Descaling composition, descaling agent, preparation method and use

Abstract

A descaling composition, comprising: a polyamino polyacid chelating agent, a synergist, a chelating catalyst, a chelating stabilizer, a permeation dispersing agent, a pH regulator and a solvent, wherein the pH value of the descaling composition is 7-8; and the polyamino polyacid chelating agent has a structure as represented by formula I: in formula I, R1 is a dialkyl amino, an alkyl amino, an amino, a hydroxyl, an alkoxy, an amido, an acyloxy, a carboxyl methyl or a carboxyl. The polyamino polyacid chelating agent used in the descaling composition contains a plurality of aminos, carboxyls and hydroxyls, and an electron-donating group R1, such that the descaling composition is more easily combined with a metal ion to form a stable chelate, and the temperature resistance of the descaling composition is enhanced; in addition, a neutral descaling agent prepared from the descaling composition has the characteristics of a good scale dissolving effect, low corrosivity, good temperature resistance, etc., and can effectively solve the problem of blockage of inorganic indissolvable scale of a high-temperature and high-pressure gas well.

Description

Descaling composition, descaling agent, preparation method and application thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202311508728.0 filed on November 13, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of oil and gas production engineering, and in particular to a descaling composition, a descaling agent, a preparation method and an application thereof. Background Art

[0004] Inorganic scale clogging of gas wells is a common problem. It has been reported in gas fields such as Saudi Arabia's Khuff, Argentina's Centenario, and Norway's Vega, as well as in domestic fields like Keshen, Dina, Anyue, Yuanba, Daniudi, and Yulin. This problem severely impacts gas field productivity and wellbore integrity. According to statistics, since 2017, 56% of gas wells in the Keshen and Dina fields have experienced scale clogging, impacting production by over 40 million cubic meters per day. In the Gaomotai margin zone of Anyue gas field, 48% of gas wells have experienced scale clogging, impacting production by 4.48 million cubic meters per day. In the Yuanba gas field, scale clogging has occurred in 8 wells / 18 well-times, accounting for 22%, with one well completely blocked. In the Daniudi gas field, 42% of gas wells have experienced scale clogging. At the same time, the higher the reservoir temperature, the greater the concentration of scaling ions in the formation water and the greater the scaling tendency. Ultra-deep gas wells generally have higher formation temperatures and scaling ion concentrations. The scaling problem in ultra-deep gas fields such as Keshen and Dina in the Tarim Basin and Yuanba and Puguang in the Sichuan Basin is relatively more serious.

[0005] Compared with physical unblocking technologies such as continuous tubing dredging and water jetting, chemical descaling and unblocking has the advantages of short operation time and unblocking near-well reservoirs. It has become the most commonly used means of descaling and unblocking gas wells, among which the unblocking fluid system is the key to the technology. Traditionally, acidic descaling and unblocking is mostly used, which has the advantage of high scale dissolution rate. However, it has poor solubility for scales such as calcium sulfate, barium sulfate, and strontium sulfate. At the same time, acidic fluids are prone to corrode metal pipelines, affecting the safe and normal operation of oil and gas field production pipelines and the normal operation of oil and gas wells. Non-acidic unblocking fluids are based on the principle of chelation descaling, which uses the coordination groups in the chelating agent molecules and the scale Ca 2+ 、Ba 2+ The formation of coordination bonds between cations and scale blocks "converts" the scale into more stable, water-soluble complexes. Chelation descaling offers the advantages of extremely low corrosion and a wide range of scale removal options, making it an ideal alternative to acid. However, non-acidic plugging removal fluids also have drawbacks, such as low scale dissolution rates. Furthermore, most commercially available non-acidic plugging removal fluids have high pH values, which can accelerate scaling in highly salinized water near the pay zone, compromising their effectiveness.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the problem of scale blockage in high-temperature oil and gas wells in the prior art and to provide a descaling composition, a descaling agent, a preparation method and an application thereof. The descaling agent is a neutral descaling agent that has the characteristics of high temperature resistance, strong scale dissolving performance and low corrosiveness and can be used for descaling high-temperature oil and gas wells.

[0008] In order to achieve the above object, the first aspect of the present invention provides a descaling composition, which comprises: a polyamino acid chelating agent, a synergist, a chelating catalyst, a chelating stabilizer, a penetrating dispersant, a pH regulator and a solvent; wherein the pH value of the descaling composition is 7 to 8; the polyamino acid chelating agent has a structure shown in Formula I:

[0009] In formula I, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

[0010] A second aspect of the present invention provides a method for preparing a descaling agent, the preparation method comprising:

[0011] Under stirring conditions, the polyamino acid chelating agent, the synergist, the chelating catalyst and the chelating stabilizer are first mixed with water to obtain a first mixture;

[0012] Adding a pH regulator to the first mixture to control the pH value to 7 to 8 at 50 to 70° C., then adding a penetrating dispersant and performing a second mixing to obtain a neutral descaling agent;

[0013] The pH value of the descaling composition is 7 to 8; the polyamino acid chelating agent has a structure shown in Formula I:

[0014] In formula I, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

[0015] The third aspect of the present invention provides a descaling agent prepared by the preparation method described in the second aspect.

[0016] The fourth aspect of the present invention provides use of the descaling composition described in the first aspect or the descaling agent described in the third aspect in oil and gas wells.

[0017] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0018] 1) The polyamino-polyacid chelating agent used in the descaling composition of the present invention contains multiple amino groups, carboxyl groups, hydroxyl groups and electron-donating groups R1, which give it a strong electron-donating ability. The carbon chain is extended by grafting modification of the carboxyl groups, thereby improving the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhancing its temperature resistance. The descaling agent prepared from the descaling composition of the present invention is a neutral descaling agent with low corrosiveness.

[0019] 2) The scale remover of the present invention has the characteristics of good scale dissolving effect (large scale dissolving rate for calcium carbonate, calcium sulfate and barium sulfate), low corrosiveness, excellent temperature resistance, wide application range, non-toxicity and environmental protection, etc., and has good compatibility with formation water, will not cause damage to the formation and pipelines, and can effectively solve the blockage problem of inorganic insoluble scale in high-temperature and high-pressure gas wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is an infrared spectrum of the composite solid electrolyte prepared in Preparation Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] The first aspect of the present invention provides a descaling composition, comprising: a polyamino acid chelating agent, a synergist, a chelating catalyst, a chelating stabilizer, a penetrating dispersant, a pH regulator, and a solvent; wherein the pH value of the descaling composition is 7 to 8; and the polyamino acid chelating agent has a structure shown in Formula I:

[0023] In formula I, R1 is a dialkylamino group (-NR2), an alkylamino group (-NHR), an amino group (-NH2), a hydroxyl group (-OH), an alkoxy group (-OR), an amide group (-NHCOR), an acyloxy group (-OCOR), a carboxymethyl group (-CH2COOH) or a carboxyl group (-COOH).

[0024] In the present invention, R is preferably selected from C1-C 10 A straight chain or branched chain alkyl group.

[0025] In the present invention, the polyamino-polyacid chelating agent contains multiple amino groups, carboxyl groups, hydroxyl groups and electron-donating groups R1, which give it a strong electron-donating ability. The carbon chain is extended by grafting modification of the carboxyl groups, thereby improving the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhancing its temperature resistance.

[0026] The descaling composition of the present invention achieves efficient descaling of high-temperature (120-180° C.) oil and gas wells through the synergistic effect of various components, and the descaling composition of the present invention is controlled to be neutral, so that it has low corrosiveness.

[0027] In some embodiments of the present invention, the synthesis route of the polyaminocarboxylic acid chelating agent is as follows:

[0028] The present invention provides a method for preparing a polyaminocarboxylic acid chelating agent, which specifically comprises the following steps:

[0029] S1. Preparation of intermediate 1:

[0030] S11, adding raw material 1 and 30% sodium hydroxide aqueous solution in a mass ratio of 1:0.9-1.1 into a three-necked flask;

[0031] S12, prepare a 50% chloroacetic acid aqueous solution with deionized water (the molar ratio of chloroacetic acid to raw material 1 is 1:0.9-1.1), and put it into a constant pressure dropping funnel for later use;

[0032] S13, the sodium hydroxide aqueous solution is placed in another constant pressure dropping funnel for later use, the reaction temperature is increased to 80-90 ° C, and the solutions obtained in S11 and S12 are added dropwise at the same time, the system temperature is maintained at 80-90 ° C, and the pH is maintained at 10-11. After the addition is completed, vacuum is applied to remove water and the reaction is continued for 2 hours. Hydrochloric acid is added to adjust the pH to about 1, and the intermediate 1 is obtained by filtration;

[0033] S2, mixing the intermediate 1 obtained in step S1 with acetic anhydride and dry pyridine and reacting the mixture at 60-70° C. for 5-6 hours to obtain intermediate 2;

[0034] S3. The intermediate 2 obtained in step S2 and ethylene glycol are added to a round-bottom flask at a molar ratio of 1:2 to 2.1, DMF is added as a solvent, and the mixture is heated in a water bath to 60 to 70° C., stirred, and p-toluenesulfonic acid is added as a catalyst in an amount of 0.1 to 1.2% of the total reaction volume. After reacting for 5 to 6 hours, a polyaminocarboxylic acid chelating agent having a structure shown in Formula I is obtained.

[0035] In the present invention, the raw material 1 is selected from the structure shown in formula (1):

[0036] In formula (1), R1 is a dialkylamino group (-NR2), an alkylamino group (-NHR), an amino group (-NH2), a hydroxyl group (-OH), an alkoxy group (-OR), an amide group (-NHCOR), an acyloxy group (-OCOR), a carboxymethyl group (-CH2COOH) or a carboxyl group (-COOH).

[0037] In some embodiments of the present invention, the descaling composition includes, by weight, 10 to 15 parts of a polyaminocarboxylic acid chelating agent, 1 to 2 parts of a synergist, 0.5 to 1 part of a chelating catalyst, 0.5 to 1 part of a chelating stabilizer, 0.5 to 1 part of a penetrating dispersant, 5 to 10 parts of a pH regulator, and 70 to 82.5 parts of a solvent.

[0038] In the present invention, the solvent is preferably water.

[0039] In some embodiments of the present invention, the synergist is a mixture of polyepoxysuccinic acid and polyaspartic acid.

[0040] In some embodiments of the present invention, based on the total weight of the synergist, the content of polyepoxysuccinic acid is 30-40 wt %, and the content of polyaspartic acid is 60-70 wt %.

[0041] In the present invention, a mixture of polyepoxysuccinic acid and polyaspartic acid is used as a synergist, which has strong permeability. Through the synergistic effect between the two, it can effectively inhibit the aggregation and nucleation of scale ions, play a role in dispersing scale samples, enhancing the scale removal and unblocking effect, and has a certain corrosion inhibition effect; at the same time, the synergist can be adsorbed and formed into a film on the pipe wall, further inhibiting the adhesion and deposition of scale samples on the pipe wall.

[0042] In some embodiments of the present invention, the chelate catalyst is a mixture of ammonium chloride and sodium nitrite.

[0043] In some embodiments of the present invention, based on the total weight of the chelate catalyst, the content of ammonium chloride is 40-50 wt%, and the content of sodium nitrite is 50-60 wt%.

[0044] In the present invention, the main functions of the chelating catalyst are: on the one hand, to increase the solubility of insoluble inorganic scale through ionic effect; on the other hand, the reaction between sodium nitrite and ammonium chloride produces a small amount of nitrogen, which can enter the tiny gaps of the scale sample, increase the permeability of the scale sample, and accelerate the chelation and dissolution rate of the chelating agent and the scale sample to a certain extent.

[0045] In some embodiments of the present invention, the chelating stabilizer is selected from one or more of sodium citrate, sodium acetate, sodium formate and sodium gluconate, preferably sodium citrate.

[0046] In the present invention, for the scale that has attached to the surface of the pipe wall, iron-containing corrosion products will be deposited on the adsorption surface with the metal pipe wall. The main function of the chelating stabilizer is to remove the insoluble iron in the scale, which can improve the peeling effect of the scale on the pipe wall.

[0047] In some embodiments of the present invention, the penetrating dispersant is selected from one or more of polyethylene glycol PEG-600, sodium sulfate of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and petroleum sulfonate.

[0048] In some embodiments of the present invention, the osmotic dispersant is a mixture of polyethylene glycol PEG-600 and petroleum sulfonate.

[0049] In some embodiments of the present invention, based on the total weight of the osmotic dispersant, the content of polyethylene glycol PEG-600 is 40-50 wt %, and the content of petroleum sulfonate is 50-60 wt %.

[0050] In the present invention, the main functions of the penetrating dispersant are: on the one hand, it plays a certain dispersing role; on the other hand, it can change the surface properties of the oily scale sample, make the scale sample surface hydrophilic, enhance the penetration of the chelating agent into the interior of the scale sample, and make the scale sample easier to peel off.

[0051] In some embodiments of the present invention, the pH adjuster is selected from one or more of sodium hydroxide, ammonia water and potassium hydroxide, preferably sodium hydroxide.

[0052] In the present invention, the descaling composition adopts a pH regulator to adjust the pH value to 7-8. Compared with acidic and alkaline descaling, the descaling composition of the present invention has the characteristics of good scale dissolving effect (large scale dissolving rate for calcium carbonate, calcium sulfate and barium sulfate), low corrosion, excellent temperature resistance, wide application range, non-toxic and environmental protection, etc., and has good compatibility with formation water, will not cause damage to the formation and pipeline, and can effectively solve the blockage problem of inorganic insoluble scale in high-temperature and high-pressure gas wells.

[0053] A second aspect of the present invention provides a method for preparing a descaling agent, the preparation method comprising:

[0054] Under stirring conditions, the polyamino acid chelating agent, the synergist, the chelating catalyst and the chelating stabilizer are first mixed with water to obtain a first mixture;

[0055] adding a pH regulator and a penetrating dispersant to the first mixture, and performing a second mixing to obtain a descaling agent;

[0056] The pH value of the descaling composition is 7 to 8; the polyamino acid chelating agent has a structure shown in Formula I:

[0057] In formula I, R1 is a dialkylamino group (-NR2), an alkylamino group (-NHR), an amino group (-NH2), a hydroxyl group (-OH), an alkoxy group (-OR), an amide group (-NHCOR), an acyloxy group (-OCOR), a carboxymethyl group (-CH2COOH) or a carboxyl group (-COOH).

[0058] In the present invention, R is preferably selected from C1-C 10 A straight chain or branched chain alkyl group.

[0059] In the present invention, the polyamino-polyacid chelating agent contains multiple amino groups, carboxyl groups, hydroxyl groups and electron-donating groups R1, which give it a strong electron-donating ability. The carbon chain is extended by grafting modification of the carboxyl groups, thereby improving the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhancing its temperature resistance.

[0060] In the present invention, a scale remover prepared from a scale removal composition adopts a pH regulator to adjust the pH value to 7-8. Compared with acidic and alkaline scale removers, the neutral scale remover of the present invention has the characteristics of good scale dissolving effect (large scale dissolving rate for calcium carbonate, calcium sulfate and barium sulfate), low corrosiveness, excellent temperature resistance, wide application range, non-toxicity and environmental protection, etc., and has good compatibility with formation water, will not cause damage to the formation and pipeline, and can effectively solve the blockage problem of inorganic insoluble scale in high-temperature and high-pressure gas wells.

[0061] The descaling composition of the present invention achieves efficient descaling of high-temperature (120-180° C.) oil and gas wells through the synergistic effect of various components. The descaling composition of the present invention is controlled to be neutral, so that it has low corrosiveness.

[0062] In some embodiments of the present invention, the polyaminocarboxylic acid chelating agent comprises 10 to 15 parts, the synergist comprises 1 to 2 parts, the chelating catalyst comprises 0.5 to 1 part, the chelating stabilizer comprises 0.5 to 1 part, the penetrating dispersant comprises 0.5 to 1 part, the pH regulator comprises 5 to 10 parts and the solvent comprises 70 to 82.5 parts.

[0063] In the present invention, the solvent is preferably water.

[0064] In the present invention, the selection range of each component is the same as that of the first aspect. Please refer to the previous description for details and will not be repeated here.

[0065] In some embodiments of the present invention, the first mixing comprises: mixing at 50-70° C. under normal pressure stirring conditions for 30-60 minutes.

[0066] In some embodiments of the present invention, the second mixing comprises: mixing at 50-70° C. for 30-60 min, and controlling the pH value at 7-8.

[0067] The third aspect of the present invention provides a descaling agent prepared by the preparation method described in the second aspect.

[0068] The fourth aspect of the present invention provides use of the descaling composition described in the first aspect or the descaling agent described in the third aspect in oil and gas wells.

[0069] The scale remover of the present invention is a neutral scale remover (pH is 7-8), which has the characteristics of good scale dissolving effect, low corrosiveness, excellent temperature resistance, wide application range, non-toxicity and environmental protection, and has good compatibility with formation water, will not cause damage to the formation and pipelines, and can effectively solve the blockage problem of inorganic insoluble scale in high-temperature and high-pressure gas wells.

[0070] The descaling agent of the present invention has a wide application range and can be used at low temperatures as well as high temperatures.

[0071] In some embodiments of the present invention, the temperature inside the oil and gas well is 80-180°C, preferably 120-180°C.

[0072] The present invention will be described in detail below through examples.

[0073] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available.

[0074] Preparation Example 1

[0075] The preparation method of the polyamino acid chelating agent specifically comprises the following steps:

[0076] (1) Add 2,3-diaminopropionic acid and 30% sodium hydroxide aqueous solution in a mass ratio of 1:1 into a three-necked flask;

[0077] (2) Prepare a 50% chloroacetic acid aqueous solution with deionized water (the molar ratio of chloroacetic acid to raw material 1 is 1:1) and place it in a constant pressure dropping funnel for later use;

[0078] (3) The sodium hydroxide aqueous solution is placed in another constant pressure dropping funnel for later use, the reaction temperature is increased to 80°C, and the solutions in (1) and (2) are added dropwise at the same time, the system temperature is maintained at 80°C, and the pH is maintained at 10-11. After the addition is completed, the system is vacuumed and water is added and the reaction is continued for 2 hours. Hydrochloric acid is added to adjust the pH to about 1, and the intermediate 1 is obtained by filtration; then the intermediate 1 is mixed with acetic anhydride and dry pyridine and reacted at 60°C for 5 hours to obtain the intermediate 2; then the intermediate 2 and ethylene glycol are added to a round-bottom flask in a molar ratio of 1:2, DMF is added as a solvent, the system is heated to 60°C in a water bath, stirring is started, and 0.1% of p-toluenesulfonic acid in the total reaction volume is added as a catalyst. After reacting for 5 hours, a product having the structure shown in Formula I-1 is obtained.

[0079] The specific synthesis reaction is as follows:

[0080] FIG1 is an infrared spectrum of the compound I-1 obtained in Preparation Example 1. As shown in FIG1 , 3411 cm -1 The peak at 1739 cm is caused by the stretching vibration of -OH. -1 The C=O stretching vibration peak of the ester group is at 1587 cm -1 and 1409cm -1 It is caused by the stretching vibration of C=O of carboxyl group, 1332cm -1 It is caused by the asymmetric stretching vibration of the ester group COC. These results indicate that the target product having the structure shown in Formula I-1 was successfully synthesized.

[0081] Preparation Example 2

[0082] The preparation method of the polyamino acid chelating agent specifically comprises the following steps:

[0083] (1) Add 3,4-diaminobutyric acid and 30% sodium hydroxide aqueous solution in a mass ratio of 1:1 into a three-necked flask;

[0084] (2) Prepare a 50% chloroacetic acid aqueous solution with deionized water (the molar ratio of chloroacetic acid to raw material 1 is 1:1) and place it in a constant pressure dropping funnel for later use;

[0085] (3) The sodium hydroxide aqueous solution is placed in another constant pressure dropping funnel for later use, the reaction temperature is increased to 85°C, and the solutions in (1) and (2) are added dropwise at the same time, the system temperature is maintained at 85°C, and the pH is maintained at 10-11. After the addition is completed, the system is vacuumed and water is added and the reaction is continued for 2 hours. Hydrochloric acid is added to adjust the pH to about 1, and the intermediate 1 is obtained by filtration; then the intermediate 1 is mixed with acetic anhydride and dry pyridine and reacted at 65°C for 6 hours to obtain the intermediate 2; then the intermediate 2 and ethylene glycol are added to a round-bottom flask in a substance ratio of 1:2, DMF is added as a solvent, the system is heated to 65°C in a water bath, stirring is started, and 0.1% of p-toluenesulfonic acid in the total reaction volume is added as a catalyst. After reacting for 6 hours, a product having the structure shown in Formula I-2 is obtained.

[0086] Example 1

[0087] A descaling composition comprises, in parts by weight: 10 parts of the polyaminopolyacid chelating agent prepared in Preparation Example 1; 1 part of a synergist; 0.5 parts of a chelating catalyst; 0.5 parts of sodium citrate; 0.5 parts of a penetrating dispersant; 5 parts of sodium hydroxide, and 82.5 parts of water; wherein the polyaminopolyacid chelating agent has a structure represented by Formula I-1, the synergist comprises 30 wt% of polyepoxysuccinic acid and 70 wt% of polyaspartic acid (based on the total weight of the synergist); the chelating catalyst comprises 40 wt% of sodium nitrite and 60 wt% of ammonium chloride (based on the total weight of the chelating catalyst); and the penetrating dispersant comprises 40 wt% of polyethylene glycol PEG-600 and 60 wt% of petroleum sulfonate (based on the total weight of the penetrating dispersant).

[0088] The preparation of a descaling agent comprises the following steps: adding an appropriate amount of water into a reaction kettle, starting stirring, sequentially adding the above-mentioned formulated amounts of a polyamino acid chelating agent, a synergist, a chelating catalyst and a chelating stabilizer, sodium citrate, stirring for 50 minutes, adding the above-mentioned formulated amount of a pH regulator, sodium hydroxide, maintaining the temperature in the kettle at 60°C and the pH value at 7, then adding the above-mentioned formulated amount of a penetrating dispersant and continuing stirring for 30 minutes to obtain the descaling agent.

[0089] Example 2

[0090] A descaling composition comprises, by weight, 15 parts of the polyamino acid chelating agent prepared in Preparation Example 1; 2 parts of a synergist; 1 part of a chelating catalyst; 1 part of sodium citrate; 1 part of a penetrant; 10 parts of sodium hydroxide, and 70 parts of water; wherein the compositions of the synergist, the chelating catalyst, and the penetrating dispersant are the same as those in Example 1.

[0091] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.5 to prepare a descaling agent.

[0092] Example 3

[0093] A descaling composition comprises, by weight, 10 parts of the polyamino-polyacid chelating agent prepared in Preparation Example 1; 2 parts of a synergist; 1 part of a chelating catalyst; 1 part of sodium citrate; 0.5 parts of a penetrating dispersant; 5 parts of sodium hydroxide; and 80.5 parts of water. The synergist comprises 40 wt% of polyepoxysuccinic acid and 60 wt% of polyaspartic acid; the chelating catalyst comprises 40 wt% of sodium nitrite and 60 wt% of ammonium chloride; and the penetrating dispersant comprises 40 wt% of polyethylene glycol PEG-600 and 60 wt% of petroleum sulfonate.

[0094] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.1 to prepare a descaling agent.

[0095] Example 4

[0096] A descaling composition comprises, by weight, 10 parts of the polyamino acid chelating agent prepared in Preparation Example 1; 1 part of a synergist; 0.5 parts of a chelating catalyst; 1 part of sodium citrate; 1 part of a penetrating dispersant; 5 parts of sodium hydroxide, and 81.5 parts of water; wherein the synergist comprises 40 wt% of polyepoxysuccinic acid and 60 wt% of polyaspartic acid; the chelating catalyst comprises 50 wt% of sodium nitrite and 50 wt% of ammonium chloride; and the penetrating dispersant comprises 50 wt% of polyethylene glycol PEG-600 and 50 wt% of petroleum sulfonate.

[0097] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.1 to prepare a descaling agent.

[0098] Example 5

[0099] A descaling composition comprises, by weight, 15 parts of the polyamino acid chelating agent prepared in Preparation Example 1; 1 part of a synergist; 0.5 parts of a chelating catalyst; 0.5 parts of sodium citrate; 0.5 parts of a penetrating dispersant; 10 parts of sodium hydroxide, and 72.5 parts of water; wherein the compositions of the synergist, the chelating catalyst, and the penetrating dispersant are the same as those in Example 1.

[0100] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.8 to prepare a descaling agent.

[0101] Example 6

[0102] A descaling composition comprises, by weight, 15 parts of the polyamino acid chelating agent prepared in Preparation Example 1; 2 parts of a synergist; 0.5 parts of a chelating catalyst; 0.5 parts of sodium citrate; 1 part of a penetrating dispersant; 10 parts of sodium hydroxide, and 71 parts of water; wherein the compositions of the synergist, the chelating catalyst, and the penetrating dispersant are the same as those in Example 1.

[0103] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 8 to prepare a descaling agent.

[0104] Example 7

[0105] A descaling composition comprises, by weight, 13 parts of the polyamino acid chelating agent prepared in Preparation Example 1; 1.5 parts of a synergist; 0.8 parts of a chelating catalyst; 0.8 parts of sodium citrate; 0.8 parts of a penetrating dispersant; 8 parts of sodium hydroxide, and 75.1 parts of water; wherein the compositions of the synergist, the chelating catalyst, and the penetrating dispersant are the same as those in Example 1.

[0106] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.6 to prepare a descaling agent.

[0107] Example 8

[0108] The formulation and method of Example 1 are the same as those of Example 1, except that the synergist comprises 35 wt % of polyepoxysuccinic acid and 65 wt % of polyaspartic acid, and the remaining components are the same as those of Example 1.

[0109] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0110] Example 9

[0111] The formulation and method of Example 1 were the same, except that the synergist was polyepoxysuccinic acid (100 wt %, based on the total weight of the synergist), and the remaining components were the same as those of Example 1.

[0112] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0113] Example 10

[0114] The formulation and method of Example 1 were the same, except that the synergist was polyaspartic acid (100 wt %, based on the total weight of the synergist), and the remaining components were the same as those of Example 1.

[0115] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0116] Example 11

[0117] The formulation and method of Example 1 are the same as those of Example 1, except that the penetrating dispersant includes 50 wt % of polyethylene glycol PEG-600 and 50 wt % of petroleum sulfonate, and the remaining components are the same as those of Example 1.

[0118] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0119] Example 12

[0120] The formula and method of Example 1 are the same, except that the chelate catalyst includes 50 wt% sodium nitrite and 50 wt% ammonium chloride, and the remaining components are the same as those of Example 1.

[0121] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0122] Example 13

[0123] The formula and method of Example 1 are the same, except that the chelate catalyst includes 35 wt% sodium nitrite and 65 wt% ammonium chloride, and the remaining components are the same as those of Example 1.

[0124] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0125] Example 14

[0126] The formulation and method of Example 1 are the same as those of Example 1, except that the synergist comprises 40 wt % of polyepoxysuccinic acid and 60 wt % of polyaspartic acid, and the remaining components are the same as those of Example 1.

[0127] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0128] Example 15

[0129] The formula and method of Example 1 are the same, except that the polyamino acid chelating agent prepared in Preparation Example 2 is used in this example. The polyamino acid chelating agent has the structure shown in Formula I-2, and the remaining components are the same as those in Example 1.

[0130] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0131] Example 16

[0132] A descaling composition comprises, by weight: a polyamino polyacid chelating agent prepared in Preparation Example 2, 15 parts of the polyamino polyacid chelating agent; 1.5 parts of a synergist; 0.8 parts of a chelating catalyst; 0.8 parts of sodium citrate; 0.8 parts of a penetrating dispersant; 8 parts of sodium hydroxide, and 73.1 parts of water; wherein the polyamino polyacid chelating agent has a structure shown in Formula I-2, and the compositions of the synergist, the chelating catalyst, and the penetrating dispersant are the same as those in Example 1.

[0133] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.3 to prepare a descaling agent.

[0134] Comparative Example 1

[0135] According to the formula and method of Example 1, the only difference is that the weight portion of sodium hydroxide is 15 parts, and the other components are the same as those in Example 1.

[0136] According to the method of Example 1, a descaling agent was prepared according to the formula of the above descaling composition, and the pH value was controlled at 12, which was an alkaline descaling agent.

[0137] Comparative Example 2

[0138] According to the formula and method of Example 1, the only difference is that the weight portion of sodium hydroxide is 1 part, and the other components are the same as those in Example 1.

[0139] According to the method of Example 1, a descaling agent was prepared according to the formula of the above descaling composition, and the pH value was controlled at 3, which was an acidic descaling agent.

[0140] Comparative Example 3

[0141] The formula and method of Example 1 are the same as those of Example 1, except that the chelating agent is diethylenetriaminepentaacetic acid, and the other components are the same as those of Example 1.

[0142] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0143] Comparative Example 4

[0144] The formula and method of Example 1 are the same as those of Example 1, except that the polyamino acid chelating agent is not added. The remaining components are the same as those of Example 1.

[0145] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0146] Comparative Example 5

[0147] The formula and method of Example 1 are the same as those of Example 1, except that no synergist is added. The remaining components are the same as those of Example 1.

[0148] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0149] Comparative Example 6

[0150] The formulation and method of Example 1 are the same as those of Example 1, except that no chelating stabilizer is added. The remaining components are the same as those of Example 1.

[0151] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0152] Comparative Example 7

[0153] The formulation and method of Example 1 are the same as those of Example 1, except that the synergist and chelating stabilizer are not added. The remaining components are the same as those of Example 1.

[0154] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0155] Comparative Example 8

[0156] The formulation and method of Example 1 are the same as those of Example 1, except that no penetrating dispersant is added. The remaining components are the same as those of Example 1.

[0157] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7 to prepare a descaling agent.

[0158] Test Case

[0159] The dissolution rate and corrosion rate are determined as follows:

[0160] (1) Determination of dissolution rate: Weigh 1 g of the scale sample and add it to 50 mL of the descaling agent prepared in Examples 1-18 and Comparative Examples 1-7, respectively. After reacting at 120° C. and 180° C. for 6 h, filter and dry the scale sample. The dissolution rate is calculated by measuring the mass difference of the scale sample before and after the reaction.

[0161] Where:

[0162] m0——mass of the scale sample before reaction, g;

[0163] m1——The mass of the scale sample after the reaction, g.

[0164] (2) Corrosion Rate Determination: Oil pipe steel (super 13Cr) was polished to a bright finish, cleaned with petroleum ether and ethanol, dried, weighed, and placed in an autoclave. 2 L of the descaling agent prepared in Examples 1-14 and Comparative Examples 1-7 were introduced, respectively. The mixture was stirred and heated to 180°C. High-purity nitrogen was then introduced to maintain the nitrogen pressure at 10 MPa. After stabilization under these conditions for 6 hours, the sample was removed, the corrosion product film on the surface of the sample was removed, and the sample was weighed after drying to calculate the corrosion rate.

[0165] Table 1

[0166] It can be seen from the results in Table 1 that the scale removers used in the embodiments of the present invention are all highly penetrating neutral scale removers. The scale dissolution rates of calcium carbonate, calcium sulfate, and barium sulfate at 120 and 180° C. are higher than those of the comparative examples. At the same time, they all have faster corrosion rates and can be used in high-temperature oil and gas wells.

[0167] The neutral descaling agent of the present invention is suitable for descaling and unblocking high-temperature gas wellbores. The results of the scale dissolution rate test show that the operating temperature thereof can reach 120-180°C.

[0168] In summary, the neutral descaling agent of the present invention has good scale dissolving effect (calcium carbonate scale dissolving rate, calcium sulfate scale dissolving rate and barium sulfate scale dissolving rate are all greater than 70%), low corrosiveness (corrosion rate is less than 0.2g / (m 2h)) It has excellent temperature resistance (80-180℃), wide application range, non-toxic and environmentally friendly, and has good compatibility with formation water. It will not cause damage to the formation and pipelines, and can effectively solve the clogging problem of inorganic insoluble scale in high-temperature and high-pressure gas wells.

[0169] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A descaling composition, It is characterized in that The descaling composition comprises: a polyamino acid chelating agent, a synergist, a chelating catalyst, a chelating stabilizer, a penetrating dispersant, a pH regulator and a solvent; wherein the pH value of the descaling composition is 7 to 8; and the polyamino acid chelating agent has a structure shown in Formula I: In Formula I, R 1 It is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

2. The descaling composition according to claim 1, in, The descaling composition comprises, by weight, 10 to 15 parts of a polyaminocarboxylic acid chelating agent, 1 to 2 parts of a synergist, 0.5 to 1 part of a chelating catalyst, 0.5 to 1 part of a chelating stabilizer, 0.5 to 1 part of a penetrating dispersant, 5 to 10 parts of a pH regulator and 70 to 82.5 parts of a solvent.

3. The descaling composition according to claim 1, in, The synergist is a mixture of polyepoxysuccinic acid and polyaspartic acid.

4. The descaling composition according to claim 3, in, Based on the total weight of the synergist, the content of polyepoxysuccinic acid is 30-40wt%, and the content of polyaspartic acid is 60-70wt%.

5. The descaling composition according to claim 1, in, The chelate catalyst is a mixture of ammonium chloride and sodium nitrite.

6. The descaling composition according to claim 5, in, Based on the total weight of the chelate catalyst, the content of ammonium chloride is 40-50wt%, and the content of sodium nitrite is 50-60wt%.

7. The descaling composition according to claim 1, in, The chelating stabilizer is selected from one or more of sodium citrate, sodium acetate, sodium formate and sodium gluconate.

8. The descaling composition according to claim 1, in, The penetrating dispersant is selected from one or more of polyethylene glycol PEG-600, sodium sulfate of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and petroleum sulfonate.

9. The descaling composition according to claim 8, in, The penetrating dispersant is a mixture of polyethylene glycol PEG-600 and petroleum sulfonate; Preferably, based on the total weight of the osmotic dispersant, the content of polyethylene glycol PEG-600 is 40-50 wt %, and the content of petroleum sulfonate is 50-60 wt %.

10. The descaling composition according to claim 1, in, The pH regulator is selected from one or more of sodium hydroxide, ammonia water and potassium hydroxide, preferably sodium hydroxide.

11. A method for preparing a descaling agent, It is characterized in that The preparation method comprises: Under stirring conditions, the polyamino acid chelating agent, the synergist, the chelating catalyst and the chelating stabilizer are first mixed with water to obtain a first mixture; adding a pH regulator and a penetrating dispersant to the first mixture, and performing a second mixing to obtain a descaling agent; Wherein, the pH value of the descaling composition is 7-8; the polyamino acid chelating agent has a structure shown in Formula I: In Formula I, R 1 It is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

12. The preparation method according to claim 11, in, By weight, the invention comprises 10 to 15 parts of polyaminocarboxylic acid chelating agent, 1 to 2 parts of synergist, 0.5 to 1 part of chelating catalyst, 0.5 to 1 part of chelating stabilizer, 0.5 to 1 part of penetrating dispersant, 5 to 10 parts of pH adjusting agent and 70 to 82.5 parts of solvent.

13. A descaling agent obtained by the preparation method according to claim 11 or 12.

14. Use of the descaling composition according to any one of claims 1 to 10 or the descaling agent according to claim 13 in oil and gas wells.

15. The use according to claim 14, in, The temperature inside the oil and gas well is 80-180°C, preferably 120-180°C.

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