Freshwater-based controllable deoxygenated annular protection fluid, preparation method and well completion displacement fluid method

Abstract

This invention discloses a water-based controlled deoxygenated annular protective fluid for gas storage facilities, comprising annular protective fluid A and annular protective fluid B. Annular protective fluid A comprises: 1-15% corrosion inhibitor, 1-5% corrosion inhibitor additive, 1-10% bactericide, 1-10% scale inhibitor, 1-5% deoxygenator, 1-5% pH adjuster, 5-15% pour point depressant, and the remainder being water. Annular protective fluid B is a deoxygenation catalyst, and the molar amount of annular protective fluid B is 0.00357%-0.0214% of the molar amount of the deoxygenator. This invention also discloses a method for preparing the water-based controlled deoxygenated annular protective fluid for gas storage facilities and a method for using the annular protective fluid as a well completion fluid replacement. The water-based controlled deoxygenated annular protective fluid provided by this invention solves the problems existing in the individual components of existing annular protective fluid formulations. Through formulation design, a low-density water-based annular protective fluid suitable for gas storage facilities with lower formation temperatures below 55℃ is produced.

Description

Technical Field

[0001] This invention belongs to the field of annular protective fluid preparation technology, and relates to a water-based controllable deoxygenation annular protective fluid, a method for preparing a water-based controllable deoxygenation annular protective fluid, and a well completion replacement method for annular protective fluid in gas storage wells. Background Technology

[0002] Corrosion is a problem that occurs in all stages of oil extraction, including drilling, well completion, production, and gathering and transportation, especially in downhole casing. Common anti-corrosion measures include using corrosion-resistant alloys, coating technologies (applying epoxy resin and its modifiers, polyethylene, polypropylene, silicone resin, etc. to the material surface), plating technologies (Ni-P plating, tungsten plating, etc.), cathodic protection, chemical corrosion inhibitors, full return cement to protect the outer wall of the casing, and using downhole packers to protect the outer wall of the tubing and the inner wall of the casing.

[0003] Annular fluid injection is currently the most widely used technology for protecting the annulus of oil casing and tubing. It helps to slow down corrosion of the casing and tubing, reduce reservoir pressure on the casing head or packer, and lower the pressure differential between the tubing and the annulus. Based on the properties of the continuous phase, annular fluids can be classified into three main categories: gas-based, oil-based, and water-based. Gas-based annular fluids are less commonly used, while oil-based annular fluids are more expensive. Water-based annular fluids are primarily used both domestically and internationally. Gas storage facilities undergo intensive injection and production operations during operation. To extend the life of injection and production wells, balance the pressure above and below the packer, and ensure stable packer operation, annular fluid should be injected into the annulus after the packer is set inside the production casing to protect the casing, tubing, downhole tools, etc.

[0004] The annulus of the oil casing is a closed, stagnant water zone, facing complex conditions such as alternating injection and production stress, high temperature and high salinity, formation water and vapor intrusion, dissolved oxygen, and bacterial growth. Therefore, the formulation design needs to comprehensively consider properties such as corrosion inhibition, sterilization, oxygen removal, scale inhibition, and buffering of acidic gases. Wu Junwen et al. developed a formulation with a density of 1.0–1.6 g / cm³. 3An adjustable annular protection fluid has the following formulation: base fluid + 5% imidazoline corrosion inhibitor GL-3 + 2% oxime oxygen scavenger dimethyl ketoxime + 1% bactericide 1227 + 1.3% organophosphate scale inhibitor ZC-21 + 0.01% pH adjuster. The application date was November 17, 2009, and the publication number was CN 102061155B. The invention title is "An Annular Protection Fluid for Water Injection Wells and Its Application," which discloses a multi-purpose annular protection fluid for oilfield water injection or wastewater reinjection well casing and its application: 0.1-2% amine compound, 0.05-0.5% complex phosphate, 0.02-0.1% complex quaternary ammonium salt cationic surfactant, 0.01-0.02% sulfite, and the remainder being water. The Chinese invention patent, filed on March 30, 2011, with publication number CN102719233B and entitled "Oil and Gas Well Annulus Protection Fluid," discloses a method using an organic acid salt solution as a density regulator, an imidazoline quaternary ammonium salt as a corrosion inhibitor, a quaternary ammonium salt-type cationic surfactant as a bacteriostatic agent, and an isoascorbic acid alkali metal salt or an optical isomer of isoascorbic acid alkali metal salt as an oxygen scavenger. Depending on the sulfur content of the oil casing annulus, a coordination compound with iron-centered divalent ions or basic zinc carbonate can also be added as a desulfurizing agent.

[0005] However, existing annular protection fluid formulations use carbonates as pH adjusters, which may react with M intrusive formation water. 2+ Ion scaling is a concern. Using sulfites as oxygen scavengers presents challenges due to their high reactivity with oxygen. During on-site preparation, storage, and injection, they react with atmospheric oxygen, reducing the effective concentration of the oxygen scavenger in the solution and affecting the performance of the annular protective fluid. Furthermore, the sulfate ions generated in the reaction provide nutrients for sulfate-reducing bacteria, exacerbating bacterial corrosion. Using oximes, isoascorbic acid alkali metal salts, or their optical isomers as oxygen scavengers results in slow reactions with dissolved oxygen at lower temperatures, leading to oxygen corrosion. Other technologies are needed to accelerate the reaction between these oxygen scavengers and dissolved oxygen. Using 1227 (dodecyl dimethyl benzyl ammonium chloride) as a bactericide may cause foaming of the solution, while isothiazolinone bactericides have poor solubility in the aqueous phase. Organophosphonic acid scale inhibitors contain phosphorus, which can cause eutrophication of the water body, and the degradation products, phosphate ions, may also precipitate with metal ions. Therefore, a new annular protective fluid is needed to address these issues. Summary of the Invention

[0006] The first objective of this invention is to provide a water-based controllable deoxygenation annular protective fluid, which solves the problems of individual components in existing annular protective fluid formulations. Through formulation design, a low-density water-based annular protective fluid suitable for gas storage facilities with lower formation temperatures below 55°C is produced. The second objective of this invention is to provide a method for preparing a water-based controllable deoxygenation annular protective liquid.

[0007] The third objective of this invention is to provide a method for replacing the annulus protection fluid in a gas storage well during completion.

[0008] The first technical solution adopted in this invention is an annular protective liquid for a water-based controllable deoxygenated gas storage facility, comprising an annular protective liquid agent A and an annular protective liquid agent B; The annular protective fluid A, by mass percentage, includes the following components: 1-15% corrosion inhibitor, 1-5% corrosion inhibitor additive, 1-10% bactericide, 1-10% scale inhibitor, 1-5% oxygen scavenger, 1-5% pH adjuster, 5-15% pour point depressant, and the remainder is water. The annular protective fluid B is an oxygen removal catalyst, and the molar amount of the annular protective fluid B is 0.00357%-0.0214% of the molar amount of the oxygen removal agent.

[0009] The invention is further characterized by: The main corrosion inhibitor is 5-cyclohexyl-1,3,5-triazine; the auxiliary corrosion inhibitor is alkyl glycoside; the bactericide is sodium dehydroacetate; the scale inhibitor is polyepoxysuccinic acid; the oxygen scavenger is any one of carbazide, acetone oxime or sodium isoascorbate; the pH adjuster is 1,8-diazabicyclo[5.4.0]undec-7-ene; and the pour point depressant is ethanol or isopropanol.

[0010] The scale inhibitor is a 10-35% aqueous solution.

[0011] The annular protective solution B is a 1-5% (w / w) aqueous solution.

[0012] The annular protective solution B is copper sulfate pentahydrate or cobalt sulfate heptahydrate.

[0013] The second technical solution adopted in this invention is, The preparation method of the annular protective fluid for water-based controlled deoxygenation gas storage is as follows: Step 1: Prepare annular protective fluid A: Weigh out 1-15% of the main corrosion inhibitor, 1-5% of the auxiliary corrosion inhibitor, 1-10% of the bactericide, 1-10% of the scale inhibitor, 1-5% of the oxygen remover, 1-5% of the pH adjuster, 5-15% of the pour point depressant, and the remainder is water. Mix all the substances and stir evenly to obtain annular protective fluid A. Step 2: Weigh out the amount of anion protection fluid B according to 0.00357%-0.0214% of the molar amount of oxygen scavenger in anion protection fluid A, and prepare a 1-5% mass concentration solution. Step 3: Dilute the annular protective fluid A to a mass concentration of 3-10%, then mix the annular protective fluid B with the diluted annular protective fluid A to obtain the annular protective fluid for water-based controllable deoxygenated gas storage. The invention is further characterized by: The specific method for step 1 is as follows: Under normal temperature conditions, first pump 5-cyclohexyl-1,3,5-triazine into the reactor, adding 80% of the water volume of the component, and stir evenly; add bactericide while stirring, and stir until completely dissolved, then pump in corrosion inhibitor and auxiliary agent, stir the above raw materials evenly, then pump in scale inhibitor and stir evenly; pump in pour point depressant and stir evenly; pump in pH adjuster DBU and stir evenly; add oxygen scavenger while stirring, and after it is completely dissolved and stirred evenly, pump in the remaining 20% ​​of the water volume of the component, and stir evenly until the entire product liquid is clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, it is discharged from the reactor and bottled. Throughout the entire preparation process, the reactor is circulated with cooling water to control the temperature of the reaction liquid inside the reactor at 20℃-25℃.

[0014] The third technical solution adopted in this invention is a completion fluid replacement method for annular protection fluid in gas storage wells, using the aforementioned annular protection fluid. The specific method is as follows: Step 1: Prepare the amount of clean water at the oil and gas field site according to the amount of annular protection fluid required for a single well in the gas storage facility, add 3-10% of annular protection fluid A agent by mass, and stir evenly; Step 2: Calculate the amount of annular protective fluid B based on the total mass of the oxygen scavenger in annular protective fluid A. Prepare a 1-5% mass concentration solution with water and mix it evenly with the diluted annular protective fluid A before starting the circulation replacement. Step 3: Take the above mixed solution and test the dissolved oxygen concentration with a dissolved oxygen concentration tester, and test the pH value with precision pH test paper; Step 4: Use a pump truck to pump the annulus protection fluid from the gas storage wellhead annulus to replace the downhole fluid and discharge it into the wellhead tubing. Take samples to monitor the dissolved oxygen concentration and pH value of the initial displacement fluid. Step 5: When the color of the solution to be replaced changes, take a sample to monitor the dissolved oxygen concentration and pH. Continue replacing the solution and monitoring until the color of the replaced solution is visually consistent with the initial annular protective solution and the pH test value is consistent. Stop pumping to complete the solution replacement.

[0015] The beneficial effects of this invention are: (1) The water-based controllable deoxygenation annular protective liquid of the present invention has a bactericidal rate of 99.0% against sulfate-reducing bacteria (SRB), a bactericidal rate of 99.2% against iron bacteria (FB), and a bactericidal rate of 100% against saprophytic bacteria (TGB); it has a scale inhibition rate of 90.5% (55℃) against calcium carbonate and a scale inhibition rate of 93.6% (55℃) against calcium sulfate. (2) The water-based controllable deoxygenating annular protective fluid of the present invention is prepared with a high-pressure autoclave temperature of 55°C and a total pressure of 10MPa. The solution is prepared with clean water on site (5% mass concentration) without deoxygenation. In static tests, the uniform corrosion rate of the N80 standard pad is 0.0217 mm / a, and the uniform corrosion rate of the N80 tubing machined pad is 0.0310 mm / a. The uniform corrosion rate of the downhole N80 corrosion monitoring pad completed by replacing the annular protective fluid of the present invention in the gas storage sealing well is 0.000665 mm / a. (3) The annular protective liquid of the present invention is a composite agent with pH adjustment components. In order to prevent conventional inorganic salt pH adjusters from causing scaling or poor solubility, this application uses water-soluble organic amine pH adjusters to avoid the above problems. Attached Figure Description

[0016] Figure 1 The corrosion morphology of the annular protective liquid in the high-pressure reactor of this invention is shown in the test. Figure 2 To use the annular protective fluid of the present invention for on-site monitoring of the corrosion morphology of N80 clips in wells; Figure 3 The figure shows the deoxygenation reaction curve of sodium isoascorbate catalyzed by copper sulfate pentahydrate at a molar concentration of 0.0107% according to the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] Water-based controllable deoxygenating annular protective fluid, including annular protective fluid A and annular protective fluid B; The annular protective fluid A, by mass percentage, includes the following components: 1-15% corrosion inhibitor, 1-5% corrosion inhibitor additive, 1-10% bactericide, 1-10% scale inhibitor, 1-5% oxygen scavenger, 1-5% pH adjuster, 5-15% pour point depressant, and the remainder is water. The annular protective fluid B is an oxygen removal catalyst, and the molar amount of the annular protective fluid B is 0.00357%-0.0214% of the molar amount of the oxygen removal agent.

[0019] The corrosion inhibitor is 5-cyclohexyl-1,3,5-triazine; the corrosion inhibitor auxiliaries are alkyl glycosides; the bactericide is sodium dehydroacetate; the scale inhibitor is polyepoxysuccinic acid, which is a 10-35% aqueous solution; the oxygen scavenger is any one of carbazide, acetone oxime, or sodium isoascorbate; the pH adjuster is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); and the pour point depressant is ethanol or isopropanol.

[0020] The annular protective solution B is copper sulfate pentahydrate or cobalt sulfate heptahydrate, and the mass concentration of the annular protective solution B is 1~5%.

[0021] The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: Step 1: Prepare annular protective fluid A: Weigh out the following components by mass percentage: corrosion inhibitor (main component), corrosion inhibitor (auxiliary component), bactericide (bacterial agent), scale inhibitor (scale inhibitor), oxygen scavenger (oxygen scavenger), pH adjuster (pH adjuster), and pour point depressant (pour point depressant) at a concentration of 1-15% and 5-15% respectively. The remainder is water. Mix all the components together and stir until homogeneous to obtain annular protective fluid A. Under normal temperature conditions, first pump 5-cyclohexyl-1,3,5-triazine into the reactor, adding 80% of the water volume of the component, and stir evenly. Add bactericide while stirring, and stir until completely dissolved. Then pump in corrosion inhibitor and auxiliary agent, and stir the above raw materials evenly. Pump in scale inhibitor and stir evenly. Pump in pour point depressant and stir evenly. Pump in pH adjuster DBU and stir evenly. Add oxygen scavenger while stirring, and after it is completely dissolved and stirred evenly, pump in the remaining 20% ​​of the water volume of the component, and stir evenly until the entire product liquid is clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, it is discharged from the reactor and bottled. Throughout the preparation process, the reactor is circulated with cooling water to control the temperature of the reaction liquid inside the reactor at 20℃-25℃.

[0022] Step 2: Based on the total mass of the oxygen scavenger in the annular protective fluid A, calculate the molar amount of the oxygen scavenger contained therein. Weigh out the amount of annular protective fluid B according to 0.00357%-0.0214% of the molar amount of the oxygen scavenger, and prepare a 1-5% mass concentration solution. Step 3: Dilute the annular protective liquid A to a mass concentration of 3-10%, then mix the annular protective liquid B with the diluted annular protective liquid A to obtain a water-based controllable deoxygenation annular protective liquid.

[0023] In this application, the main corrosion inhibitor and the auxiliary corrosion inhibitor can prevent metal corrosion in the annulus of the oil casing; the bactericide, sodium dehydroacetate, can inhibit bacterial growth in the downhole environment and prevent bacterial corrosion; the addition of the scale inhibitor can prevent the deposition and blockage of the tubing by calcium and magnesium ions in the solution and the generation of under-deposit corrosion, while also enhancing the corrosion inhibition performance; the oxygen scavenger is used to remove dissolved oxygen in the solution during operation and the small amount of oxygen leaked in during production, preventing oxygen corrosion; the addition of the pH adjuster is to adjust the pH value of the reagent system, and the entire solution system has lower corrosivity in an alkaline environment; the addition of the pour point depressant can enhance the solubility of each component, lower the product pour point, facilitate operation in low-temperature environments in winter, and prevent freezing and precipitation of components at low temperatures that would reduce product performance.

[0024] The method for replacing the annular protective fluid in a gas storage well, using the aforementioned annular protective fluid, is as follows: Step 1: Prepare the amount of clean water at the oil and gas field site according to the amount of annular protection fluid required for a single well in the gas storage facility, add 3-10% of annular protection fluid A agent by mass, and stir evenly; Step 2: Calculate the amount of annular protective fluid B based on the total mass of the oxygen scavenger in annular protective fluid A. Prepare a 1-5% mass concentration solution with water and mix it evenly with the diluted annular protective fluid A before starting the circulation replacement. Step 3: Take the above mixed solution and test the dissolved oxygen concentration with a dissolved oxygen concentration tester, and test the pH value with precision pH test paper; Step 4: Use a pump truck to pump the annulus protection fluid from the gas storage wellhead annulus to replace the downhole fluid and discharge it into the wellhead tubing. Take samples to monitor the dissolved oxygen concentration and pH value of the initial displacement fluid. Step 5: When the color of the solution to be replaced changes, take a sample to monitor the dissolved oxygen concentration and pH. Continue replacing the solution and monitoring until the color of the replaced solution is visually consistent with the initial annular protective solution and the pH test value is consistent. Stop pumping to complete the solution replacement.

[0025] The performance of the annular protective fluid prepared in this invention was tested: like Figure 1 As shown, the corrosion test was conducted in an indoor high-temperature and high-pressure autoclave using on-site clean water solution preparation. The test conditions were: autoclave temperature 55℃, total pressure 10MPa, on-site clean water solution preparation (5% mass concentration), no deoxygenation, static test, and uniform corrosion rate of 0.0217mm / a for N80 standard coupons.

[0026] like Figure 2 As shown, the agent of this invention was applied to the annulus of a gas storage well in an oilfield. An N80 type hanging plate was hung 15m downhole in the plugging well. After 90 days, the hanging plate was removed for monitoring, and the uniform corrosion rate was 0.000665mm / a.

[0027] like Figure 3 As shown, this is a controlled deoxygenation evaluation test. On-site clean water was added to two flasks in the room, dissolved oxygen concentration detectors were installed, and a certain amount of deoxygenating agent sodium isoascorbate and catalyst copper sulfate pentahydrate solution were added. The change of dissolved oxygen concentration over time was then monitored.

[0028] Example 1 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: The following method was used to prepare 4000 kg of annular protective liquid A in a 5-ton reactor: At room temperature, 200 kg of the corrosion inhibitor 5-cyclohexyl-1,3,5-triazine was first pumped into the reactor using a vacuum pump, followed by 2176 kg of factory water, and stirred until homogeneous. While stirring, 40 kg of sodium dehydroacetate solid was added as a bactericide, and after complete dissolution and stirring, 120 kg of alkyl glycoside, an auxiliary corrosion inhibitor, was pumped in. After stirring all the above raw materials evenly, 200 kg of polyepoxysuccinic acid (35% aqueous solution), a scale inhibitor, was pumped in and stirred until homogeneous. 600 kg of isopropanol, a pour point depressant, was pumped in and stirred until homogeneous. 80 kg of DBU, a pH adjuster, was pumped in and stirred until homogeneous. 40 kg of carbazide solid, an oxygen scavenger, was added while stirring, and after complete dissolution and stirring, 544 kg of factory water was pumped in and stirred until the entire solution was clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, the solution was discharged from the reactor and packaged. Throughout the preparation process, cooling water was circulated through the reactor to control the temperature of the reaction solution inside the reactor at 20℃~25℃.

[0029] Based on the total mass of the deoxygenating agent, weigh 2.224 g of annular protective liquid B and prepare a 5% mass concentration solution. Mix annular protective fluid B with an annular protective fluid A diluted with water to obtain a water-based controllable deoxygenation annular protective fluid.

[0030] Example 2 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: The following method was used to prepare 4000 kg of annular protective liquid A in a 5-ton reactor: Formula 1 for preparing 4000 kg of annular protective fluid A in a 5-ton reactor: At room temperature, first, pump 600 kg of the corrosion inhibitor 5-cyclohexyl-1,3,5-triazine into the reactor using a vacuum pump, then pump in 2099 kg of factory water and stir until homogeneous. While stirring, add 200 kg of sodium dehydroacetate solid as a bactericide, and after complete dissolution and stirring, pump in 40 kg of alkyl glycoside as a corrosion inhibitor. After stirring the above raw materials evenly, pump in 40 kg of polyepoxysuccinic acid (35% aqueous solution) as a scale inhibitor, and stir until homogeneous. Pump in 200 kg of ethanol as a pour point depressant, and stir until homogeneous. Pump in 200 kg of DBU as a pH adjuster, and stir until homogeneous. While stirring, add 96 kg of sodium isoascorbate as an oxygen scavenger, and after complete dissolution and stirring, pump in 525 kg of factory water and stir until the entire solution is clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, remove from the reactor and package. Throughout the preparation process, cooling water is circulated through the reactor to control the temperature of the reaction liquid inside the reactor at 20℃~25℃.

[0031] Based on the total mass of the deoxygenating agent, weigh 2.504 g of annular protective liquid B and prepare a 5% mass concentration solution. Mix annular protective fluid B with an annular protective fluid A diluted with water to obtain a water-based controllable deoxygenation annular protective fluid.

[0032] Example 3 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: The following method was used to prepare 4000 kg of annular protective liquid A in a 5-ton reactor: Formula 1 for preparing 4000 kg of annular protective fluid A in a 5-ton reactor: At room temperature, first, pump 300 kg of the corrosion inhibitor 5-cyclohexyl-1,3,5-triazine into the reactor using a vacuum pump, then pump in 1811 kg of factory water and stir until homogeneous. While stirring, add 400 kg of sodium dehydroacetate solid as a bactericide, and after complete dissolution and stirring, pump in 200 kg of alkyl glycoside as a corrosion inhibitor. After stirring the above raw materials evenly, pump in 400 kg of polyepoxysuccinic acid (35% aqueous solution) as a scale inhibitor and stir until homogeneous. Pump in 300 kg of ethanol as a pour point depressant and stir until homogeneous. Pump in 40 kg of DBU as a pH adjuster and stir until homogeneous. While stirring, add 96 kg of sodium isoascorbate as an oxygen scavenger, and after complete dissolution and stirring, pump in 453 kg of factory water and stir until the entire solution is clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, remove from the reactor and package. Throughout the preparation process, cooling water is circulated through the reactor to control the temperature of the reaction liquid inside the reactor at 20℃~25℃.

[0033] Based on the total mass of the deoxygenating agent, weigh 2.504 g of annular protective liquid B and prepare a 5% mass concentration solution. Mix annular protective fluid B with an annular protective fluid A diluted with water to obtain a water-based controllable deoxygenation annular protective fluid.

[0034] Example 4 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: Gas storage well annulus protection fluid usage per well: 15m³ 3 The density of the annular fluid injected into the well is 1.00 g / cm³. 3 The annular protective fluid A is formulated as in Example 1: the stock solution of annular protective fluid A has a mass concentration of 5%, and the amount of A is 750 kg. This is added to a container holding 14.5 m³ of... 3 In the on-site clean water mixing tank, stir well and set aside. The annular protection solution A contains 1% carbohydrazine as the oxygen scavenger, totaling 7.5 kg of oxygen scavenger (83.26 mol molar amount). The amount of copper sulfate pentahydrate catalyst is 0.0107% of the carbohydrazine amount (8.91 mmol molar amount), and the amount of copper sulfate pentahydrate is 2.224 g. Dissolve this in 50 mL of on-site clean water and set aside.

[0035] After transporting the on-site diluted solution of annular protective fluid A and the on-site diluted solution of annular protective fluid B to the well site of the fluid to be replaced, they were mixed evenly. The dissolved oxygen concentration was tested using a dissolved oxygen concentration tester, and the pH value was tested using precision pH test paper.

[0036] Using a pump truck, the annular protective fluid is used to replace the downhole fluid in the annulus at the gas storage wellhead and discharged into the wellhead tubing. Samples are taken to monitor the dissolved oxygen concentration and pH value of the initially replaced fluid. Once the color of the replaced fluid changes, samples are taken to monitor the dissolved oxygen concentration and pH value. Fluid replacement is continued, and monitoring is maintained until the color and pH value of the replaced fluid are visually consistent with the initial annular protective fluid. Pumping is then stopped, and fluid replacement is completed.

[0037] Example 5 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: Gas storage well annulus protection fluid usage per well: 15m³ 3 The density of the annular fluid injected into the well is 1.00 g / cm³. 3 The annular protective fluid A is formulated as in Example 2: the stock solution of annular protective fluid A has a concentration of 5% by mass, and the amount of A is 750 kg. This is added to a container holding 14.5 m³ of... 3 In the on-site clean water mixing tank, stir well and set aside. The annular protection solution A contains 2.4% sodium isoascorbate as an oxygen scavenger, totaling 18 kg of oxygen scavenger (83.26 mol molar amount). The catalyst, cobalt sulfate heptahydrate, is 0.0107% of the sodium isoascorbate amount (8.91 mmol molar amount), and the cobalt sulfate heptahydrate amount is 2.504 g. Dissolve this in 50 mL of on-site clean water and set aside.

[0038] After transporting the on-site diluted solution of annular protective fluid A and the on-site diluted solution of annular protective fluid B to the well site of the fluid to be replaced, they were mixed evenly. The dissolved oxygen concentration was tested using a dissolved oxygen concentration tester, and the pH value was tested using precision pH test paper.

[0039] Using a pump truck, the annular protective fluid is used to replace the downhole fluid in the annulus at the gas storage wellhead and discharged into the wellhead tubing. Samples are taken to monitor the dissolved oxygen concentration and pH value of the initially replaced fluid. Once the color of the replaced fluid changes, samples are taken to monitor the dissolved oxygen concentration and pH value. Fluid replacement is continued, and monitoring is maintained until the color and pH value of the replaced fluid are visually consistent with the initial annular protective fluid. Pumping is then stopped, and fluid replacement is completed.

[0040] Example 6 The preparation method of water-based controllable deoxygenation annular protective fluid is as follows: Gas storage well annulus protection fluid usage per well: 15m³ 3 The density of the annular fluid injected into the well is 1.00 g / cm³. 3 The annular protective fluid A is formulated as in Example 3: the stock solution of annular protective fluid A has a mass concentration of 5%, and the amount of A is 750 kg. This is added to a container holding 14.5 m³ of... 3In the on-site clean water mixing tank, stir well and set aside. The annular protection solution A contains 2.4% sodium isoascorbate as an oxygen scavenger, totaling 18 kg of oxygen scavenger (83.26 mol molar amount). The catalyst, cobalt sulfate heptahydrate, is 0.0107% of the sodium isoascorbate amount (8.91 mmol molar amount), and the cobalt sulfate heptahydrate amount is 2.504 g. Dissolve this in 50 mL of on-site clean water and set aside.

[0041] After transporting the on-site diluted solution of annular protective fluid A and the on-site diluted solution of annular protective fluid B to the well site of the fluid to be replaced, they were mixed evenly. The dissolved oxygen concentration was tested using a dissolved oxygen concentration tester, and the pH value was tested using precision pH test paper.

[0042] Using a pump truck, the annular protective fluid is used to replace the downhole fluid in the annulus at the gas storage wellhead and discharged into the wellhead tubing. Samples are taken to monitor the dissolved oxygen concentration and pH value of the initially replaced fluid. Once the color of the replaced fluid changes, samples are taken to monitor the dissolved oxygen concentration and pH value. Fluid replacement is continued, and monitoring is maintained until the color and pH value of the replaced fluid are visually consistent with the initial annular protective fluid. Pumping is then stopped, and fluid replacement is completed.

Claims

1. A water-based controllable deoxygenated gas storage annular protective fluid, characterized in that, Includes annular protective fluid A and annular protective fluid B; The annular protective fluid A, by mass percentage, comprises the following components: 1-15% corrosion inhibitor, 1-5% corrosion inhibitor additive, 1-10% bactericide, 1-10% scale inhibitor, 1-5% oxygen scavenger, 1-5% pH adjuster, 5-15% pour point depressant, and the remainder is water. The annular protective liquid B is an oxygen removal catalyst, and the molar amount of the annular protective liquid B is 0.00357%-0.0214% of the molar amount of the oxygen removal agent.

2. The annular protective fluid for a water-based controllable deoxygenated gas storage tank according to claim 1, characterized in that, The main component of the corrosion inhibitor is 5-cyclohexyl-1,3,5-triazine; the auxiliary component of the corrosion inhibitor is an alkyl glycoside; the bactericide is sodium dehydroacetate; the scale inhibitor is polyepoxysuccinic acid; the oxygen scavenger is any one of carbazide, acetone oxime, or sodium isoascorbate; the pH adjuster is 1,8-diazabicyclo[5.4.0]undec-7-ene; and the pour point depressant is ethanol or isopropanol.

3. The annular protective fluid for a water-based controllable deoxygenated gas storage tank according to claim 2, characterized in that, The scale inhibitor is a 10-35% (w / w) aqueous solution.

4. The annular protective fluid for a water-based controllable deoxygenated gas storage tank according to claim 1, characterized in that, The annular protective fluid B is a 1-5% (w / w) aqueous solution.

5. The annular protective fluid for a water-based controllable deoxygenated gas storage tank according to claim 1, characterized in that, The annular protective liquid B is copper sulfate pentahydrate or cobalt sulfate heptahydrate.

6. The method for preparing the annular protective fluid for a water-based controllable deoxygenated gas storage facility as described in any one of claims 1 to 5, characterized in that, The method is as follows: Step 1: Prepare annular protective fluid A: Weigh out 1-15% of the main corrosion inhibitor, 1-5% of the auxiliary corrosion inhibitor, 1-10% of the bactericide, 1-10% of the scale inhibitor, 1-5% of the oxygen remover, 1-5% of the pH adjuster, 5-15% of the pour point depressant, and the remainder is water. Mix all the substances and stir evenly to obtain annular protective fluid A. Step 2: Weigh out the amount of anion protection fluid B according to 0.00357%-0.0214% of the molar amount of oxygen scavenger in anion protection fluid A, and prepare a 1-5% mass concentration solution. Step 3: Dilute the annular protective fluid A to a mass concentration of 3-10%, then mix the annular protective fluid B with the diluted annular protective fluid A to obtain the annular protective fluid for water-based controllable deoxygenated gas storage.

7. The method for preparing the annular protective fluid for a water-based controllable deoxygenated gas storage facility according to claim 6, characterized in that, The specific method of step 1 is as follows: Under normal temperature conditions, 5-cyclohexyl-1,3,5-triazine is first pumped into the reactor, along with 80% of the water volume of the component, and stirred evenly; bactericide is added under stirring, and after being stirred until completely dissolved, corrosion inhibitor is pumped in, and after the above raw materials are stirred evenly, scale inhibitor is pumped in and stirred evenly; pour point depressant is pumped in and stirred evenly; pH ​​adjuster DBU is pumped in and stirred evenly; oxygen scavenger is added under stirring, and after being completely dissolved and stirred evenly, the remaining 20% ​​of the water volume of the component is pumped in and stirred evenly until the entire product liquid is clear and transparent, without insoluble suspended matter or stratification. After cooling to room temperature, it is discharged from the reactor and bottled. Throughout the entire preparation process, cooling water is circulated through the reactor to control the temperature of the reaction liquid inside the reactor at 20℃-25℃.

8. A method for replacing annular protective fluid in a gas storage well during completion, characterized in that, The specific method for using the annular protective fluid as described in claim 7 is as follows: Step 1: Prepare the amount of clean water at the oil and gas field site according to the amount of annular protection fluid required for a single well in the gas storage facility, add 3-10% of annular protection fluid A agent by mass, and stir evenly; Step 2: Calculate the amount of annular protective fluid B based on the total mass of the oxygen scavenger in annular protective fluid A. Prepare a 1-5% mass concentration solution with water and mix it evenly with the diluted annular protective fluid A before starting the circulation replacement. Step 3: Take the above mixed solution and test the dissolved oxygen concentration with a dissolved oxygen concentration tester, and test the pH value with precision pH test paper; Step 4: Use a pump truck to pump the annulus protection fluid from the gas storage wellhead annulus to replace the downhole fluid and discharge it into the wellhead tubing. Take samples to monitor the dissolved oxygen concentration and pH value of the initial displacement fluid. Step 5: When the color of the solution to be replaced changes, take a sample to monitor the dissolved oxygen concentration and pH. Continue replacing the solution and monitoring until the color of the replaced solution is visually consistent with the initial annular protective solution and the pH test value is consistent. Stop pumping to complete the solution replacement.

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