Carbon dioxide oil displacement injection well pressure-reducing and injection-increasing blocking remover and preparation method thereof

Abstract

The invention discloses a pressure-reducing and injection-increasing blocking remover for a carbon dioxide oil-displacing injection well and a preparation method of the pressure-reducing and injection-increasing blocking remover. The blocking remover comprises the following components in percentage by weight: 3.0%-10.0% of alkylphenol polyoxyethylene ether, 1.0%-3.0% of sodium alkyl naphthalene sulfonate, 2.0%-3.0% of isopropyl phenyl phosphate, 1.0%-10.0% of polyether amine, 1.0%-5.0% of carboxylate-sulfonate-nonionic terpolymer, 3.0%-5.0% of low molecular weight sulfonated polystyrene, 1.0%-2.0% of pentanedione, 0.1%-2.0% of hydroxyethyl cellulose and the balance of water. 2.0%-6.0% of sorbitan fatty acid ester polyoxyethylene ether and the balance of water. The blocking remover disclosed by the invention has better asphaltene dissolving and dispersing performance, inorganic scale inhibition performance and lower corrosivity, and can be used for improving the recovery ratio of a carbon dioxide flooding injection well.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemicals for petroleum industry, and relates to a carbon dioxide flooding injection well pressure reducing and injection enhancing plugging agent suitable for low permeability sandstone reservoirs, extra-low permeability sandstone reservoirs, ultra-low permeability sandstone reservoirs and tight sandstone reservoirs, and a preparation method thereof. Background Art

[0002] With the continuous exploration and development of oil and gas resources, conventional medium and high permeability oil and gas fields have entered the middle and late development stage, while the demand for oil and gas resources is constantly increasing. Therefore, it is an urgent task to accelerate the exploration and development of low permeability, extra-low permeability, ultra-low permeability and even unconventional oil and gas resources. Low permeability, extra-low permeability, ultra-low permeability sandstone reservoirs and tight sandstone reservoirs have received more and more attention in recent years, and the scale of development has become larger and larger. Due to low permeability, small pore throats and complex pore structures, conventional exploitation methods such as water injection cannot achieve significant results. Problems such as difficulty in establishing displacement, high injection pressure and failure to inject often occur.

[0003] Studies have shown that CO2 injection is an effective means to improve the recovery rate of low-permeability, extra-low-permeability, ultra-low-permeability sandstone reservoirs and tight sandstone reservoirs. After CO2 is injected into the formation, it dissolves in the crude oil, which can improve the recovery rate of crude oil by reducing the viscosity of crude oil, improving the physical properties of crude oil, reducing the surface / interfacial tension and improving the flow capacity of crude oil. Compared with conventional water injection development, CO2 is easier to inject into the formation and replenish the energy of the reservoir faster, so that the crude oil in some small pores and micropores can be effectively mobilized. However, the injection of CO2 will cause certain changes in the properties of crude oil, causing the colloids and asphaltene in the crude oil to precipitate and aggregate and grow, which is easy to deposit and block the pores and throats of the reservoir. As the porosity and permeability of the reservoir decrease, it will not only cause certain damage to the reservoir, but also there will be problems such as high injection pressure, insufficient injection or even failure to inject in the later stage of CO2 injection. Studies have shown that the amount of asphaltene deposition during CO2 injection is related to injection pressure, injection rate, temperature, and asphaltene content. Asphaltene deposition not only reduces reservoir permeability and changes the pore structure of the formation, but also may affect the recovery rate of tight sandstone reservoirs by changing the wettability of the rock surface. Therefore, removing and preventing the deposition of asphaltene and the like during CO2 injection in carbon dioxide flooding injection wells is of great significance for improving the recovery rate of low permeability, extra-low permeability, ultra-low permeability sandstone reservoirs and tight sandstone reservoirs.

[0004] At present, the asphaltene dispersing plugging remover commonly used in oil fields is mainly developed for the blockage of the formation near the wellbore in oil wells or heavy oil wells, and has poor applicability to carbon dioxide oil injection wells, and is mainly used in the process of oil well repair operations. The main components of this type of plugging remover are selected from aromatic hydrocarbons, cycloalkanes and solvent oil [CN108690589A; CN114517084A; Analysis and prevention measures of asphaltene precipitation in CO2 flooding in Caoshe Oilfield. Journal of Southwest Petroleum University (Natural Science Edition), December 2010], among which benzene homologues (toluene, xylene, etc.) are more toxic, and cycloalkanes and solvent oils have lower flash points and are more dangerous under high temperature and high pressure environments. Among the plugging removers that do not contain benzene homologues, acid plugging removers are usually corrosive, such as CN108517204A; neutral plugging removers, although less corrosive, are mainly used to remove inorganic scale and organic scale film on their surface, and are not effective in removing organic scale that blocks reservoir pores, such as CN108102624A. In addition, the existing emulsified asphalt process, such as CN107903397A, can use an emulsifier containing a surfactant (such as nonylphenol polyoxyethylene ether) to disperse asphalt at a higher temperature, but the main purpose of the process is to modify the asphalt, rather than dissolving asphaltene, and emulsification needs to be performed under lower pH conditions.

[0005] Therefore, in order to solve the problem of asphaltene precipitation and formation blockage caused by carbon dioxide oil recovery, it is urgent to develop a highly efficient and safe (including low toxicity, low corrosiveness, suitable for use in high temperature and high pressure environments, etc.) carbon dioxide oil recovery injection well pressure reduction and injection increase plugging agent. Summary of the invention

[0006] The object of the present invention is to provide a pressure-reducing and injection-increasing plugging agent for carbon dioxide flooding injection wells in low permeability, extra-low permeability, ultra-low permeability and tight sandstone reservoirs and a preparation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A carbon dioxide flooding injection well plugging remover comprises an asphaltene dispersant, an inorganic scale dispersant, a dispersing aid and a dispersing stabilizer; the asphaltene dispersant comprises alkylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate and triisopropylphenyl phosphate.

[0009] Preferably, the inorganic scale dispersant comprises a carboxylate-sulfonate-nonionic terpolymer.

[0010] Preferably, the dispersing aid comprises polyetheramine, low molecular weight sulfonated polystyrene and diketone.

[0011] Preferably, the dispersion stabilizer includes hydroxyethyl cellulose and sorbitan fatty acid ester polyoxyethylene ether.

[0012] Preferably, the blocking agent is made of the following raw materials by weight percentage: 3.0% to 10.0% of alkylphenol polyoxyethylene ether, 1.0% to 3.0% of alkylnaphthalene sodium sulfonate, 2.0% to 3.0% of triisopropylphenyl phosphate, 1.0% to 10.0% of polyetheramine, 1.0% to 5.0% of carboxylate-sulfonate-nonionic terpolymer (for example, HM-3100), 3.0% to 5.0% of low molecular weight sulfonated polystyrene, 1.0% to 2.0% of diketone (for example, pentanedione), 0.1% to 2.0% of hydroxyethyl cellulose, 2.0% to 6.0% of sorbitan fatty acid ester polyoxyethylene ether (for example, span80), and the balance is water (for example, the weight percentage of water is 60% to 80%).

[0013] Preferably, the alkylphenol polyoxyethylene ether is selected from one or more of nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether; and the molecular weight of the polyetheramine is 300 to 5000.

[0014] Preferably, the plugging remover is a compound (specifically an aqueous solution with a pH of 6 to 7) formed by uniformly mixing an asphaltene dispersant, an inorganic scale dispersant, a dispersing aid and a dispersing stabilizer in water.

[0015] The method for preparing the above-mentioned carbon dioxide flooding oil injection well plugging remover comprises the following steps:

[0016] 1) stirring and mixing alkylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate, triisopropylphenyl phosphate and a portion of water in the raw materials under heating conditions;

[0017] 2) stirring and mixing the inorganic scale dispersant, the dispersing aid and the mixture obtained in step 1;

[0018] 3) The dispersion stabilizer, the remaining water in the raw material and the mixture obtained in step 2 are stirred and mixed, and then kept warm for a certain period of time to obtain a uniformly dispersed carbon dioxide oil recovery injection well plugging remover.

[0019] Preferably, in step 1, the heating condition is specifically: heating to ≥45°C.

[0020] Preferably, in step 3, the specific conditions for heat preservation are: keeping the mixture at a constant temperature of 40 to 50° C. for 60 to 80 minutes.

[0021] The beneficial effects of the present invention are embodied in:

[0022] The carbon dioxide flooding injection well plugging remover provided by the present invention is mainly aimed at the problem of asphaltene precipitation and blockage of seepage channels (composed of reservoir pores) during carbon dioxide flooding in low permeability, extra-low permeability, ultra-low permeability and tight sandstone reservoirs. The developed high-efficiency and safe water-based composite system with strong asphaltene dissolution and dispersion ability can dissolve and disperse the precipitation of asphaltene, colloid, paraffin and other macromolecular organic substances generated in the carbon dioxide flooding process or the asphaltene particles aggregated and grown during the migration process, thereby facilitating the improvement of the carbon dioxide injection air intake capacity, reducing the injection pressure, and realizing pressure reduction and injection increase.

[0023] Furthermore, the carbon dioxide flooding oil injection well plugging remover provided by the present invention aims at the actual situation that water needs to be injected before carbon dioxide injection, and utilizes the carboxylate-sulfonate-nonionic terpolymer contained in it to enhance the cleaning effect of inorganic scale generated after water injection, and has low corrosiveness.

[0024] Furthermore, the carbon dioxide flooding injection well plugging remover provided by the present invention utilizes the components contained therein, such as hydroxyethyl cellulose, sorbitan fatty acid ester polyoxyethylene ether (such as span80), etc., to enhance the inhibitory effect on the aggregation and enlargement of small asphaltene particles, thereby stabilizing the colloid and asphaltene in the formation crude oil during the carbon dioxide injection process in the later stage of carbon dioxide flooding, preventing the precipitation of colloid and asphaltene caused by the extraction of light components of crude oil during the carbon dioxide flooding process, thereby facilitating improving the recovery rate. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the embodiments. The embodiments are only used to explain the technical solution of the present invention, but not to limit the protection scope of the present invention.

[0026] (I) The mechanism of asphaltene precipitation in deep formations during CO2 flooding and its adverse effects on oil and gas resource exploration and development

[0027] The solubility of asphaltene determines its solubility in crude oil. Once saturated, asphaltene deposition will occur. According to the colloid theory of paraffin deposition, asphaltene exists in crude oil in the form of dispersed colloids. The core of the micelle is the asphaltene molecular cluster, and the periphery of the asphaltene molecular cluster is attached with colloid, thus forming micelles dispersed in the crude oil system. As a peptizing agent, colloid is the key medium for asphaltene to be dispersed in the crude oil system. If the colloid content in the system is insufficient, micelles cannot be formed or the thickness of the solvation layer of the micelle is not enough, the asphaltene molecular clusters will further associate to form larger molecular clusters, thereby causing asphaltene flocculation and deposition. When CO2 is flooded, as CO2 dissolves in the formation crude oil, the CO2 concentration in the crude oil increases, and a large number of CO2 small molecules occupy the surface space of the asphaltene molecular clusters, resulting in a relative decrease in the colloid concentration. The higher the injection pressure, the stronger the solubility of CO2 in the formation crude oil, the more the CO2 small molecule components in the crude oil increase, and the more the colloid concentration as an "asphaltene stabilizer" decreases, the more likely it is that the asphaltene molecular clusters will associate with each other to form precipitation. When CO2 is injected at miscible pressure, the amount of CO2 dissolved in crude oil is quite large, so asphaltene precipitation is most likely to occur in the miscible area of ​​CO2 flooding. Ultra-low permeability sandstone reservoirs are more likely to block pore throats due to asphaltene precipitation (compared with low permeability sandstone reservoirs, ultra-low permeability sandstone reservoirs, and tight sandstone reservoirs).

[0028] (II) Process for preparing highly efficient and safe blood pressure reducing and injection-enhancing plugging agent

[0029] Example 1

[0030] This example provides a pressure-reducing and injection-enhancing plugging agent for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs, and the weight percentage of each component is as follows:

[0031]

[0032] The method for preparing the above-mentioned ultra-low permeability sandstone reservoir carbon dioxide flooding injection well pressure reduction and injection increase plugging agent specifically comprises the following steps:

[0033] Step 1: Take the above-mentioned proportion of nonylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate and triisopropylphenyl phosphate, add them into an acid-resistant and alkali-resistant reaction kettle, stir while adding, heat to 45-50° C., and stir at a constant temperature to ensure that the materials (solutions) in the kettle are evenly mixed to obtain a mixed solution A1. A small amount of water can be added first in step 1.

[0034] Step 2: Take the above-mentioned polyetheramine, carboxylate-sulfonate-nonionic (terpolymer HM-3100), low molecular weight sulfonated polystyrene and pentanedione in the above-mentioned dosage ratio, add them to the above-mentioned mixed solution A1, stir evenly, and obtain mixed solution B1.

[0035] Step 3: Take the hydroxyethyl cellulose and span80 in the above-mentioned dosage ratio, add them to the above-mentioned mixed solution B1, add enough water in the dosage ratio, stir evenly, keep it at a constant temperature of 45°C for 60 minutes, and then cool it to room temperature to obtain the pressure reduction and injection enhancement plugging agent for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs.

[0036] Example 2

[0037] This example provides a pressure-reducing and injection-enhancing plugging agent for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs, and the weight percentage of each component is as follows:

[0038]

[0039] The method for preparing the above-mentioned ultra-low permeability sandstone reservoir carbon dioxide flooding injection well pressure reduction and injection increase plugging agent specifically comprises the following steps:

[0040] Step 1: Take the above-mentioned proportion of nonylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate and triisopropylphenyl phosphate, add them into an acid-resistant and alkali-resistant reaction kettle, stir while adding, heat to 45-50°C, and stir at a constant temperature to ensure that the materials (solutions) in the kettle are evenly mixed to obtain a mixed solution A2. A small amount of water can be added first in step 1.

[0041] Step 2: Take the above-mentioned proportion of polyetheramine, carboxylate-sulfonate-nonionic (terpolymer HM-3100), low molecular weight sulfonated polystyrene and pentanedione, add them to the above-mentioned mixed solution A2, stir evenly, and obtain mixed solution B2.

[0042] Step 3: Take the hydroxyethyl cellulose and span80 in the above-mentioned dosage ratio, add them to the above-mentioned mixed solution B2, add enough water in the dosage ratio, stir evenly, keep it at a constant temperature of 45°C for 60 minutes, and then cool it to room temperature to obtain the pressure reduction and injection enhancement plugging agent for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs.

[0043] In the above examples, the nonylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate, triisopropylphenyl phosphate, polyetheramine, carboxylate-sulfonate-nonionic (terpolymer HM-3100), low molecular weight sulfonated polystyrene, pentanedione, hydroxyethyl cellulose, span80 are all industrial products and can be purchased directly.

[0044] (III) Evaluation experiment

[0045] The pressure-reducing and injection-enhancing plugging agents for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs prepared in Example 1 and Example 2 are respectively denoted as 1 # and 2 # The plugging remover product is used to evaluate the asphaltene dissolution performance, corrosion performance and scale inhibition performance.

[0046] The evaluation method of asphaltene solubility performance refers to "China Petroleum and Natural Gas Industry Standard SY / T5886-2018 "Acidizing Working Fluid Performance Evaluation Method"". The evaluation method of asphaltene solubility performance of plugging remover is as follows:

[0047] Take 1.0 g of asphalt powder and put it into a plastic beaker, then add 100 ml of 1 # or 2 # For the blockage remover product, record the time as the start time of the reaction, stir quickly until the powder is completely wetted, put it into a constant temperature oven at 60℃, 70℃, 80℃, and >80℃, let it stand, design an appropriate reaction time (72 hours), and after the predetermined time, take out the beaker and filter it quickly, rinse it with distilled water until the filtrate is neutral. Then put the residual sample together with the filter paper into a 105℃ drying oven and dry it until constant weight is calculated to calculate the dissolution rate. The results show that 1 # and 2 # The asphaltene dissolution rates of the plugging remover products at temperatures above 60°C are above 90.5% and 91.8% respectively, showing good dissolution ability.

[0048] The corrosion performance evaluation refers to the "China Petroleum and Natural Gas Industry Standard SY / T5329-2012 "Recommended Indicators and Analysis Methods for Water Quality in Clastic Reservoirs"". The corrosion performance evaluation method of the plugging remover is as follows:

[0049] After the N80 coupons were processed, they were weighed and their geometric dimensions were measured. They were then placed in a plastic reaction container and 1 # or 2 # The plugging remover product was used to immerse the coupon, which was sealed with a lid and placed in a constant temperature oven for reaction for 4 hours. After the reaction reached the predetermined time, the coupon was immediately taken out and rinsed with distilled water, then cleaned with anhydrous ethanol, dried with cold air, and placed in a dryer for 30 minutes before weighing and calculating the corrosion rate. The results showed that 1 # and 2 # The corrosion rates of the plugging remover products are 0.0643 g / (m 2 ·h)、0.0613g / (m 2 h), which is less than the corrosion rate control index of 0.076g / (m 2 h), low corrosiveness.

[0050] The scale inhibition performance evaluation refers to the "China National Petroleum Corporation Enterprise Standard Q / SY126-2014 "Technical Specifications for Corrosion and Scale Inhibition for Oilfield Water Treatment"". The results show that 1 # and 2 #The scale inhibition rate of the plugging remover product for carbonate scale is over 85%, and the scale inhibition rate for barium sulfate scale is over 65%. The plugging remover has both good organic scale inhibition ability and good inorganic scale inhibition function.

[0051] In summary, the pressure-reducing and injection-increasing plugging agent for carbon dioxide flooding injection wells in ultra-low permeability sandstone reservoirs provided by the present invention has good asphaltene dissolution and dispersion performance and scale inhibition performance, and at the same time has low corrosiveness, and is suitable for carbon dioxide flooding under high temperature and high pressure environments, so that the carbon dioxide flooding injection well can achieve online continuous injection (continuous injection through a high-pressure plunger pump) or measures to remove blockage (the oil well is shut down for a period of time after the plugging remover is added).

Claims

1. A carbon dioxide flooding injection well plugging remover, characterized in that: The plugging remover comprises an asphaltene dispersant, an inorganic scale dispersant, a dispersing aid and a dispersing stabilizer; the asphaltene dispersant comprises alkylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate and triisopropylphenyl phosphate.

2. A carbon dioxide flooding oil injection well plugging remover according to claim 1, characterized in that: The inorganic scale dispersant includes a carboxylate-sulfonate-nonionic terpolymer.

3. A carbon dioxide flooding oil injection well plugging remover according to claim 1, characterized in that: The dispersing aid includes polyetheramine, low molecular weight sulfonated polystyrene and diketone.

4. A carbon dioxide flooding oil injection well plugging remover according to claim 1, characterized in that: The dispersion stabilizer includes hydroxyethyl cellulose and sorbitan fatty acid ester polyoxyethylene ether.

5. The carbon dioxide flooding injection well plugging remover according to claim 1, characterized in that: The blocking remover is prepared from the following raw materials by weight percentage: 3.0% to 10.0% of alkylphenol polyoxyethylene ether, 1.0% to 3.0% of alkylnaphthalene sodium sulfonate, 2.0% to 3.0% of triisopropylphenyl phosphate, 1.0% to 10.0% of polyetheramine, 1.0% to 5.0% of carboxylate-sulfonate-nonionic terpolymer, 3.0% to 5.0% of low molecular weight sulfonated polystyrene, 1.0% to 2.0% of diketone, 0.1% to 2.0% of hydroxyethyl cellulose, 2.0% to 6.0% of sorbitan fatty acid ester polyoxyethylene ether, and the balance is water.

6. A carbon dioxide flooding oil injection well plugging remover according to claim 5, characterized in that: The alkylphenol polyoxyethylene ether is selected from one or more of nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether; the molecular weight of the polyetheramine is 300-5000.

7. A plugging remover for carbon dioxide flooding injection wells according to claim 1, characterized in that: The blocking remover is a compound formed by uniformly mixing an asphaltene dispersant, an inorganic scale dispersant, a dispersing aid and a dispersing stabilizer in water.

8. A method for preparing a plugging remover for carbon dioxide oil flooding injection wells according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) stirring and mixing alkylphenol polyoxyethylene ether, sodium alkylnaphthalene sulfonate, triisopropylphenyl phosphate and water under heating conditions; 2) stirring and mixing the inorganic scale dispersant, the dispersing aid and the mixture obtained in step 1; 3) stirring and mixing the dispersion stabilizer, water and the mixture obtained in step 2 and then keeping the mixture warm for a certain period of time to obtain a uniformly dispersed carbon dioxide oil recovery injection well plugging remover.

9. The preparation method according to claim 8, characterized in that: In step 1, the heating condition is specifically: heating to ≥45°C.

10. The preparation method according to claim 8, characterized in that: In step 3, the specific conditions for heat preservation are: keeping the mixture at a constant temperature of 40 to 50° C. for 60 to 80 minutes.

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