A scale inhibitor, its preparation method and a method for removing scale in oilfield pipelines

Abstract

This application relates to the technical field of scale inhibitors, and discloses a scale inhibitor, a preparation method thereof, and a method for removing scale from oilfield pipelines. The scale inhibitor described in this application includes 10 - 50 parts of citric acid, 0 - 20 parts of oxalic acid, 0 - 20 parts of acetic acid, 0 - 20 parts of maleic acid, 0 - 15 parts of malic acid, 5 - 15 parts of salicylic acid, 5 - 15 parts of mercaptosuccinic acid, 5 - 40 parts of penetrant, 5 - 20 parts of suspending agent, and 20 - 60 parts of water. This application selects a variety of suitable short-chain organic acids and auxiliary compatibility agents for combined use, enabling the scale inhibitor to fully contact the pipeline scale and undergo a chemical reaction, which can improve the scale removal efficiency, achieve a rapid reaction of scale at normal temperature, and realize the rapid and deep degradation and removal of scale in oilfield pipelines.

Description

Technical Field

[0001] This application relates to the technical field of scale inhibitors, and particularly relates to a scale inhibitor for efficiently removing scale from oilfield pipelines at room temperature, a preparation method thereof, and a method for removing scale from oilfield pipelines. Background Art

[0002] After water breakthrough in oil wells, in the complex seepage environment near the wellbore, the acid radical ions in the injected water are strongly mixed with the metal ions in the formation water, forming a large amount of scale, which enters the production well pipes and processes together. The common scale deposits in oilfields are mainly carbonate substances such as calcium carbonate and magnesium carbonate. The scale deposition greatly reduces the heat transfer effect of the equipment in the oil and gas gathering and transportation system, cuts down the cross-sectional area of fluid flow, increases the flow resistance and transportation energy, thus causing serious energy waste, and is extremely prone to local under-scale corrosion of pipelines, causing corrosion perforation and scrapping of pipelines.

[0003] In the prior art, the main components of acidic scale inhibitors are mainly strong acidic inorganic acids such as hydrochloric acid. Although scale inhibitors mainly composed of inorganic acids have advantages such as high scale removal efficiency and low cost, the characteristics of high corrosivity and irritation of inorganic acids themselves also cause harm to the human body and the environment. Moreover, inorganic acid components are prone to secondary scale formation due to the deposition of products during the scale removal process.

[0004] Chinese Patent CN202010726087.6 discloses a high-efficiency scale inhibitor and a preparation method thereof. The scale inhibitor is prepared from raw materials comprising the following parts by weight: 10 - 20 parts of hydroxyethylidene diphosphonic acid, 10 - 20 parts of 2-phosphonobutane-1,2,4-tricarboxylic acid, 5 - 12 parts of acrylic acid, 1 - 3 parts of hydroxypropyl acrylate, 5 - 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5 - 12 parts of sulfuric acid, and 20 - 40 parts of deionized water. A large amount of high molecular weight long-chain organic acids are used in the scale inhibitor formula of this patent. Although it has lower corrosivity compared to inorganic acids, the groups on these organic acids are themselves water pollutants, and discharging them without treatment will cause serious environmental pollution. Moreover, the procurement cost of high molecular weight long-chain organic acids is relatively expensive, resulting in poor economic applicability of the scale inhibitor. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a scale inhibitor for removing scale from oilfield pipelines, so that the scale inhibitor can not only efficiently dissolve and remove scale and avoid secondary scale formation, but also reduce the damage to pipeline equipment;

[0006] Another purpose of this application is to provide a method for removing scale from oilfield pipelines based on the above scale inhibitor.

[0007] To solve the above technical problems / achieve the above object or at least partially solve the above technical problems / achieve the above object, as the first aspect of the present application, a descaling agent for removing scale from oilfield pipelines is provided. By weight, it includes 10 - 50 parts of citric acid, 0 - 20 parts of oxalic acid, 0 - 20 parts of acetic acid, 0 - 20 parts of maleic acid, 0 - 15 parts of malic acid, 5 - 15 parts of salicylic acid, 5 - 15 parts of mercaptosuccinic acid, 5 - 40 parts of penetrant, 5 - 20 parts of suspending agent, and 20 - 60 parts of water.

[0008] Optionally, the weight parts of the citric acid are 15 - 40 parts, 15 - 30 parts or 15 - 20 parts, and specifically can be selected as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts or 50 parts;

[0009] Optionally, the weight parts of the oxalic acid are 0 - 10 parts, 0 - 5 parts, 1 - 5 parts or 3 - 5 parts, and specifically can be selected as 0, 1 part, 3 parts, 5 parts, 10 parts, 15 parts or 20 parts;

[0010] Optionally, the weight parts of the acetic acid are 0 - 10 parts, 0 - 5 parts, 1 - 5 parts or 3 - 5 parts, and specifically can be selected as 0, 1 part, 3 parts, 5 parts, 10 parts, 15 parts or 20 parts;

[0011] Optionally, the weight parts of the maleic acid are 0 - 10 parts, 0 - 5 parts, 1 - 5 parts or 3 - 5 parts, and specifically can be selected as 0, 1 part, 3 parts, 5 parts, 10 parts, 15 parts or 20 parts;

[0012] Optionally, the weight parts of the malic acid are 0 - 10 parts, 0 - 5 parts, 1 - 5 parts or 3 - 5 parts, and specifically can be selected as 0, 1 part, 3 parts, 5 parts, 10 parts or 15 parts;

[0013] Optionally, the weight parts of the salicylic acid are 10 - 15 parts, and specifically can be selected as 5 parts, 10 parts or 15 parts;

[0014] Optionally, the weight parts of the mercaptosuccinic acid are 10 - 15 parts, and specifically can be selected as 5 parts, 10 parts or 15 parts;

[0015] Optionally, the weight parts of the penetrant are 5 - 30 parts, 5 - 20 parts or 5 - 10 parts, and specifically can be selected as 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts;

[0016] Optionally, the weight parts of the suspending agent are 5 - 15 parts or 5 - 10 parts, and specifically can be selected as 5 parts, 10 parts, 15 parts or 20 parts;

[0017] Optionally, the parts by weight of water are 30 - 50 parts or 30 - 40 parts, and specifically, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts can be selected.

[0018] In some embodiments of the present application, the scale inhibitor, by weight, includes 15 - 40 parts of citric acid, 0 - 10 parts of oxalic acid, 0 - 10 parts of acetic acid, 0 - 10 parts of maleic acid, 0 - 10 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 30 parts of penetrant, 5 - 15 parts of suspending agent, and 30 - 50 parts of water; in some other embodiments of the present application, the scale inhibitor, by weight, includes 15 - 2030 parts of citric acid, 0 - 5 parts of oxalic acid, 0 - 5 parts of acetic acid, 0 - 5 parts of maleic acid, 0 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 20 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water; in some other embodiments of the present application, the scale inhibitor, by weight, includes 15 - 20 parts of citric acid, 1 - 5 parts of oxalic acid, 1 - 5 parts of acetic acid, 0 - 5 parts of maleic acid, 0 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water; in some other embodiments of the present application, the scale inhibitor, by weight, includes 15 - 20 parts of citric acid, 1 - 5 parts of oxalic acid, 1 - 5 parts of acetic acid, 1 - 5 parts of maleic acid, 1 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water; in some other embodiments of the present application, the scale inhibitor, by weight, includes 15 - 20 parts of citric acid, 3 - 5 parts of oxalic acid, 3 - 5 parts of acetic acid, 3 - 5 parts of maleic acid, 3 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water.

[0019] In specific embodiments of the present application, the scale inhibitor, by weight, can arbitrarily select any one of the following:

[0020] (1) 30 parts of citric acid, 10 parts of salicylic acid, 10 parts of mercaptosuccinic acid, 5 parts of penetrant, 5 parts of suspending agent, and 40 parts of water;

[0021] (2) 20 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 15 parts of salicylic acid, 15 parts of mercaptosuccinic acid, 5 parts of penetrant, 5 parts of suspending agent, and 30 parts of water;

[0022] (3) 20 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 10 parts of salicylic acid, 10 parts of mercaptosuccinic acid, 5 parts of penetrant, 5 parts of suspending agent, and 30 parts of water;

[0023] (4) 15 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 15 parts of salicylic acid, 10 parts of mercaptosuccinic acid, 5 parts of penetrant, 5 parts of suspending agent, and 30 parts of water;

[0024] (5) 15 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 10 parts of salicylic acid, 15 parts of mercaptosuccinic acid, 5 parts of penetrant, 5 parts of suspending agent, and 30 parts of water.

[0025] In some embodiments of the present application, the penetrant is JFC penetrant; the suspending agent is magnesium aluminum carbonate, such as one or two selected from hydrotalcite and sodium magnesium aluminum bicarbonate. In some other embodiments of the present application, the penetrant is JFC penetrant and the suspending agent is hydrotalcite or sodium magnesium aluminum bicarbonate.

[0026] As the second aspect of the present application, a preparation method of the descaling agent is provided, including: forming a homogeneous solution of citric acid, oxalic acid, acetic acid, maleic acid, malic acid, salicylic acid, mercaptosuccinic acid, penetrant, suspending agent and water to obtain the descaling agent;

[0027] In some embodiments of the present application, the preparation method of the descaling agent includes: adding water to citric acid, oxalic acid, acetic acid, maleic acid, malic acid, salicylic acid, mercaptosuccinic acid to form a homogeneous solution, then adding the penetrant and mixing well, and then adding the suspending agent and mixing well, and filtering the uniformly mixed solution to obtain the descaling agent. Among them, the filtration can be selected as filtration through a 200-300 mesh sieve.

[0028] As the third aspect of the present application, a method for removing scale in oilfield pipelines is provided, using the descaling agent of the present application to circulate and treat in the scaled pipeline. In some embodiments of the present application, the method for removing scale in oilfield pipelines is to pump the descaling agent of the present application into the scaled pipeline with an acid-resistant diaphragm pump and circulate for 30 h. In addition, in the circulating treatment, the dynamic balance of the descaling agent flow rate and the reaction rate is achieved by controlling the pump power to ensure the relative stability of the overall reaction system and the full removal of the scale in the pipeline. The pump power can be selected as 85-120 W.

[0029] Compared with conventional inorganic acid descaling agents and long-chain organic acid descaling agents, the present application selects a variety of suitable short-chain organic acids and auxiliary compatibility agents for combined use, so that the descaling agent can fully contact the pipeline scale and undergo a chemical reaction, which can improve the descaling efficiency, realize the rapid reaction of scale at normal temperature, and achieve the rapid and deep degradation and removal of scale in oilfield pipelines. Detailed Embodiments

[0030] The present application discloses a scale inhibitor, a preparation method thereof, and a method for removing scale from oilfield pipelines. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The processes and applications described in this application have been described through preferred embodiments. Relevant personnel can obviously make changes, or make appropriate changes and combinations, to the processes and applications described in this article without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention. Obviously, the described embodiments are part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0031] It should be noted that in this article, relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0032] The fluid properties in oilfield wellsite pipelines are special. Petroleum is rich in a large amount of hydrocarbon derivatives such as naphthenes and aromatic hydrocarbons. These substances form a dense hydrophobic film in the thin layer gaps of the scale, hindering the contact between the water-based scale inhibitor and the scale. This application uses a combination of salicylic acid, mercaptosuccinic acid, and citric acid, and comprehensively utilizes the chelating ability, oxidizing property, and acidity of the active groups of the three to quickly dissolve and destroy the hydrophobic film layer formed by hydrocarbon derivatives; on this basis, oxalic acid, acetic acid, maleic acid, and malic acid can be optionally combined to further improve the scale removal effect;

[0033] At the same time, by adding a penetrant, the contact reaction between the scale inhibitor and the scale changes from the original two-dimensional planar contact reaction of surface-to-surface to a three-dimensional stereoscopic penetration contact reaction, significantly improving the reaction efficiency and the scale removal rate, and achieving rapid and deep removal of the scale on the inner wall of the pipeline at room temperature; adding a suspending agent component effectively avoids the problem of reduced scale removal efficiency caused by the deposition of reactants and secondary scale formation, and at the same time can suspend the scale detached due to the reaction or under the action of fluid impact in the solution and discharge it from the pipeline, causing no damage to the pipeline and equipment.

[0034] This application takes calcium carbonate and magnesium carbonate, the main scale-forming substances, as the detection objects. By simulating the actual working conditions of fluid flow in pipelines, the scale removal and stripping efficiency of the added calcium carbonate and magnesium carbonate are detected. The results show that the stripping efficiency of calcium carbonate and magnesium carbonate of the scale remover in this application is between 70% and 91%, and the stripping efficiency of each other control group differs from this application by more than 15%.

[0035] In the comparative experiments in the specific implementation manners of this application, except for the marked differences in each group, other process environments, reagent materials, etc. that are not clearly stated are kept consistent.

[0036] The following further describes a scale remover provided by this application, its preparation method, and a method for removing oilfield pipeline scale.

[0037] Example 1: Scale remover of this application

[0038] (1) 30 parts of citric acid, 10 parts of salicylic acid, 10 parts of mercapto succinic acid, 5 parts of JFC penetrant, 5 parts of hydrotalcite, and 40 parts of water;

[0039] (2) 20 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 15 parts of salicylic acid, 15 parts of mercapto succinic acid, 5 parts of JFC penetrant, 5 parts of magnesium aluminum bicarbonate, and 30 parts of water;

[0040] (3) 20 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 10 parts of salicylic acid, 10 parts of mercapto succinic acid, 5 parts of JFC penetrant, 5 parts of magnesium aluminum bicarbonate, and 30 parts of water;

[0041] (4) 15 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 15 parts of salicylic acid, 10 parts of mercapto succinic acid, 5 parts of JFC penetrant, 5 parts of magnesium aluminum bicarbonate, and 30 parts of water;

[0042] (5) 15 parts of citric acid, 5 parts of oxalic acid, 5 parts of acetic acid, 5 parts of maleic acid, 5 parts of malic acid, 10 parts of salicylic acid, 15 parts of mercapto succinic acid, 5 parts of JFC penetrant, 5 parts of magnesium aluminum bicarbonate, and 30 parts of water.

[0043] Example 2: Preparation method of scale remover of this application

[0044] At room temperature, add each acid to the chemical addition mixing water tank, and then add water and stir to fully dissolve and mix the materials to finally form a uniform solution;

[0045] Add the penetrant to the acid solution that has been fully mixed and dissolved and continue to stir;

[0046] When the solution is fully mixed, add the suspending agent and continue to stir.

[0047] Filter the uniformly mixed solution through a polyester mesh with 200 - 300 meshes to obtain the prepared scale inhibitor.

[0048] Example 3: Scale removal performance detection

[0049] Prepare scale inhibitors according to the groups listed in Table 1. Among them, the penetrant in Experimental Groups 1 - 7 and Experimental Groups 19 - 21 is JFC, and the suspending agent is magnesium aluminum sodium bicarbonate; Experimental Groups 8 - 12 are the scale inhibitors (1) - (5) in Example 1; the penetrant in Experimental Groups 13 - 18 is sodium alkylbenzene sulfonate, and the suspending agent is Nekal BX;

[0050] Using calcium carbonate and magnesium carbonate as the main scale - forming substances, add the organic acid scale inhibitor products prepared in each experimental group to 50 g of 99.9 wt% calcium carbonate and magnesium carbonate solids respectively, and test their scale dissolution and stripping efficiency under the condition of a rotation speed of 100 r / min (i.e., simulating the actual working condition of fluid flow in the pipeline). The calculation formula is as follows:

[0051]

[0052]

[0053] The results are shown in Table 2;

[0054] Table 1 Composition of scale inhibitors in each experimental group (unit: parts by weight)

[0055]

[0056]

[0057]

[0058] Table 2

[0059] Calcium carbonate / % Magnesium carbonate / % Experimental group 1 12.6 14.8 Experimental group 2 18.3 13.7 Experimental group 3 23.8 29.8 Experimental group 4 57.5 48.6 Experimental group 5 44.7 45 Experimental group 6 51.2 53.6 Experimental group 7 53.3 56.3 Experimental group 8 70.8 70.1 Experimental group 9 78.7 80.2 Experimental group 10 91.6 90.3 Experimental group 11 90.2 88.2 Experimental group 12 89.3 89.1 Experimental group 13 35.2 24.8 Experimental group 14 43.6 42.8 Experimental group 15 46.7 39.8 Experimental group 16 34.1 28.3 Experimental group 17 31.6 25.3 Experimental group 18 32.6 31.7 Experimental group 19 30.4 32.4 Experimental group 20 38.2 32.1 Experimental group 21 36.3 33.3

[0060] As can be seen from the results in Table 2, in Experimental Groups 1 - 7, citric acid, salicylic acid, and mercapto - succinic acid were not used simultaneously, resulting in the stripping efficiency of calcium carbonate and magnesium carbonate not exceeding 60%;

[0061] Experimental Groups 8 - 12 are the scale inhibitors of this application. On the premise of using citric acid, salicylic acid, and mercapto - succinic acid simultaneously, other organic acids are selectively added. The stripping efficiency of calcium carbonate and magnesium carbonate of scale inhibitors with different compositions is above 70%, and the highest stripping efficiency of both can reach about 90%;

[0062] In Experimental Groups 13 - 18, different penetrants and suspending agents were replaced on the basis of Experimental Group 10 with the best scale removal effect. The results show that the stripping efficiency of calcium carbonate and magnesium carbonate did not exceed 50%;

[0063] In Experimental Group 19 - 21, a scale inhibitor with an organic acid species composition different from that of the present application was used. The results showed that the stripping efficiency of calcium carbonate and magnesium carbonate did not exceed 40%.

[0064] The results of the above comparative experiments can show that specific organic acid species, suspending agents, and penetrants can improve the scale removal effect on calcium carbonate and magnesium carbonate. Compared with scale inhibitors with other different combinations, the stripping efficiency of the scale inhibitor of the present application on calcium carbonate and magnesium carbonate can be increased by at least more than 15%. At the same time, the expected purposes of rapid and deep degradation and removal of scale in oilfield pipelines and reduction of damage to pipeline equipment are achieved.

[0065] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A descaling agent for removing scale in oilfield pipelines, characterized in that, By weight, it includes 10 - 50 parts of citric acid, 0 - 20 parts of oxalic acid, 0 - 20 parts of acetic acid, 0 - 20 parts of maleic acid, 0 - 15 parts of malic acid, 5 - 15 parts of salicylic acid, 5 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 20 - 60 parts of water; the penetrant is JFC penetrant, and the suspending agent is magnesium aluminum carbonate.

2. The scale inhibitor according to claim 1, wherein, By weight, it includes 15 - 40 parts of citric acid, 0 - 10 parts of oxalic acid, 0 - 10 parts of acetic acid, 0 - 10 parts of maleic acid, 0 - 10 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 50 parts of water.

3. The scale inhibitor according to claim 2, characterized in that, By weight, it includes 15 - 30 parts of citric acid, 0 - 5 parts of oxalic acid, 0 - 5 parts of acetic acid, 0 - 5 parts of maleic acid, 0 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water.

4. The descaling agent according to claim 3, characterized in that, By weight, it includes 15 - 20 parts of citric acid, 1 - 5 parts of oxalic acid, 1 - 5 parts of acetic acid, 0 - 5 parts of maleic acid, 0 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water.

5. The descaling agent according to claim 4, wherein By weight, it includes 15 - 20 parts of citric acid, 1 - 5 parts of oxalic acid, 1 - 5 parts of acetic acid, 1 - 5 parts of maleic acid, 1 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water.

6. The scale inhibitor according to claim 5, characterized in that, By weight, it includes 15 - 20 parts of citric acid, 3 - 5 parts of oxalic acid, 3 - 5 parts of acetic acid, 3 - 5 parts of maleic acid, 3 - 5 parts of malic acid, 10 - 15 parts of salicylic acid, 10 - 15 parts of mercaptosuccinic acid, 5 - 10 parts of penetrant, 5 - 10 parts of suspending agent, and 30 - 40 parts of water.

7. The preparation method of the descaling agent according to claim 1, characterized in that, The descaling agent is obtained by forming a homogeneous solution of citric acid, oxalic acid, acetic acid, maleic acid, malic acid, salicylic acid, mercaptosuccinic acid, penetrant, suspending agent and water.

8. A method for removing scale in oilfield pipelines, characterized in that, The descaling agent according to any one of claims 1 - 6 is used to conduct cyclic treatment by passing it into the scaling pipeline.

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