Sandstone retarded acid and its application

Abstract

The application provides a sandstone retarded acid and application thereof. The sandstone retarded acid comprises, in parts by weight, 5-15 parts of an amino acid chelating agent, 1-10 parts of a hydroxyl carboxylic acid chelating agent, 2-8 parts of an inorganic acid and 65-90 parts of a solvent. The sandstone retarded acid has the functions of retarding and chelating metal ions, and can improve the core permeability after acidification and inhibit the generation of secondary precipitates such as calcium fluoride, potassium fluosilicate and silicic acid when applied in the field of oil and gas field development technology. Limiting the parts by weight of the amino acid chelating agent, the hydroxyl carboxylic acid chelating agent, the inorganic acid and the solvent in the above range is beneficial to improving the chelation reaction efficiency, improving the generation rate of chelates, improving the core permeability after acidification and inhibiting the generation of secondary precipitates.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and more specifically, to a sandstone slow-relief acid and its application. Background Technology

[0002] For low-permeability sandstone oil and gas reservoirs or those with severe near-wellbore contamination, acidizing is necessary to unblock and enhance production. Conventional sandstone unblocking acid is terrine acid, a mixture of hydrochloric acid and hydrofluoric acid in varying proportions. When used for acidizing operations, terrine acid systems react too quickly with the rock, leading to excessive consumption of the acid near the wellbore, resulting in a short effective range and limited unblocking distance. This often fails to meet the required stimulation targets. Furthermore, the hydrofluoric acid in terrine acid reacts with the anions and cations in the solution after the reaction, generating secondary precipitates such as calcium fluoride, potassium fluorosilicate, and silicic acid, severely restricting the effectiveness of acidizing stimulation.

[0003] The rate of acidizing in sandstone has a significant impact on the acidizing effect, making its research crucial. Current research utilizes principles such as multi-stage ionization of phosphoric acid and ester hydrolysis to study the rate of acidizing in sandstone. Existing literature (publication number CN101712864A) discloses a polyhydrogen acid injection enhancer for sandstone oilfields, whose main component is phosphoric acid. Utilizing multi-stage ionization of phosphoric acid, it exhibits a certain rate-retarding effect. Another existing literature (publication number CN1524922A) discloses a composite acidizing and unblocking agent for thin-layer sandstone reservoirs. This agent is composed of hydrochloric acid, citric acid, acetic acid, organic phosphoric acid, ammonium bifluoride, sodium dodecylbenzenesulfonate, ethanol, and the organic quaternary ammonium salt CT-3, while specifying its dosage ratio. Existing literature (publication number CN105295886A) discloses a composite slow-reacting acid, the main component of which is methyl formate. Formic acid is obtained by hydrolysis, and the formic acid then reacts with ammonium fluoride to generate the required hydrofluoric acid, thereby slowing down the reaction rate between the acid and the rock.

[0004] Regarding the problem of secondary precipitation caused by sandstone acidification, many scholars have used chelating agents to chelate metal ions, thereby reducing the damage from secondary precipitation. Existing literature (publication number CN108373911A) discloses a chelating and unblocking fluid for medium-to-high permeability sandstone reservoirs, with DOTA derivatives as the main component. This fluid avoids the shortcomings of conventional acidification and solves the problem that ordinary chelating agents cannot dissolve clay. Existing literature (publication number CN103261364A) discloses a method and fluid for improving the permeability of sandstone formations using chelating agents. The method involves introducing a fluid containing N,N-diacetic glutamic acid or its salts with a pH of 1-14 into the formation. In the above methods, the use of GLDA chelating agents can effectively improve the permeability of sandstone formations.

[0005] Existing sandstone retarding acids mostly improve the retarding effect by increasing acid viscosity, utilizing multi-stage ionization of phosphoric acid, and ester hydrolysis. However, using thickeners to increase acid concentration can cause polymer damage and reservoir pollution. Phosphoric acid retarding acids pollute the environment and are difficult to degrade biologically, while ester retarding acids do not have the ability to inhibit secondary precipitation.

[0006] As can be seen from the above, there are many types of sandstone acidification solutions, but the following problems still exist: (1) the acid system cannot simultaneously achieve the effects of slowing down and chelating metal ions; (2) the acid additives have poor biological and environmental protection properties, such as phosphate chelating agents which can cause eutrophication of water bodies, and aminocarboxylic acid chelating agents which have poor biodegradability and environmental protection properties.

[0007] Therefore, it is necessary to research and develop an environmentally friendly sandstone slowing acid that can simultaneously satisfy the functions of slowing down precipitation and chelating metal ions, thereby inhibiting secondary precipitation. Summary of the Invention

[0008] The main objective of this invention is to provide a sandstone retarding acid and its application, in order to solve the problem that existing sandstone retarding acids cannot simultaneously satisfy the functions of retarding and chelating metal ions, thereby inhibiting secondary precipitation.

[0009] To achieve the above objectives, the present invention provides a sandstone retarded acid, which, by weight, comprises: 5-15 parts of an amino acid chelating agent, 1-10 parts of a hydroxycarboxylic acid chelating agent, 2-8 parts of an inorganic acid, and 65-90 parts of a solvent.

[0010] Furthermore, the amino acid chelating agent is selected from amino acids and / or amino acid polymers.

[0011] Further, the amino acid is selected from one or more of the group consisting of aspartic acid, lysine, and glutamic acid; the amino acid polymer is selected from one or more of the group consisting of polyaspartic acid, polylysine, and polyglutamic acid; preferably, the number average molecular weight of the amino acid polymer is 13,000 to 1,300,000, or the degree of polymerization of the amino acid polymer is 100 to 10,000; more preferably, the number average molecular weight of the amino acid polymer is 13,000 to 130,000, or the degree of polymerization of the amino acid polymer is more preferably 100 to 1,000.

[0012] Furthermore, the weight ratio of amino acid chelating agents to hydroxycarboxylic acid chelating agents is (7-10):(5-8).

[0013] Further, the hydroxycarboxylic acid chelating agent is selected from one or more of the group consisting of sodium gluconate, sodium citrate and sodium maleate; preferably, the hydroxycarboxylic acid chelating agent is selected from sodium gluconate; more preferably, when the amino acid chelating agent is selected from polyaspartic acid and the hydroxycarboxylic acid chelating agent is selected from sodium gluconate, the weight ratio of polyaspartic acid to sodium gluconate is (7-9):(7-8).

[0014] Further, the inorganic acid is selected from hydrofluoric acid, or a mixture of hydrochloric acid and hydrofluoric acid; preferably, the inorganic acid includes a mixture of hydrochloric acid and hydrofluoric acid, and the weight ratio of hydrochloric acid to hydrofluoric acid is (1-5):(1-3).

[0015] Furthermore, by weight, the sandstone slow-retarding acid also includes: 0.5 to 1 part corrosion inhibitor; preferably, the corrosion inhibitor is selected from Mannich bases and / or quinoline quaternary ammonium salt compounds.

[0016] Furthermore, the solvent is selected from one or more of the group consisting of water and methanol with a weight concentration of 1% to 5%.

[0017] Further, by weight, the sandstone retarding acid comprises: 7-9 parts of amino acid chelating agent, 7-8 parts of hydroxycarboxylic acid chelating agent, 3-5 parts of hydrochloric acid, 2-3 parts of hydrofluoric acid, 0.5-1 parts of corrosion inhibitor, and 74-80.5 parts of solvent.

[0018] To achieve the above objectives, another aspect of the present invention provides an application of the sandstone slow-relief acid provided in this application in the field of oil and gas field development technology.

[0019] The technical solution of this invention utilizes amino acid chelating agents, which possess both amino and carboxyl groups. These chelating agents undergo multi-stage ionization, exhibiting slowing properties. Both amino and carboxyl groups can chelate with metal ions (such as calcium and iron ions) in the oil reservoir, forming chelates. Applying these chelating agents to oil and gas field development increases the acid-rock reaction distance and improves acidification efficiency. Simultaneously, it reduces the formation of secondary precipitation during sandstone acidification. Furthermore, amino acid chelating agents are environmentally friendly and biodegradable, posing no harm to the reservoir during oil and gas field development. Carboxylic acid chelating agents, possessing both hydroxyl and carboxyl groups, also undergo multi-stage ionization and exhibit slowing properties. The hydroxyl and carboxyl groups can chelate metal ions (such as calcium and iron ions) in the oil reservoir to form chelates, thereby achieving a scale removal effect. The combined use of amino acid chelating agents and carboxylic acid chelating agents leverages their synergistic effect, better utilizing the slowing effect of sandstone acidification and the chelation of metal ions, thus inhibiting secondary precipitation.

[0020] Limiting the weight proportions of amino acid chelating agents, hydroxycarboxylic acid chelating agents, inorganic acids, and solvents within the above-mentioned range is beneficial to improving the efficiency of the chelation reaction, increasing the formation rate of chelates, and also improving the permeability of the core after acidification, thereby helping to suppress the formation of secondary precipitation. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As described in the background section, existing sandstone retarding acids cannot simultaneously satisfy the requirements of retarding and chelating metal ions, thereby failing to inhibit secondary precipitation. To address the aforementioned technical problem, this application provides a sandstone retarding acid, which, by weight, comprises: 5-15 parts of an amino acid chelating agent, 1-10 parts of a hydroxycarboxylic acid chelating agent, 2-8 parts of an inorganic acid, and 65-90 parts of a solvent.

[0023] Amino acid chelating agents possess both amino and carboxyl groups, enabling multi-stage ionization and exhibiting slowing properties. Both amino and carboxyl groups can chelate with metal ions (such as calcium and iron ions) in the oil reservoir, forming chelates. Applying these chelating agents in oil and gas field development can increase the acid-rock reaction distance and improve acidizing efficiency. Simultaneously, it can reduce the formation of secondary precipitation during sandstone acidification. Furthermore, amino acid chelating agents are environmentally friendly and biodegradable, posing no harm to the reservoir during oil and gas field development. Carboxylic acid chelating agents possess both hydroxyl and carboxyl groups, also enabling multi-stage ionization and slowing properties. The hydroxyl and carboxyl groups can chelate metal ions (such as calcium and iron ions) in the oil reservoir to form chelates, thereby removing scale. The combined use of amino acid chelating agents and carboxylic acid chelating agents can leverage their synergistic effects, better utilizing the slowing effect of sandstone acidification and the chelation of metal ions, thus inhibiting secondary precipitation.

[0024] Limiting the weight proportions of amino acid chelating agents, hydroxycarboxylic acid chelating agents, inorganic acids, and solvents within the above-mentioned range is beneficial to improving the efficiency of the chelation reaction, increasing the formation rate of chelates, and also improving the permeability of the core after acidification, thereby helping to suppress the formation of secondary precipitation.

[0025] It should be noted that, in this application, the acid-rock reaction distance refers to the distance that sandstone slow-release acid travels from fresh acid to residual acid.

[0026] Amino acids are organic compounds containing basic amino and acidic carboxyl groups. In a preferred embodiment, amino acid chelating agents include, but are not limited to, amino acids and / or amino acid polymers.

[0027] In a preferred embodiment, the amino acids include, but are not limited to, one or more of the group consisting of aspartic acid, lysine, and glutamic acid; the amino acid polymers include, but are not limited to, one or more of the group consisting of polyaspartic acid, polylysine, and polyglutamic acid. Compared to other types, using the above-mentioned preferred types of amino acids and / or amino acid polymers is beneficial for further enhancing their chelating effect, improving chelation efficiency, and thus improving core permeability and inhibiting the formation of secondary precipitation.

[0028] To further enhance the chelating ability of the amino acid polymer, thereby improving the chelating efficiency of sandstone slow-release acid and core permeability, preferably, the number-average molecular weight of the amino acid polymer is 13,000 to 1,300,000, or the degree of polymerization of the amino acid polymer is 100 to 10,000. More preferably, the number-average molecular weight of the amino acid polymer is 13,000 to 130,000, and the degree of polymerization of the amino acid polymer is 100 to 1,000. For example, polyaspartic acid with a degree of polymerization of 200, 300, or 500 can be used.

[0029] In a preferred embodiment, the weight ratio of the amino acid chelating agent to the hydroxycarboxylic acid chelating agent is (7-10):(5-8). The weight ratio of the amino acid chelating agent to the hydroxycarboxylic acid chelating agent includes, but is not limited to, the above range. Limiting it to this range is beneficial for better leveraging the synergistic effect of the two, further improving the chelation reaction efficiency and the chelate formation rate; simultaneously, it is beneficial for further improving the permeability of the core after acidification and for further suppressing the formation of secondary precipitation.

[0030] In a preferred embodiment, the hydroxycarboxylic acid chelating agent includes, but is not limited to, one or more of the group consisting of sodium gluconate, sodium citrate, and sodium maleate. Compared to other types, using the above-mentioned hydroxycarboxylic acid chelating agents is beneficial to improving the chelation effect of divalent and / or trivalent metal ions, further enhancing the descaling effect, and simultaneously helping to further reduce the formation of secondary precipitates. To further enhance the descaling effect and further reduce the formation of secondary precipitates, preferably, the hydroxycarboxylic acid chelating agent includes, but is not limited to, sodium gluconate.

[0031] In a preferred embodiment, when the amino acid chelating agent includes, but is not limited to, polyaspartic acid, and the hydroxycarboxylic acid chelating agent includes, but is not limited to, sodium gluconate, the weight ratio of polyaspartic acid to sodium gluconate is (7-9):(7-8). The weight ratio of polyaspartic acid to sodium gluconate is not limited to the above range; limiting it to this range is beneficial for further improving the chelation reaction efficiency and the formation rate of chelates; it is also beneficial for further improving the permeability of the core after acidification and for further suppressing the formation of secondary precipitation.

[0032] The inorganic acid can be a weak acid, or a combination of a weak acid and a strong acid, commonly used in the art. In a preferred embodiment, the inorganic acid includes, but is not limited to, hydrofluoric acid, or a mixture of hydrochloric acid and hydrofluoric acid. Compared to using a strong acid system, using an incompletely ionized inorganic acid is beneficial for further enhancing the retarding properties of sandstone retarding acids.

[0033] In a preferred embodiment, the inorganic acid includes, but is not limited to, a mixture of hydrochloric acid and hydrofluoric acid, wherein the weight ratio of hydrochloric acid to hydrofluoric acid is (1-5):(1-3). The weight ratio of hydrochloric acid to hydrofluoric acid includes, but is not limited to, the above range. Limiting it to this range is beneficial for further utilizing the retarding properties of the sandstone retarding acid, resulting in better retarding and chelation effects on metal ions.

[0034] In a preferred embodiment, the sandstone retarding acid further comprises, by weight, 0.5 to 1 part corrosion inhibitor. Preferably, the corrosion inhibitor includes, but is not limited to, Mannich bases and / or quinoline quaternary ammonium salt compounds. Using the above-mentioned amount of corrosion inhibitor by weight facilitates the formation of a more complete hydrophobic protective film on the surface of the wellbore steel, thereby inhibiting the corrosion of the rock formation by the sandstone retarding acid. For example, DCA-6 or KMS-6 (Beijing Kemaishi Oilfield Chemical Technology Co., Ltd.) can be used.

[0035] In a preferred embodiment, the solvent includes, but is not limited to, one or more of the group consisting of water and methanol with a weight concentration of 1% to 5%.

[0036] In a preferred embodiment, the sandstone retarding acid, by weight, comprises: 7-9 parts of an amino acid chelating agent, 7-8 parts of a hydroxycarboxylic acid chelating agent, 3-5 parts of hydrochloric acid, 2-3 parts of hydrofluoric acid, 0.5-1 parts of a corrosion inhibitor, and 74-80.5 parts of a solvent. Compared to other ranges, limiting the amounts of each component in the sandstone retarding acid to the above ranges is beneficial for further improving the chelation reaction efficiency, further increasing the chelate formation rate, and simultaneously improving the permeability of the core after acidification, thereby further suppressing the formation of secondary precipitation.

[0037] The second aspect of this application also provides an application of the aforementioned sandstone slow-reducing acid in the field of oil and gas field development technology.

[0038] The sandstone slowing acid provided in this application has both a slowing effect and a chelating effect on metal ions. When applied to the field of oil and gas field development technology, it can improve the permeability of cores after acidizing, and at the same time inhibit the formation of secondary precipitates such as calcium fluoride, potassium fluorosilicate, and silicic acid.

[0039] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0040] Example 1

[0041] By weight, the sandstone retarding acid comprises: 5 parts polyaspartic acid, 1 part sodium gluconate, 1 part corrosion inhibitor (DCA-6, Beijing Kemaishi Oilfield Chemical Technology Co., Ltd.), 3 parts hydrofluoric acid, and 90 parts water, as detailed in Table 1. The degree of polymerization of the polyaspartic acid is 200.

[0042] (1) Take 30 mL of the slow-release acid of the sandstone to be tested and mix it with 1.5 g of rock powder (Ziniquanzi Formation, particle size range of 0.27-0.55 mm). Stir and react at 90 °C until 1 h or 4 h. Then stop the reaction and cool it with water. Filter the reaction liquid, dry it and weigh the remaining rock powder. The percentage of the weight of the rock powder that is eroded to the weight of the original rock powder is recorded as the erosion rate. Calculate the erosion rate at 1 h and the erosion rate at 4 h.

[0043] (2) Prepare a 1 mol / L mixed dispersion of polyaspartic acid and sodium gluconate for later use (the weight ratio of polyaspartic acid to sodium gluconate is 5:1); take V1 = 5 mL of the above mixed dispersion into an Erlenmeyer flask, add 7.5 mL of 5% hydrofluoric acid solution to make the concentration of hydrofluoric acid in the mixed system 3%, adjust the pH of the mixed system to the range of 3-4 with hydrochloric acid solution or sodium hydroxide solution (simulating an acidic environment), titrate with 1 mol / L FeCl3 or CaCl2 solution (a chelation reaction occurs during this process), and keep the pH at 3-4 throughout the process until a precipitate is formed and does not disappear. Record the amount of FeCl3 or CaCl2 solution used, V2, and calculate the chelation value C (weight of metal ion, mg / weight of pure chelating agent, g) according to the following formula. Repeat the test 3 times and take the average value.

[0044]

[0045] Where C is the chelation value, mg·g -1 V1 is the volume of the chelating agent solution taken, mL; V2 is the volume of the metal ion solution consumed in the titration, mL; M1 is the molecular weight of the metal ion, g / mol; M2 is the molecular weight of the chelating agent, g / mol.

[0046] (3) Using a core flow meter, the permeability of the core before and after acidizing was measured with formation water, and the percentage increase in permeability was calculated (referred to as core permeability / %).

[0047] Example 2

[0048] By weight, the sandstone slow-retar acid comprises: 5 parts polyaspartic acid, 5 parts sodium gluconate, 1 part corrosion inhibitor (DCA-6, Beijing Kemaishi Oilfield Chemical Technology Co., Ltd.), 3 parts hydrofluoric acid, and 86 parts water, as detailed in Table 1.

[0049] In this embodiment, all test conditions are the same as in Example 1.

[0050] Table 1

[0051]

[0052] Example 3

[0053] By weight, the sandstone retarding acid comprises: 5 parts polyaspartic acid, 5 parts sodium gluconate, 1 part corrosion inhibitor (DCA-6, Beijing Kemaishi Oilfield Chemical Technology Co., Ltd.), 3 parts hydrofluoric acid, 5 parts hydrochloric acid, and 71 parts water, as detailed in Table 2. The inorganic acid is a mixture of hydrofluoric acid and hydrochloric acid, with a weight ratio of hydrochloric acid to hydrofluoric acid of 5:3.

[0054] In this embodiment, all test conditions are the same as in Example 1.

[0055] Example 4

[0056] The difference from Example 3 is that the mixture of hydrochloric acid and hydrofluoric acid is 1:1.

[0057] In this embodiment, all test conditions are the same as in Example 3.

[0058] Example 5

[0059] The difference from Example 3 is that the weight ratio of hydrochloric acid to hydrofluoric acid is 10:3.

[0060] In this embodiment, all test conditions are the same as in Example 3.

[0061] Example 6

[0062] The difference from Example 1 is that the inorganic acid is a mixture of hydrofluoric acid and hydrochloric acid, and the weight ratio of hydrofluoric acid to hydrochloric acid is 3:10, as detailed in Table 2.

[0063] In this embodiment, all test conditions are the same as in Example 1.

[0064] Table 2

[0065]

[0066]

[0067] Example 7

[0068] The difference from Example 1 is that the amount of each component in the sandstone slow acid is different, as detailed in Table 3.

[0069] In this embodiment, all test conditions are the same as in Example 1.

[0070] Example 8

[0071] The difference from Example 1 is that the amount of each component in the sandstone slow acid is different, as detailed in Table 3.

[0072] In this embodiment, all test conditions are the same as in Example 1.

[0073] Table 3

[0074]

[0075] Example 9

[0076] The difference from Example 1 is that the number-average molecular weight of polyaspartic acid is 13,000.

[0077] In this embodiment, all test conditions are the same as in Example 1.

[0078] Example 10

[0079] The difference from Example 1 is that the number-average molecular weight of polyaspartic acid is 130,000.

[0080] In this embodiment, all test conditions are the same as in Example 1.

[0081] Example 11

[0082] The difference from Example 1 is that the number-average molecular weight of polyaspartic acid is 10,000.

[0083] In this embodiment, all test conditions are the same as in Example 1.

[0084] Example 12

[0085] The difference from Example 1 is that the weight ratio of polyaspartic acid to sodium gluconate is 7:8.

[0086] In this embodiment, all test conditions are the same as in Example 1.

[0087] Example 13

[0088] The difference from Example 1 is that the weight ratio of polyaspartic acid to sodium gluconate is 10:8.

[0089] Example 14

[0090] The difference from Example 1 is that the weight ratio of polyaspartic acid to sodium gluconate is 9:7.

[0091] In this embodiment, all test conditions are the same as in Example 1.

[0092] Example 15

[0093] The difference from Example 1 is that the amino acid chelating agent is aspartic acid.

[0094] In this embodiment, all test conditions are the same as in Example 1.

[0095] Example 16

[0096] The difference from Example 1 is that the amino acid chelating agent is lysine.

[0097] In this embodiment, all test conditions are the same as in Example 1.

[0098] Example 17

[0099] The difference from Example 1 is that the amino acid chelating agent is glutamic acid.

[0100] In this embodiment, all test conditions are the same as in Example 1.

[0101] Comparative Example 1

[0102] The difference from Example 1 is that the sandstone slow acid does not contain sodium gluconate.

[0103] The test method for the slow acid chelation performance of the sandstone prepared in Comparative Example 1 is as follows:

[0104] Prepare a 1 mol / L polyaspartic acid dispersion. Take 5 mL of the dispersion and place it in an Erlenmeyer flask. Add 7.5 mL of a 5% hydrofluoric acid solution to make the hydrofluoric acid concentration in the mixture reach 3%. Adjust the pH to the range of 3-4 with hydrochloric acid solution or sodium hydroxide solution (simulating an acidic environment). Titrate with a 1 mol / L FeCl3 or CaCl2 solution. The pH should be maintained at 3-4 throughout the process until a precipitate is formed and does not disappear. Calculate the chelation value (calculation method is the same as in Example 4).

[0105] The retardation performance test conditions for the sandstone retardant acid prepared in Comparative Example 1 were the same as those in Example 1.

[0106] Comparative Example 2

[0107] The difference from Example 1 is that the sandstone slow acid does not contain polyaspartic acid, while the other components and amounts are the same as in Example 1.

[0108] In this comparative example 2, all test conditions are the same as in example 1.

[0109] The sandstone retarding acid prepared in Examples 1 to 17 and the sandstone retarding acid prepared in the comparative example were tested using the same test method as in Example 1. The retarding performance (including the rock powder dissolution rate at 1h and 4h and the rate of change of dissolution rate) was tested. The test results are summarized in Table 4. The rate of change of dissolution rate refers to the percentage (%) of the difference between the rock powder dissolution rate at 4h and the rock powder dissolution rate at 1h to the rock powder dissolution rate at 1h.

[0110] The chelating performance (Ca) of sandstone retarded acids prepared in Examples 1 to 17 and the comparative examples was tested using the same testing method as in Example 1. 2+ Chelation value, Fe 3+ Chelation value and core permeability were tested, and the test results are summarized in Table 5.

[0111] Table 4

[0112] Dissolution rate (%) in 1 hour Dissolution rate (%) after 4 hours Change rate of dissolution rate (%, 90℃) over a period of 1 hour to 4 hours Example 1 12.4 23.9 92.74 Example 2 11.3 24.4 83.46 Example 3 15.2 30.5 100.66 Example 4 13.6 28.5 109.56 Example 5 15.9 31.0 87.88 Example 6 16.3 32.3 98.16 Example 7 12.1 24.6 103.31 Example 8 13.5 28.7 100.70 Example 9 12.5 24.4 95.20 Example 10 12.2 25.4 111.67 Example 11 12.4 26.0 120.34 Example 12 10.7 22.5 110.28 Example 13 10.3 22.4 117.48 Example 14 10.9 22.8 117.14 Example 15 13.1 23.8 81.68 Example 16 11.9 23.5 97.48 Example 17 12.6 24.1 91.27 Comparative Example 1 14.3 24.4 21.35 Comparative Example 2 19.2 23.3 92.74

[0113] Table 5

[0114]

[0115]

[0116] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0117] Comparing Examples 1 and 2, 7 and 8, and Comparative Examples 1 and 2, it can be seen that the 1-hour dissolution rate of rock powder in Comparative Examples 1 and 2 is greater than that in Examples 1, 2, 7 and 8. This indicates that in the initial stage (0-1h at 90℃), the retarding performance of the sandstone retarding acid prepared in Examples 1 and 2, 7 and 8 is superior to that in Comparative Examples 1 and 2. The combined use of amino acid chelating agents and carboxylic acid chelating agents can leverage their synergistic effect, better utilizing the retarding effect and chelating effect of the sandstone retarding acid, thereby inhibiting secondary precipitation. Furthermore, limiting the weight proportions of amino acid chelating agents, hydroxylic acid chelating agents, inorganic acids, and solvents within the preferred range of this application is beneficial for improving the chelation reaction efficiency, increasing the chelate formation rate, and simultaneously improving the permeability of the core after acidification, thus further inhibiting the formation of secondary precipitation. It should be noted that the 4-hour dissolution rate of rock powder in Examples 1 and 2 and Comparative Examples 1 and 2 is basically the same. This is because the inorganic acid components in the sandstone slow acid are almost completely consumed after 4 hours. In other words, the sandstone slow acid has completely dissolved the rock powder.

[0118] The 1-hour dissolution rates of Examples 3 and 4 were 15.2% and 13.6%, respectively, while the 1-hour dissolution rate of the rock powder in Example 5 was higher than that of Examples 3 and 4, reaching 15.9%. This indicates that in the initial stage (0–1 hour at 90°C), the retarding performance of the sandstone retarding acid prepared in Example 5 was inferior to that of Examples 3 and 4. Similarly, comparing Examples 1 and 6, the 1-hour dissolution rate of the rock powder in Example 6 was as high as 16.3%, significantly higher than that of Example 1. Therefore, the weight ratio of hydrochloric acid to hydrofluoric acid includes, but is not limited to, the preferred range of this application. Limiting it to the preferred range of this application is beneficial for further enhancing the retarding characteristics of the sandstone retarding acid, resulting in better retarding and chelation effects on metal ions. It should be noted that after 4 hours, the dissolution effect of the sandstone slow-release acid on the rock powder in Examples 3 to 5 reached its maximum, and the inorganic acid components in the sandstone slow-release acid were almost completely consumed. Therefore, the fact that the rate of change of dissolution rate in Example 5 from 1 hour to 4 hours in Table 4 is greater than that in Examples 3 and 4 is normal.

[0119] Comparing Examples 1, 9 to 11, it can be seen that the sandstone retarding acid prepared in Examples 1, 9 to 11 showed no significant difference in retarding performance in the initial stage (0-1h at 90℃), while the retarding performance only became apparent in the second stage (1h-4h at 90℃). According to the data in Table 4, it is clear that the sandstone retarding acid prepared in Examples 1, 9, and 10 has better retarding performance than that in Example 12. The number-average molecular weight of the amino acid polymer includes, but is not limited to, the preferred range of this application. Limiting it to the preferred range of this application is beneficial to further improve the chelating ability of the amino acid polymer, thereby further improving the chelating efficiency and core permeability of the sandstone retarding acid.

[0120] Comparing Examples 1, 12, and 13, it can be seen that the weight ratio of polyaspartic acid to sodium gluconate includes, but is not limited to, the preferred range of this application. Limiting it to the preferred range of this application is beneficial to better exert the synergistic effect of the two, and is beneficial to further improve the chelation reaction efficiency and the formation rate of chelates. At the same time, it is beneficial to further improve the permeability of the core after acidification and to further suppress the formation of secondary precipitation.

[0121] Comparing Examples 1, 15 to 17, it can be seen that, compared with other types, using the preferred type of amino acid or amino acid polymer of this application is beneficial to further exert its chelating effect, to improve chelating efficiency, and thus to improve core permeability and inhibit the formation of secondary precipitation.

[0122] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sandstone slow-repairing acid, characterized in that, By weight, the sandstone slow-release acid comprises: 5-15 parts of amino acid chelating agent, 1-10 parts of hydroxycarboxylic acid chelating agent, 2-8 parts of inorganic acid, and 65-90 parts of solvent. The amino acid chelating agent is selected from amino acids and / or amino acid polymers; the amino acid is selected from one or more of the group consisting of aspartic acid, lysine, and glutamic acid; the amino acid polymer is selected from polyaspartic acid. The hydroxycarboxylic acid chelating agent is selected from sodium gluconate; The inorganic acid is selected from hydrofluoric acid, or a mixture of hydrochloric acid and hydrofluoric acid.

2. The sandstone retarding acid according to claim 1, characterized in that, The amino acid polymer has a number-average molecular weight of 13,000 to 1,300,000, or a degree of polymerization of 100 to 10,000.

3. The sandstone retarded acid according to claim 1, characterized in that, The amino acid polymer has a number average molecular weight of 13,000 to 130,000, or a degree of polymerization of 100 to 1,000.

4. The sandstone slow-reducing acid according to any one of claims 1 to 3, characterized in that, The weight ratio of the amino acid chelating agent to the hydroxycarboxylic acid chelating agent is (7-10):(5-8).

5. The sandstone retarded acid according to claim 4, characterized in that, When the amino acid chelating agent is selected from polyaspartic acid, and the hydroxycarboxylic acid chelating agent is selected from sodium gluconate, the weight ratio of polyaspartic acid to sodium gluconate is (7-9):(7-8).

6. The sandstone retarded acid according to claim 1, characterized in that, The inorganic acid includes a mixture of hydrochloric acid and hydrofluoric acid, and the weight ratio of the hydrochloric acid to the hydrofluoric acid is (1-5):(1-3).

7. The sandstone retarded acid according to claim 6, characterized in that, By weight, the sandstone retarding acid also includes 0.5 to 1 part corrosion inhibitor.

8. The sandstone retarding acid according to claim 7, characterized in that, The corrosion inhibitor is selected from Mannich bases and / or quinoline quaternary ammonium salts.

9. The sandstone retarded acid according to claim 7, characterized in that, The solvent is selected from one or more of the group consisting of water and methanol with a weight concentration of 1% to 5%.

10. The sandstone retarded acid according to claim 9, characterized in that, By weight, the sandstone retarding acid comprises: 7-9 parts of the amino acid chelating agent, 7-8 parts of the hydroxycarboxylic acid chelating agent, 3-5 parts of the hydrochloric acid, 2-3 parts of the hydrofluoric acid, 0.5-1 parts of the corrosion inhibitor, and 74-80.5 parts of the solvent.

11. The application of sandstone slow-reducing acid according to any one of claims 1 to 10 in the field of oil and gas field development technology.

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