Weighting authigenic acid as well as preparation method and application thereof

Abstract

The invention relates to a weighted authigenic acid as well as a preparation method and application thereof. The weighted authigenic acid comprises an acid generating component and a weighting component, the acid generating component comprises an acid generating agent, a product solubilizer, a catalyst and a corrosion inhibitor; the acid generator comprises organic weak acid and a chlorine-containing acid generator; the weighting component comprises weighting salt, a resistance reducing agent and water; the aggravated authigenic acid is high in acid generation efficiency and controllable in acid generation concentration, the concentration of generated H < + > can reach up to 4.95 mol / L, the aggravated authigenic acid has high corrosion inhibition capacity, the corrosion rate is as low as 30 g / (m < 2 >. H) or below, the preparation method is simple, raw materials are easy to obtain, and the aggravated authigenic acid can be used for efficient transformation of ultra-deep high-temperature carbonate reservoirs with the temperature reaching up to 120-200 DEG C.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a weighted autogenous acid, its preparation method, and its application. Background Technology

[0002] Deep / ultra-deep oil and gas resources are mainly distributed in the Tarim, Sichuan, and Junggar Basins. The Tarim Basin has large resources (oil accounting for 56% and natural gas for 41%) and is a key area for deep-ultra-deep exploration and development. Exploration depths are increasing, mostly between 6,000 and 8,000 meters, and currently, efforts are being made to reach depths of 10,000 meters. The reservoir temperatures encountered are also increasing, mostly exceeding 160°C, and even reaching 230°C. Carbonate reservoirs are characterized by strong heterogeneity, low permeability and tightness, and high stress. Previous carbonate reservoir stimulation technologies were suitable for reservoirs with depths below 7,000 meters and temperatures below 160°C. Acid technology mainly includes ordinary hydrochloric acid, slow-release hydrochloric acid, emulsified acid, thickened acid, cross-linked gel acid, and surfactant-based self-directing acid, which have achieved good results. In practice, slow-release acid fracturing or polymer linear gel fracturing combined with these acid solutions are often used.

[0003] However, with increasing exploration depth and rising reservoir temperatures, existing acid technologies and processes are no longer suitable, posing greater challenges to both tools and fluids. In high-temperature deep wells, existing acid systems react too quickly, leading to increased filtration loss and preventing acid from reaching the fracture front. The rapid reaction rate causes acid to enter high-permeability zones, while low-permeability zones remain unstimulated. Simultaneously, the unevenness of reservoir stimulation intensifies, significantly increasing the difficulty of uniform acid distribution. Furthermore, ultra-deep reservoirs typically exhibit both ultra-high temperature and ultra-high pressure. Higher operating pressure is a significant factor restricting reservoir stimulation, and higher reservoir temperatures pose a greater threat to wellbore integrity from previously used slow-reacting acids. Existing corrosion inhibitors also struggle to effectively protect the tubing string.

[0004] Compared to other acids, autogenous acid has advantages such as being non-acidic or weakly acidic at room temperature, generating acid at certain temperatures, low corrosion rate, and low acid rock reaction rate, making it an important approach to solving the problem of slow acidizing in high-temperature deep wells. Types of autogenous acids include autogenous hydrofluoric acid, autogenous hydrochloric acid, autogenous organic acids, and composite autogenous acids. Currently reported acid-generating temperatures are typically below 150℃, which still has limitations for current ultra-deep and ultra-high-temperature wells. For example, CN113755149A discloses an autogenous acid crosslinking fracturing fluid and its application. This fluid comprises 0.6%–1% thickener, 0.6%–1% crosslinking agent, 40%–45% acid-generating agent, 8%–10% activator, and 40%–45% water. It can only be applied to high-temperature carbonate rocks at 130℃–150℃, which cannot meet current requirements for exploration depth and reservoir temperature. CN106833596A discloses a fracturing fluid capable of self-generating acid, its preparation method, and its application. This fracturing fluid consists of 10%–40% organic ester, 0.3%–1% thickener, 1%–4% biodegradable filtration reducer, and the balance being water. However, it is only suitable for reservoirs at 120℃–160℃, and the acid-generating concentration is only 2–2.4 mol / L, indicating significant room for improvement and insufficient for current exploration in ultra-deep and ultra-high temperature wells. CN111500276A discloses a thickened self-generating acid for high-viscosity, low-acid rock reaction rates, comprising thickener: 4–0.8%, acid-generating agent A: 10–30%, acid-generating agent B: 1–10%, clay stabilizer: 1–2%, corrosion inhibitor: 2–4%, and the balance being water. However, its applicable temperature and high-temperature corrosion inhibition effect remain limited.

[0005] Therefore, how to develop a weighted autogenous acid suitable for the stimulation of ultra-deep and ultra-high temperature carbonate reservoirs has become an urgent problem to be solved. Summary of the Invention

[0006] To solve the above-mentioned technical problems, this invention combines liquid weighting and self-generating acid technology to effectively reduce wellhead construction pressure and construction friction. It can carry out acid etching reaction with the reservoir at different stages of construction, effectively increasing the acid etching distance and achieving the purpose of effectively modifying the reservoir.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a weighted autogenous acid, the weighted autogenous acid comprising: an acid-generating component and a weighting component; the acid-generating component comprising an acid-generating agent, a product solubilizer, a catalyst, and a corrosion inhibitor; the acid-generating agent comprising an organic weak acid and a chlorine-containing acid-generating agent; the weighting component comprising a weighting salt, a drag-reducing agent, and water.

[0009] This invention utilizes a synergistic combination of specific weighting components and specific acid-generating components. The acid-generating agent is selected from organic weak acids and chlorine-containing acid-generating agents to obtain a weighted self-generating acid with high acid-generating efficiency, controllable acid-generating rate, and acid-generating concentration. The initial acid concentration is low, enabling it to continuously conduct acid etching reactions with the reservoir at different stages of construction, effectively increasing the acid etching distance and effectively transforming the reservoir. At the same time, the weighted self-generating acid can also effectively reduce wellhead construction pressure and construction friction, reduce construction difficulty, and achieve efficient transformation of high-temperature deep reservoirs.

[0010] It is worth noting that this invention selects a combination of organic weak acid and chlorinated acid-generating agent as the acid-generating agent. The organic weak acid plays a role in the acid-rock reaction at low temperatures, while the chlorinated acid-generating agent begins to generate acid and etch the reservoir when the reservoir temperature reaches 100–200°C. This allows for continuous acid-rock reaction with the reservoir at different stages of construction, effectively increasing the acid etching distance and achieving efficient stimulation of high-temperature deep reservoirs. If the acid-generating agent contains only organic weak acid, the acid-rock reaction occurs near the wellbore, resulting in low acid etching efficiency and failing to achieve the goal of deep acidification. If only a high-temperature acid-generating agent is used, the temperature near the wellbore is low, the acid-rock reaction is weak, and the conductivity near the wellbore is low, thus the reservoir cannot be effectively stimulated.

[0011] Preferably, by weight, the weighted self-generating acid comprises: 12-37 parts of the acid-generating component and 63-88 parts of the weighting component; more preferably, the weighted self-generating acid comprises: 25-33 parts of the acid-generating component and 67-75 parts of the weighting component.

[0012] By weight, the weighted self-generating acid system includes 12-37 parts of acid-generating components, for example, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, 32 parts, 35 parts, or 37 parts, etc.

[0013] By weight, the weighted acid system comprises 63-88 parts of weighting components, for example, 63 parts, 65 parts, 68 parts, 70 parts, 73 parts, 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, or 88 parts, etc.

[0014] Preferably, by weight, the acid-generating component comprises: 9-33 parts of acid-generating agent, 0.5-2 parts of product solubilizer, 0.5-2 parts of catalyst, and 1-2 parts of corrosion inhibitor. More preferably, the acid-generating component comprises: 26.5-30 parts of acid-generating agent, 0.5-2 parts of product solubilizer, 1-2 parts of catalyst, and 1-2 parts of corrosion inhibitor.

[0015] The acid-generating component comprises 9-33 parts by weight, for example, 9 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, or 33 parts.

[0016] By weight, the acid-generating component includes 0.5-2 parts of product solubilizer, for example, 0.5 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts, etc.

[0017] The acid-generating component comprises 0.5-2 parts of catalyst by weight, for example, 0.5 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts, etc.

[0018] By weight, the acid-generating component includes 1-2 parts of corrosion inhibitor, for example, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, or 2 parts, etc.

[0019] Preferably, by weight, the added heavy components include 20-53 parts of weighting salt, 0.1-0.3 parts of drag-reducing agent, and 30-68 parts of water. More preferably, the added heavy components include 30-40 parts of weighting salt, 0.1-0.3 parts of drag-reducing agent, and 33-43 parts of water.

[0020] The added component, by weight, includes 20-53 parts of added salt, for example, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts or 53 parts, etc.

[0021] The added heavy components include 0.1-0.3 parts by weight of drag-reducing agent, for example, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts or 0.3 parts, etc.

[0022] The added component comprises 30-68 parts by weight, for example, 30, 35, 40, 45, 50, 55, 60, 65 or 68 parts of water.

[0023] Preferably, the mass ratio of the organic weak acid to the chlorinated acid-producing agent is 1:(0.5-4), for example, it can be 1:0.5, 1:0.7, 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc.

[0024] Preferably, the organic weak acid includes any one or a combination of at least two of formic acid, acetic acid, or lactic acid, wherein typical but non-limiting combinations include combinations of formic acid and acetic acid, combinations of formic acid and lactic acid, or combinations of acetic acid and lactic acid, etc.

[0025] Preferably, the chlorinated acid-producing agent includes any one or a combination of at least two of chloroacetic acid, 2-chloropropionic acid, 3-chloropropionic acid, 2-chlorobutyric acid, or 3-chlorobutyric acid. For example, it can be a combination of chloroacetic acid and 2-chloropropionic acid, a combination of 2-chloropropionic acid and 3-chloropropionic acid, a combination of 3-chloropropionic acid and 2-chlorobutyric acid, or a combination of 2-chlorobutyric acid and 3-chlorobutyric acid, etc.

[0026] Preferably, the product solubilizer includes gluconic acid and / or sodium gluconate, with gluconic acid being the preferred solubilizer.

[0027] Preferably, the catalyst comprises any one or a combination of at least two of chlorides, bromides, or iodides, preferably bromides and / or iodides.

[0028] The present invention further preferably uses bromide and / or iodide as the catalyst, which is beneficial to the generation of hydrochloric acid, thereby efficiently acid etching the reservoir.

[0029] Preferably, the corrosion inhibitor comprises a main corrosion inhibitor or a combination of a main corrosion inhibitor and an auxiliary corrosion inhibitor. More preferably, it is a combination of a main corrosion inhibitor and an auxiliary corrosion inhibitor.

[0030] Preferably, by weight, the corrosion inhibitor comprises 8-30 parts of quinoline benzyl quaternary ammonium salt, 5-8 parts of aldehyde compound, 8-18 parts of dispersant, 10-18 parts of alkynol and 26-62 parts of alcohol solvent.

[0031] By weight, the main component of the corrosion inhibitor includes 8-30 parts of quinoline benzyl quaternary ammonium salt, for example, 8 parts, 10 parts, 15 parts, 17 parts, 19 parts, 20 parts, 25 parts or 30 parts, etc.

[0032] The corrosion inhibitor main component comprises 5-8 parts by weight, for example, 5 parts, 6 parts, 7 parts or 8 parts, etc.

[0033] By weight, the corrosion inhibitor main component includes 8-18 parts of dispersant, for example, 8 parts, 10 parts, 13 parts, 15 parts or 18 parts, etc.

[0034] The corrosion inhibitor main component comprises 10-18 parts of alkynol by weight, for example, 10 parts, 13 parts, 15 parts or 18 parts, etc.

[0035] The corrosion inhibitor comprises 26-62 parts by weight of alcohol solvent, for example, 26 parts, 30 parts, 35 parts, 40 parts, 50 parts, 60 parts or 62 parts.

[0036] Preferably, the quinoline benzyl quaternary ammonium salt comprises 3-methylquinoline benzyl quaternary ammonium salt and / or 3-ethylquinoline benzyl quaternary ammonium salt.

[0037] Preferably, the aldehyde compound includes cinnamaldehyde.

[0038] Preferably, the dispersant comprises any one or a combination of at least two of fatty alcohol polyoxyethylene ether-15, fatty alcohol polyoxyethylene ether-12, or fatty alcohol polyoxyethylene ether-14, wherein typical but non-limiting combinations include combinations of fatty alcohol polyoxyethylene ether-15 and fatty alcohol polyoxyethylene ether-12, combinations of fatty alcohol polyoxyethylene ether-12 and fatty alcohol polyoxyethylene ether-14, or combinations of fatty alcohol polyoxyethylene ether-15 and fatty alcohol polyoxyethylene ether-14, etc.

[0039] Preferably, the alkynols include octynyl alcohol and / or pentynyl alcohol.

[0040] Preferably, the alcohol solvent includes any one or a combination of at least two of ethanol, isobutanol, or ethylene glycol, wherein typical but non-limiting combinations include combinations of ethanol and isobutanol, combinations of isobutanol and ethylene glycol, or combinations of ethanol and ethylene glycol, etc.

[0041] Preferably, the corrosion inhibitor adjuvant includes 0.1-1 parts of antimony trioxide.

[0042] The present invention further optimizes the synergistic combination of the main corrosion inhibitor and the auxiliary corrosion inhibitor, so that the acid-generating component is resistant to high temperature and has good dispersibility, which can meet the needs of deep and ultra-deep reservoirs, and can also reduce the corrosion risk to the downhole tubing.

[0043] Preferably, the acid-generating component further includes an iron ion stabilizer.

[0044] Preferably, the acid-producing component further includes 0.05-0.5 parts by weight of an iron ion stabilizer, such as 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts.

[0045] The present invention further preferably includes an iron ion stabilizer in the acid-generating component, which is beneficial to reducing the corrosion of the downhole tubing by the acid component.

[0046] Preferably, the weighting salt includes any one or a combination of at least two of calcium chloride, potassium chloride, potassium formate, potassium bromide, or calcium bromide, wherein typical but non-limiting combinations include combinations of calcium chloride and potassium chloride, combinations of potassium chloride and potassium formate, or combinations of potassium formate and potassium bromide, etc.

[0047] The weighting salt described in this invention is used to increase the net pressure of the liquid column, reduce the construction pressure, and ensure the success of the construction; the drag-reducing agent helps to reduce construction friction, reduce the construction pressure of the modification, and improve the construction safety.

[0048] Preferably, the drag-reducing agent comprises guar gum and / or polyacrylamide polymer.

[0049] Preferably, the guar gum includes hydroxypropyl guar gum.

[0050] Preferably, the polyacrylamide polymer comprises an acid-resistant polyacrylamide polymer.

[0051] The raw materials for preparing the acid-resistant polyacrylamide polymer include acrylamide monomer, 2-acrylamide-2-methylpropanesulfonic acid (AMPS), methacryloyloxyethyltrimethylammonium chloride (DMC), 2-2-hydroxyethyl acrylate, and water, as well as ammonium persulfate initiator.

[0052] In a second aspect, the present invention provides a method for preparing the weighted authigenic acid described in the first aspect, the method comprising the following steps:

[0053] (1) Mix the acid-generating agent, product solubilizer, catalyst and corrosion inhibitor to obtain the acid-generating component;

[0054] (2) Mix the weighting salt, drag-reducing agent and water to obtain the weighted components;

[0055] (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2) to obtain the weighted self-generating acid;

[0056] There is no specific order between steps (1) and (2).

[0057] Optionally, step (1) may also include mixing iron ion stabilizers.

[0058] Thirdly, the present invention provides an application of the weighted authigenic acid described in the first aspect, wherein the weighted authigenic acid is used for carbonate reservoir stimulation.

[0059] Preferably, the mixing order in step (2) is to first mix the weighting salt and water, and then add the drag-reducing agent.

[0060] In a further preferred embodiment of the present invention, the mixing order in step (2) is to first mix the heavy salt and water, and then add the drag-reducing agent; and the drag-reducing agent needs to be added slowly, and exert its drag-reducing effect after dissolving and thickening.

[0061] Preferably, the temperature of the carbonate reservoir is 120-200℃, for example, it can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃.

[0062] Compared with the prior art, the present invention has at least the following beneficial effects:

[0063] (1) The weighted authigenic acid provided by the present invention combines a specific weighting component with a specific acid-generating component to obtain a weighted authigenic acid with high acid-generating efficiency and controllable acid-generating concentration, generating H +The concentration can be as high as 4.95 mol / L; at the same time, the construction pressure is reduced, and by further optimizing the component composition of the acid generator, the type of catalyst, the type of corrosion inhibitor and other process parameters, a weighted self-generating acid formula suitable for different reservoirs is formed.

[0064] (2) The method for preparing weighted authigenic acid provided by the present invention is simple to operate, the raw materials are readily available, and the production cost is low.

[0065] (3) The application of the weighted authigenic acid provided by the present invention can be used to modify ultra-deep carbonate reservoirs with a temperature of 120-200℃, which is of great guiding significance for the modification of ultra-deep and ultra-high temperature carbonate reservoirs. Detailed Implementation

[0066] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0067] The iron ion stabilizers used in the following examples and comparative examples are commercially available products. As long as they meet industry standards and are compatible with the weighted acidification system described in this invention, they can be used. The iron ion stabilizers used in the following examples and comparative examples are the same commercially available iron ion stabilizers.

[0068] I. Implementation Examples

[0069] Example 1

[0070] This embodiment provides a weighted autogenous acid, which, by weight, comprises: 30 parts of an acid-generating component and 70 parts of a weighting component;

[0071] The acid-generating component includes 26.5 parts acid-generating agent, 1 part gluconic acid, 1 part potassium bromide, 1 part corrosion inhibitor and 0.5 parts iron ion stabilizer;

[0072] The acid-generating agent comprises formic acid and 2-chloropropionic acid in a mass ratio of 1:1;

[0073] The corrosion inhibitor comprises a main corrosion inhibitor and an auxiliary corrosion inhibitor; the main corrosion inhibitor comprises 8 parts of 3-methylquinoline benzylammonium chloride, 6 parts of cinnamaldehyde, 16 parts of fatty alcohol polyoxyethylene ether-15, 11 parts of octyryne alcohol and 59 parts of ethanol; the auxiliary corrosion inhibitor comprises 0.1 parts of antimony trioxide.

[0074] The added components include 33 parts calcium chloride, 0.2 parts hydroxypropyl guar gum, and 36.8 parts water.

[0075] This embodiment also provides a method for preparing the above-mentioned weighted authigenic acid, which is prepared according to the above-mentioned component ratio of the weighted authigenic acid. The preparation method includes the following steps:

[0076] (1) Mix acid-generating agent, gluconic acid, potassium bromide, corrosion inhibitor and iron ion stabilizer, and stir evenly to obtain acid-generating component;

[0077] (2) Mix calcium chloride and water to obtain a calcium chloride solution, then add hydroxypropyl guanidine gum and stir for 10 min to obtain the added component;

[0078] (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2), and stir evenly to obtain weighted self-generating acid.

[0079] Example 2

[0080] This embodiment provides a weighted autogenous acid, which, by weight, comprises: 25 parts of an acid-generating component and 75 parts of a weighting component;

[0081] The acid-generating component includes 28 parts acid-generating agent, 0.5 parts sodium gluconate, 1.5 parts potassium iodide, and 1.5 parts corrosion inhibitor;

[0082] The acidifying agent comprises acetic acid and chloroacetic acid in a mass ratio of 1:1;

[0083] The corrosion inhibitor comprises a main corrosion inhibitor and an auxiliary corrosion inhibitor; the main corrosion inhibitor comprises 12 parts of 3-methylquinoline benzyl ammonium chloride, 7 parts of cinnamaldehyde, 10 parts of 3-ethylquinoline benzyl ammonium chloride, 16 parts of fatty alcohol polyoxyethylene ether-14, 10 parts of octyne alcohol, and 45 parts of ethylene glycol; the auxiliary corrosion inhibitor comprises 0.2 parts of antimony trioxide;

[0084] The added weighting components include 30 parts weighting salt, 0.1 parts hydroxypropyl guanidine gum, and 33.8 parts water.

[0085] The weighting salt comprises potassium formate and potassium bromide in a mass ratio of 1:1.

[0086] This embodiment also provides a method for preparing the above-mentioned weighted authigenic acid, which is prepared according to the above-mentioned component ratio of the weighted authigenic acid. The preparation method includes the following steps:

[0087] (1) Mix acid-generating agent, sodium gluconate, potassium iodide and corrosion inhibitor, and stir evenly to obtain acid-generating component;

[0088] (2) Mix the weighting salt and water to obtain a weighting salt solution, then add hydroxypropyl guanidine gum and stir for 10 minutes to obtain the weighting component;

[0089] (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2), and stir evenly to obtain weighted self-generating acid.

[0090] Example 3

[0091] This embodiment provides a weighted autogenous acid, which, by weight, comprises: 33 parts of an acid-generating component and 67 parts of a weighting component;

[0092] The acid-generating component includes 30 parts acid-generating agent, 2 parts sodium gluconate, 2 parts sodium iodide, 2 parts corrosion inhibitor and 0.25 parts iron ion stabilizer;

[0093] The acid-generating agent comprises acetic acid, 2-chloropropionic acid, and 3-chloropropionic acid in a mass ratio of 4:3:3;

[0094] The corrosion inhibitor comprises a main corrosion inhibitor and an auxiliary corrosion inhibitor; the main corrosion inhibitor comprises 5 parts of 3-methylquinoline benzyl ammonium chloride, 8 parts of cinnamaldehyde, 20 parts of 3-ethylquinoline benzyl ammonium chloride, 12 parts of fatty alcohol polyoxyethylene ether-15, 15 parts of pentyne alcohol, and 40 parts of ethanol; the auxiliary corrosion inhibitor comprises 0.15 parts of antimony trioxide;

[0095] The added weighting components include 40 parts weighting salt, 0.3 parts acid-resistant polyacrylamide polymer, and 43 parts water.

[0096] The weighting salt comprises calcium chloride and calcium bromide in a mass ratio of 1:1.5;

[0097] The raw materials for preparing the acid-resistant polyacrylamide polymer include acrylamide monomer, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) monomer, methacryloyloxyethyltrimethylammonium chloride (DMC), and 2-hydroxyethyl acrylate in a mass ratio of 4:2:3:1.

[0098] This embodiment also provides a method for preparing the above-mentioned weighted authigenic acid, which is prepared according to the above-mentioned component ratio of the weighted authigenic acid. The preparation method includes the following steps:

[0099] (1) Mix acid-generating agent, sodium gluconate, sodium iodide, corrosion inhibitor and iron ion stabilizer, and stir evenly to obtain acid-generating component;

[0100] (2) Mix the weighting salt and water to obtain a weighting salt solution, then add acid-resistant polyacrylamide polymer and stir for 8 minutes to obtain the weighting component;

[0101] (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2), and stir evenly to obtain weighted self-generating acid;

[0102] The preparation method of the acid-resistant polyacrylamide polymer in step (3) includes: adding acrylamide monomer, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) monomer, methacryloyloxyethyltrimethylammonium chloride (DMC) and 2-2-hydroxyethyl acrylate in a mass ratio of 4:2:3:1 to water and stirring evenly, adding 0.01 parts of ammonium persulfate as an initiator, and polymerizing under nitrogen protection to obtain the acid-resistant polyacrylamide polymer.

[0103] Example 4

[0104] This embodiment provides a weighted autogenous acid, which, by weight, comprises: 25 parts of an acid-generating component and 75 parts of a weighting component;

[0105] The acid-generating components include 23 parts acid-generating agent, 1 part sodium gluconate, 0.5 parts potassium iodide, and 1 part corrosion inhibitor;

[0106] The acid-generating agent comprises lactic acid, acetic acid, and chloroacetic acid in a mass ratio of 1:1:3;

[0107] The corrosion inhibitor comprises a main corrosion inhibitor and an auxiliary corrosion inhibitor; the main corrosion inhibitor comprises 30 parts of 3-methylquinoline benzylammonium chloride, 8 parts of cinnamaldehyde, 18 parts of fatty alcohol polyoxyethylene ether-14, 10 parts of octyne alcohol and 34 parts of ethylene glycol; the auxiliary corrosion inhibitor comprises 0.2 parts of antimony trioxide.

[0108] The added weighting components include 40 parts weighting salt, 0.2 parts hydroxypropyl guanidine gum, and 34.8 parts water.

[0109] The weighting salt comprises potassium formate and potassium bromide in a mass ratio of 7:3.

[0110] This embodiment also provides a method for preparing the above-mentioned weighted authigenic acid, which is prepared according to the above-mentioned component ratio of the weighted authigenic acid. The preparation method includes the following steps:

[0111] (1) Mix acid-generating agent, sodium gluconate, potassium iodide and corrosion inhibitor, and stir evenly to obtain acid-generating component;

[0112] (2) Mix the weighting salt and water to obtain a weighting salt solution, then add hydroxypropyl guanidine gum and stir for 10 minutes to obtain the weighting component;

[0113] (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2), and stir evenly to obtain weighted self-generating acid.

[0114] Example 5

[0115] This embodiment provides a weighted autogenous acid, which differs from Example 1 only in that potassium bromide is replaced with potassium acetate in the weighted autogenous acid. The other components, dosages, and preparation methods are the same as in Example 1.

[0116] II. Comparative Example

[0117] Comparative Example 1

[0118] This comparative example provides a weighted autogenous acid, which differs from Example 1 only in that the weighted autogenous acid does not contain a product solubilizer (gluconic acid). The reduced amount is distributed proportionally to the other components of the acid-generating component. The other components, amounts, and preparation methods are the same as in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a weighted autogenous acid, which differs from Example 1 only in that the weighted autogenous acid does not contain a corrosion inhibitor component. The reduced portion is distributed proportionally to the other components of the autogenous acid component. The other components, dosages, and preparation methods are the same as in Example 1.

[0121] Comparative Example 3

[0122] This comparative example provides a weighted autogenous acid, which differs from Example 1 only in that the acid-generating agent in the weighted autogenous acid contains only 2-chloropropionic acid, and the amount of 2-chloropropionic acid used is the sum of the amounts of formic acid and 2-chloropropionic acid used in Example 1. Other components, amounts, and preparation methods are the same as in Example 1.

[0123] III. Tests and Results

[0124] The acid-generating capacity and corrosion rate of the weighted autogenous acid provided in the above embodiments and comparative examples were tested using the following methods, and the test results are shown in Table 1.

[0125] ① Acid-generating ability test

[0126] The weighted autogenous acid obtained in the above examples and comparative examples was added to a reaction vessel. After placing marble blocks in the vessel, the reaction vessel was sealed and heated at 160°C for 6 hours. The hydrogen ion concentration was calculated by the change in the mass of the marble blocks, and the state of the reaction solution was observed.

[0127] ② Corrosion rate test

[0128] The corrosion rate of the weighted autogenous acid obtained in the above examples and comparative examples was tested using the plate corrosion method. Specifically, the method included: adding the prepared weighted autogenous acid to the reactor, placing N80 metal plates in the weighted autogenous acid, ensuring that the metal plates did not contact the inner wall of the reactor, maintaining a constant temperature of 180°C, and statically corroding for 4 hours. The corrosion rate was calculated by the change in the mass of the metal plates before and after corrosion.

[0129] Table 1

[0130]

[0131]

[0132] As can be seen from Table 1:

[0133] (1) As can be seen from Examples 1 to 4, the present invention, by combining the weighted component and the acid-generating component, obtains a weighted autogenous acid with high acid-generating efficiency and controllable acid-generating concentration. The weighted autogenous acid reacts with calcium carbonate at 160°C for 6 hours to generate H. + The concentration can reach up to 4.95 mol / L, which translates to an HCl concentration of over 16%, and the reaction solution is clear. When reacted on an N80 metal sheet at 180℃ for 4 hours, the corrosion rate is as low as 25.69 g / (m³). 2 The following values ​​(·h) indicate that the weighted autogenous acid has good corrosion inhibition properties, which is beneficial for acid fracturing.

[0134] (2) A comparison between Example 1 and Example 5 shows that, compared to Example 1, Example 5 uses potassium acetate as a catalyst, which generates H... + The concentration decreased to 3.17 mol / L. Therefore, it can be seen that the catalyst of the present invention is further preferably bromide and / or iodide, which further improves the acid-generating ability of the obtained weighted authigenic acid, thereby improving the acid rock modification effect.

[0135] (3) As can be seen from Example 1 and Comparative Examples 1-3, compared with Example 1, the absence of gluconic acid in the weighted authigenic acid of Comparative Example 1 resulted in a large amount of precipitation in the reaction solution, causing well pipe blockage; the absence of corrosion inhibitor components in the weighted authigenic acid of Comparative Example 2 led to a significant increase in the corrosion rate to 303.26 g / (m³). 2 In Comparative Example 3, since the acid-generating agent only contains 2-chloropropionic acid, there is no acid at low temperatures, and the acid-rock reaction occurs at the far end of the reservoir, resulting in ineffective acid etching near the wellbore and ineffective reservoir stimulation. Therefore, this invention, by combining heavy components with specific acid-generating components and selecting acid-generating agents that include both organic weak acids and chlorinated acid-generating agents, achieves synergistic effects among the components, improving the acid-generating efficiency of weighted self-generating acid, reducing reservoir damage, and ensuring that acid-rock reactions occur wherever the acid reaches.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A weighted autogenous acid, characterized in that, The weighted self-generating acid includes: an acid-generating component and a weighting component; The acid-generating components include an acid-generating agent, a product solubilizer, a catalyst, and a corrosion inhibitor; the acid-generating agent includes organic weak acids and chlorine-containing acid-generating agents; The weighting components include weighting salts, drag-reducing agents, and water.

2. The weighted autogenous acid according to claim 1, characterized in that, By weight, the weighted self-generating acid comprises: 12-37 parts of the acid-generating component and 63-88 parts of the weighting component, and more preferably, the weighted self-generating acid comprises: 25-33 parts of the acid-generating component and 67-75 parts of the weighting component; Preferably, by weight, the acid-generating component comprises: 9-33 parts of acid-generating agent, 0.5-2 parts of product solubilizer, 0.5-2 parts of catalyst, and 1-2 parts of corrosion inhibitor; more preferably, the acid-generating component comprises: 26.5-30 parts of acid-generating agent, 0.5-2 parts of product solubilizer, 1-2 parts of catalyst, and 1-2 parts of corrosion inhibitor; Preferably, by weight, the added heavy components include 20-53 parts of weighting salt, 0.1-0.3 parts of drag-reducing agent, and 30-68 parts of water. More preferably, the added heavy components include 30-40 parts of weighting salt, 0.1-0.3 parts of drag-reducing agent, and 33-43 parts of water.

3. The weighted autogenous acid according to claim 1, characterized in that, The mass ratio of the organic weak acid to the chlorinated acid-producing agent is 1:(0.5-4); Preferably, the organic weak acid includes any one or a combination of at least two of formic acid, acetic acid, or lactic acid; Preferably, the chlorinated acid-producing agent includes any one or a combination of at least two of chloroacetic acid, 2-chloropropionic acid, 3-chloropropionic acid, 2-chlorobutyric acid, or 3-chlorobutyric acid.

4. The weighted authigenic acid according to any one of claims 1 to 3, characterized in that, The product solubilizer includes gluconic acid and / or sodium gluconate, preferably gluconic acid; Preferably, the catalyst comprises any one or a combination of at least two of chlorides, bromides, or iodides, preferably bromides and / or iodides.

5. The weighted authigenic acid according to any one of claims 1-4, characterized in that, The corrosion inhibitor includes a main corrosion inhibitor or a combination of a main corrosion inhibitor and an auxiliary corrosion inhibitor. Preferably, by weight, the corrosion inhibitor comprises 8-30 parts of quinoline benzyl quaternary ammonium salt, 5-8 parts of aldehyde compound, 8-18 parts of dispersant, 10-18 parts of alkynol and 26-62 parts of alcohol solvent; Preferably, the quinoline benzyl quaternary ammonium salt comprises 3-methylquinoline benzyl quaternary ammonium salt and / or 3-ethylquinoline benzyl quaternary ammonium salt; Preferably, the aldehyde compound includes cinnamaldehyde; Preferably, the dispersant comprises any one or a combination of at least two of fatty alcohol polyoxyethylene ether-15, fatty alcohol polyoxyethylene ether-12, or fatty alcohol polyoxyethylene ether-14; Preferably, the alkynols include octynyl alcohol and / or pentynyl alcohol; Preferably, the alcohol solvent includes any one or a combination of at least two of ethanol, isobutanol, or ethylene glycol; Preferably, the corrosion inhibitor adjuvant includes antimony trioxide.

6. The weighted authigenic acid according to any one of claims 1-5, characterized in that, The weighting salt includes any one or a combination of at least two of calcium chloride, potassium chloride, potassium formate, potassium bromide, or calcium bromide; Preferably, the drag-reducing agent comprises guar gum and / or polyacrylamide polymer; Preferably, the guar gum includes hydroxypropyl guar gum; Preferably, the polyacrylamide polymer comprises an acid-resistant polyacrylamide polymer.

7. A method for preparing weighted authigenic acid as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Mix the acid-generating agent, product solubilizer, catalyst and corrosion inhibitor to obtain the acid-generating component; (2) Mix the weighting salt, drag-reducing agent and water to obtain the weighted components; (3) Mix the acid-generating component described in step (1) and the weight-adding component described in step (2) to obtain the weighted self-generating acid system; There is no specific order between steps (1) and (2).

8. The preparation method according to claim 7, characterized in that, The mixing order in step (2) is to first mix the heavy salt and water, and then add the drag-reducing agent.

9. An application of the weighted authigenic acid as described in any one of claims 1-6, characterized in that, The weighted authigenic acid is used for carbonate reservoir stimulation.

10. The application according to claim 9, characterized in that, The temperature of the carbonate reservoir is 120-200℃.

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