A kind of neutral chelating enzyme working well fluid and preparation method thereof

Abstract

This invention proposes a neutral chelating enzyme-based well workover fluid, comprising the following components by weight: 12-30 parts tetrasodium iminodisuccinate, 1-10 parts aminotrimethylphosphonic acid, 2-10 parts amylase, 0.5-5 parts protease, 5-15 parts alkyl glucosamide, 0.5-2 parts coconut oil diethanolamide, 0.5-8 parts trehalose, 1-5 parts chitosan, and 25-60 parts deionized water. This invention also proposes a method for preparing the well workover fluid. In summary, this invention is biodegradable, environmentally friendly, effectively removes inorganic and organic scale deposits and blockages, eliminates emulsion blockages, improves well permeability, and possesses excellent anti-swelling, chelating, and scale inhibition properties. It also relieves and prevents water-sensitive and salt-sensitive damage, and extends the effective service life.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield well repairing operation, in particular to a neutral chelating enzyme well repairing fluid and a preparation method thereof. Background Art

[0002] In order to solve the reservoir damage caused during oilfield operations and improve the production increase and production efficiency of oilfield operations, well-repair fluids are generally used for supporting treatment during operations. At present, there are many types of well-repair fluids in oilfields, such as clean salt water well-repair fluids, invisible acid, high-density well-killing fluids, etc., but there are still the following problems: clean salt water well-repair fluids have little reservoir damage, but the cleaning power is insufficient; invisible acid has the effect of improving permeability, but it is acidic in the formation environment and is easy to cause formation damage; high-density well-killing fluids generally add barium sulfate to increase density, which is easy to cause barium sulfate blockage, and ordinary acid cannot remove barium sulfate.

[0003] For some wells with obvious scaling, hydrochloric acid, earth acid, etc. are often used in the process of well repair. Excessive acidity will destroy the reservoir skeleton and cause sand production. Due to the influence of environmental protection, backflow, demulsification and gathering systems, the use of these strong acids will also be restricted. In addition, the damage of acid to the formation tubing cannot be ignored.

[0004] Patent No. CN 107699220 A discloses an offensive workover fluid system for offshore oilfield workover and its preparation method and application; Patent No. CN 104531105 B discloses a temporary plugging workover fluid for low-pressure sandstone reservoir gas wells and its preparation method; Patent No. CN 108641689 B discloses a liquid that can be simultaneously mixed with formation water and brine workover fluid and its preparation method. However, none of the above patent technologies involve the green environmental protection and efficiency-enhancing performance of the workover fluid. Summary of the invention

[0005] In view of this, the present invention proposes a neutral chelate enzyme workover fluid and a preparation method thereof, which can systematically solve the problems of scaling, wax deposition, corrosion, low production, etc. in oil, water and gas wells under the premise of safety and environmental protection, so as to achieve the purpose of improving workover efficiency, protecting oil reservoirs, increasing production and efficiency, and extending the effective period of operations.

[0006] The technical solution of the present invention is achieved in this way:

[0007] On the one hand, the present invention provides a neutral chelate enzyme workover fluid, which comprises the following components by weight: 12-30 parts of tetrasodium iminodisuccinate, 1-10 parts of aminotri(methylenephosphonic acid), 2-10 parts of amylase, 0.5-5 parts of protease, 5-15 parts of alkyl glucamide, 0.5-2 parts of coconut oil diethanolamide, 0.5-8 parts of trehalose, 1-5 parts of chitosan, and 25-60 parts of deionized water.

[0008] In the present invention, the volume concentration of tetrasodium iminodisuccinate is 98%, the volume concentration of aminotri(methylenephosphonic acid) is ≥50%, the effective substance content of amylase and protease is 99%, the volume concentration of alkylglucosamide is greater than 50%, the volume concentration of coconut oil diethanolamide is greater than 98%, and the purity of trehalose and chitosan is 99.9%. All of the above components can be purchased directly from the market, and the above concentrations, purities, and effective substance contents are all specifications of commercially available products.

[0009] Preferably, the above-mentioned well repair fluid comprises the following components by weight: 18 parts of tetrasodium iminodisuccinate, 5 parts of aminotri(methylenephosphonic acid), 6 parts of amylase, 3 parts of protease, 8 parts of alkyl glucosamide, 1.2 parts of coconut oil diethanolamide, 2.5 parts of trehalose, 2 parts of chitosan, and 36 parts of deionized water.

[0010] On the other hand, the present invention also provides a method for preparing the well servicing fluid used in the above-mentioned operation, comprising the following steps:

[0011] Step 1: grinding the mixture of trehalose and chitosan through a 210-mesh sieve, and vacuum drying to obtain a mixture 1;

[0012] Step 2: After heating deionized water, add mixture 1 and stir evenly to obtain mixture 2;

[0013] Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to the mixture 2, mix well, then add amylase and protease, and continue mixing to obtain a mixture 3;

[0014] Step 4: adding aminotri (methylenephosphonic acid) and coconut oil diethanolamide to the mixture 3 in sequence, mixing well and then subjecting to ultrasonic treatment to obtain a neutral chelate enzyme operation workover fluid.

[0015] In the above step 1, the mixture of trehalose and chitosan is ground for 5-10 minutes using a solid grinder, passed through a 210-mesh sieve, and vacuum dried at 40-50° C. for 4.5-5.5 hours to obtain a mixture 1, which is placed in a desiccator for later use.

[0016] In the above step 2, deionized water is added to the reaction device, the temperature is raised to 90-98° C., mixture 1 is added to the solid feed port, and a stirrer is used to stir at a speed of 45-55 r / min for 16-24 minutes to obtain mixture 2.

[0017] In the above step three, add alkyl glucamide and tetrasodium iminodisuccinate to mixture two, continue stirring for 26-35 minutes, cool to 28-36°C, add amylase and protease, continue stirring for 25-35 minutes, and stop heating after all solid materials are dissolved to obtain mixture three.

[0018] In the above step 4, aminotri(methylenephosphonic acid) and coconut oil diethanolamide are added to the mixture 3 in sequence through the liquid feed port, the stirrer speed is adjusted to 40-45 r / min, stirred for 0.8-1.3 h, all the raw materials are mixed evenly, and stirring is stopped to obtain a mixture 4. The conditions for ultrasonic treatment are: frequency 15-25 kHz, ultrasonic treatment 12-18 min.

[0019] Preferably, in the present invention, the agitator is a three-pitch blade paddle agitator.

[0020] The working principle of the present invention is:

[0021] In the work well fluid of the present invention, tetrasodium iminodisuccinate and aminotri(methylenephosphonic acid) are first used as chelating agents to prevent scaling of system equipment and pipelines; after the system equipment and pipelines are treated and protected, the liquid in the pipelines needs to be further treated, so the present invention adds amylase and protease to the work well fluid to treat gel in water and polymers, debris, mudstone and the like in the oil reservoir; further, after the system equipment, pipelines and the liquid in the pipelines are treated, the present invention also treats the oil pollution on the interface between the two phases by alkyl glucosamide to eliminate organic pollutants in the reservoir; although alkyl glucosamide can treat the oil pollution on the interface between the two phases, it will inevitably affect the metal. The present invention has the anti-corrosion performance of the surface. Therefore, in order to protect the metal surface, the present invention further adds coconut oil diethanolamide, which is adsorbed on the metal surface to form an adsorptive protective film to prevent the metal from being corroded by water and oxygen; further, chitosan is used to prevent clay expansion; further, the above-mentioned multiple raw materials are combined together to jointly treat the pipeline, the liquid in the pipeline, and the oil pollution on the two-phase interface to achieve the purpose of improving the operation well repair efficiency and protecting the oil reservoir. However, after the multiple raw materials are combined together, the stability needs to be adjusted to achieve the maximum effect or the maximum adaptability of the operation well repair fluid. Therefore, the present invention adds trehalose to stabilize the formula system and ensure that the formula system can adapt to extreme environments such as high temperature, high salt, acid and alkali.

[0022] The neutral chelate enzyme workover fluid of the present invention has the following beneficial effects compared with the prior art:

[0023] 1. Safety and environmental protection

[0024] Safe ingredients: biodegradable, free of Cl, F, S, P, Si, harmless to workers, equipment, natural environment, and strata, meeting green environmental protection requirements;

[0025] Ultra-low corrosion: pH is neutral, neither acidic nor alkaline, protecting the pipeline from corrosion damage;

[0026] Self-demulsification: It can directly enter the process without affecting the demulsification and gathering and transportation system. After demulsification, the oil-water separation interface is clear. Figure 1 .

[0027] 2. Increase production and efficiency

[0028] Increase production: effectively remove the deposition blockage of inorganic and organic scale, eliminate emulsification blockage; replace micropore throat crude oil, release water lock; eliminate water lock blockage in micropore throat dense rock core, and improve well permeability.

[0029] Efficiency enhancement: Rapid flowback shortens the operation recovery cycle; effectively protects pipelines from corrosion and scale, avoids rust and scale blocking the oil reservoir, and extends the well repair and production increase period.

[0030] 3. Reservoir protection

[0031] Eliminate the "five sensitivities" damage (acid sensitivity, alkali sensitivity, salt sensitivity, water sensitivity, speed sensitivity), operate in a neutral environment throughout the process, react gently, will not over-stimulate the reservoir, over-unblock, cause sand production and particle migration in the reservoir. It has good anti-swelling, chelating and scale inhibition properties, eliminates and avoids water sensitivity and salt sensitivity damage, and extends the effective period of operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a demulsification diagram of the working well fluid of the neutral chelate enzyme of the present invention;

[0034] Figure 2 This is a picture of a N80 steel sheet placed in the well-repair fluid for neutral chelating enzyme of the present invention after 24 hours;

[0035] Figure 3 This is a picture taken 24 hours after placing an N80 steel sheet in the well repair fluid in Comparative Example 14. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] A neutral chelate enzyme workover fluid comprises the following components by weight: 12 parts of tetrasodium iminodisuccinate, 1 part of aminotri(methylenephosphonic acid), 2 parts of amylase, 0.5 parts of protease, 5 parts of alkylglucamide, 0.5 parts of coconut oil diethanolamide, 0.5 parts of trehalose, 0.1 parts of chitosan and 25 parts of deionized water.

[0039] The preparation method of the workover fluid comprises the following steps:

[0040] Step 1: Grind the mixture of trehalose and chitosan using a solid grinder for 5 minutes, pass it through a 210-mesh sieve, and vacuum dry it at 40° C. for 4.5 hours to obtain a mixture 1, which is placed in a desiccator for later use.

[0041] Step 2: Add deionized water to the reaction device, heat it to 90° C., add mixture 1 to the solid feeding port, use a three-paddle stirrer to stir at a speed of 45 r / min for 16 minutes to obtain mixture 2.

[0042] Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to mixture 2, continue stirring for 26 minutes, cool to 28°C, add amylase and protease, continue stirring for 25 minutes, and stop heating after all solid materials are dissolved to obtain mixture 3.

[0043] Step 4: Add aminotri(methylenephosphonic acid) and coconut oil diethanolamide to mixture 3 in sequence through the liquid feeding port, adjust the speed of the three-paddle stirrer to 40 r / min, stir for 0.8 h to mix all the raw materials evenly, stop stirring, and obtain mixture 4.

[0044] Step 5: subjecting the mixture 4 to ultrasonic treatment at a frequency of 15 kHz for 12 minutes to obtain a neutral chelate enzyme workover fluid.

[0045] Example 2

[0046] A neutral chelate enzyme workover fluid comprises the following components by weight: 30 parts of tetrasodium iminodisuccinate, 10 parts of aminotri(methylenephosphonic acid), 10 parts of amylase, 5 parts of protease, 15 parts of alkylglucamide, 2 parts of coconut oil diethanolamide, 8 parts of trehalose, 5 parts of chitosan and 60 parts of deionized water.

[0047] The preparation method of the workover fluid comprises the following steps:

[0048] Step 1: Grind the mixture of trehalose and chitosan using a solid grinder for 10 minutes, pass it through a 210-mesh sieve, and vacuum dry it at 50° C. for 5.5 hours to obtain a mixture 1, which is placed in a desiccator for later use.

[0049] Step 2: Add deionized water to the reaction device, heat it to 98° C., add mixture 1 to the solid feed port, and stir for 24 minutes at a speed of 55 r / min using a three-paddle stirrer to obtain mixture 2.

[0050] Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to mixture 2, continue stirring for 35 minutes, cool to 36° C., add amylase and protease, continue stirring for 35 minutes, and stop heating after all solid materials are dissolved to obtain mixture 3.

[0051] Step 4: Add aminotri(methylenephosphonic acid) and coconut oil diethanolamide to mixture 3 in sequence through the liquid feeding port, adjust the speed of the three-paddle stirrer to 45 r / min, stir for 1.3 h to mix all the raw materials evenly, stop stirring, and obtain mixture 4.

[0052] Step 5: subjecting the mixture 4 to ultrasonic treatment at a frequency of 25 kHz for 18 minutes to obtain a neutral chelate enzyme workover fluid.

[0053] Example 3

[0054] A neutral chelate enzyme workover fluid comprises the following components by weight: 18 parts of tetrasodium iminodisuccinate, 5 parts of aminotri(methylenephosphonic acid), 6 parts of amylase, 3 parts of protease, 8 parts of alkylglucosamide, 1.2 parts of coconut oil diethanolamide, 2.5 parts of trehalose, 2 parts of chitosan and 36 parts of deionized water.

[0055] The preparation method of the workover fluid comprises the following steps:

[0056] Step 1: Grind the mixture of trehalose and chitosan using a solid grinder for 7 minutes, pass it through a 210-mesh sieve, and vacuum dry it at 42° C. for 4.9 hours to obtain a mixture 1, which is placed in a desiccator for later use.

[0057] Step 2: Add deionized water to the reaction device, heat it to 92° C., add mixture 1 to the solid feed port, and stir for 18 minutes at a speed of 50 r / min using a three-paddle stirrer to obtain mixture 2.

[0058] Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to mixture 2, continue stirring for 30 minutes, cool to 31° C., add amylase and protease, continue stirring for 28 minutes, and stop heating after all solid materials are dissolved to obtain mixture 3.

[0059] Step 4: Add aminotri(methylenephosphonic acid) and coconut oil diethanolamide to mixture 3 in sequence through the liquid feeding port, adjust the speed of the three-paddle stirrer to 42 r / min, stir for 1 hour to mix all the raw materials evenly, stop stirring, and obtain mixture 4.

[0060] Step 5: subjecting the mixture 4 to ultrasonic treatment at a frequency of 20 kHz for 14 minutes to obtain a neutral chelate enzyme workover fluid.

[0061] Example 4

[0062] A neutral chelate enzyme workover fluid comprises the following components by weight: 26 parts of tetrasodium iminodisuccinate, 7 parts of aminotri(methylenephosphonic acid), 8 parts of amylase, 3.5 parts of protease, 11 parts of alkylglucamide, 1.6 parts of coconut oil diethanolamide, 6 parts of trehalose, 4 parts of chitosan and 52 parts of deionized water.

[0063] The preparation method of the workover fluid comprises the following steps:

[0064] Step 1: Grind the mixture of trehalose and chitosan using a solid grinder for 8 minutes, pass it through a 210-mesh sieve, and vacuum dry it at 44° C. for 5.2 hours to obtain a mixture 1, which is placed in a desiccator for later use.

[0065] Step 2: Add deionized water to the reaction device, heat it to 96° C., add mixture 1 to the solid feed port, and stir for 21 minutes using a three-paddle stirrer at a speed of 52 r / min to obtain mixture 2.

[0066] Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to mixture 2, continue stirring for 32 minutes, cool to 33° C., add amylase and protease, continue stirring for 32 minutes, and stop heating after all solid materials are dissolved to obtain mixture 3.

[0067] Step 4: Add aminotri(methylenephosphonic acid) and coconut oil diethanolamide to mixture 3 in sequence through the liquid feeding port, adjust the speed of the three-paddle stirrer to 42 r / min, stir for 1.1 h to mix all the raw materials evenly, stop stirring, and obtain mixture 4.

[0068] Step 5: subjecting the mixture 4 to ultrasonic treatment at a frequency of 23 kHz for 17 minutes to obtain a neutral chelate enzyme workover fluid.

[0069] Comparative Example 1

[0070] On the basis of Example 3, tetrasodium iminodisuccinate and aminotri(methylenephosphonic acid) in the workover fluid were deleted, and other conditions were the same.

[0071] Comparative Example 2

[0072] On the basis of Example 3, tetrasodium iminodisuccinate in the workover fluid was deleted, and other conditions were the same.

[0073] Comparative Example 3

[0074] On the basis of Example 3, aminotri(methylenephosphonic acid) was deleted from the workover fluid, and other conditions were the same.

[0075] Comparative Example 4

[0076] On the basis of Example 3, the chelating agent disodium EDTA was used to replace tetrasodium iminodisuccinate and aminotri(methylenephosphonic acid) in the workover fluid, and the amount of disodium EDTA was 23 parts (the total amount of tetrasodium iminodisuccinate and aminotri(methylenephosphonic acid), and other conditions were the same.

[0077] Comparative Example 5

[0078] On the basis of Example 3, the amylase and protease in the workover fluid were deleted, and other conditions were the same.

[0079] Comparative Example 6

[0080] On the basis of Example 3, the amylase in the workover fluid was deleted, and other conditions were the same.

[0081] Comparative Example 7

[0082] On the basis of Example 3, the protease in the workover fluid was deleted, and other conditions were the same.

[0083] Comparative Example 8

[0084] On the basis of Example 3, the alkyl glucosamide in the workover fluid was deleted, and other conditions were the same.

[0085] Comparative Example 9

[0086] On the basis of Example 3, an equal amount of alkyl glycoside was used to replace the alkyl glucosamide in the workover fluid, and other conditions were the same.

[0087] Comparative Example 10

[0088] On the basis of Example 3, coconut oleic acid diethanolamide in the workover fluid was deleted, and other conditions were the same.

[0089] Comparative Example 11

[0090] On the basis of Example 3, an equal amount of sodium alkylbenzene sulfonate was used to replace the coconut oil diethanolamide in the workover fluid, and other conditions were the same.

[0091] Comparative Example 12

[0092] On the basis of Example 3, chitosan in the workover fluid was deleted, and other conditions were the same.

[0093] Comparative Example 13

[0094] The preparation method of the workover fluid comprises the following steps:

[0095] Step 1 is the same as step 2;

[0096] Step 3: Add alkyl glucamide, tetrasodium iminodisuccinate, amylase and protease to mixture 2 in sequence, continue to add aminotri(methylenephosphonic acid) and coconut oil diethanolamide, continue stirring for 120 minutes at a speed of 42 r / min, cool to 31° C., and then perform ultrasonic treatment at a frequency of 20 kHz for 14 minutes to obtain a neutral chelating enzyme operation workover fluid.

[0097] Other conditions are the same.

[0098] Comparative Example 14

[0099] A conventional well repairing fluid is selected, which consists of a clay stabilizer, a high-valent metal ion chelating agent, a corrosion inhibitor and a bactericide and an aqueous solution, wherein the clay stabilizer is potassium chloride with a mass fraction of 2% to 2.5%; the high-valent metal ion chelating agent is a mixture of disodium ethylenediaminetetraacetic acid, hydrofluoric acid and benzoic anhydride with a mass fraction of 0.3% to 1.5%; the mass fraction of the corrosion inhibitor and bactericide is 0.8% to 1.5%; and the rest is an aqueous solution.

[0100] Comparative Example 15

[0101] On the basis of Example 3, trehalose in the workover fluid was deleted, and other conditions were the same.

[0102] The performance of the workover fluids prepared in the above embodiments and comparative examples was measured, and the measured indicators included pH value, surface tension, anti-swelling rate, corrosion rate, dissolution rate, enzyme catalytic degradation rate, oil washing rate, natural sedimentation dehydration rate and permeability recovery value. The standards of the above indicators are shown in Table 1.

[0103] Table 1 Performance standards of various indicators

[0104]

[0105] The evaluation methods of the above indicators are: (the volume concentration of the sample solution is 60%, the volume concentration of the sample stock solution is 100%)

[0106] 1. pH value: Take the sample solution and measure it with a wide range pH test paper.

[0107] 2. Surface interfacial tension: Take the sample solution and measure it using a fully automatic surface interfacial tension meter.

[0108] 3. Anti-swelling rate: Use centrifugation to determine the anti-swelling volume of the sample and calculate the anti-swelling rate based on the formula.

[0109]

[0110] 4. Corrosion rate: Take 200g of sample solution and soak it in standard N80 steel sheet (the material of N80 steel sheet is the same as that of downhole pipe string), place it in 90℃ water bath, and react for 24h. Calculate the corrosion rate based on the mass of N80 steel sheet before and after the reaction. Figure 2 .

[0111]

[0112] 5. Dissolution rate: Take the sample solution and add solid calcium carbonate and calcium sulfate reagent (the mass ratio of sample solution to reagent is 100:2), place it in a 90℃ water bath, and react for 24 hours. Calculate the dissolution rate based on the mass of calcium carbonate and calcium sulfate reagents before and after the reaction.

[0113]

[0114] 6. Enzyme catalytic degradation rate: Prepare 0.35% guar gum base liquid, add cross-linking agent to form a hanging gel. Use a six-speed viscometer at 170s -1 The initial viscosity of the gel is measured as μ 1 Take 100 mL of frozen gel, add the sample stock solution, place it in a constant temperature 50℃ water bath for 2 hours, and measure the colloid viscosity as μ 2 The enzyme-catalyzed degradation rate was calculated based on the change in colloid viscosity.

[0115]

[0116] 7. Oil washing rate: Use artificial oil (83% crude oil, 12% oil asphalt, 5% paraffin) and quartz sand in a ratio of 1.5:1 to make oil sand. Take 3.0g of newly prepared oil sand in a 50mL colorimetric tube, add 10mL of sample solution, place in a 60℃ constant temperature water bath, take out every 0.5h and shake vigorously 10 times, place for a total of 1h before taking out. Use cotton to wipe off the oil floating on the liquid surface and the tube wall, carefully pour off the washing liquid, use a measuring cylinder to measure 20mL of distilled water at 20℃ and pour it into the colorimetric tube, mix it with the remaining sample, use cotton to wipe off the oil on the liquid surface and the tube wall, carefully pour off the washing liquid, and repeat the above steps until the washing liquid is transparent. Add an appropriate amount of petroleum ether with a boiling range of (60-90)℃ to the colorimetric tube, shake it thoroughly, and dilute to the scale. Take petroleum ether as blank sample, test absorbance on spectrophotometer, and calculate oil washing rate according to residual oil amount.

[0117]

[0118] 8. Natural sedimentation dehydration rate: Add 50 ml of sample solution to a conical flask, then add 50 ml of crude oil, stir the solution at 1500 rpm for 10 min to obtain an oil emulsion, pour it into a stoppered measuring cylinder and let it stand for 2 h. Calculate the natural sedimentation dehydration rate based on the volume of water at the bottom of the measuring cylinder.

[0119]

[0120] 9. Permeability recovery value: Take a core with a diameter of 2.5 cm and a length of 3.0 cm. First, pass salt water in a forward direction at 70°C to measure the permeability K 1 ; Then pass 2pv crude oil to form a blockage; pass 6pv of sample solution of specified concentration in the reverse direction and soak for 24h (70℃ environment); pass salt water in the forward direction and measure the permeability K of the salt water after unblocking 2 . Calculate the permeability recovery value.

[0121]

[0122] Table 2 Results of pH value, surface tension, anti-swelling rate and corrosion rate

[0123]

[0124]

[0125] Table 3 Determination results of dissolution rate, enzyme catalytic degradation rate, oil washing rate, natural sedimentation dehydration rate and permeability recovery value

[0126]

[0127]

[0128] The data in Table 2 and Table 3 are as follows:

[0129] Tetrasodium iminodisuccinate is an environmentally friendly chelating agent that is green and biodegradable. It can effectively prevent metal ions such as calcium and magnesium from forming precipitates in chemical reactions, thereby preventing scaling of system equipment and pipelines, and can gradually remove the original scaling. It has a certain ability to disperse scale and can improve the dispersibility of scale.

[0130] Aminotrimethylphosphonic acid has good chelation, low limit inhibition and lattice distortion effects. It can prevent scale-forming salts in water from forming scale, especially calcium carbonate scale. It also has good corrosion inhibition effect, which can reduce corrosion and scaling of metal equipment or pipelines.

[0131] Compared with Comparative Examples 1-4, Example 3 uses tetrasodium iminodisuccinate and aminotri(methylenephosphonic acid) as chelating agents, which have good solubility and do not produce secondary precipitation. Ordinary chelating agents, such as disodium EDTA and tetrasodium EDTA, have poor solubility. Although they can reduce precipitation and scale formation in equipment and pipelines, the chelating agent itself will produce secondary precipitation during the reaction process.

[0132] Amylase can reduce the gel concentration and polymerization in the injected water, increase the permeability of the water phase, and promote the development of carbonate oil and gas reservoirs.

[0133] Proteases can degrade sediment waste such as polymers, debris, mudstone, etc. in oil reservoirs, expand oil layer permeability, improve oil layer reservoir quality, and increase oil and gas production.

[0134] Compared with Comparative Examples 5-7, Example 3 shows that amylase and protease have greater effects on oil washing rate, permeability and enzyme-catalyzed degradation rate.

[0135] Alkyl glucosamide is green and non-toxic, easily biodegradable, can be directionally adsorbed on the interface between two phases, reduce the surface tension, has a good wetting and cleaning effect on oil stains, can also eliminate organic pollutants in the reservoir and promote biodegradation.

[0136] Comparing Example 3 with Comparative Examples 8-9, it can be seen that the alkyl-free glucamide has a greater impact on the surface tension, interfacial tension, and natural sedimentation dehydration rate.

[0137] Coconut oil diethanolamide has a good anti-corrosion effect. The polar groups in its molecules can be tightly adsorbed on the metal surface by relying on the charge effect to form an adsorptive protective film, which protects the metal from corrosion by water and oxygen. When used in combination with alkyl glucamide, it can effectively improve the cleaning power.

[0138] Comparing Example 3 with Comparative Examples 10-11, it can be seen that coconut oil diethanolamide affects the corrosion rate.

[0139] Chitosan is a natural product with good stability and viscosity properties, which can effectively prevent clay swelling.

[0140] Trehalose is non-reducing, stable, and anti-freezing. It has a protective effect on biological macromolecules and has very good stability to heat and acid and alkali. It can stabilize the formula system and ensure that the system formula can adapt to extreme environments such as high temperature, high salt, acid and alkali.

[0141] By comparing Example 3 with Comparative Example 13, it can be seen that in the present invention, alkyl glucamide and tetrasodium iminodisuccinate; amylase and protease; aminotri(methylenephosphonic acid) and coconut oil diethanolamide; the three components are added three times, which can improve the mixing uniformity of the components, improve the final indicators of the workover fluid, and avoid precipitation, flocculation or stratification due to uneven mixing during the preparation of the workover fluid, which affects the indicators of the workover fluid.

[0142] It can be seen from Comparative Example 14 that the well working fluid of the present invention is superior to the well working fluid in the prior art in all indicators.

[0143] In addition, through Figure 2 and Figure 3 It can be seen that after placing N80 steel sheet in the working well fluid of the neutral chelate enzyme of the present invention, the surface is bright as new after 24 hours; in Comparative Example 14, after placing N80 steel sheet in the common working well fluid of the prior art for 24 hours, rust is attached to the surface.

[0144] The performance of the workover fluids prepared in Example 3 and Comparative Example 15 were tested at 0°C, 40°C, 60°C, 80°C, 100°C, 120°C, 150°C and 160°C, respectively. The test results are shown in Tables 4 and 5.

[0145] Table 4 Results of pH value, surface tension, anti-swelling rate and corrosion rate

[0146]

[0147]

[0148] Table 5 Determination results of dissolution rate, enzyme catalytic degradation rate, oil washing rate, natural sedimentation dehydration rate and permeability recovery value

[0149]

[0150]

[0151]

[0152] The data in Table 4 and Table 5 are as follows:

[0153] The working well fluid in Example 3 still meets the standard in all indicators at 150°C, and is lower than the standard requirements at 160°C, indicating that it can be adapted to a well depth greater than 5,000 meters. The working well fluid in Comparative Example 15 has all indicators lower than the standard requirements at 80°C, indicating that it can only be adapted to a well depth of less than 2,000 meters. Therefore, the addition of trehalose has a great influence on the stability of the working well fluid.

[0154] It can be seen from the above data that the workover fluid of the present invention is neutral, non-acidic and non-alkaline, and can protect pipelines from corrosion damage; and the workover fluid is composed of a special formula of tetrasodium iminodisuccinate, aminotri(methylenephosphonic acid), amylase, protease, alkylglucamide, coconut oil diethanolamide, chitosan and deionized water, which work together to exert a synergistic effect, so that the workover fluid has good surface tension, anti-swelling rate, corrosion rate, dissolution rate, enzyme-catalyzed degradation rate, oil washing rate, natural sedimentation dehydration rate and permeability recovery value; at the same time, through the effect of trehalose, the workover fluid has high stability and a wide temperature range.

[0155] The present invention can be applied to the operation of well cleaning, well completion and production, and daily unblocking of production wells (oil, gas, water), and can stably protect oil reservoirs and equipment, and is compatible with various well fluids. In a neutral environment, it can safely and effectively remove inorganic scale and organic scale in the wellbore and near-well area to improve permeability, improve well repair efficiency and oil and gas well production.

[0156] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A neutral chelating enzyme workover fluid, characterized in that: The invention comprises the following components by weight: 12-30 parts of tetrasodium iminodisuccinate, 1-10 parts of aminotri(methylenephosphonic acid), 2-10 parts of amylase, 0.5-5 parts of protease, 5-15 parts of alkylglucamide, 0.5-2 parts of coconut oil diethanolamide, 0.5-8 parts of trehalose, 1-5 parts of chitosan and 25-60 parts of deionized water.

2. The neutral chelate enzyme workover fluid according to claim 1, characterized in that: The composition comprises the following components by weight: 18 parts of tetrasodium iminodisuccinate, 5 parts of aminotri(methylenephosphonic acid), 6 parts of amylase, 3 parts of protease, 8 parts of alkylglucosamide, 1.2 parts of coconut oil diethanolamide, 2.5 parts of trehalose, 2 parts of chitosan and 36 parts of deionized water.

3. The neutral chelate enzyme workover fluid according to claim 1, characterized in that: The volume concentration of tetrasodium iminodisuccinate is 98%, the volume concentration of aminotri(methylenephosphonic acid) is ≥50%, the effective substance content of amylase and protease is 99%, the volume concentration of alkylglucosamide is greater than 50%, the volume concentration of coconut oil diethanolamide is greater than 98%, and the purity of trehalose and chitosan is 99.9%.

4. The method for preparing a workover fluid according to claim 1, wherein: The steps include: Step 1: grinding the mixture of trehalose and chitosan through a 210-mesh sieve, and vacuum drying to obtain a mixture 1; Step 2: After heating deionized water, add mixture 1 and stir evenly to obtain mixture 2; Step 3: Add alkyl glucamide and tetrasodium iminodisuccinate to the mixture 2, mix well, then add amylase and protease, and continue mixing to obtain a mixture 3; Step 4: adding aminotri (methylenephosphonic acid) and coconut oil diethanolamide to the mixture 3 in sequence, mixing well and then subjecting to ultrasonic treatment to obtain a neutral chelate enzyme operation workover fluid.

5. The method for preparing a workover fluid according to claim 4, characterized in that: In the step 1, the mixture of trehalose and chitosan is ground for 5-10 minutes using a solid grinder, and then vacuum dried at 40-50° C. for 4.5-5.5 hours to obtain a mixture 1.

6. The method for preparing a well working fluid according to claim 4, characterized in that: In the step 2, deionized water is added to the reaction device, the temperature is raised to 90-98° C., mixture 1 is added to the solid feed port, and the mixture is stirred at a rotation speed of 45-55 r / min for 16-24 min to obtain mixture 2.

7. The method for preparing a well working fluid according to claim 4, characterized in that: In the step three, alkyl glucamide and tetrasodium iminodisuccinate are added to the mixture two, stirred for 26-35 minutes, cooled to 28-36° C., amylase and protease are added, and stirring is continued for 25-35 minutes to obtain a mixture three.

8. The method for preparing a well working fluid according to claim 4, characterized in that: In the step 4, the mixing conditions are: rotation speed 40-45 r / min, stirring 0.8-1.3 h; the ultrasonic treatment conditions are: frequency 15-25 kHz, ultrasonic treatment 12-18 min.

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