Alcohol-based chelating acid liquid system as well as preparation method, use method and application thereof

Abstract

The invention belongs to the technical field of oil-gas field development and exploitation, and particularly relates to an alcohol-based chelating acid liquid system and a preparation method, a use method and application thereof. The alcohol-based chelating acid liquid system provided by the invention comprises the following components in percentage by weight: 20%-80% of alcohol, 0.1%-20% of acid liquid, 5%-60% of a chelating agent, 0.1%-10% of a corrosion inhibitor, 0.1%-10% of a discharge aiding agent and 14.7%-74.7% of water. The alcohol-based chelating acid liquid system can effectively chelate various ions generated by acid etching reaction, prevent generation of precipitates and natural gas hydrates, ensure that pores dredged by acid etching are not polluted and blocked, and ensure that a production pipeline is not blocked by ice. After acidification, the pH value of the flow-back liquid is kept at 6-8, and the residual liquid does not need to be neutralized, so that the flow-back liquid of the system can directly enter a tank or a production process, does not need special treatment, and is of great significance to oil-gas field development and exploitation.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development and exploitation technology, specifically relating to an alcohol-based chelated acid liquid system and its preparation method, usage method and application. Background Technology

[0002] Deep-water, low-permeability, and ultra-low-permeability carbonate reservoirs suffer from poor reservoir properties and seepage channels filled with clay and other matrix. During acid fracturing, conventional acid systems react with carbonate minerals to produce large amounts of divalent calcium and magnesium ions, easily leading to secondary precipitation. This causes the pores, which have been cleared by dissolution, to become blocked again, making acid injection difficult and hindering the effective expansion of seepage channels. This severely impacts the production enhancement effect of acid fracturing in these reservoirs. Furthermore, deep-water reservoirs, characterized by low temperatures and high pressures, often generate natural gas hydrates. Conventional acid systems used in acid fracturing of carbonate reservoirs cannot effectively lower the freezing point of natural gas hydrates to inhibit their formation. This results in natural gas hydrates easily causing "ice blockage" in production pipelines, posing a significant challenge to traditional acidizing processes.

[0003] Existing patents include: Chinese invention patent CN106590616A, which discloses an organic chelating acid system for oil and water well acidizing. This invention can effectively remove formation blockages, as well as waxes, asphalt, and inorganic scale. It has strong metal ion chelating ability, effectively preventing secondary precipitation during acidizing from damaging the formation; however, this system does not inhibit hydrate formation. Chinese invention patent CN108219767A discloses an offshore oilfield acidizing and production enhancement system and its preparation method. This invention uses chelating acid to provide H₂O. + It forms a chelated soil acid system with NH4F in the system. After entering the well, when encountering clay minerals and mud, the chelated acid continuously provides H2O. + At the same time, it consumes F in the system. Because chelating acids have a strong chelating ability for metals, they can ensure the chelation of heavy metals such as iron during the process, avoiding secondary sedimentation that could damage the reservoir; however, this system does not have the ability to inhibit hydrate formation. Chinese invention patent CN117683524A discloses an oilfield unblocking agent and method. This patent shows that an oilfield unblocking agent system integrating oil washing, oil displacement, and acidification is prepared using mixed benzene, multi-element organic acids, nonionic surfactants, chelating agents, and alcohols, which has the advantage of strong oil-based core dissolution ability; however, this system does not have the ability to dissolve clay minerals or inhibit hydrate formation.

[0004] Problems: Currently, the best method for suppressing secondary precipitation during acid fracturing in low-permeability and ultra-low-permeability reservoirs is to introduce chelating agents into the acid system. These chelating agents capture the metal cations generated by the acid-rock reaction, thus significantly inhibiting the formation of secondary precipitation. However, the unique low-temperature and high-pressure environment of deep-water reservoirs provides ideal conditions for the formation of natural gas hydrates, which can easily cause "ice blockage" in production pipelines during acid fracturing in deep-water low-permeability and ultra-low-permeability reservoirs. Unfortunately, the currently widely used acid systems have limited effectiveness in suppressing natural gas hydrate formation, severely affecting the effectiveness of acid fracturing in deep-water low-permeability and ultra-low-permeability reservoirs. Therefore, there is an urgent need to develop an acid system that can suppress both secondary precipitation and natural gas hydrate formation, in order to achieve a breakthrough in enhancing production through acid fracturing in complex lithology and oil and gas reservoirs in deep-water low-permeability and ultra-low-permeability environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an alcohol-based chelating acid system, its preparation method, usage method, and application.

[0006] Specifically, the alcohol-based chelated acid system provided by the present invention comprises, by weight percentage: 20%-80% alcohol, 0.1%-20% acid, 5%-60% chelating agent, 0.1%-10% corrosion inhibitor, 0.1%-10% drainage aid, and 14.7%-74.7% water.

[0007] The above-mentioned alcohol-based chelated acid system, by weight percentage, comprises: 25%-40% alcohol, 1%-10% acid, 40%-50% chelating agent, 0.1%-1% corrosion inhibitor, 0.1%-1% drainage aid, and 18.8%-33.8% water.

[0008] The alcohol-based chelating acid system described above includes one or more of isopropanol, n-butanol, n-pentanol, n-hexanol, ethylene glycol, and propylene glycol.

[0009] The above-mentioned alcohol-based chelated acid system includes one or more of industrial hydrochloric acid, formic acid, acetic acid, lactic acid, and aminosulfonic acid.

[0010] The chelating agent in the above-mentioned alcohol-based chelating acid system includes one or more of the following: sodium citrate, trisodium hypozide triacetate, trisodium hydroxyethyl ethylenediamine triacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium aminotrimethylene phosphate, tetrasodium hydroxyethylidene diphosphate, pentasodium diethylenetriaminepentamethoxyate, pentasodium diethylenetriaminepentaacetate, and tetrasodium glutamate diacetate.

[0011] In the above-mentioned alcohol-based chelating acid system, the corrosion inhibitor includes one or more of the following: chromate, nitrite, silicate, molybdate, tungstate, polyphosphate, zinc salt, thiolamine, imidazoline, hexamethylenetetramine, phosphonic acid, phosphate, phosphonic acid, thiobenzothiazole, benzotriazole, sulfonated lignin, polyethylene, and polyaspartic acid.

[0012] The above-mentioned alcohol-based chelated acid liquid system includes one or more of the following: anionic fluorocarbon surfactants, cationic fluorocarbon surfactants, nonionic fluorocarbon surfactants, amphoteric fluorocarbon surfactants, silicone-containing fluorocarbon surfactants, hybrid fluorocarbon surfactants, long-chain fluorocarbon surfactants, and hydrophilic-free fluorocarbon surfactants.

[0013] The method for preparing the alcohol-based chelated acid system provided by the present invention includes: mixing alcohol, acid, chelating agent, corrosion inhibitor, drainage aid and water in proportion, and stirring at 0-50°C for 0.5-2 hours to obtain the alcohol-based chelated acid system.

[0014] The method of using the alcohol-based chelating acid system provided by the present invention is characterized by comprising: (1) Inject test fluid into the well; (2) Inject an alcohol-based chelated acid system into the well; (3) Inject displacement fluid into the well; (4) Well shut-in reaction time: 4-48 hours; (5) Backflow; The method for using the above-mentioned alcohol-based chelating acid solution system involves a test solution displacement of 0.1-1.5 m³. 3 / min; the displacement of the alcohol-based chelated acid system is 0.1-1.5 m³ / min. 3 / min; the displacement fluid displacement is 0.1-1.5 m³ / min. 3 / min.

[0015] This invention also provides the application of the above-mentioned alcohol-based chelated acid system in the development and exploitation of carbonate oil and gas reservoirs.

[0016] Compared with the prior art, the alcohol-based chelating acid system of the present invention has the following beneficial effects: (1) The alcohol-based chelating acid system of the present invention can effectively remove clay and carbonate rock sediments in the reservoir, with a dissolution capacity of 41 kg / m³ at 80°C. 3 above; (2) The alcohol-based chelating acid system of the present invention can effectively avoid secondary precipitation during the reaction with clay, and the secondary precipitation inhibition rate is above 95%; (3) The alcohol-based chelated acid liquid system of the present invention has a freezing point of -15°C, which can effectively inhibit the formation of natural gas hydrates and avoid causing "ice blockage" in production pipelines; (4) The alcohol-based chelated acid liquid system of the present invention has good anti-swelling performance, with an average anti-swelling rate of 96%. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0018] Figure 1 The appearance of the alcohol-based chelating acid system of the present invention; Figure 2 The on-site construction curve for well X-1 is shown. Detailed Implementation

[0019] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0020] When a range of values ​​is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0021] Specifically, in a first aspect, the present invention provides an alcohol-based chelating acid system, comprising an alcohol, an acid, a chelating agent, a corrosion inhibitor, and a drainage aid.

[0022] An alcohol-based chelated acid system can be prepared from alcohols, acids, chelating agents, corrosion inhibitors, and drainage aids. Because it consists of alcohols, acids, and chelating agents, it can effectively dissolve clay and carbonate rock sediments in reservoirs, chelate metal ions to prevent secondary precipitation, lower the freezing point of natural gas hydrates, inhibit the formation of natural gas hydrates, and prevent "ice blockage" in production pipelines.

[0023] The components of the alcohol-based chelating acid system of the present invention are described in detail below: alcohol Alcohols inhibit the formation of natural gas hydrates by lowering their freezing point.

[0024] In some preferred embodiments, the alcohol includes one or more of isopropanol, n-butanol, n-pentanol, n-hexanol, ethylene glycol, and propylene glycol.

[0025] This invention uses the aforementioned alcohol to lower the freezing point of natural gas hydrates, thereby inhibiting the formation of natural gas hydrates in deep water environments and preventing damage from "ice blockage" in production pipelines.

[0026] In some preferred embodiments, the alcohol content in the alcohol-based chelating acid system of the present invention is 20%-80% by weight, for example 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%.

[0027] In practice, when the alcohol content is too high, the chelating agent content decreases accordingly, and the ability to inhibit secondary precipitation is limited; when the alcohol content is low, the ability to inhibit natural gas hydrates decreases, and "ice blockage" is easily caused.

[0028] More preferably, the alcohol content in the alcohol-based chelating acid system is 25%-40% by weight.

[0029] acid Acid can effectively dissolve blockages in the matrix pores, dissolve reservoir minerals, connect reservoir storage spaces, and form high-permeability channels.

[0030] In some preferred embodiments, the acid solution includes one or more of industrial hydrochloric acid, formic acid, acetic acid, lactic acid, and aminosulfonic acid.

[0031] In some preferred embodiments, the content of acid in the alcohol-based chelated acid system of the present invention is 0.1%-10% by weight, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%.

[0032] In practice, excessively high acid content leads to excessively high corrosion rates and severe corrosion of the construction tubing; while insufficient acid content has limited ability to dissolve clay and carbonate rock precipitates in the reservoir. More preferably, the acid content in the alcohol-based chelated acid system is 1%-10% by weight.

[0033] Chelating agents Chelating agents extract metal ions (such as calcium, magnesium, barium, and strontium) from clay lattices by chelating them, forming nano-sized soluble oxygen clusters that disrupt the clay lattice and dissolve clay minerals. At the same time, they can chelate divalent cations formed by acid-rock reactions to prevent secondary precipitation and damage to the reservoir.

[0034] In some preferred embodiments, the chelating agent includes one or more of sodium citrate, trisodium hypotriacetate, trisodium hydroxyethylethylenediaminetriacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium aminotrimethylene phosphate, tetrasodium hydroxyethylidene diphosphate, pentasodium diethylenetriaminepentamethoxyate, pentasodium diethylenetriaminepentaacetate, and tetrasodium glutamate diacetate.

[0035] In some preferred embodiments, the content of the chelating agent in the alcohol-based chelating acid system of the present invention is 5%-60% by weight, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%.

[0036] In practice, when the chelating agent content is too low, the ability to remove clay minerals and inorganic scale decreases, and the ability to inhibit secondary precipitation decreases; when the chelating agent content is too high, the alcohol content decreases accordingly, and the ability to inhibit natural gas hydrates decreases.

[0037] More preferably, the content of chelating agent in the alcohol-based chelating acid system is 40%-50% by weight.

[0038] corrosion inhibitor Corrosion inhibitors are used to protect metal equipment and pipes from corrosion.

[0039] In some preferred embodiments, the corrosion inhibitor includes one or more of the following: chromates, nitrites, silicates, molybdates, tungstates, polyphosphates, zinc salts, thiolamides, imidazolines, hexamethylenetetramine, phosphonic acids (salts), phosphonic acids, thiobenzothiazoles, benzotriazoles, sulfonated lignins, polyethylenes, and polyaspartic acid.

[0040] In some preferred embodiments, the content of the corrosion inhibitor in the alcohol-based chelated acid system of the present invention is 0.1%-10% by weight, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%.

[0041] In practice, when the corrosion inhibitor content is too low, the corrosion of the construction pipe column by the acid solution is more severe; when the corrosion inhibitor content is too high, excess precipitates may form, leading to instability in the structure of the alcohol-based chelate acid solution.

[0042] More preferably, the content of corrosion inhibitor in the alcohol-based chelated acid system is 0.1%-1% by weight.

[0043] Drainage aid Drainage aids are used to reduce interfacial tension, increase the speed and extent of drainage, and prevent clogging and emulsification.

[0044] In some preferred embodiments, the discharge aid is one or more of the following: anionic fluorocarbon surfactant, cationic fluorocarbon surfactant, nonionic fluorocarbon surfactant, amphoteric fluorocarbon surfactant, silicone-containing fluorocarbon surfactant, hybrid fluorocarbon surfactant, long-chain fluorocarbon surfactant, and hydrophilic-free fluorocarbon surfactant.

[0045] In some preferred embodiments, the content of the excretion aid in the alcohol-based chelated acid system of the present invention is 0.1%-10% by weight, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%.

[0046] In practice, when the content of the drainage aid is too low, the viscosity is too high, making preparation and use difficult; when the content of the drainage aid is too high, it is difficult to form a structurally stable alcohol-based chelated acid liquid system.

[0047] More preferably, the content of the discharge aid in the alcohol-based chelated acid system is 0.1%-1% by weight.

[0048] The alcohol-based chelating acid system provided by this invention can effectively expand and connect pores filled with argillaceous matrix, while having the characteristics of not damaging the rock skeleton, inhibiting secondary precipitation and natural gas hydrate formation, and has a good effect on acid fracturing and acid treatment of deep-water high-porosity and low-permeability limestone reservoirs.

[0049] Secondly, the present invention provides a method for preparing the above-mentioned alcohol-based chelated acid system, comprising: mixing alcohol, acid, chelating agent, corrosion inhibitor and drainage aid in proportion, and stirring at 0-50°C for 0.5-2 hours to obtain the alcohol-based chelated acid system.

[0050] The preparation method of the alcohol-based chelated acid system of the present invention is simple to prepare and convenient to operate on site, which is of great significance for oil and gas field development and exploitation.

[0051] Thirdly, the present invention provides a method for using the above-mentioned alcohol-based chelating acid system, comprising: (1) Inject test fluid into the well; (2) Inject an alcohol-based chelated acid system into the well; (3) Inject displacement fluid into the well; (4) Well shut-in reaction time: 4-48 hours; (5) Backflow.

[0052] The alcohol-based chelating acid system of the present invention is simple to use and can effectively chelate various ions generated by the acid etching reaction, prevent precipitation, ensure that the pores cleared by acid etching are not contaminated and blocked, and at the same time lower the freezing point of natural gas hydrate, inhibit the formation of natural gas hydrate, avoid "ice blockage" in production pipelines, and greatly improve acidification efficiency.

[0053] In some preferred embodiments, the flow rate of the test liquid is 0.1-1.5 m³. 3 / min; the displacement of the alcohol-based chelated acid system is 0.1-1.5 m³ / min. 3 / min; the displacement fluid displacement is 0.1-1.5 m³ / min. 3 / min.

[0054] Fourthly, the present invention also provides the application of the above-mentioned alcohol-based chelated acid system in the development and exploitation of carbonate oil and gas reservoirs.

[0055] The alcohol-based chelating acid system of this invention can effectively chelate various ions generated by the acid etching reaction, preventing the formation of precipitates and natural gas hydrates, ensuring that the pores cleared by acid etching are not contaminated or blocked, and preventing "ice blockage" of production pipelines. After acidification, the pH of the return liquid remains at 6-8, and the residual liquid does not require neutralization, indicating that the return liquid of this system can be directly fed into tanks or the production process without special treatment, which is of great significance for oil and gas field development and exploitation.

[0056] Example The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0057] Raw material source: Ethylene glycol, Tianjin Economic-Technological Development Area Kuayue Industry & Trade Co., Ltd.; Isopropyl alcohol, Tianjin Economic-Technological Development Area Kuayue Industry and Trade Co., Ltd.; Hydrochloric acid, concentration 31%, Tianjin Economic-Technological Development Area Kuayue Industry and Trade Co., Ltd. Imidazoline corrosion inhibitor, Tianjin Development Zone Kuayue Industry and Trade Co., Ltd., product number W01062; Fluorocarbon surfactant, Tianjin Economic-Technological Development Area Kuayue Industry & Trade Co., Ltd., product number A166370.

[0058] Trisodium hydroxyethyl ethylenediamine triacetate, Tianjin Development Zone Kuayue Industry and Trade Co., Ltd. Disodium ethylenediaminetetraacetate, Tianjin Development Zone Kuayue Industry and Trade Co., Ltd.

[0059] Example 1 First material preparation: In a ceramic reactor, add 320g of ethylene glycol, 75g of hydrochloric acid, 2g of imidazoline corrosion inhibitor, and 3g of fluorocarbon surfactant. Second material preparation: In a ceramic reactor, add 230g of trisodium hydroxyethyl ethylenediamine triacetate, 200g of disodium ethylenediaminetetraacetate, and 170g of water.

[0060] Compound preparation: Seal the reactor and continue stirring. When the temperature is heated to 50°C by steam, the reaction temperature is controlled at around 50°C by the automatic control system. The pressure inside the reactor does not need to be controlled and should not exceed 1.0 MPa. After 1 hour, when the solution is completely dissolved, circulate water to cool it down. When the temperature drops below 30°C, release it from the bottom of the reactor to obtain 1000g of alcohol-based chelated acid solution system.

[0061] Performance testing: The alcohol-based chelated acid solution system prepared in Example 1 was tested.

[0062] 1. Testing the dissolution rate of rock fragments. 1.1 Test Method 1) Place the rock cuttings sample in a constant temperature drying oven, dry it, and then place it in a desiccator to cool it for later use; 2) Dry the filter paper to a constant weight, weigh it and record the weight as m1; 3) Weigh 2.0g of rock fragments sample, accurate to 0.001g, record as m, add 40mL of alcohol-based chelating acid solution system, keep the temperature constant at 80℃ in a water bath, and react for 4h.

[0063] 4) Filter with constant weight filter paper, then dry the filter paper to constant weight, weigh it, and record it as m2. Two sets of parallel experiments were conducted using the above method. 5) Calculate the solubility.

[0064] In the formula: x2—Solubility of the sample by the solution, % m1—Weight of pretreated filter paper, in g; m2—The weight of the sample after filtering the acid solution and drying the filter paper to constant weight, in grams; m — the weight of the sample, in grams.

[0065] 1.2 Test Results The rock fragment dissolution rate test results of the alcohol-based chelated acid system prepared in Example 1 are shown in Table 1.

[0066] Table 1 Dissolution data of rock fragment samples

[0067] 2. Determination of static corrosion rate under normal pressure 2.1 Test Method 1) Weigh the N80 steel hanging strips in the desiccator for 20 minutes, accurate to 0.0001g, and record the weight; 2) Mark the hanging pieces: Measure and record the dimensions of the hanging pieces using calipers; 3) Calculate the required alcohol chelating acid solution system based on the amount of acid solution used per square centimeter of tablets, which is 20 mL. Pour the alcohol chelating acid solution system into the reaction vessel, connect the device, and place the reaction vessel in a constant temperature water bath to raise the temperature of the reaction vessel to 80°C. 4) Place the tablets into the alcohol chelating acid solution system, ensuring that the tablets are completely in contact with the alcohol chelating acid solution system and do not contact the container wall, and record the reaction time; 5) After reacting for 72 hours, remove the trays, rinse them immediately with water, scrub them with a soft brush, and place them on clean filter paper.

[0068] 6) Weigh the hanging tablets, dry them with cold air, place them in a desiccator to dry for 20 minutes, and weigh them to an accuracy of 0.0001g. 7) The corrosion rate is calculated using the following formula:

[0069] In the formula: V i —Corrosion rate, g / (m 2 ·h); t —Reaction time, h; m i —Corrosion loss of the coupon, g; A i — Surface area of ​​the hanging plate, mm 2 ; The surface area of ​​the mounting plate is calculated using the following formula:

[0070] In the formula: L —Length of the hanging piece, mm; a —Width of the hanging piece, mm; b —Thickness of the hanging piece, mm.

[0071] 2.2 Test Results The corrosion rates of the alcohol-based chelated acid solution system prepared in Example 1 on the coated tablets are summarized below: Table 2. Experimental results for evaluating corrosion rate

[0072] 3. Methods for measuring permeability improvement The procedure shall be performed in accordance with the method specified in 9.4.3 of "SY-T 5358-2010 Evaluation Method for Reservoir Sensitivity Flow Test".

[0073] Well X-1 is a deepwater gas well in the eastern South China Sea oilfield. Its reservoir is mainly composed of biological cavity pores. This reservoir has high porosity, low permeability, and poor connectivity. It also contains two types of matrix: limestone and mudstone. When using conventional acid systems for dissolution, secondary precipitation is easily generated, causing the pores to be blocked again after dissolution and clearing. This poses a great challenge to traditional acidizing processes.

[0074] The well was acidized using the alcohol-based chelated acid system described in Example 1. The on-site construction curves are shown below. Figure 2 The amount of alcohol-based chelating acid solution used was 251m. 3 After acidizing and shutting in the well for 4 hours, the unhindered natural gas flow rate reached 430,000 m³ after production resumed. 3 / d, which indicates that the alcohol-based chelating acid system of this embodiment can effectively expand and connect the pores filled with argillaceous matrix, protect the rock skeleton and inhibit secondary precipitation, thus helping my country achieve a major breakthrough in the field of deep-water carbonate rock exploration for the first time.

[0075] 3.2 Test Results The displacement experimental data of the alcohol-based chelated acid solution system prepared in Example 1 are summarized as follows: Table 3 Displacement Experiment Data

[0076] Example 2 First material preparation: In a ceramic reactor, add 150g of ethylene glycol, 170g of propylene glycol, 50g of acid, 3g of imidazoline corrosion inhibitor, and 2g of fluorocarbon surfactant. Second material preparation: In a ceramic reactor, add 200g of trisodium hydroxyethyl ethylenediamine triacetate, 200g of disodium ethylenediaminetetraacetate, and 225g of water.

[0077] Compound preparation: Seal the reactor and continue stirring. When the temperature is heated to 50°C by steam, the reaction temperature is controlled at around 50°C by the automatic control system. The pressure inside the reactor does not need to be controlled and should not exceed 1.0 MPa. After 1 hour, when the solution is completely dissolved, circulate water to cool it down. When the temperature drops below 30°C, release it from the bottom of the reactor to obtain 1000g of alcohol-based chelated acid solution system.

[0078] Performance testing: The method for determining the rock fragment dissolution rate is the same as in Example 1, and the test results are shown in Table 4.

[0079] Table 4 Dissolution data of rock fragments

[0080] The static corrosion rate under normal pressure was determined according to Example 1, and the test results are shown in Table 5.

[0081] Table 5. Experimental results for evaluating corrosion rate

[0082] The method for measuring permeability improvement was performed in accordance with the method specified in 9.4.3 of "SY-T 5358-2010 Evaluation Method for Reservoir Sensitivity Flow Test". The test results are shown in Table 6.

[0083] Table 6 Displacement Experiment Data

[0084] Example 3 First material preparation: In a ceramic reactor, add 100g of ethylene glycol, 150g of isopropanol, 90g of acid, 2g of imidazoline corrosion inhibitor, and 3g of fluorocarbon surfactant. Second material preparation: In a ceramic reactor, add 280g of trisodium hydroxyethyl ethylenediamine triacetate, 200g of tetrasodium ethylenediaminetetraacetate, and 175g of water.

[0085] Compound preparation: Seal the reactor and continue stirring. When the temperature is heated to 50°C by steam, the reaction temperature is controlled at around 50°C by the automatic control system. The pressure inside the reactor does not need to be controlled and should not exceed 1.0 MPa. After 1 hour, when the solution is completely dissolved, circulate water to cool it down. When the temperature drops below 30°C, release it from the bottom of the reactor to obtain 1000g of alcohol-based chelated acid solution system.

[0086] Performance testing: The method for determining the rock fragment dissolution rate is the same as in Example 1, and the test results are shown in Table 7.

[0087] Table 7 Dissolution data of rock fragment samples

[0088] The static corrosion rate under normal pressure was determined according to Example 1, and the test results are shown in Table 8.

[0089] Table 8. Experimental Results for Corrosion Rate Evaluation

[0090] The method for measuring permeability improvement was performed in accordance with the method specified in 9.4.3 of "SY-T 5358-2010 Evaluation Method for Reservoir Sensitivity Flow Test". The test results are shown in Table 9.

[0091] Table 9 Displacement Experiment Data

[0092] Example 4 First material preparation: In a ceramic reactor, add 200g of ethylene glycol, 80g of n-butanol, 90g of acid, 3g of imidazoline corrosion inhibitor, and 2g of fluorocarbon surfactant. Second material preparation: Add 300g of trisodium hydroxyethyl ethylenediamine triacetate, 150g of tetrasodium hydroxyethylidene diphosphate, and 175g of water to a ceramic reactor.

[0093] Compound preparation: Seal the reactor and continue stirring. When the temperature is heated to 50°C by steam, the reaction temperature is controlled at around 50°C by the automatic control system. The pressure inside the reactor does not need to be controlled and should not exceed 1.0 MPa. After 1 hour, when the solution is completely dissolved, circulate water to cool it down. When the temperature drops below 30°C, release it from the bottom of the reactor to obtain 1000g of alcohol-based chelated acid solution system.

[0094] Performance testing: The method for determining the rock fragment dissolution rate is the same as in Example 1, and the test results are shown in Table 10.

[0095] Table 10 Dissolution data of rock fragment samples

[0096] The static corrosion rate under normal pressure was determined according to Example 1, and the test results are shown in Table 11.

[0097] Table 11 Experimental Results for Corrosion Rate Evaluation

[0098] The method for measuring permeability improvement was performed in accordance with the method specified in 9.4.3 of "SY-T 5358-2010 Evaluation Method for Reservoir Sensitivity Flow Test". The test results are shown in Table 12.

[0099] Table 12 Displacement Experiment Data

[0100] Comparative Example 1: 20% hydrochloric acid system Prepare a 20% hydrochloric acid system: 20% HCl + 1% corrosion inhibitor + 1% iron stabilizer + 1% drainage aid + the remainder water.

[0101] The HCl was 31% industrial hydrochloric acid, purchased from Tianjin Development Zone Kuayue Industry & Trade Co., Ltd.; the corrosion inhibitor was an imidazoline corrosion inhibitor, also purchased from Tianjin Development Zone Kuayue Industry & Trade Co., Ltd.; the iron stabilizer was citric acid, also purchased from Tianjin Development Zone Kuayue Industry & Trade Co., Ltd.; and the discharge aid was a fluorocarbon surfactant (C8F). 17 SO2NHC3H7NR2(O) was purchased from Tianjin Development Zone Kuayue Industry and Trade Co., Ltd.

[0102] The rock fragment dissolution rate and permeability improvement rate of the hydrochloric acid system were tested using the same method as in Example 1. The rock fragment dissolution rate of the 20% hydrochloric acid system was 42%. Core displacement experiments (20% HCl, temperature: 50-60℃, pressure difference: 20-30MPa) showed that the core was dense with no obvious cracks. During acid displacement, the core was held under pressure for 2 hours, and the acid did not penetrate the core. After acid etching, the core inlet face was relatively smooth, and no obvious visible wormholes were formed.

[0103] Comparative experiments show that the hydrochloric acid system alone is less effective than the alcoholic acid system in improving the seepage capacity of tight cores and cannot effectively improve tight reservoirs.

[0104] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An alcohol-based chelated acid system, characterized in that, By weight percentage, it includes: 20%-80% alcohol, 0.1%-20% acid, 5%-60% chelating agent, 0.1%-10% corrosion inhibitor, 0.1%-10% drainage aid, and 14.7%-74.7% water.

2. The alcohol-based chelating acid system according to claim 1, characterized in that, By weight percentage, it includes: 25%-40% alcohol, 1%-10% acid, 40%-50% chelating agent, 0.1%-1% corrosion inhibitor, 0.1%-1% drainage aid, and 18.8%-33.8% water.

3. The alcohol-based chelating acid system according to claim 1, characterized in that, The alcohols include one or more of isopropanol, n-butanol, n-pentanol, n-hexanol, ethylene glycol, and propylene glycol.

4. The alcohol-based chelating acid system according to claim 1, characterized in that, The acid solution includes one or more of industrial hydrochloric acid, formic acid, acetic acid, lactic acid, and aminosulfonic acid.

5. The alcohol-based chelating acid system according to claim 1, characterized in that, The chelating agent includes one or more of the following: sodium citrate, trisodium hypotriacetate, trisodium hydroxyethyl ethylenediaminetriacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium aminotrimethylene phosphate, tetrasodium hydroxyethylidene diphosphate, pentasodium diethylenetriaminepentamethoxyate, pentasodium diethylenetriaminepentaacetate, and tetrasodium glutamate diacetate.

6. The alcohol-based chelating acid system according to claim 1, characterized in that, The corrosion inhibitors include one or more of the following: chromates, nitrites, silicates, molybdates, tungstates, polyphosphates, zinc salts, thiolamines, imidazolines, hexamethylenetetramine, phosphonic acids, phosphates, phosphonic acids, thiobenzothiazoles, benzotriazoles, sulfonated lignins, polyethylenes, and polyaspartic acid.

7. The alcohol-based chelating acid system according to claim 1, characterized in that, The discharge aid includes one or more of the following: anionic fluorocarbon surfactants, cationic fluorocarbon surfactants, nonionic fluorocarbon surfactants, amphoteric fluorocarbon surfactants, silicone-containing fluorocarbon surfactants, hybrid fluorocarbon surfactants, long-chain fluorocarbon surfactants, and hydrophilic-free fluorocarbon surfactants.

8. The method for preparing the alcohol-based chelating acid system according to any one of claims 1-7, characterized in that, include: The alcohol, acid, chelating agent, corrosion inhibitor, drainage aid and water are mixed in proportion and stirred at 0-50℃ for 0.5-2 hours to obtain the alcohol-based chelated acid system.

9. A method of using the alcohol-based chelating acid system according to any one of claims 1-7, characterized in that, include: (1) Inject test fluid into the well; (2) Inject an alcohol-based chelated acid system into the well; (3) Inject displacement fluid into the well; (4) Well shut-in reaction time: 4-48 hours; (5) Backflow.

10. The method of using the alcohol-based chelated acid system according to claim 9, characterized in that, The displacement of the test solution is 0.1-1.5 m³. 3 / min; the displacement of the alcohol-based chelated acid system is 0.1-1.5 m³ / min. 3 / min; the displacement fluid displacement is 0.1-1.5 m³ / min. 3 / min.

11. The application of the alcohol-based chelating acid system according to any one of claims 1-7 in the development and exploitation of carbonate oil and gas reservoirs.

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