers. 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 to ensure its viscosity retention rate and reaction with glyoxal under formation conditions. The polyacrylamide polymers in the present invention can use commercially available products, for example, acrylamide / 2-acrylamide-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-acrylamide-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 1It is a schematic diagram of the change curve of the apparent viscosity of the polyacrylamide polymer solution C1 and the oil-displacing agents B1 and B2 at 25° C. over time in the experimental example of the present invention;

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

[0027] Figure 3 It is a schematic diagram of the change curve of the apparent viscosity of the polyacrylamide polymer solution C3 at 70°C over time and the change curve of the apparent viscosity 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 It is a schematic diagram of the change curve of the viscosity retention rate of the polyacrylamide polymer solution C3 at 70°C over time in the experimental example of the present invention 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. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0030] The polymer oil displacement agent of Examples 1-4 comprises a polyacrylamide polymer, a modifier and high brine, 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 agent of Examples 1-4 is 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, stirred for 1 hour, and then the dialdehyde compound, the chelating agent and the multivalent 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 brine used to prepare the modifier dispersions in each example, 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 are shown in Table 1;

[0034] Table 1 The mineralization degree of the high brine used in preparing the modifier dispersion in each embodiment, the chemical name and the added molar amount of the charge introducing agent, the chemical name and the added molar amount of the dialdehyde compound, the chemical name and the added molar amount of the chelating agent, and the chemical name and the 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 salt water, wherein the high salt water used in preparing the polyacrylamide polymer solution in each embodiment is the same as the high salt 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, wherein the concentration of the polyacrylamide polymer in the oil-displacing agent is 1500 mg / L; the oil-displacing agents of embodiments 1-4 are numbered B1, B2, B3, and B4, respectively; the names of the polyacrylamide polymers used in the polymer oil-displacing agents of embodiments 1-4 and the weight parts of the modifier dispersion and the polyacrylamide polymer solution used in preparing the oil-displacing agent 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 the 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 Chemical Research Institute, 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 salt water, and the polyacrylamide polymer solutions prepared using the polyacrylamide polymer used in Examples 1-4 were numbered C1, C2, C3, and C4, respectively, and the high salt water used when preparing the polyacrylamide polymer solutions C1, C2, C3, and C4 was the same as the high salt water used in Examples 1-4. Then, the oil-displacing agent of each embodiment and the polyacrylamide polymer solutions C1, C2, C3, and C4 were tested for their temperature and salt resistance, using a Brookfield DV-III rotary viscometer, with a ULA rotor, a speed of 6RPM, and a shear rate of 7.341s. -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 It can be seen that at room temperature (25°C), oil-displacing agents B1, B2, B3, and B4 began to crosslink after 7 minutes of placement, and the viscosity remained stable at around 35 mP·s after 30 minutes, and the viscosity at 30 days was no more than 2% different from the viscosity at 30 minutes of placement. However, the viscosity of polymer solutions C1 and C2 did not change after being placed at room temperature (25°C) for a certain period of time. Therefore, at room temperature, the apparent viscosity of oil-displacing agents B1, B2, B3, and B4 is significantly better than that 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 3It can be seen that the apparent viscosity of the oil-displacing agent B3 is significantly better than that of the polyacrylamide polymer solution C3, and as the temperature increases, the apparent viscosity of the oil-displacing agent B3 increases, which is opposite to the viscosity-temperature characteristics of the polyacrylamide polymer solution C3. In addition, when the temperature is constant, the apparent viscosity of the oil-displacing agent B3 increases slightly with the extension of the storage time, while the apparent viscosity of the polyacrylamide polymer solution C3 decreases with the extension of the storage time, and the viscosity of the oil-displacing agent B3 at 70°C, 80°C, and 90°C when the storage time is 90d is 51, 53, and 55mP·s, respectively. When the above method is used to test the apparent viscosity of the oil-displacing agents B1, B2, and B4 at different temperatures with time, the test results show that the viscosity of the oil-displacing agents B1, B2, and B4 at 70°C, 80°C, and 90°C when the storage time is 90d is slightly less than the viscosity of the oil-displacing agent B3 tested under the same conditions, but both are between 40 and 50mP·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 It can be seen that the viscosity retention rate of the oil-displacing agent B3 is significantly higher than that of the polyacrylamide polymer solution C3, and as the temperature increases, the viscosity retention rate of the oil-displacing agent B3 increases, which is opposite to the viscosity-temperature characteristics of the polyacrylamide polymer solution C3. Among them, the viscosity retention rate of the test liquid (oil-displacing agent or polyacrylamide polymer solution) at a certain time = the ratio of the viscosity of the test liquid after being placed for 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 multivalent 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 multivalent metal salt is (0.1-20):(0.1-5):(0.1-5):

1.

2. The polymer oil-displacing agent according to claim 1, characterized in that 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 2, characterized in that: The halogenated hydrocarbon compound is a saturated halogenated hydrocarbon compound.

4. The polymer oil displacing agent according to any one of claims 1 to 3, characterized in that The carbon atoms in the halogenated hydrocarbon compound are 3 to 7.

5. The polymer oil-displacing agent according to claim 4, characterized in that: The halogenated hydrocarbon compounds are butyl chloride, butyl bromide, butyl fluoride, pentyl chloride, pentyl bromide and pentyl fluoride.

6. The polymer oil displacing agent according to any one of claims 1 to 3, characterized in that: 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.

7. The polymer oil displacing agent according to any one of claims 1 to 3, characterized in that: The chelating agent is selected from one or any combination of carboxylates, hydroxycarboxylates, sulfosalicylate, alkyldiaminetetracarboxylates, hydroxyalkylalkyldiaminetricarboxylates, and ammoniatricarboxylates.

8. The polymer oil-displacing agent according to claim 7, characterized in that: 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.

9. The polymer oil displacing agent according to any one of claims 1 to 3, characterized in that: The multivalent metal salt is a water-soluble multivalent metal salt.

10. The polymer oil-displacing agent according to claim 9, characterized in that: 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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