A gel plugging remover, its preparation method and application, and gel plugging remover method

Abstract

This invention provides a gel unblocking agent, its preparation method, application, and gel unblocking method. The gel unblocking agent comprises agent A and agent B in a volume ratio of 3-4:2-3. Based on the total weight of agent A (100%), agent A contains 10-20% sodium silicate, 5-8% pH adjuster, 15-20% organic solvent, 2-5% dispersant, and the balance being water. Based on the total weight of agent B (100%), agent B contains 8-15% selenium powder, 3-5% corrosion inhibitor, 10-15% emulsifier, 15-20% tert-butyl hydrogen peroxide, 3-5% penetrant, and the balance being water. The corrosion rate of this gel unblocking agent is far superior to the industry standard for first-grade products, providing a guarantee for operations without moving the tubing. The reaction time of this gel unblocking agent is over 7 hours, far exceeding the reaction time of conventional oxidants, making it suitable for deep unblocking. The high degradation rate and pressure reduction rate of this gel unblocking agent indicate its effective dissolution of gels / polymers.

Description

Technical Field

[0001] This invention relates to a gel unblocking agent, its preparation method and application, and a gel unblocking method, belonging to the field of oil and water well production enhancement and injection technology in the petroleum industry. Background Technology

[0002] With the development of oilfields and the demand for enhanced oil recovery, polymers are being used extensively, causing a gradual increase in the oil pressure of injection wells and under-injection of water injection wells. Conventional acidizing and fracturing are not ideal. Analysis suggests that the under-injection is mainly caused by gel blockage formed by the slightly soluble and undissolved molecular groups in the polymer solution entangled around the inorganic core (including inorganic scale, clay and suspended matter).

[0003] Currently, there are three main gel unblocking methods: automatic hydrolysis, oxidation, and non-oxidation. Automatic hydrolysis has the drawback of being time-consuming (at least several decades), which cannot meet the needs of oilfield production. Non-oxidation is currently the most popular and widely discussed gel unblocking method, and it is also the main method for gel unblocking water injection wells without moving the tubing string. However, its production and use are limited by temperature and environmental conditions, hindering its widespread adoption. Therefore, the oxidation method remains the most widely used gel unblocking method in oilfields.

[0004] CN103881674A discloses a polymer injection plugging well section plugging combination unblocking agent, preparation method and application. The unblocking agent is mainly composed of sodium percarbonate, activator, corrosion inhibitor and mutual solvent. Sodium percarbonate is a solid bleaching agent that is easy to oxidize the water injection tubing, is unstable at high temperature, and is easy to decompose. The reaction rate is too fast, so the reaction must be carried out at low temperature.

[0005] CN101928557A discloses a deblocking agent for polymer gel profile control. The deblocking agent is mainly composed of hydrogen peroxide and industrial hydrochloric acid. Hydrogen peroxide is a strong oxidant with a reaction time of no more than 2 hours. It has poor stability, easily releases a large amount of gas when heated, and has poor construction safety. In addition, hydrochloric acid is highly corrosive to the tubing.

[0006] CN111607371A discloses a high-efficiency unblocking system for polymer flooding injection wells, its preparation method, and its application. The unblocking system mainly consists of oxidants, such as Na2S2O8, sodium bromate or NaClO7, H2O2 or mixtures thereof, and reducing agents, such as FeSO4, sodium bisulfite, Na2S2O3, FeCl2 or mixtures thereof. The oxidants used in this unblocking system have poor stability and are prone to explosion. They react completely within 3 hours and easily generate a large amount of gas.

[0007] CN104650837A discloses a plugging agent for removing near-wellbore blockages in polymer flooding, its preparation and application. The plugging agent is mainly composed of ferrous chloride, polyferric sulfate, aminosulfonic acid, acid corrosion inhibitor, potassium chloride, etc. The reaction temperature of ferrous chloride degrading gel is 20℃-70℃, which is lower than the formation temperature of most oilfields. Moreover, the main oxidant, such as ferrous chloride, needs to be stored in a sealed, cool, dry and light-proof place.

[0008] In summary, current oxidizing agents used to remove gel blockages, such as hydrogen peroxide, chlorine dioxide, sodium percarbonate, and ferrous chloride, suffer from problems including rapid reaction rates, poor stability, and complex application processes. Therefore, there is an urgent need to develop a gel unblocking agent that can control the reaction rate, ensure safe operation even when the tubing is not in use, and guarantees safe application. Summary of the Invention

[0009] To address the aforementioned drawbacks and shortcomings, one objective of this invention is to provide a gel unblocking agent.

[0010] Another object of the present invention is to provide a method for preparing the gel unblocking agent described above.

[0011] Another object of the present invention is to provide the application of the above-described gel unblocking agent in clearing gel blockages in water injection wells.

[0012] Another object of the present invention is to provide a gel unblocking method, which utilizes the gel unblocking agent described above.

[0013] To achieve the above objectives, on the one hand, the present invention provides a gel unblocking agent, wherein the gel unblocking agent comprises agent A and agent B, the volume ratio of agent A to agent B is 3-4:2-3, wherein, based on the total weight of agent A as 100%, agent A comprises 10-20% sphagnum molybdenum, 5-8% pH adjuster, 15-20% organic solvent, 2-5% dispersant and the balance being water;

[0014] Of which, based on the total weight of Agent B as 100%, Agent B contains 8-15% selenium powder, 3-5% corrosion inhibitor, 10-15% emulsifier, 15-20% tert-butyl hydrogen peroxide, 3-5% penetrant and the balance water.

[0015] As a specific embodiment of the gel unblocking agent described above in this invention, the organic solvent includes one or a combination of several of xylene, toluene, cyclohexane, methanol, ethanol, acetone, and diethyl ether.

[0016] As a specific embodiment of the gel unblocking agent described above in this invention, the pH adjuster includes one or a combination of several of sodium hydroxide solution, sodium bicarbonate and disodium hydrogen phosphate.

[0017] In one specific embodiment of the gel unblocking agent described above in this invention, the dispersant includes nonionic surfactants, etc.

[0018] As a specific embodiment of the gel unblocking agent described above in this invention, the nonionic surfactant includes one or a combination of several of BASF isomeric alcohol ethers XL-80, fatty acid polyoxyethylene esters, alkyl alcohol amide polyoxyethylene ethers, and octanol polyoxyethylene ethers.

[0019] As a specific embodiment of the gel unblocking agent described above in this invention, the corrosion inhibitor includes one or a combination of several of triethylamine, phosphonic acid, hexadecylamine, and benzotriazole.

[0020] In one specific embodiment of the gel unblocking agent described above in this invention, the emulsifier includes one or a combination of several of isooctanol polyoxyethylene ether phosphate, alkyl glycosides, and Tween 80.

[0021] As a specific embodiment of the gel unblocking agent described above in this invention, the penetrant includes one or a combination of several of sodium alkylbenzene sulfonate, sodium aminosulfonate, and fatty alcohol polyoxyethylene.

[0022] In the gel unblocking agent described above in this invention, the sphagnum moss in agent A acts as a reducing agent, which can undergo a redox reaction with the selenium powder (oxidizing agent) in agent B to generate selenide. This selenide, together with tert-butyl hydrogen peroxide in agent B, acts as an oxidizing agent to degrade the gel. The tert-butyl hydrogen peroxide is mainly used to degrade macromolecular polymers, while the presence of selenide can improve the unblocking efficiency of the gel unblocking agent. The dispersant is mainly used to disperse the sphagnum moss. The organic solvent can prevent agent A from entering the formation and reacting, and is also conducive to storage and transportation. The pH adjuster is used to adjust the pH value and can also control the reaction rate. The penetrant in agent B mainly plays a penetrating role, improving the depth of the agent into the formation and the unblocking ability.

[0023] On the other hand, the present invention also provides a method for preparing the above-described gel unblocking agent, wherein the preparation method includes:

[0024] Organic solvent, pH adjuster, dispersant, succulent powder and water are mixed evenly to form a water-in-oil suspension, which is agent A.

[0025] Selenium powder, corrosion inhibitor, emulsifier, tert-butyl hydrogen peroxide, penetrant and water are mixed evenly to obtain agent B.

[0026] This invention does not impose specific requirements on the order of adding raw materials when preparing Agent A and Agent B. The order of adding raw materials can be reasonably adjusted according to the needs of on-site operations, as long as Agent A and Agent B can be obtained.

[0027] In another aspect, the present invention also provides the application of the above-described gel unblocking agent in clearing gel blockages in water injection wells.

[0028] In another aspect, the present invention also provides a gel unblocking method for water injection wells, wherein the gel unblocking method for water injection wells utilizes the gel unblocking agent described above.

[0029] As a specific embodiment of the method described above in this invention, the method includes:

[0030] Step 1: Inject the pre-flush fluid into the bottom of the well;

[0031] Step 2: Inject water using a periodic water injection process;

[0032] Step 3: Inject Agent A into the bottom of the well, then inject the isolation fluid into the bottom of the well, followed by water injection, and then inject Agent B into the bottom of the well;

[0033] Step 4: Inject post-flush fluid into the bottom of the well;

[0034] Step 5: Inject water using a periodic water injection process;

[0035] The volume ratio of the pre-treatment solution, agent A, isolation solution, agent B, and post-treatment solution is 1-2:3-4:0.1-0.3:2-3:0.5-1.

[0036] As a specific embodiment of the method described above in this invention, the method specifically includes:

[0037] Step 1: Inject 10-20 cubic meters of pre-flush fluid into the bottom of the well;

[0038] Step 2: Inject water using a periodic water injection process;

[0039] Step 3: Inject 30-40 cubic meters of Agent A into the bottom of the well, then inject 2-3 cubic meters of isolation fluid into the bottom of the well, followed by water injection, and then inject 20-30 cubic meters of Agent B into the bottom of the well.

[0040] Step 4: Inject 5-10 cubic meters of post-flush fluid into the bottom of the well;

[0041] Step 5: Inject water using a periodic water injection process.

[0042] As a specific embodiment of the method described above in this invention, in step one, the pretreatment solution contains acetone, ethylenediaminetetramethylenepentasodium phosphate, sodium pyrophosphate, and ammonium persulfate in a mass ratio of 1.5-2:0.8-1:0.8-1:0.01-0.02.

[0043] In step one of the methods described above in this invention, a pre-fluid is first injected into the bottom of the well. The pre-fluid can remove sludge, control clay stability, and dissolve gel.

[0044] In one specific embodiment of the method described above, in step two, the water injection time is 18-24 hours, and the water injection rate is adjusted every 7-8 hours based on the actual daily injection schedule. This invention does not impose specific requirements on the water injection rate before and after adjustment; it can be reasonably adjusted according to the actual on-site operating conditions.

[0045] In one specific embodiment of the method described above in this invention, in step three, the separating liquid is an aqueous solution of phosphonic acid and / or phosphonate.

[0046] In one specific embodiment of the method described above in this invention, in step three, the phosphonic acid includes hydroxyethylidene diphosphonic acid, etc., and the phosphonate includes pentasodium aminotrimethylphosphonate and / or pentasodium ethylenediaminetetramethylidenephosphonate, etc. In this invention, when the phosphonic acid and phosphonate are liquids, they can be directly used as a separating liquid; when they are solids, they can be prepared into a solution using a suitable solvent and then used as a separating liquid.

[0047] In step three of the method described above, injecting a separating liquid between agent A and agent B can slow down the reaction rate of agent A and agent B.

[0048] In one specific embodiment of the method described above in this invention, the water injection time in step three is 0.5-1 hour.

[0049] In one specific embodiment of the method described above in this invention, in step three, the injection rate of agent A is 1.5-2 cubic meters per hour, and the injection rate of agent B is 1-1.5 cubic meters per hour.

[0050] In one specific embodiment of the method described above in this invention, in step one, the injection rate of the pre-filled fluid is 2-3 cubic meters per hour. In step four, the post-filled fluid is alternately injected into the bottom of the well at injection rates of 1-1.5 cubic meters per hour and 0.3-0.5 cubic meters per hour to expand the reaction area between the blockage and agent A and agent B, thereby achieving gradual reaction, stepwise dissolution of the gel, and deep unblocking.

[0051] In one specific embodiment of the method described above, in step four, the post-treatment solution comprises acetic acid, aminosulfonic acid, ammonium fluoride, ribonucleotides, and sodium dioctyl succinate sulfonate in a mass ratio of 0.8-1:0.3-0.5:0.2-0.3:0.3-0.5:0.1-0.5. This post-treatment solution is mainly used to dissolve scale and clay minerals, with the sodium dioctyl succinate sulfonate in the solution primarily serving a wetting and detergency function.

[0052] As a specific embodiment of the method described above in this invention, the method includes the following specific steps:

[0053] Step 1: Add 10-20 cubic meters of pre-flush fluid to the well site dosing tank and inject it into the bottom of the well at an injection rate of 2-3 cubic meters per hour;

[0054] Step 2: Close the dosing tank and use a periodic water injection process to inject water and clean the dosing tank;

[0055] Step 3: Add 30-40 cubic meters of Agent A to the dosing tank and inject it into the bottom of the well at an injection rate of 1.5-2 cubic meters / hour. Then add 2-3 cubic meters of isolation fluid to the dosing tank and inject it into the bottom of the well. After that, inject water and rinse the dosing tank with clean water. Then add 20-30 cubic meters of Agent B to the dosing tank and inject it into the bottom of the well at an injection rate of 1-1.5 cubic meters / hour.

[0056] Step 4: After cleaning the dosing tank, add 5-10 cubic meters of post-filling fluid to the dosing tank and inject it alternately into the bottom of the well at an injection rate of 1-1.5 cubic meters / hour and 0.3-0.5 cubic meters / hour.

[0057] Step 5: Close the dosing tank, fill it with water using a periodic water injection process, and rinse the dosing tank with clean water.

[0058] In one specific embodiment of the method described above in this invention, in step two, a mixed solution of acetamide and ethanol-methyl ether in a mass ratio of 0.8-1:0.8-1 is used to clean the dosing tank.

[0059] In one specific embodiment of the method described above in this invention, in step four, a mixed solution of ethanol and ethylene glycol monomethyl ether in a volume ratio of 1-1.5:1.5-2 is used to clean the dosing tank.

[0060] The corrosion rate of the gel unblocking agent provided by this invention is far superior to the industry's first-grade standard (typically 3g / (m²). 2 The gel unblocking agent provides a guarantee for operations without moving the tubing; the reaction time of this gel unblocking agent can reach more than 7 hours, which is much longer than the reaction time of conventional oxidants (usually 3 hours), and it can be used for deep unblocking; in addition, the high degradation rate and pressure reduction rate of this gel unblocking agent indicate that it can effectively dissolve gel / polymer.

[0061] In summary, the gel unblocking agent provided by this invention has a good pressure reduction and injection enhancement effect. Detailed Implementation

[0062] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0063] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0064] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0065] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0066] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0067] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0068] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the appendices and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0069] Example 1

[0070] This embodiment provides a gel unblocking agent, which includes agent A and agent B;

[0071] Based on a total weight of 100 wt% for Agent A, it comprises: 12% sodium bleaching powder, 6% sodium hydroxide solution with a mass concentration of 30%, 17% xylene, 2% BASF isomeric alcohol ether XL-80, and the balance being water;

[0072] The preparation method of Agent A is to mix the above raw materials evenly to form a water-in-oil suspension, thereby obtaining Agent A;

[0073] Based on a total weight of 100wt% for Agent B, it comprises: 10% selenium powder, 3% triethylamine, 11% isooctanol polyoxyethylene ether phosphate, 15% tert-butyl hydrogen peroxide, 4% sodium alkylbenzene sulfonate, and the balance being water.

[0074] The preparation method of Agent B is to mix the above raw materials evenly to obtain Agent B.

[0075] Example 2

[0076] This embodiment provides a gel unblocking agent, which includes agent A and agent B;

[0077] Based on a total weight of 100 wt% for Agent A, it comprises: 14% sodium bleaching powder, 8% sodium hydroxide solution with a mass concentration of 30%, 19% xylene, and 4% BASF isomeric alcohol ether XL-80, with the balance being water;

[0078] The preparation method of Agent A is to mix the above raw materials evenly to form a water-in-oil suspension, thereby obtaining Agent A;

[0079] Based on a total weight of 100wt% for Agent B, it comprises: 12% selenium powder, 4% triethylamine, 12% isooctanol polyoxyethylene ether phosphate, 18% tert-butyl hydrogen peroxide, 5% sodium alkylbenzene sulfonate, and the balance being water.

[0080] The preparation method of Agent B is to mix the above raw materials evenly to obtain Agent B.

[0081] Example 3

[0082] This embodiment provides a gel unblocking agent, which includes agent A and agent B;

[0083] Based on a total weight of 100 wt% for Agent A, it comprises: 18% sodium bleaching powder, 7% sodium hydroxide solution with a mass concentration of 30%, 16% xylene, 3% BASF isomeric alcohol ether XL-80, and the balance being water;

[0084] The preparation method of Agent A is to mix the above raw materials evenly to form a water-in-oil suspension, thereby obtaining Agent A;

[0085] Based on a total weight of 100wt% for Agent B, it comprises: 11% selenium powder, 5% triethylamine, 13% isooctanol polyoxyethylene ether phosphate, 19% tert-butyl hydrogen peroxide, 4% sodium alkylbenzene sulfonate and the balance water.

[0086] The preparation method of Agent B is to mix the above raw materials evenly to obtain Agent B.

[0087] Test Example 1

[0088] This test example uses SY / T5405-1996 "Test Methods and Evaluation Indicators for Corrosion Inhibitors for Acidizing", Q / SY5358-2020 "Evaluation Methods for Reservoir Sensitivity Flow Experiments" and the weighing method to test the appearance, corrosion performance, degradation performance, reaction performance and pressure reduction performance of the gel unblocking agent provided in Example 1. The test results are shown in Table 1.

[0089] Table 1

[0090] Serial Number Testing items Test results 1 Appearance of Agent A and Agent B uniform 2 Corrosion rate (Agent A: Agent B: Isolation fluid = 15:10:1) <![CDATA[1.02g / (m 2 ·h)]]> 3 Degradation rate (Agent A: Agent B: Isolation liquid = 15:10:1) 85.5％ 4 Reaction time (Agent A: Agent B: Isolation solution = 15:10:1) 7 hours 5 Pressure reduction rate (Agent A: Agent B: Isolation fluid = 15:10:1) 20.2％

[0091] Note: The isolation solution is sodium trimethylphosphonate pentasodium aminotrimethylphosphonate, and the ratio of agent A, agent B and isolation solution is by volume.

[0092] As can be seen from Table 1, the corrosion rate of the gel unblocking agent provided in Example 1 of this invention is far superior to the industry-standard first-grade product (typically 3g / (m²). 2 The gel unblocking agent provides a guarantee for operations without moving the tubing; the reaction time of this gel unblocking agent can reach 7 hours, which is much longer than the reaction time of conventional oxidants (usually 3 hours), and it can be used for deep unblocking; in addition, the high degradation rate and pressure reduction rate of this gel unblocking agent indicate that it can effectively dissolve gel.

[0093] Test Example 2

[0094] This test example tested the appearance, corrosion performance, degradation performance, reaction performance, and pressure reduction performance of the gel unblocking agent provided in Example 2 according to SY / T5405-1996 "Test Method and Evaluation Index of Corrosion Inhibitors for Acidizing", Q / SY5358-2020 "Evaluation Method of Reservoir Sensitivity Flow Experiment" and the weighing method. The test results are shown in Table 2.

[0095] Table 2

[0096] Serial Number Testing items Test results 1 Appearance of Agent A and Agent B uniform 2 Corrosion rate (Agent A: Agent B: Isolation fluid = 10:10:1) <![CDATA[1.03g / (m 2 ·h)]]> 3 Degradation rate (Agent A: Agent B: Isolation liquid = 10:10:1) 86.2％ 4 Reaction time (Agent A: Agent B: Isolation solution = 15:10:1) 7.2 hours 5 Pressure reduction rate (Agent A: Agent B: Isolation fluid = 15:10:1) 19.7％

[0097] Note: The isolation solution is an aqueous solution of hydroxyethylidene diphosphonic acid, with a mass concentration of 50%, and the ratio of agent A, agent B, and isolation solution is a volume ratio.

[0098] As can be seen from Table 2, the corrosion rate of the gel unblocking agent provided in Example 2 of this invention is far superior to the industry-standard grade 1 product (typically 3g / (m²). 2 The gel unblocking agent provides a guarantee for operations without moving the tubing; the reaction time of this gel unblocking agent can reach 7.2 hours, which is much longer than the reaction time of conventional oxidants (usually 3 hours), making it suitable for deep unblocking; in addition, the high degradation rate and pressure reduction rate of this gel unblocking agent indicate that it can effectively dissolve gel / polymer.

[0099] Application Example 1

[0100] This application example provides a gel unblocking method for water injection wells, wherein the gel unblocking method utilizes the gel unblocking agent provided in Example 3, and includes the following specific steps:

[0101] Step 1: When the oil pressure gradually rises due to the formation of gel blockage in the injection well, causing the actual daily water injection volume to fall below the daily allocation volume, the injection well needs to be treated. At this time, without changing the water injection process, i.e., while injecting water normally, add 15 cubic meters of pre-filled fluid to the well site chemical dosing tank and inject it into the bottom of the well at an injection rate of 2 cubic meters per hour.

[0102] The pretreatment solution is obtained by uniformly mixing acetone, ethylenediaminetetramethylenepentasodium phosphate, sodium pyrophosphate and ammonium persulfate in a weight ratio of 1.5:0.8:0.8:0.01.

[0103] Step 2: Close the dosing tank and use the normal cycle water injection process to inject water for 24 hours. Adjust the water injection rate every 8 hours based on the actual daily injection. At the same time, use 500 liters of mixed solution obtained by mixing acetamide and ethanol-methyl ether at a weight ratio of 0.8:1 to clean the dosing tank.

[0104] Step 3: Add 40 cubic meters of Agent A from the gel unblocking agent to the well site dosing tank at a rate of 2 cubic meters per hour to the bottom of the well; then add 2 cubic meters of isolation fluid to the dosing tank and inject it into the bottom of the well, followed by normal water injection for 1 hour, while simultaneously rinsing the dosing tank with tap water / clean water; then add 30 cubic meters of Agent B from the gel unblocking agent to the dosing tank at a rate of 1.5 cubic meters per hour to the bottom of the well.

[0105] The isolation fluid is pentasodium ethylenediaminetetramethylenephosphonate.

[0106] Step 4: Clean the dosing tank with a mixed solution obtained by mixing ethanol and ethylene glycol monomethyl ether at a volume ratio of 1:2. The volume of the mixed solution is 300 liters. Then add 8 cubic meters of post-filling fluid to the dosing tank. The post-filling fluid is injected alternately into the bottom of the well at an injection rate of 1 cubic meter / hour and 0.4 cubic meters / hour to expand the reaction area with agent A and agent B, so as to achieve gradual reaction, dissolve the gel step by step, and achieve deep unblocking.

[0107] The post-treatment solution is obtained by uniformly mixing acetic acid, aminosulfonic acid, ammonium fluoride, ribonucleotide and sodium dioctyl succinate in a weight ratio of 0.8:0.4:0.2:0.4:0.4.

[0108] Step 5: Close the dosing tank, inject water according to the normal water injection cycle, and rinse the dosing tank with clean water.

[0109] Field application examples

[0110] Since its initial injection, Well 4 in Zhenbei Oilfield (Zhen 300) has produced water. In 2016, due to substandard water quality, injection was insufficient. After acid leaching and surfactant unblocking, injection returned to normal. At the end of 2020, to increase the injection sweep volume, polymer gel injection was initiated, leading to a continuous increase in injection pressure. In early 2022, injection was insufficient again. In October 2022, the gel unblocking agent provided in Example 3 was used, and the well was treated according to the above-described construction steps in Application Example 1. Before the treatment, 20m³ of pre-treatment solution was injected. 3 / d, actual bet 5m 3 / d, injection pressure 20.2MPa, actual injection depth after measures: 20m 3 / d, that is, after constructing the Zhen 4 well according to the above construction steps provided in Application Example 1, the daily water injection volume of the Zhen 4 well is 20m³. 3 The injection pressure was 15.6 MPa, and the pressure dropped by 4.6 MPa, reaching the injection target. This demonstrates that the gel-based unblocking agent provided by this invention has a good pressure-reducing and injection-enhancing effect.

[0111] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A gel unblocking agent, characterized in that, The gel unblocking agent includes Agent A and Agent B, with a volume ratio of 3-4:2-3. Agent A, based on 100% of its total weight, contains 10-20% styrax powder, 5-8% pH adjuster, 15-20% organic solvent, 2-5% dispersant, and the remainder water. Of which, based on the total weight of Agent B as 100%, Agent B contains 8-15% selenium powder, 3-5% corrosion inhibitor, 10-15% emulsifier, 15-20% tert-butyl hydrogen peroxide, 3-5% penetrant and the balance water; The corrosion inhibitor includes one or a combination of triethylamine, hexadecylamine, and benzotriazole.

2. The gel unblocking agent according to claim 1, characterized in that, The organic solvent includes one or a combination of several of xylene, toluene, cyclohexane, methanol, ethanol, acetone, and diethyl ether.

3. The gel unblocking agent according to claim 1 or 2, characterized in that, The pH adjuster includes one or a combination of sodium hydroxide solution, sodium bicarbonate and disodium hydrogen phosphate.

4. The gel unblocking agent according to claim 1 or 2, characterized in that, The dispersant includes a nonionic surfactant.

5. The gel unblocking agent according to claim 4, characterized in that, The nonionic surfactant includes one or a combination of several of BASF isomeric alcohol ethers XL-80, fatty acid polyoxyethylene esters, alkyl alcohol amide polyoxyethylene ethers, and octanol polyoxyethylene ethers.

6. The gel unblocking agent according to claim 1, characterized in that, The emulsifier includes one or a combination of several of isooctanol polyoxyethylene ether phosphate, alkyl glycosides, and Tween 80.

7. The gel unblocking agent according to claim 1, characterized in that, The penetrant includes one or a combination of several of sodium alkylbenzene sulfonate, sodium aminosulfonate, and fatty alcohol polyoxyethylene.

8. A method for preparing the gel unblocking agent according to any one of claims 1-7, characterized in that, The preparation method includes: Organic solvent, pH adjuster, dispersant, succulent powder and water are mixed evenly to form a water-in-oil suspension, which is agent A. Selenium powder, corrosion inhibitor, emulsifier, tert-butyl hydrogen peroxide, penetrant and water are mixed evenly to obtain agent B.

9. The use of the gel unblocking agent according to any one of claims 1-7 in removing gel blockages in water injection wells.

10. A method for unclogging injection wells with gel, characterized in that, The method for unblocking injection wells using gel is implemented using the gel unblocking agent described in any one of claims 1-7.

11. The method according to claim 10, characterized in that, The method includes: Step 1: Inject pre-flush fluid into the bottom of the well; Step 2: Inject water using a periodic water injection process; Step 3: Inject Agent A into the bottom of the well, then inject the isolation fluid into the bottom of the well, followed by water injection, and then inject Agent B into the bottom of the well; Step 4: Inject post-flush fluid into the bottom of the well; Step 5: Inject water using a periodic water injection process; The volume ratio of the pre-treatment solution, agent A, isolation solution, agent B, and post-treatment solution is 1-2:3-4:0.1-0.3:2-3:0.5-1.

12. The method according to claim 11, characterized in that, In step one, the pretreatment solution contains acetone, ethylenediaminetetramethylenepentasodium phosphate, sodium pyrophosphate, and ammonium persulfate in a mass ratio of 1.5-2:0.8-1:0.8-1:0.01-0.

02.

13. The method according to claim 11, characterized in that, In step two, the water injection time is 18-24 hours, and the water injection speed is adjusted every 7-8 hours.

14. The method according to claim 11, characterized in that, The isolation solution is an aqueous solution of phosphonic acid and / or phosphonate.

15. The method according to claim 14, characterized in that, The phosphonic acid includes hydroxyethylidene diphosphonic acid, and the phosphonate includes pentasodium aminotrimethylphosphonate and / or pentasodium ethylenediaminetetramethylidenephosphonate.

16. The method according to any one of claims 11, 14-15, characterized in that, In step three, the water injection time is 0.5-1 hour.

17. The method according to any one of claims 11, 14-15, characterized in that, In step three, the injection rate of agent A is 1.5-2 cubic meters per hour, and the injection rate of agent B is 1-1.5 cubic meters per hour.

18. The method according to claim 11, characterized in that, In step one, the injection rate of the pre-flush fluid is 2-3 cubic meters per hour. In step four, the post-flush fluid is injected alternately into the bottom of the well at injection rates of 1-1.5 cubic meters per hour and 0.3-0.5 cubic meters per hour.

19. The method according to claim 11 or 18, characterized in that, In step four, the post-treatment solution contains acetic acid, aminosulfonic acid, ammonium fluoride, ribonucleotides, and sodium dioctyl succinate in a mass ratio of 0.8-1:0.3-0.5:0.2-0.3:0.3-0.5:0.1-0.5.