Water-based-oil-based cleaning agent for cleaning oil-gas pipeline, compounding method and application of water-based-oil-based cleaning agent

Abstract

The invention discloses a water-based-oil-based cleaning agent for cleaning oil and gas pipelines, a compounding method and application, and relates to the technical field of cleaning agents, the cleaning agent comprises an oil-based component and a water-based component; the oil-based component is prepared from the following raw materials in parts by weight: 60 to 80 parts of C11-C14 isoparaffin solvent oil, 5 to 10 parts of a first composite surfactant, 3 to 7 parts of a dispersing agent and 5 to 10 parts of a polar cosolvent; the water-based component is prepared from the following raw materials in parts by weight: 5 to 15 parts of a second composite surfactant, 1 to 3 parts of triethanolamine, 5 to 10 parts of an organic solvent, 0.5 to 1.5 parts of a chelating agent, 0.5 to 1.5 parts of a corrosion inhibitor and 70 to 90 parts of water. The water-based and oil-based cleaning agent disclosed by the invention can be used for fully cleaning oil and gas pipelines.

Description

Technical Field

[0001] This invention relates to the field of cleaning agent technology, and in particular to water-based and oil-based cleaning agents for cleaning oil and gas pipelines, their compounding methods, and applications. Background Technology

[0002] With the widespread development of oil and gas resources and the ever-increasing demand for long-distance transportation, the cleaning and maintenance of oil and gas pipelines, as crucial infrastructure connecting oil fields, refineries, and end-user markets, is becoming increasingly prominent. Because crude oil and natural gas commonly contain waxes, asphaltenes, heavy hydrocarbons, inorganic salts, rust particles, and other complex impurities, after a period of operation, pipelines often accumulate large amounts of contaminants on their inner walls. This not only affects transportation efficiency but also increases energy consumption and can even lead to operational risks such as corrosion, blockages, and abnormal pressure differences. Therefore, developing high-performance cleaning agents to efficiently, safely, and environmentally friendly remove fouling from oil and gas pipelines is a critical technical problem that urgently needs to be solved in the current oil and gas industry.

[0003] Existing oil and gas pipeline cleaning agents are mainly divided into two categories: water-based and oil-based. Water-based cleaning agents have advantages such as low cost, good environmental performance, and convenient waste liquid treatment. They are usually used to remove inorganic scale and polar contaminants. However, their cleaning ability is limited for strongly hydrophobic organic scale such as waxes and asphalt, and problems such as incomplete emulsification and dispersion often occur during the cleaning process, resulting in low cleaning efficiency. Conversely, oil-based cleaning agents, due to their lower solvent polarity, have a strong dissolving ability for non-polar organic dirt such as crude oil residue, and are therefore widely used in practical applications. However, these cleaning agents generally have problems such as high volatility, flammability and explosiveness, environmental and operator-friendly effects, and a greater risk of corrosion to pipeline materials. In addition, existing water-based and oil-based cleaning agents have poor treatment effects when dealing with complex dirt (such as oil-inorganic complex scale and multi-layered scale), and there is a risk of cleaning residue.

[0004] In summary, existing oil and gas pipeline cleaning technologies have significant shortcomings in addressing complex contamination systems, improving cleaning efficiency, and ensuring safety and environmental friendliness. They fail to meet the urgent needs of the modern oil and gas industry for efficient, safe, and environmentally friendly cleaning agents. Therefore, there is a pressing need to develop a composite cleaning agent that is highly efficient, compatible, environmentally friendly, and suitable for various pipeline materials to overcome the aforementioned deficiencies and limitations of existing technologies. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a water-based / oil-based cleaning agent, a compounding method and application for cleaning oil and gas pipelines, which can achieve thorough cleaning of oil and gas pipelines.

[0006] This invention proposes a water-based / oil-based cleaning agent for cleaning oil and gas pipelines, comprising an oil-based component and a water-based component; The oil-based component comprises the following raw materials in parts by weight: 60-80 parts of C11-C14 isoalkane solvent oil, 5-10 parts of the first composite surfactant, 3-7 parts of dispersant, and 5-10 parts of polar cosolvent. The water-based component comprises the following raw materials in parts by weight: 5-15 parts of the second composite surfactant, 1-3 parts of triethanolamine, 5-10 parts of organic solvent, 0.5-1.5 parts of chelating agent, 0.5-1.5 parts of corrosion inhibitor, and 70-90 parts of water.

[0007] Preferably, the first composite surfactant is composed of a 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and a Gemini-type alkyl glycoside derivative surfactant in a mass ratio of 3:1-9.

[0008] Preferably, the dispersant is one or more of castor oil polyoxyethylene ether, caprylic / capric triglyceride, sorbitan monostearate polyoxyethylene ether, isopropyl palmitate, and isooctyl lactate.

[0009] Preferably, the polar co-solvent is one or more of propylene glycol butyl ether, dipropylene glycol methyl ether, ethylene glycol monobutyl ether, N-methylpyrrolidone and γ-butyrolactone.

[0010] Preferably, the second composite surfactant is composed of a dehydroabsinolate grafted copolymerized shell oligosaccharide surfactant and a sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant in a mass ratio of 2:1-4.

[0011] Preferably, the organic solvent is one or more of ethanol, propylene glycol, butanediol and glycerol.

[0012] Preferably, the chelating agent is one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, and sodium hypotriacetate.

[0013] Preferably, the corrosion inhibitor is one or more of benzotriazole, methylbenzotriazole, triethanolamine oleate, and imidazoline corrosion inhibitor.

[0014] This invention proposes a method for compounding a water-based and oil-based cleaning agent for cleaning oil and gas pipelines. The cleaning agent is as described above, and the method steps are as follows: S1: Add the first composite surfactant and dispersant to the C11-C14 isoalkane solvent oil while stirring at 300-400 rpm. After mixing, add the polar cosolvent and increase the speed to 500-700 rpm. Stir for 20-40 minutes to obtain the oil-based component. S2: Heat deionized water to 40-60℃, add the second composite surfactant while stirring, mix well, and then add triethanolamine, organic solvent, chelating agent and corrosion inhibitor in sequence. After mixing well, the water-based component is obtained.

[0015] The present invention relates to the application of the above-mentioned water-based / oil-based cleaning agent in the cleaning of oil and gas pipelines.

[0016] Beneficial technical effects of the present invention: 1. Regarding the oil-based component, this invention preferably uses C11-C14 isoalkane solvent oil as the base solvent, whose shorter carbon chain isomeric structure endows it with good scale-dissolving ability and high safety. This solvent oil has low toxicity, low vapor pressure, and excellent wetting and penetrating ability, and can quickly penetrate waxes, asphaltenes, and heavy oil residues adhering to the pipe wall, effectively softening and dissolving non-polar contaminants. More importantly, the first composite surfactant designed in the oil-based component is a two-component system composed of 1,3-2-(octadecylamidopropyldimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant. The synergistic mechanism between the two lies in the fact that the neopentyl glycol group provides branching steric hindrance, enhancing the directional alignment of molecules at the oil-water interface, while the Gemini-type alkyl glycoside derivative achieves multi-point distribution of hydrophilic ends in the molecular structure, forming a stable interfacial layer structure. The synergistic effect of the two significantly improves the emulsification stability, temperature and shear resistance of the system, as well as the dissolution rate of heavy oil contaminants. This synergistic effect enables the oil-based component to not only quickly penetrate and remove most of the non-polar fouling in oil and gas pipelines, but also lays a good foundation for subsequent water-based cleaning.

[0017] 2. Regarding the water-based components, the second composite surfactant of this invention is a two-component system composed of dehydroabsinolate-grafted copolymerized chitosan oligosaccharide surfactant and sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate. This combination achieves an organic integration of the biocompatibility of natural oligosaccharides and the enhanced hydrophobicity resulting from graft modification. The synergistic mechanism of the second composite surfactant lies in the fact that chitosan oligosaccharides provide good biodegradability and a hydrophobic chain structure, enhancing the dispersion and stabilization effect on residual organic dirt, while the surfactant containing siloxane groups deeply penetrates the residual oil phase through hydrophobic segments, interacting with the residual surfactant components therein, thereby further promoting the stripping and cleaning of contaminants; the two together construct a stable micromicelle system in a water-based environment, maintaining good stability even in high-shear flow fields, significantly enhancing the ability of the water-based cleaning section to remove dissolved but not completely stripped contaminants.

[0018] 3. The combined operation of "oil-based pre-cleaning + water-based post-rinsing" employed in this invention creates a significant dynamic synergistic effect in the two-stage cleaning process. During oil-based cleaning, some incompletely emulsified oil residue remains on the pipe wall surface, still containing a certain proportion of the first composite surfactant and polar co-solvent. When the water-based components enter, the surfactants in these oil residues and the second composite surfactants in the water-based system can form a transitional composite micelle structure through hydrophobic chain interactions and interface reconstruction, enhancing the synergistic emulsification and descaling capabilities of the two-phase system. This staged dynamic synergistic effect not only improves the stripping rate of complex scale layers but also effectively reduces the problem of "intercalated contaminants" residue in traditional cleaning, thereby improving overall cleaning efficiency and quality. Detailed Implementation

[0019] The present invention will be further explained below with reference to specific embodiments.

[0020] The preparation method of the 1,3-2-(octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant in this invention is as follows: 1 mol of 3-didimethylamino-1-propane and phosphoric acid (0.5 wt%) were added, followed by 0.6 mol of octadecanoic acid. The mixture was reacted at 150°C for 8 hours to obtain an intermediate product. The intermediate product was mixed with isopropanol, and then 0.01 mol (2.62 g) of 1,3-dibromo-2,2-dihydroxymethylpropane was added. The mixture was refluxed in a water bath at 85°C for 24 hours, and the 1,3-2-(octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant was obtained by recrystallization from acetone. The specific structural formula is as follows:

[0021] The preparation method of Gemini-type alkyl glycoside derivative surfactant is as follows: 1 mol of alkyl glycoside APG0814 was dissolved in pyridine, and then 1.15 mol of chloroacetyl chloride was added and reacted at room temperature for 5 h to obtain intermediate product I; 0.008 mol of boron trifluoride diethyl ether complex and excess epichlorohydrin were added to 1 mol of polyethylene glycol monomethyl ether and reacted to obtain intermediate product II; intermediate product II was mixed with DMAC and reacted to obtain intermediate product III; 1 mol of intermediate product I and 1.15 mol of intermediate product III were dissolved in DMF, and then 0.01 mol of potassium iodide was added and refluxed at 105 °C for 48 h to obtain Gemini-type alkyl glycoside derivative surfactant. The specific structural formula is as follows:

[0022] The preparation method of the dehydroabscisic acid allyl ester grafted copolymer chitosan oligosaccharide surfactant is as follows: 2g of chitosan oligosaccharide is dispersed in 30ml of dimethyl sulfoxide, then 10g of dehydroabscisic acid allyl ester, a polymerization inhibitor, and an initiator are added sequentially. After reacting for 24h, the mixture is filtered, freeze-dried, extracted with acetone, and freeze-dried again to obtain the dehydroabscisic acid allyl ester grafted copolymer chitosan oligosaccharide surfactant. Both chitosan oligosaccharide and dehydroabscisic acid allyl ester are prepared using existing known methods. The specific structural formula is as follows:

[0023] The preparation method of sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant is as follows: The specific structural formula is as follows: 200 mmol of hexamethyldisiloxane, 20 mmol of γ-aminopropyldiethoxymethylsilane, and 0.5 mmol of tetramethylammonium hydroxide pentahydrate were reacted at 85 °C for 2 h to obtain intermediate product I; 1.1 mmol of maleic anhydride and 1 mmol of intermediate product I were reacted in dichloromethane in an ice bath for 2 h, and then reacted at room temperature for 2 h. Excess triethylamine was added, and the mixture was filtered and distilled under reduced pressure to obtain intermediate product II; intermediate product II was then reacted with sodium bicarbonate to obtain sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant.

[0024] Example 1

[0025] While stirring at 350 rpm, 8 parts of a first composite surfactant and 5 parts of a dispersant were added to 70 parts of C11-C14 isoalkane solvent oil. After mixing, 8 parts of a polar co-solvent were added, and the stirring speed was increased to 600 rpm. The mixture was stirred for 30 minutes to obtain the oil-based component. 80 parts of deionized water were heated to 50°C, and 10 parts of a second composite surfactant were added while stirring. After mixing, 2 parts of triethanolamine, 8 parts of an organic solvent, 1 part of a chelating agent, and 1 part of a corrosion inhibitor were added sequentially. After mixing, the water-based component was obtained. When cleaning oil and gas pipelines, the oil-based component and the water-based component were used sequentially.

[0026] The first composite surfactant is composed of 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant in a 1:1 mass ratio.

[0027] The dispersant is composed of castor oil polyoxyethylene ether and dehydrated sorbitan monostearate polyoxyethylene ether in a 1:1 mass ratio; the polar cosolvent is propylene glycol butyl ether.

[0028] The second composite surfactant is composed of a dehydroabsinolate-grafted copolymerized shell oligosaccharide surfactant and a sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant in a 1:1 mass ratio.

[0029] The organic solvent is propylene glycol; the chelating agent is disodium ethylenediaminetetraacetate; and the corrosion inhibitor is benzotriazole.

[0030] Example 2

[0031] While stirring at 300 rpm, 5 parts of a first composite surfactant and 3 parts of a dispersant were added to 60 parts of C11-C14 isoalkane solvent oil. After mixing, 5 parts of a polar co-solvent were added, and the stirring speed was increased to 500 rpm. The mixture was stirred for 20 minutes to obtain the oil-based component. 70 parts of deionized water were heated to 40°C, and 5 parts of a second composite surfactant were added while stirring. After mixing, 1 part of triethanolamine, 5 parts of organic solvent, 0.5 parts of chelating agent, and 0.5 parts of corrosion inhibitor were added sequentially. The mixture was then stirred to obtain the water-based component. When cleaning oil and gas pipelines, the oil-based component and the water-based component were used sequentially for cleaning.

[0032] The first composite surfactant is composed of 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant in a mass ratio of 3:1.

[0033] The dispersant is triglyceride decanoate; the polar cosolvent is N-methylpyrrolidone.

[0034] The second composite surfactant is composed of a dehydroabsinolate-grafted copolymerized shell oligosaccharide surfactant and a sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant in a mass ratio of 2:1.

[0035] The organic solvent is butanediol; the chelating agent is tetrasodium ethylenediaminetetraacetate; and the corrosion inhibitor is triethanolamine oleate.

[0036] Example 3

[0037] While stirring at 400 rpm, 10 parts of a first composite surfactant and 7 parts of a dispersant were added to 80 parts of C11-C14 isoalkane solvent oil. After mixing, 10 parts of a polar co-solvent were added, and the stirring speed was increased to 700 rpm. The mixture was stirred for 40 minutes to obtain the oil-based component. 90 parts of deionized water were heated to 60°C, and 15 parts of a second composite surfactant were added while stirring. After mixing, 3 parts of triethanolamine, 10 parts of an organic solvent, 1.5 parts of a chelating agent, and 1.5 parts of a corrosion inhibitor were added sequentially. The mixture was then stirred to obtain the water-based component. When cleaning oil and gas pipelines, the oil-based component and the water-based component were used sequentially for cleaning.

[0038] The first composite surfactant is composed of 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant in a mass ratio of 1:3.

[0039] The dispersant is isopropyl palmitate; the polar cosolvent is ethylene glycol monobutyl ether.

[0040] The second composite surfactant is composed of a dehydroabsinolate-grafted copolymerized shell oligosaccharide surfactant and a sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant in a mass ratio of 1:2.

[0041] The organic solvent is glycerol; the chelating agent is sodium hypotriacetate; and the corrosion inhibitor is methylbenzotriazole.

[0042] Comparative Example 1 The first composite surfactant was a 1,3-2-(octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant. All other conditions were the same as in Example 1.

[0043] Comparative Example 2 The first composite surfactant was a Gemini-type alkyl glycoside derivative surfactant. All other conditions were the same as in Example 1.

[0044] Comparative Example 3 The second composite surfactant is a dehydroabietic acid allyl ester grafted copolymerized chitosan oligosaccharide surfactant. All other conditions are the same as in Example 1.

[0045] Comparative Example 4 The second composite surfactant is sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate. All other conditions are the same as in Example 1.

[0046] The cleaning performance of the cleaning agents obtained in Examples 1-3 and Comparative Examples 1-4 was measured, and the test results are shown in Table 1.

[0047] The testing method is as follows: Cut pipes of the same size, collect oil stains from the oil and gas pipelines, mix them evenly and apply them to the pipes in equal amounts, then clean them with a cleaning agent, and calculate the oil stain removal rate according to the following formula.

[0048] In the formula, m0 is the initial pipe mass; m1 is the pipe mass after applying oil; and m2 is the pipe mass after treatment with cleaning agent.

[0049] Table 1 Cleaning effect test results Group Oil removal rate (%) Example 1 98.4 Example 2 96.1 Example 3 97.7 Comparative Example 1 80.2 Comparative Example 2 78.5 Comparative Example 3 82.6 Comparative Example 4 84.3 As can be seen from the test results of Examples 1-3 in Table 1, the combined operation method of "oil-based pre-cleaning + water-based post-rinsing" adopted in this invention, during the oil-based cleaning process, some incompletely emulsified oil residue remains on the pipe wall surface, still containing a certain proportion of the first composite surfactant and polar co-solvent. When the water-based components enter, the surfactant in these oil residues and the second composite surfactant in the water-based system can form a transitional composite micelle structure through hydrophobic chain interactions and interface reconstruction, enhancing the synergistic emulsification and descaling capabilities of the two-phase system. This staged dynamic synergistic effect not only improves the peeling rate of complex scale layers but also effectively reduces the problem of "intercalated contaminants" residue in traditional cleaning, significantly improving the cleaning effect of oil and gas pipelines, with an oil removal rate of over 98%.

[0050] As can be seen from the experimental results of Example 1 and Comparative Examples 1-2 in Table 1, in terms of the oil-based component, the first composite surfactant is a combination of 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant. It has a synergistic promoting effect on improving the oil removal rate. The relevant mechanism is that the neopentyl glycol group provides branched steric hindrance, which enhances the directional alignment ability of molecules at the oil-water interface, while the Gemini-type alkyl glycoside derivative achieves multi-point distribution of hydrophilic ends in the molecular structure, forming a stable interfacial layer structure. The synergistic effect of the two significantly improves the emulsification stability, temperature and shear resistance of the system, and the dissolution rate of heavy oil contaminants. This synergistic effect enables the oil-based component to not only quickly penetrate and remove most of the non-polar dirt in oil and gas pipelines, but also lay a good foundation for subsequent water-based cleaning.

[0051] As can be seen from the experimental results of Example 1 and Comparative Examples 3-4 in Table 1, in terms of water-based components, the second composite surfactant, which is a combination of dehydroabsinolate-grafted copolymerized chitosan oligosaccharide surfactant and sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate, also has a synergistic promoting effect on improving the oil removal rate. The relevant mechanism is that chitosan oligosaccharide provides good biodegradability and hydrophobic chain structure, which enhances the dispersion and stabilization effect on residual organic dirt, while the surfactant containing siloxane groups deeply penetrates the residual oil phase through hydrophobic segments and interacts with the residual surfactant components therein, thereby further promoting the stripping and cleaning of pollutants. The two together construct a stable micromicelle system in the water-based environment, which still maintains good stability in the high shear flow field, significantly enhancing the ability of the water-based cleaning section to remove dissolved but not completely stripped pollutants.

[0052] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A water-based / oil-based cleaning agent for cleaning oil and gas pipelines, characterized in that, Includes oil-based and water-based components; The oil-based component comprises the following raw materials in parts by weight: 60-80 parts of C11-C14 isoalkane solvent oil, 5-10 parts of the first composite surfactant, 3-7 parts of dispersant, and 5-10 parts of polar cosolvent. The water-based component comprises the following raw materials in parts by weight: 5-15 parts of the second composite surfactant, 1-3 parts of triethanolamine, 5-10 parts of organic solvent, 0.5-1.5 parts of chelating agent, 0.5-1.5 parts of corrosion inhibitor, and 70-90 parts of water.

2. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The first composite surfactant is composed of 1,3-2 (octadecylamidopropyl dimethylammonium bromide) neopentyl glycol surfactant and Gemini-type alkyl glycoside derivative surfactant in a mass ratio of 3:1-9.

3. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The dispersant is one or more of castor oil polyoxyethylene ether, caprylic / capric triglyceride, sorbitan monostearate polyoxyethylene ether, isopropyl palmitate, and isooctyl lactate.

4. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The polar cosolvent is one or more of propylene glycol butyl ether, dipropylene glycol methyl ether, ethylene glycol monobutyl ether, N-methylpyrrolidone and γ-butyrolactone.

5. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The second composite surfactant is composed of dehydroabsinolate grafted copolymerized shell oligosaccharide surfactant and sodium 4-(trisiloxane-2-propylamino)-4-oxobutenoate surfactant in a mass ratio of 2:1-4.

6. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The organic solvent is one or more of ethanol, propylene glycol, butanediol, and glycerol.

7. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The chelating agent is one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, and sodium hypotriacetate.

8. The water-based / oil-based cleaning agent for cleaning oil and gas pipelines according to claim 1, characterized in that, The corrosion inhibitor is one or more of benzotriazole, methylbenzotriazole, triethanolamine oleate, and imidazoline corrosion inhibitor.

9. A method for compounding a water-based and oil-based cleaning agent for cleaning oil and gas pipelines, wherein the cleaning agent is as described in any one of claims 1-8, characterized in that... The steps are as follows: S1: Add the first composite surfactant and dispersant to the C11-C14 isoalkane solvent oil while stirring at 300-400 rpm. After mixing, add the polar cosolvent and increase the speed to 500-700 rpm. Stir for 20-40 minutes to obtain the oil-based component. S2: Heat deionized water to 40-60℃, add the second composite surfactant while stirring, mix well, and then add triethanolamine, organic solvent, chelating agent and corrosion inhibitor in sequence. After mixing well, the water-based component is obtained.

10. The application of the water-based / oil-based cleaning agent as described in any one of claims 1-8 in the cleaning of oil and gas pipelines.

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