CN115478817A - Polymer and carbon dioxide miscible flooding method and application thereof - Google Patents
Polymer and carbon dioxide miscible flooding method and application thereof Download PDFInfo
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- CN115478817A CN115478817A CN202110599092.XA CN202110599092A CN115478817A CN 115478817 A CN115478817 A CN 115478817A CN 202110599092 A CN202110599092 A CN 202110599092A CN 115478817 A CN115478817 A CN 115478817A
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 140
- 229920000642 polymer Polymers 0.000 title claims abstract description 109
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 70
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 36
- 239000002738 chelating agent Substances 0.000 claims abstract description 34
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 32
- 238000006073 displacement reaction Methods 0.000 claims abstract description 19
- 238000011084 recovery Methods 0.000 claims abstract description 8
- 238000002347 injection Methods 0.000 claims description 73
- 239000007924 injection Substances 0.000 claims description 73
- 239000000243 solution Substances 0.000 claims description 72
- 229920002401 polyacrylamide Polymers 0.000 claims description 23
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 claims description 12
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 239000013043 chemical agent Substances 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 2
- 125000000129 anionic group Chemical group 0.000 claims description 2
- -1 gaseous Substances 0.000 claims description 2
- 239000004094 surface-active agent Substances 0.000 claims description 2
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 claims 1
- 239000003921 oil Substances 0.000 abstract description 41
- 239000010779 crude oil Substances 0.000 abstract description 23
- 238000010276 construction Methods 0.000 abstract description 12
- 238000000605 extraction Methods 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 description 18
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 13
- 230000000694 effects Effects 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 239000007864 aqueous solution Substances 0.000 description 9
- 230000009471 action Effects 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000010008 shearing Methods 0.000 description 5
- 238000004132 cross linking Methods 0.000 description 4
- YQGOJNYOYNNSMM-UHFFFAOYSA-N eosin Chemical compound [Na+].OC(=O)C1=CC=CC=C1C1=C2C=C(Br)C(=O)C(Br)=C2OC2=C(Br)C(O)=C(Br)C=C21 YQGOJNYOYNNSMM-UHFFFAOYSA-N 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000002354 daily effect Effects 0.000 description 3
- 229960001484 edetic acid Drugs 0.000 description 3
- 230000003203 everyday effect Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000003129 oil well Substances 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- UEUXEKPTXMALOB-UHFFFAOYSA-J tetrasodium;2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]C(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O UEUXEKPTXMALOB-UHFFFAOYSA-J 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/588—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific polymers
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
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- General Life Sciences & Earth Sciences (AREA)
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- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
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Abstract
The invention provides a method for miscible flooding of a polymer and carbon dioxide and application thereof. The method comprises the following steps: injecting a chelating agent solution firstly, and then injecting a viscosity reducer and a polymer solution respectively for oil displacement, wherein the viscosity reducer is injected before the polymer solution or simultaneously, and comprises carbon dioxide. The invention further provides application of the method in thin oil extraction construction. The polymer and carbon dioxide miscible flooding method can reduce the fluidity ratio difference between the polymer solution and the crude oil and effectively improve the crude oil recovery rate.
Description
Technical Field
The invention relates to the technical field of thin oil chemical flooding oil extraction, in particular to a polymer and carbon dioxide miscible phase flooding method and application thereof.
Background
The polymer is used as a common oil displacement agent, and the oil displacement principle of the polymer is mainly to improve the fluidity ratio of water and oil by utilizing the polymer to increase the viscosity of water and reduce the effective permeability of a water tank. Specifically, the polymer can increase the low viscosity of water, adsorb or retain in pores of an oil layer to reduce the water phase permeability and greatly reduce the fluidity of the water; on the other hand, as the polymer is insoluble in crude oil and has almost no influence on the viscosity of the crude oil, and oil drops of the crude oil are gathered at the front edge of the polymer, the oil phase permeability is increased, the fluidity of the crude oil is increased, and finally the fluidity ratio of water and oil is greatly reduced, so that the plane sweep efficiency is improved, the water injection sweep efficiency is overcome, the vertical sweep efficiency is improved, and the water absorption thickness is increased.
The existing problem is that the chemical flooding process of the polymer generally increases the viscosity of the aqueous solution of the polymer to improve the flooding effect. However, workers can only directly control the viscosity of the polymer solution formulated at the surface, and in the vicinity of the injection well, although the viscosity can be indirectly measured by the surface injection pressure, the polymer viscosity cannot be completely controlled in the downhole formation. Furthermore, mechanical shear forces have a large effect on the viscosity of the aqueous polymer solution, whereas shear forces in the formation have an effect on the viscosity of the polymer that cannot be controlled by human power. The polymer produced by the oil well can be detected only by spectral analysis, which shows that the viscosity of the polymer solution is not different from that of water, and in this case, even if the viscosity of the polymer solution is increased on the ground, the viscosity of the polymer solution is rapidly reduced under the action of formation shear force when the polymer solution is injected into the formation, and the polymer solution has larger viscosity difference with crude oil, so the improvement degree of the oil displacement effect by increasing the preparation viscosity of the polymer solution is very limited.
In addition, in order to increase the viscosity of the polymer, chelating agents are usually added to the polymer, and the chelating agents mainly play a role in crosslinking the broken polymer, so that the polymer is changed from a plane into a solid. Specifically, it is common practice in the prior art to mix the chelating agent with the aqueous polymer solution at the surface and then inject it into the ground, so that there is inevitably a shearing action during injection, reducing the crosslinking action of the chelating agent on the polymer.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a method for miscible-phase flooding of a polymer and carbon dioxide and application thereof, wherein the method can reduce the fluidity ratio difference between a polymer solution and crude oil and effectively improve the recovery rate of the crude oil.
In order to achieve the above object, the present invention provides a method for miscible flooding of a polymer with carbon dioxide, comprising: injecting a chelating agent solution, and then injecting a viscosity reducer and a polymer solution for oil displacement, wherein the viscosity reducer is injected before or simultaneously with the polymer solution, and comprises carbon dioxide; the injection mass ratio of the chelating agent solution to the polymer solution is (1-3): 1; when the carbon dioxide is in a gaseous state, the injection amount of the carbon dioxide is 100 to 300 standard square/day.
In a specific embodiment of the invention, when the viscosity reducer is mixed with the polymer solution in a well, carbon dioxide in the viscosity reducer can be dissolved in the polymer solution to play a role of the viscosity reducer and the oil washing agent, and the viscosity of the polymer solution is effectively improved; meanwhile, the viscosity reducer can also reduce the viscosity of crude oil, so that the viscosity difference between a polymer solution and the underground crude oil can be reduced, the fluidity ratio of the polymer to the crude oil is reduced, and the oil displacement effect of the polymer solution is improved. In a particular embodiment, the above method comprises continuously injecting the viscosity reducer during the injection of the polymer solution.
In the specific embodiment of the invention, the state of the carbon dioxide in the viscosity reducer can be selected according to actual needs, and is not particularly limited, and liquid, gaseous, solid carbon dioxide and the like are generally adopted.
Hereinafter, unless otherwise specified, the injection conditions of carbon dioxide, the ratio of carbon dioxide to each substance (polymer, gas such as nitrogen, chemical agent) all refer to the injection conditions of gaseous carbon dioxide, and the ratio of gaseous carbon dioxide to each substance, and the parameters corresponding to solid and liquid carbon dioxide can be converted according to the corresponding parameters of gaseous carbon dioxide.
According to the method, the chelating agent solution is injected first, and then the polymer solution is injected, so that the chelating agent and the polymer are crosslinked underground to improve the viscosity of the polymer, further the oil displacement capability of the polymer is improved, and the problem that the chelating agent and the polymer are reduced due to the shearing action when injected into a stratum in the conventional method is solved. In a specific embodiment, the chelating agent injection well is generally injected in the polymer flooding direction according to a geological well arrangement mode so as to avoid shearing action generated in the chelating agent injection process.
In a particular embodiment of the invention, the chelating agent generally comprises sodium ethylenediaminetetraacetic acid (EDTA-2 Na). The chelating agent is used for crosslinking a polymer, and the injection volume ratio of the chelating agent solution to the polymer solution is 1:4.
In a specific embodiment of the invention, the mass concentration of the chelating agent solution is generally 4-5.5%; the injection amount of the chelating agent solution is generally 0.8 to 1.5 tons/day. In a specific embodiment, the injection pressure of the chelating agent is not particularly limited in the above method, and the injection amount may be satisfied.
In a specific embodiment of the invention, after the viscosity reducer and the polymer solution are mixed in the well, the concentration of carbon dioxide in the polymer solution is generally above the lowest saturated concentration of carbon dioxide in water, so as to obtain better viscosity regulation effect.
In a specific embodiment of the present invention, the degree of dissolution of the viscosity reducer in the polymer solution can be adjusted by the injection pressure of the two. The injection pressure of the viscosity reducer and the polymer solution should be such that the degree of carbon dioxide dissolution in the polymer solution is maintained at a high level without exceeding the formation fracture pressure. For example, the injection pressure of the polymer solution may be controlled to 10MPa to 18MPa, and when carbon dioxide in the viscosity reducing agent is gaseous, the injection pressure of the viscosity reducing agent (e.g., gaseous carbon dioxide) may be controlled to 10MPa to 18MPa.
In a specific embodiment of the invention, when the carbon dioxide is gaseous (e.g., carbon dioxide from a fireflood tail gas), the ratio of the injection volume of the gaseous carbon dioxide to the injection volume of the polymer solution is generally controlled to be in the range of 10 to 15, where the volume units of carbon dioxide to polymer solution are in the range of rate squares.
In particular embodiments of the invention, the carbon dioxide may be injected in an amount (as gaseous carbon dioxide) of from 100 to 150, 150 to 300, etc. standard/day.
In a specific embodiment of the present invention, the polymer solution may be injected in an amount of 20 to 30 squares/day. Alternatively, the injection amount of the polymer solution may be 100 to 200 tons/day.
In a specific embodiment of the invention, the viscosity reducer can also comprise nitrogen, and the addition of the nitrogen is not only beneficial to the injection of carbon dioxide into the stratum, but also has a certain gas flooding effect. The volume ratio of the nitrogen to the carbon dioxide can be controlled to be 70-80.
In a specific embodiment of the present invention, the viscosity reducer may further comprise solid or liquid chemical agents, such as surfactants commonly used in viscosity reduction in oil field, etc., to further enhance the viscosity reduction effect on crude oil.
In a specific embodiment of the present invention, the volume ratio of the above chemical agent to the carbon dioxide is generally controlled to be 1:40.
in a particular embodiment of the invention, the polymer may comprise polyacrylamide. In a particular embodiment, polyacrylamide having a weight average molecular weight of 2000 to 3000 ten thousand, for example 2500 ten thousand, is generally selected. The polyacrylamide is preferably anionic polyacrylamide.
In a particular embodiment of the invention, the polymer solution is typically present in a mass concentration of 100ppm to 900ppm, for example 180ppm, which is not higher than the concentration of the commonly used flooding polymer solution.
In a particular embodiment of the invention, when the viscosity reducing agent is a mixture containing carbon dioxide, the mixture is generally free of elemental sulfur to avoid reducing the viscosity of the polymer solution.
In a specific embodiment of the invention, when the viscosity reducer is injected into the reservoir simultaneously with the polymer solution for flooding, the injection well of the viscosity reducer can be positioned around the polymer solution injection well, so that the polymer solution is not earlier than the viscosity reducer is contacted with the crude oil, and the maximum injection effect is achieved; when the viscosity reducer is injected prior to the polymer solution, the positions of the viscosity reducer injection well and the polymer solution injection well are not particularly limited.
The invention further provides the application of the method in thin oil extraction construction, such as thin oil extraction construction with viscosity of 10-100mPa. In some specific embodiments, the oil recovery rate can be improved by more than 40% by adopting the method for 5-10 days.
The invention has the beneficial effects that:
according to the miscible-phase flooding method provided by the invention, the chelating agent is injected before the polymer is injected, so that the crosslinking effect of the water chelating agent on the polymer can be effectively exerted, and the polymer is prevented from losing effectiveness due to the stratum shearing effect, so that the viscosity and the oil displacement capability of the polymer solution are improved; and the viscosity reducer containing carbon dioxide is injected at the same time or before the polymer solution is injected, so that the viscosity of the polymer solution can be effectively improved and the viscosity of crude oil can be reduced underground, thereby reducing the viscosity difference between the polymer solution and the crude oil, reducing the fluidity ratio of the polymer and the crude oil, improving the oil displacement effect and ensuring the continuity of oil displacement.
Drawings
FIG. 1 is a schematic diagram of the locations of wells in the drive construction of example 1.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
The weight average molecular weight of the polyacrylamide used in the following examples is 2000 to 3000 ten thousand.
Example 1
The embodiment provides a method for miscible flooding of a polymer and carbon dioxide, which comprises the following steps:
arranging chelating agent injection wells around the polymer injection well, and injecting a chelating agent disodium ethylene diamine tetraacetate aqueous solution with the mass concentration of 5% into a construction section, wherein the injection amount is 1 ton/day; injecting gaseous carbon dioxide with the injection amount of 300 standard square/day and the injection pressure of 15MPa; and then injecting a polyacrylamide solution with the mass concentration of 180ppm into the construction section, wherein the injection amount is 192 tons/day, the injection pressure is 15MPa, and ethylene diamine tetraacetic acid, carbon dioxide and polyacrylamide are injected every day (so as to ensure that the carbon dioxide can continuously reduce the viscosity of the polymer and ensure the continuity of oil displacement) for 10 days.
Dilute well eosin 3-3-01 is a polymer injection well, which controls 10 production wells in total. When only polyacrylamide solution (192 tons/day) is injected for oil displacement, the liquid production per well is 10 tons/day, and the oil production per well is 4 tons/day; after 10 days of oil displacement according to the method, the liquid production amount of a single well is increased to 12 tons/day, the oil production amount is increased to 6 tons/day, and the recovery ratio is obviously improved.
In this embodiment, the positional relationship of the wells is shown in fig. 1, and as can be seen from fig. 1, the position for injecting the chelating agent and the position for injecting the carbon dioxide (viscosity reducing agent) are arranged around the position for injecting the polymer. Specifically, the chelating agent injection well is distributed and injected in the polymer flooding direction according to a geological well distribution mode; the injection ports of the polymer injection device and the carbon dioxide injection device are independent from each other, and the polymer solution and the carbon dioxide which are respectively injected are finally mixed in the injection well.
The pattern of the following examples 2-4 may be the same as in figure 1.
Example 2
The embodiment provides a method for miscible flooding of a polymer and carbon dioxide, which comprises the following steps:
pouring a chelating agent disodium ethylene diamine tetraacetate aqueous solution with the mass concentration of 4.5% into a construction section, wherein the weight concentration of the chelating agent disodium ethylene diamine tetraacetate aqueous solution is 1.5 tons/day; injecting gaseous carbon dioxide with the injection amount of 200 standard square/day and the injection pressure of 16MPa; and then injecting a polyacrylamide solution with the mass concentration of 180ppm into the construction section, wherein the injection amount is 168 tons/day, the injection pressure is 16MPa, and the injection of the disodium ethylene diamine tetraacetate, the carbon dioxide and the polyacrylamide is kept every day for 5 days.
Dilute well eosin 4-2-1 is a polymer injection well with a total of 8 production wells controlled by it. When only polyacrylamide solution (168 tons/day) is injected for oil displacement, the liquid production amount of the crude oil of a single well is 8 tons/day, and the oil production amount is 3.2 tons/day; after the oil is displaced for 5 days by the method, the liquid production amount of a single well is increased to 9.5 tons per day, the oil production amount is increased to 4.5 tons per day, the recovery ratio is obviously improved, the oil production and the liquid production amount are stable, and the stable production can be continuously carried out for more than 60 days.
Example 3
The embodiment provides a method for miscible flooding of a polymer and carbon dioxide, which comprises the following steps:
firstly, injecting a chelating agent disodium ethylene diamine tetraacetate aqueous solution with the mass concentration of 5.5% into a construction section, wherein the injection amount is 0.8 ton/day; then injecting gaseous carbon dioxide, wherein the injection pressure is 14.2MPa; and then injecting a polyacrylamide solution with the mass concentration of 180ppm into the construction section, wherein the injection amount is 132 tons/day, the injection pressure is 14.2MPa, disodium ethylene diamine tetraacetate, carbon dioxide and polyacrylamide are injected every day, and the injection lasts for 9 days, wherein the injection volume ratio of the polymer solution to the carbon dioxide is 1.
The diluted oil well is 4-3-1 polymer injection wells, and a production well (namely a production well) controlled by the diluted oil well has the oil production amount of the crude oil of a single well of 12 tons/day and 4.2 tons/day when only polyacrylamide solution (132 tons/day) is injected for oil displacement; after 10 days of oil displacement according to the method, the liquid production amount of a single well is increased to 14 tons/day, the oil production is increased to 6.3 tons/day, and the recovery ratio is obviously improved.
Example 4
(1) Injecting a polyacrylamide solution with the mass concentration of 180ppm into the poly-ethylene diamine tetraacetic acid injection well 2-3-02, and injecting a disodium ethylene diamine tetraacetate aqueous solution with the mass concentration of 4% through the chelating agent injection well, wherein the injection amount of the disodium ethylene diamine tetraacetate aqueous solution is 1.2 tons/day, the injection amount of polyacrylamide is 130 tons/day respectively, and the injection pressure of the polyacrylamide and the disodium ethylene diamine tetraacetate aqueous solution is 13.8MPa; carbon dioxide was injected through a carbon dioxide injection device at 156 sq/day at 13.8MP. Simultaneously, polyacrylamide, ethylene diamine tetraacetic acid and gaseous carbon dioxide are injected, the three are continuously injected for 30 days, the average single-well daily crude oil of 13 affected wells (namely extraction wells) around the three is increased to 2.5 tons/day from 1.9 tons/day originally, 2-3-10 eosins are most obvious, and the average single-well daily crude oil is increased to 3.5 tons/day from 2.0 tons/day originally.
(2) In order to avoid the influence of shearing on oil displacement, oil displacement construction is continuously carried out by using the same injection well on the basis of the step (1), and the construction method comprises the following steps: injecting a disodium ethylene diamine tetraacetate aqueous solution with the mass concentration of 5% into the oil flow direction of the eosin 2-3-02 through a chelating agent injection well, and then simultaneously injecting polyacrylamide and gaseous carbon dioxide through a polymer injection device and a carbon dioxide injection device respectively, wherein the injection parameters of the disodium ethylene diamine tetraacetate, the polyacrylamide and the gaseous carbon dioxide are the same as those in the step (1), and the average daily oil yield of a single well of a affected well around the eosin 2-3-02 after 10 days of injection is increased to 3.0 tons per day from the original 2.5 tons per day, so that the effect is obvious.
The results show that the polymer and carbon dioxide miscible flooding method provided by the invention can effectively reduce the fluidity ratio difference between the polymer solution and the crude oil and obviously improve the crude oil recovery rate.
Claims (12)
1. A method for miscible flooding of a polymer with carbon dioxide, comprising: injecting a chelating agent solution, and then injecting a viscosity reducer and a polymer solution for oil displacement, wherein the viscosity reducer is injected before the polymer solution or simultaneously, and comprises carbon dioxide;
the injection mass ratio of the chelating agent solution to the polymer solution is (1-3): 1; when the carbon dioxide is in a gaseous state, the injection amount of the carbon dioxide is 100 to 300 standard square/day.
2. The method of claim 1, wherein the chelating agent comprises disodium ethylenediaminetetraacetate;
preferably, the injection amount of the chelating agent solution is 0.8-1.5 tons/day; the mass concentration of the chelating agent solution is 4-5.5%.
3. The method of claim 1, wherein the carbon dioxide is one or a combination of two or more of liquid, gaseous, and solid; the injection pressure of the polymer solution is 10MPa-18MPa;
preferably, when the carbon dioxide in the viscosity reducer is in a gaseous state, the injection pressure of the viscosity reducer is 10MPa to 18MPa.
4. The method of claim 1, wherein the polymer solution is injected in an amount of 20 to 30 squares/day, or the polymer solution is injected in an amount of 100 to 200 tons/day.
5. The process according to claim 1 or 4, wherein, when the carbon dioxide is gaseous, the ratio of the injection volume of carbon dioxide to the injection volume of the polymer solution is from 10 to 15.
6. The process according to claim 1, wherein the viscosity reducer further comprises nitrogen, and when the carbon dioxide and nitrogen are gaseous, the volume ratio of the nitrogen to the carbon dioxide is preferably 70-80.
7. The method of claim 1, wherein the viscosity reducer further comprises a chemical agent comprising a surfactant;
preferably, when the carbon dioxide is gaseous, the volume ratio of the chemical agent to gaseous carbon dioxide is 1.
8. The method of claim 1, wherein the polymer comprises polyacrylamide.
9. The method according to claim 1 or 8, wherein the mass concentration of the polymer solution is between 100ppm and 900ppm, preferably 180ppm.
10. The method of claim 8, wherein the polyacrylamide has a weight average molecular weight of 2000-3000 ten thousand, preferably comprising an anionic polyacrylamide.
11. The method of claim 1, wherein the viscosity reducer does not contain elemental sulfur.
12. The use of the polymer of any one of claims 1 to 11 in miscible flooding with carbon dioxide in thin oil recovery applications; preferably, the viscosity of the thin oil is 10-100mPa.s.
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| US4569393A (en) * | 1984-02-09 | 1986-02-11 | Phillips Petroleum Company | CO2 -Induced in-situ gelation of polymeric viscosifiers for permeability contrast correction |
| US5555936A (en) * | 1990-10-29 | 1996-09-17 | Societe Nationale Elf Aquitaine | Scleroglucan gel applied to the oil industry |
| CN104863554A (en) * | 2014-02-26 | 2015-08-26 | 中国石油天然气股份有限公司 | Super heavy oil well profile control agent and application |
| US20180010035A1 (en) * | 2016-01-05 | 2018-01-11 | Halliburton Energy Services, Inc. | Secondary hydrocarbon-fluid recovery enhancement |
| CN106567698A (en) * | 2016-11-07 | 2017-04-19 | 中国石油大学(北京) | Method for increasing oil recovery rate through self-generation carbon dioxide system after polymer flooding |
| CN111607371A (en) * | 2020-04-30 | 2020-09-01 | 中海石油（中国）有限公司天津分公司 | Efficient blockage removing system for polymer flooding injection well, preparation method and application of efficient blockage removing system |
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