Descaling composition, descaling agent, preparation method and application

Abstract

The invention discloses a descaling composition. The descaling composition comprises a polyamino polyacid chelating agent, a synergist, a chelating catalyst, a chelating stabilizer, a permeation dispersant, a pH regulator and a solvent, wherein the pH value of the descaling composition is 7 to 8; the polyamino polyacid chelating agent has a structure as shown in a formula I, wherein R1 is dialkylamino, alkylamino, amino, hydroxyl, alkoxy, acylamino, acyloxy, carboxyl methyl or carboxyl. The polyamino polyacid chelating agent adopted by the descaling composition contains a plurality of amino groups, carboxyl groups, hydroxyl groups and electron donating groups R1, so that the polyamino polyacid chelating agent can be combined with metal ions more easily to form a stable chelate, and the temperature resistance of the polyamino polyacid chelating agent is enhanced; and the prepared neutral scale remover has the characteristics of good scale dissolving effect, low corrosivity, excellent temperature resistance and the like, and can effectively solve the problem of blockage of inorganic insoluble scale in a high-temperature and high-pressure gas well. # imgabs0 #

Description

Technical Field

[0001] The 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 application thereof. Background Art

[0002] Inorganic scale blockage in gas wells is a common problem. Compared with physical unblocking technologies such as coiled tubing dredging and water jetting, chemical descaling and unblocking has the advantages of short operation time and unblocking near-well reservoir blockages. It has become the most commonly used means of descaling and unblocking in gas wells, among which the unblocking fluid system is the key to the technology. Traditionally, acidic liquids are used for descaling and unblocking, which has the advantage of a 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 liquids 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, using the coordination groups in the chelating agent molecules and the scale Ca 2+ , Ba 2+ The cations form coordination bonds, "converting" the scale into a more stable and water-soluble complex. Chelating descaling has two major advantages: extremely low corrosion and a wide range of descaling types, and is an ideal substitute for acid. However, non-acidic plugging removal fluids also have shortcomings such as low dissolution rate, and most non-acidic plugging removal fluids currently on the market have a high pH value, which may accelerate scaling of water with high mineralization near the production layer during use, affecting its effectiveness. Summary of the invention

[0004] 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. The descaling agent is a neutral descaling agent, 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.

[0005] 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; and the polyamino acid chelating agent has a structure shown in Formula I:

[0006]

[0007] In formula I, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

[0008] A second aspect of the present invention provides a method for preparing a descaling agent, the preparation method comprising:

[0009] 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;

[0010] Adding a pH regulator to the first mixture, controlling the pH value to be between 7 and 8 at 50 to 70° C., then adding a penetrating dispersant, and performing a second mixing to obtain a neutral descaling agent;

[0011] Wherein, the pH value of the descaling composition is 7-8; the polyamino acid chelating agent has a structure shown in Formula I:

[0012]

[0013] In formula I, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

[0014] The third aspect of the present invention provides a descaling agent prepared by the preparation method described in the second aspect.

[0015] 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 an oil and gas well.

[0016] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0017] 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, so that it has a strong electron-donating ability, and the carbon chain is extended by grafting modification of the carboxyl group to improve the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhance its temperature resistance; the descaling agent prepared from the descaling composition of the present invention is a neutral descaling agent with low corrosiveness.

[0018] 2) The descaling agent of the present invention has the characteristics of good scale dissolving effect (the scale dissolving rate of calcium carbonate, calcium sulfate and barium sulfate is relatively large), low corrosion, excellent temperature resistance, wide application range, non-toxic and environmentally friendly, and has good compatibility with formation water, will not cause damage to the formation and pipeline, and can effectively solve the clogging problem of inorganic insoluble scale in high-temperature and high-pressure gas wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the infrared spectrum of the composite solid electrolyte prepared in Preparation Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0021] 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; and the polyamino acid chelating agent has a structure shown in Formula I:

[0022]

[0023] In formula I, R1 is dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), hydroxyl (-OH), alkoxy (-OR), amide (-NHCOR), acyloxy (-OCOR), carboxymethyl (-CH2COOH) or carboxyl (-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, so that it has a strong electron-donating ability, and the carbon chain is extended by grafting modification of the carboxyl group to improve the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhance its temperature resistance.

[0026] The descaling composition of the present invention realizes 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 as to have low corrosivity.

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

[0028]

[0029] The present invention provides a method for preparing a polyaminocarboxylic acid chelating agent, which specifically comprises the following steps:

[0030] S1. Preparation of intermediate 1:

[0031] S11, adding raw material 1 and 30% sodium hydroxide aqueous solution into a three-necked flask in a mass ratio of 1:0.9-1.1;

[0032] S12, prepare a chloroacetic acid aqueous solution with a mass concentration of 50% (the molar ratio of chloroacetic acid to raw material 1 is 1:0.9-1.1) with deionized water, and put it into a constant pressure dropping funnel for use;

[0033] S13, put the sodium hydroxide aqueous solution into another constant pressure dropping funnel for later use, increase the reaction temperature to 80-90°C, and simultaneously drop the solutions obtained in S11 and S12, keep the system temperature at 80-90°C, and keep the pH at 10-11. After the dropwise addition is completed, vacuumize and remove the water, and continue the reaction for 2h, add hydrochloric acid to adjust the pH to about 1, and filter to obtain intermediate 1;

[0034] 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;

[0035] S3, adding the intermediate 2 obtained in step S2 and ethylene glycol in a molar ratio of 1:2 to 2.1 into a round-bottom flask, adding DMF as a solvent, heating in a water bath to 60 to 70° C., starting stirring, and adding 0.1 to 1.2% of p-toluenesulfonic acid as a catalyst accounting for the total reaction amount, reacting for 5 to 6 hours, to obtain a polyaminocarboxylic acid chelating agent having a structure shown in formula I.

[0036] In the present invention, the raw material 1 is selected from the structure shown in formula (1):

[0037]

[0038] 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).

[0039] 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 adjuster and 70 to 82.5 parts of a solvent.

[0040] In the present invention, the solvent is preferably water.

[0041] In some embodiments of the present invention, the synergist is a mixture of polyepoxysuccinic acid and polyaspartic acid.

[0042] 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 %.

[0043] 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 on the pipe wall to form a film, further inhibiting the adhesion and deposition of scale samples on the pipe wall.

[0044] In some embodiments of the present invention, the chelate catalyst is a mixture of ammonium chloride and sodium nitrite.

[0045] 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 %.

[0046] In the present invention, the main functions of the chelating catalyst are: on the one hand, it increases the solubility of the sparingly soluble inorganic scale through the ion effect; on the other hand, the sodium nitrite and ammonium chloride react to produce 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.

[0047] 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.

[0048] In the present invention, for the scale that has been 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.

[0049] 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.

[0050] In some embodiments of the present invention, the osmotic dispersant is a mixture of polyethylene glycol PEG-600 and petroleum sulfonate.

[0051] 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 %.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] A second aspect of the present invention provides a method for preparing a descaling agent, the preparation method comprising:

[0056] 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;

[0057] adding a pH regulator and a penetrating dispersant to the first mixture, and performing a second mixing to obtain a descaling agent;

[0058] Wherein, the pH value of the descaling composition is 7-8; the polyamino acid chelating agent has a structure shown in Formula I:

[0059]

[0060] In formula I, R1 is dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), hydroxyl (-OH), alkoxy (-OR), amide (-NHCOR), acyloxy (-OCOR), carboxymethyl (-CH2COOH) or carboxyl (-COOH).

[0061] In the present invention, R is preferably selected from C1-C 10 A straight chain or branched chain alkyl group.

[0062] In the present invention, the polyamino polyacid chelating agent contains multiple amino groups, carboxyl groups, hydroxyl groups and electron-donating groups R1, so that it has a strong electron-donating ability, and the carbon chain is extended by grafting modification of the carboxyl group to improve the surface activity of the molecule, making it easier to combine with metal ions to form a stable chelate and enhance its temperature resistance.

[0063] In the present invention, the descaling agent prepared from the descaling composition adopts a pH adjusting agent to adjust the pH value to 7-8. Compared with acidic and alkaline descaling agents, the neutral descaling agent 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 environmentally friendly, 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.

[0064] The descaling composition of the present invention realizes 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 as to have low corrosiveness.

[0065] In some embodiments of the present invention, by weight, there are 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 adjuster and 70 to 82.5 parts of solvent.

[0066] In the present invention, the solvent is preferably water.

[0067] 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.

[0068] In some embodiments of the present invention, the first mixing comprises: mixing at 50 to 70° C. under normal pressure stirring conditions for 30 to 60 minutes.

[0069] 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.

[0070] The third aspect of the present invention provides a descaling agent prepared by the preparation method described in the second aspect.

[0071] 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 an oil and gas well.

[0072] In some embodiments of the present invention, the temperature inside the oil and gas well is 120-180°C.

[0073] The present invention will be described in detail below through examples.

[0074] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available.

[0075] Preparation Example 1

[0076] The preparation method of the polyamino acid chelating agent specifically comprises the following steps:

[0077] (1) Add 2,3-diaminopropionic acid and 30% sodium hydroxide aqueous solution in a mass ratio of 1:1 into a three-necked flask;

[0078] (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 put it into a constant pressure dropping funnel for later use;

[0079] (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 evacuated 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 at 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 p-toluenesulfonic acid accounting for 0.1% of 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.

[0080] The specific synthesis reaction is as follows:

[0081]

[0082] Figure 1 is the infrared spectrum of Formula I-1 obtained in Preparation Example 1. Figure 1 It can be seen that 3411cm -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.

[0083] Preparation Example 2

[0084] The preparation method of the polyamino acid chelating agent specifically comprises the following steps:

[0085] (1) Add 3,4-diaminobutyric acid and 30% sodium hydroxide aqueous solution in a mass ratio of 1:1 into a three-necked flask;

[0086] (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 put it into a constant pressure dropping funnel for later use;

[0087] (3) Pour the sodium hydroxide aqueous solution into another constant pressure dropping funnel for later use, raise the reaction temperature to 85°C, and simultaneously drop the solutions in (1) and (2), maintain the system temperature at 85°C, and maintain the pH at 10-11. After the dropwise addition is completed, evacuate the system, add water, and continue the reaction for 2 hours. Add hydrochloric acid to adjust the pH to about 1, and filter to obtain intermediate 1; then mix intermediate 1 with acetic anhydride and dry pyridine and react at 65°C for 6 hours to obtain intermediate 2; then add intermediate 2 and ethylene glycol in a molar ratio of 1:2 into a round-bottom flask, add DMF as a solvent, heat in a water bath to 65°C, start stirring, and add 0.1% of p-toluenesulfonic acid as a catalyst to the total reaction volume. After reacting for 6 hours, a product having the structure shown in Formula I-2 is obtained.

[0088]

[0089] Example 1

[0090] A descaling composition comprises, by weight: 10 parts of a 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; 5 parts of sodium hydroxide, and 82.5 parts of water; wherein the polyamino acid chelating agent has a structure as shown in 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).

[0091] 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 formula 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 formula 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 formula amount of a penetrating dispersant and continuing stirring for 30 minutes to obtain the descaling agent.

[0092] Example 2

[0093] 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 respectively the same as those in Example 1.

[0094] 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.

[0095] Example 3

[0096] A descaling composition comprises, by weight: 10 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; 0.5 parts of a penetrating dispersant; 5 parts of sodium hydroxide and 80.5 parts of water; wherein 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.

[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 4

[0099] 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.

[0100] 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.

[0101] Example 5

[0102] 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 respectively 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 7.8 to prepare a descaling agent.

[0104] Example 6

[0105] 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 respectively 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 is controlled at 8 to prepare a descaling agent.

[0107] Example 7

[0108] A descaling composition, comprising, 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 respectively the same as those in Example 1.

[0109] According to the method of Example 1 and the formula of the above descaling composition, the pH value was controlled at 7.6 to prepare a descaling agent.

[0110] Example 8

[0111] 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.

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

[0113] Example 9

[0114] The formula and method of Example 1 are the same as those of Example 1, except that the synergist is polyepoxysuccinic acid (100 wt %, based on the total weight of the synergist), and the other components are 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 is controlled at 7 to prepare a descaling agent.

[0116] Example 10

[0117] The formulation and method of Example 1 are the same as those of Example 1, except that the synergist is polyaspartic acid (100 wt %, based on the total weight of the synergist), 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 is controlled at 7 to prepare a descaling agent.

[0119] Embodiment 11

[0120] 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.

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

[0122] Example 12

[0123] According to the formula and method of Example 1, the only difference is that the chelate catalyst includes 50wt% sodium nitrite and 50wt% ammonium chloride, and the other 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 is controlled at 7 to prepare a descaling agent.

[0125] Example 13

[0126] According to the formula and method of Example 1, the only difference is that the chelate catalyst includes 35wt% sodium nitrite and 65wt% ammonium chloride, and the other 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 is controlled at 7 to prepare a descaling agent.

[0128] Embodiment 14

[0129] 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.

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

[0131] Embodiment 15

[0132] According to the formula and method of Example 1, the only difference is that this example uses the polyamino polyacid chelating agent prepared in Preparation Example 2, and the polyamino polyacid chelating agent has the structure shown in Formula I-2, and the other components are the same as Example 1.

[0133] According to the method of Example 1 and the formula of the above descaling composition, the pH value is controlled at 7 to prepare a descaling agent.

[0134] Example 16

[0135] A descaling composition, comprising, 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 respectively the same as those in Example 1.

[0136] 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.

[0137] Comparative Example 1

[0138] 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.

[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 12, which was an alkaline descaling agent.

[0140] Comparative Example 2

[0141] 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.

[0142] 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.

[0143] Comparative Example 3

[0144] According to the formula and method of Example 1, the only difference is that the chelating agent is diethylenetriaminepentaacetic acid, and the other 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 is controlled at 7 to prepare a descaling agent.

[0146] Comparative Example 4

[0147] 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 other 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 is controlled at 7 to prepare a descaling agent.

[0149] Comparative Example 5

[0150] According to the formula and method of Example 1, the only difference is that no synergist is added, and the other 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 is controlled at 7 to prepare a descaling agent.

[0152] Comparative Example 6

[0153] The formula 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.

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

[0155] Comparative Example 7

[0156] The formula and method of Example 1 are the same as those of Example 1, except that the synergist and chelating stabilizer are not added. The other 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 is controlled at 7 to prepare a descaling agent.

[0158] Comparative Example 8

[0159] The formula 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.

[0160] According to the method of Example 1 and the formula of the above descaling composition, the pH value is controlled at 7 to prepare a descaling agent.

[0161] Test Case

[0162] The dissolution rate and corrosion rate are determined as follows:

[0163] (1) Determination of dissolution rate: Weigh 1 g of the scale sample and add it to 50 mL of the descaling agent prepared in the above Examples 1-18 and Comparative Examples 1-7, respectively. After reacting at 120° C. and 180° C. for 6 h, filter and dry. The dissolution rate is calculated by measuring the mass difference of the scale sample before and after the reaction.

[0164]

[0165] Where:

[0166] m0——mass of the scale sample before the scale sample reaction, g;

[0167] m1——The mass of the scale sample after the reaction, g.

[0168] (2) Determination of corrosion rate: After polishing the steel (super 13Cr) for oil pipes, clean and dry it with petroleum ether and ethanol, weigh it, and place it in an autoclave. Then, introduce 2L of the descaling agent prepared in the above Examples 1-14 and Comparative Examples 1-7, respectively, stir and heat to 180°C, then introduce high-purity N2 to maintain the N2 pressure at 10MPa. After stabilizing under this condition for 6 hours, take out the sample, remove the corrosion product film on the surface of the sample, dry it, weigh it, and calculate the corrosion rate.

[0169] Table 1

[0170]

[0171] It can be seen from the results in Table 1 that the descaling agents used in the embodiments of the present invention are all strong penetrating neutral descaling agents, and the scale dissolution rates of calcium carbonate, calcium sulfate and barium sulfate at 120 and 180° C. are higher than those of the control examples. At the same time, they all have faster corrosion rates and can be used in high-temperature oil and gas wells.

[0172] The neutral descaling agent of the present invention is suitable for descaling and unblocking of high-temperature gas wellbore. The test result of the descaling rate shows that the use temperature thereof can reach 120-180°C.

[0173] 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 2 h)) has the characteristics of excellent temperature resistance (90-180℃), wide application range, non-toxic and environmentally friendly, and has good compatibility with formation water, will not cause damage to the formation and pipeline, and can effectively solve the clogging problem of inorganic insoluble scale in high-temperature and high-pressure gas wells.

[0174] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A descaling composition, 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, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

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

4. The descaling composition according to claim 3, wherein 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, wherein The chelate catalyst is a mixture of ammonium chloride and sodium nitrite.

6. The descaling composition according to claim 5, wherein 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, wherein 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, wherein 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, wherein 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, wherein 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, 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, R1 is dialkylamino, alkylamino, amino, hydroxy, alkoxy, amide, acyloxy, carboxymethyl or carboxyl.

12. The preparation method according to claim 11, wherein 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, wherein: The temperature inside the oil and gas well is 120-180°C.

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