A paraffin removal and prevention agent for oil well boreholes and its preparation process

Abstract

The present invention relates to the technical field of paraffin removal and inhibition in oil wells, and discloses a paraffin removal and inhibition agent for oil well casings and a preparation process. The paraffin removal and inhibition agent for oil well casings of the present invention comprises the following components in parts by weight: 10-25 parts of a compound surfactant, 15-30 parts of a mutual solvent, 5-10 parts of a stabilizer, 1-10 parts of a novel wax crystal improver, 0.2-0.5 parts of a rapid penetrant, 0.5-1.5 parts of an alkali, and 25-70 parts of water; the novel wax crystal improver has a structure similar to that of paraffin, and wax crystals can dissolve therein, making it difficult for wax crystals to aggregate and deposit on the pipe wall, thereby increasing the dissolution rate of wax crystals; the sodium sulfonate in its structure has strong polarity and hydrophilicity, can adjust the crystallinity of the paraffin removal and inhibition agent molecules, plays a synergistic role with asphalt, gum, etc. in crude oil, reduces the surface tension of water at the same time, has a good wetting effect, and improves the low-temperature fluidity of crude oil at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of paraffin removal and prevention in oil wells, and specifically to a paraffin removal and prevention agent for oil well casings and a preparation process therefor. Background Art

[0002] Wax in crude oil usually exists in a liquid form under formation conditions. During the production and development process, as the temperature and pressure decrease and the light components in the crude oil continuously escape, the dissolving ability of the crude oil for wax is reduced, and the wax precipitates and deposits in the form of crystals, adsorbs on the inner wall of the oil well pipe, around the well wall and inside the production casing, causing the oil and gas migration channels to be blocked, damaging the reservoir, and serious wax deposition in the oil well leading to an increase in the viscosity of the crude oil, a decrease in the oil and gas production, and even possible production suspension; therefore, paraffin removal and prevention in oil wells is an important technical measure to ensure the normal production of waxy crude oil, and paraffin removal and prevention in oil wells has become an important content in the management of oil wells and is also a necessary measure to maintain the normal exploitation and transportation of crude oil.

[0003] At present, the commonly used paraffin removal and prevention technologies in China mainly include mechanical paraffin removal technology, thermal paraffin removal and prevention technology, surface energy paraffin prevention technology, magnetic paraffin prevention technology, microbial paraffin removal and prevention technology, and chemical agent paraffin removal and prevention technology, etc.; relatively speaking, the chemical paraffin removal and prevention technology has the advantages of simple dosing method, good paraffin removal and prevention effect, and wide application range, and is currently the most commonly used paraffin removal and prevention method; chemical paraffin removal agents are mainly divided into water-based paraffin removal agents, oil-based paraffin removal agents, and emulsion-type paraffin removal agents. Among them, oil-based paraffin removal agents mostly use benzene and xylene as organic solvents, which are highly toxic, easily diluted by crude oil, have a low flash point, and cause great harm to operators; emulsion-type paraffin removal agents must have stable preparation and storage conditions, and must be demulsified immediately after reaching the bottom of the well, otherwise they cannot play a role in paraffin removal and prevention, and the conditions during preparation and storage are harsh; while water-based paraffin removal agents can overcome the above-mentioned disadvantages of oil-based paraffin removal agents and emulsion-type paraffin removal agents, have no peculiar smell and no pollution, and are environmentally friendly and safe during use, but have the problems of low paraffin removal efficiency and poor paraffin prevention effect.

[0004] The present invention synthesizes a new wax crystal modifier with a structure similar to that of paraffin molecules and hydrophilic groups, and utilizes the structural characteristics of the hydrophilic and lipophilic groups of the compound surfactant to uniformly disperse the new wax crystal modifier in water, and then compound it with a mutual solvent, a stabilizer, a fast penetrant, an alkali, etc. to form an environmentally friendly and pollution-free water-based paraffin removal and prevention agent, avoiding the use of harmful solvents such as xylene, having a strong paraffin removal effect, a fast wax dissolving speed, and further improving the low-temperature fluidity of the crude oil. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies existing in the prior art, and provides a paraffin removal and prevention agent for oil well casings and a preparation process therefor, solves the problem of poor paraffin removal and prevention effect in the prior art, and further improves the low-temperature fluidity of the crude oil.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A paraffin removal and prevention agent for oil well casings, the paraffin removal and prevention agent for oil well casings comprising the following components in parts by weight: 10-25 parts of a compound surfactant, 15-30 parts of a mutual solvent, 5-10 parts of a stabilizer, 1-10 parts of a novel wax crystal improver, 0.2-0.5 parts of a rapid penetrant, 0.5-1.5 parts of an alkali, and 25-70 parts of water.

[0008] The preparation process of the novel wax crystal improver comprises the following steps:

[0009] (1) Add an aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate, tetrafluoroboric acid, and tetrahydrofuran to a reaction flask. After mixing evenly, add epoxidized soybean oil, and carry out a reflux reaction at a rotation speed of 150-300 r / min. After the reaction is completed, add an aqueous solution of sodium bicarbonate to adjust the pH of the system to neutral, extract with ethyl acetate and water, concentrate the organic phase, and dry to obtain sodium alkenylsulfonate-modified soybean oil.

[0010] (2) Pass nitrogen into a reaction flask equipped with a reflux condenser, add styrene and an aqueous ethanol solution, disperse evenly, add sodium alkenylsulfonate-modified soybean oil, heat up to 45-55 °C, stir and dissolve, add the initiator azobisisobutyronitrile, stir and react. After the reaction is completed, cool and filter, wash with ethanol, and dry to obtain the novel wax crystal improver.

[0011] Further, in step (1), by weight, the sodium 3-allyloxy-2-hydroxy-1-propanesulfonate solution is 6-15 parts, the tetrafluoroboric acid is 0.8-1.3 parts, and the epoxidized soybean oil is 100 parts.

[0012] Further, in step (1), the reflux reaction temperature is 65-75 °C and the reflux reaction time is 3-8 h.

[0013] Further, in step (2), by weight, the styrene is 100 parts, the sodium alkenylsulfonate-modified soybean oil is 15-70 parts, and the azobisisobutyronitrile is 1-1.5 parts.

[0014] Further, in step (2), the reaction temperature is 70-85 °C and the reaction time is 5-8 h.

[0015] Further, the preparation process of the compound surfactant is carried out according to the following steps: Add 30-60 parts of alkylphenol polyoxyethylene polyoxypropylene ether, 25-40 parts of sodium lauryl sulfate, and 10-20 parts of limonene by weight to a reaction flask, stir evenly, add 5-10 parts of alkyl glycoside, and mix at 50-70 °C for 2-4 h to obtain the compound surfactant.

[0016] Further, the mutual solvent is any one of isopropanol, ethylene glycol monobutyl ether, and diethylene glycol ethyl ether.

[0017] Further, the stabilizer is ethylene glycol; the fast penetrant is sodium 5-sulfoisophthalate.

[0018] Further, the base is any one of sodium hydroxide, sodium orthosilicate, sodium phosphate, and sodium hexametaphosphate.

[0019] Further, the preparation process is carried out according to the following steps: adding the compound surfactant, mutual solvent, base, and water into a reaction flask, stirring at a temperature of 20 - 35 °C and a rotation speed of 300 - 500 r / min for 10 - 20 min. After uniform dispersion, add the stabilizer and fast penetrant, continue stirring for 5 - 15 min, then add the novel wax crystal modifier, stir and mix evenly to obtain the paraffin removal and inhibition agent for oil well boreholes.

[0020] Adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0021] When preparing the paraffin removal and inhibition agent for oil well boreholes of the present invention, alkylphenol polyoxyethylene polyoxypropylene ether, sodium lauryl sulfate, limonene, and alkyl glycoside are formulated in a certain proportion to obtain a compound surfactant; then, an epoxy ring-opening reaction occurs between an aqueous solution of 3-allyloxy-2-hydroxy-1-propanesulfonate and epoxidized soybean oil under the catalysis of tetrafluoroboric acid to obtain alkenyl sulfonate-modified soybean oil; then, alkenyl sulfonate-modified soybean oil and styrene are initiated to polymerize to obtain a novel wax crystal modifier; finally, it is mixed evenly with a mutual solvent, stabilizer, fast penetrant, and alkaline substance, etc. to obtain the paraffin removal and inhibition agent for oil well boreholes.

[0022] The novel wax crystal modifier molecule contains a long branched-chain structure of epoxidized soybean oil, which plays a role in eutectic during the paraffin inhibition process, can better adsorb to the solid-liquid interface, increases the compatibility with the oil sample, plays a role in wetting inversion, and enhances the paraffin inhibition effect; the sulfonate in the structure of the novel wax crystal modifier has strong polarity and hydrophilicity. Its strong polarity can change the polarity of the paraffin inhibition agent molecule, can adjust the crystallinity of the paraffin inhibition agent molecule, and at the same time plays a synergistic role with asphaltenes, resins, etc. in crude oil, thereby enhancing the paraffin inhibition effect of the paraffin removal and inhibition agent; its hydrophilicity is reflected in that the sulfonate acts as a hydrophilic group, can greatly reduce the surface tension of water, has a good wetting effect, and can also adsorb on the surface of wax crystals, making the wax crystals form a polar surface that is not conducive to continued growth, and the wax crystals are maintained in a fine state; the synthesized novel wax crystal modifier has a structure similar to that of paraffin. According to the principle of "like dissolves like", the wax crystals can dissolve in the paraffin removal and inhibition agent, further improving the dissolution rate of the wax crystals.

[0023] The compound surfactant combines the advantages of wetting inversion of alkylphenol polyoxyethylene polyoxypropylene ether, sodium lauryl sulfate and alkyl glycoside, reverses the wettability of the wax deposition surface from lipophilic to hydrophilic, has strong wetting and dispersing effects, can adsorb on the surface of wax crystals, prevent the adsorption and deposition of non-polar wax crystals on the metal surface, weaken the adhesion force between the wax block and the wellbore wall, facilitate the shedding of wax, and achieve the purpose of wax prevention; Limonene contains double bonds in its molecule and has good chemical stability at room temperature, and has a good dissolving effect on the wax crystals on the reservoir rock and tubing surface; the penetration and dispersion properties of the compound surfactant help the paraffin control and removal agent penetrate into the gaps of the loose-structured wax crystals. At the same time, it can reduce the interfacial tension between oil and wax, and the surfactant molecules can penetrate the structure of wax, weaken the binding force between wax molecules, and destroy the adhesion force between individual wax molecules and the pipe wall, resulting in the disassembly of wax crystals and their dispersion in the oil flow, flowing out of the oil well with the produced fluid, thus playing a role in wax removal.

[0024] The addition of the mutual solvent solves the problem of poor mutual solubility between the oil phase and the water phase, makes the solution system a homogeneous and stable whole, improves the permeability of the water-based paraffin control and removal agent to waxy crude oil, enables the surfactant to better contact the wax in the crude oil, and at the same time increases the mutual solubility of oil including wax and water, dissolves the wax crystals and thus improves the wax dissolution rate; the role of adding alkali is to make the asphaltenes in the oilfield wax easily disperse in water. Because groups such as carboxyl and hydroxyl in asphaltenes can react with alkali to turn into sodium carboxylate and sodium hydroxyl, the dispersion ability in water is improved, forming numerous crystal nuclei. These crystal nuclei are suspended in the oil flow in a dispersed form and are carried away to achieve the purpose of paraffin control and removal; the addition of the penetrant can weaken the adhesion force between wax molecules and the pipe wall, which is beneficial to the shedding and removal of wax; the addition of the stabilizer can lower the freezing point of the paraffin control and removal agent, thereby broadening the application range of the paraffin control and removal agent.

[0025] The paraffin control and removal agent prepared by the present invention dissolves the wax deposited on the pipe wall with the help of the mutual solvent, disperses in the crude oil under the action of the compound surfactant, and penetrates along the gaps of the wax and the gaps between the wax and the oil well pipe wall, causing the wax deposited on the pipe wall surface to fall off from the pipe wall surface and be carried out of the oil well by the oil flow; the wax crystal improver changes the structure of wax crystals, making the wax crystals not easily aggregate and deposit on the pipe wall, can effectively prevent wax deposition in the oil well, thus achieving the dual effects of wax removal and wax prevention, and further improving the low-temperature fluidity of crude oil. Detailed implementation manners

[0026] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention will be further described in detail below in combination with specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0027] The aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate, CAS number: 52556-42-0.

[0028] Tetrafluoroboric acid, CAS No. 16872-11-0.

[0029] Epoxidized soybean oil, CAS No. 8013-07-8.

[0030] Example 1

[0031] (1) Add 1.2 g of a 40% aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate, 0.12 g of tetrafluoroboric acid and 60 mL of tetrahydrofuran to a reaction flask. After mixing evenly, add 10 g of epoxidized soybean oil. Under a rotation speed of 200 r / min and a temperature of 70 °C, reflux for 5 h. After the reaction is completed, add a 15% aqueous solution of sodium bicarbonate to adjust the pH of the system to neutral. Extract with ethyl acetate and water, concentrate the organic phase, and dry to obtain sodium alkenylsulfonate modified soybean oil.

[0032] (2) Pass nitrogen into a reaction flask equipped with a reflux condenser, add 20 g of styrene and 260 mL of an 80% aqueous ethanol solution. After dispersing evenly, add 7 g of sodium alkenylsulfonate modified soybean oil, heat up to 50 °C, stir to dissolve, add 0.22 g of initiator azobisisobutyronitrile, react at 75 °C for 7 h, then cool and filter, wash with ethanol, and dry to obtain a novel wax crystal modifier.

[0033] (3) Add 15 g of alkylphenol polyoxyethylene polyoxypropylene ether, 10 g of sodium lauryl sulfate and 5 g of limonene to a reaction flask. After stirring evenly, add 2.7 g of alkyl polyglycoside and mix at 60 °C for 3 h to obtain a compound surfactant.

[0034] (4) Add 10 g of the compound surfactant, 25 g of diethylene glycol ethyl ether, 1 g of sodium hydroxide and 58 g of water to a reaction bottle. Stir at a temperature of 25 °C and a rotation speed of 400 r / min for 15 min. After dispersing evenly, add 6 g of ethylene glycol and 0.4 g of sodium 5-sulfoisophthalate, continue to stir for 10 min, then add 1 g of the novel wax crystal modifier and stir to mix evenly to obtain a paraffin control and removal agent for oil well boreholes.

[0035] Example 2

[0036] (1) Add 15 g of a 40% aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate, 1.3 g of tetrafluoroboric acid and 800 mL of tetrahydrofuran to a reaction flask. After mixing evenly, add 100 g of epoxidized soybean oil. Under a rotation speed of 150 r / min and a temperature of 65 °C, reflux for 8 h. After the reaction is completed, add a 20% aqueous solution of sodium bicarbonate to adjust the pH of the system to neutral. Extract with ethyl acetate and water, concentrate the organic phase, and dry to obtain sodium alkenylsulfonate modified soybean oil.

[0037] (2) Nitrogen was introduced into a reaction flask equipped with a reflux condenser. 5 g of styrene and 75 mL of an aqueous ethanol solution with a volume fraction of 80% were added. After being dispersed evenly, 3.5 g of sodium alkenyl sulfonate modified soybean oil was added. The temperature was raised to 45 °C, stirred and dissolved. 0.075 g of initiator azobisisobutyronitrile was added. After reacting at 70 °C for 8 h, it was cooled, filtered, washed with ethanol, and dried to obtain a novel wax crystal modifier.

[0038] (3) 3 g of alkylphenol polyoxyethylene polyoxypropylene ether, 2 g of sodium lauryl sulfate and 1 g of limonene were added to the reaction flask. After stirring evenly, 0.5 g of alkyl glucoside was added. It was mixed at 50 °C for 4 h to obtain a compound surfactant.

[0039] (4) 14 g of the compound surfactant, 30 g of isopropanol, 1.5 g of sodium phosphate and 41 g of water were added to the reaction flask. It was stirred at a temperature of 20 °C and a rotation speed of 300 r / min for 20 min. After being dispersed evenly, 10 g of ethylene glycol and 0.5 g of sodium 5-sulfoisophthalate were added. It was stirred continuously for 15 min. Then 3 g of the novel wax crystal modifier was added and stirred evenly to obtain a paraffin inhibitor and anti-wax agent for oil well boreholes.

[0040] Example 3

[0041] (1) 3 g of an aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate with a mass fraction of 40%, 0.4 g of tetrafluoroboric acid and 250 mL of tetrahydrofuran were added to the reaction flask. After mixing evenly, 50 g of epoxy soybean oil was added. It was refluxed at a rotation speed of 300 r / min and a temperature of 75 °C for 3 h. After the reaction was completed, an aqueous solution of sodium bicarbonate with a mass fraction of 10% was added to adjust the pH of the system to neutral. It was extracted with ethyl acetate and water. The organic phase was concentrated and dried to obtain sodium alkenyl sulfonate modified soybean oil.

[0042] (2) Nitrogen was introduced into a reaction flask equipped with a reflux condenser. 40 g of styrene and 400 mL of an aqueous ethanol solution with a volume fraction of 80% were added. After being dispersed evenly, 6 g of sodium alkenyl sulfonate modified soybean oil was added. The temperature was raised to 55 °C, stirred and dissolved. 0.6 g of initiator azobisisobutyronitrile was added. After reacting at 85 °C for 5 h, it was cooled, filtered, washed with ethanol, and dried to obtain a novel wax crystal modifier.

[0043] (3) 15 g of alkylphenol polyoxyethylene polyoxypropylene ether, 12.5 g of sodium lauryl sulfate and 5 g of limonene were added to the reaction flask. After stirring evenly, 2.5 g of alkyl glucoside was added. It was mixed at 70 °C for 2 h to obtain a compound surfactant.

[0044] (4) Add 18 g of the compound surfactant, 15 g of ethylene glycol monobutyl ether, 0.5 g of sodium metasilicate, and 56 g of water into a reaction flask, stir for 10 min at a temperature of 35 °C and a rotation speed of 500 r / min. After uniform dispersion, add 5 g of ethylene glycol and 0.2 g of sodium 5-sulfoisophthalate, continue to stir for 5 min, then add 6 g of the novel wax crystal modifier, and stir and mix evenly to obtain the paraffin inhibitor and paraffin remover for oil well boreholes.

[0045] Example 4

[0046] (1) Add 3.6 g of an aqueous solution of 3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt with a mass fraction of 40%, 0.4 g of tetrafluoroboric acid, and 300 mL of tetrahydrofuran into a reaction flask. After mixing evenly, add 40 g of epoxidized soybean oil, reflux for 6 h at a rotation speed of 280 r / min and a temperature of 70 °C. After the reaction is completed, add an aqueous solution of sodium bicarbonate with a mass fraction of 20% to adjust the pH of the system to neutral, extract with ethyl acetate and water, concentrate the organic phase, and dry to obtain alkenyl sulfonate modified soybean oil.

[0047] (2) Pass nitrogen into a reaction flask equipped with a reflux condenser, add 25 g of styrene and 325 mL of an aqueous ethanol solution with a volume fraction of 80%. After uniform dispersion, add 15 g of alkenyl sulfonate modified soybean oil, heat up to 50 °C, stir to dissolve, add 0.325 g of initiator azobisisobutyronitrile, react at 80 °C for 6 h, then cool and filter, wash with ethanol, and dry to obtain the novel wax crystal modifier.

[0048] (3) Add 4.5 g of alkylphenol polyoxyethylene polyoxypropylene ether, 3.5 g of sodium lauryl sulfate, and 2 g of limonene into a reaction flask, stir evenly, then add 0.9 g of alkyl polyglycoside, and mix at 55 °C for 4 h to obtain the compound surfactant.

[0049] (4) Add 22 g of the compound surfactant, 20 g of isopropyl alcohol, 1.2 g of sodium hexametaphosphate, and 40 g of water into a reaction flask, stir for 20 min at a temperature of 30 °C and a rotation speed of 420 r / min. After uniform dispersion, add 8 g of ethylene glycol and 0.3 g of sodium 5-sulfoisophthalate, continue to stir for 8 min, then add 8 g of the novel wax crystal modifier, and stir and mix evenly to obtain the paraffin inhibitor and paraffin remover for oil well boreholes.

[0050] Example 5

[0051] (1) Add 2.8 g of an aqueous solution of sodium 3 - allyloxy - 2 - hydroxy - 1 - propanesulfonate with a mass fraction of 40%, 0.18 g of tetrafluoroboric acid, and 132 mL of tetrahydrofuran to a reaction flask. After mixing evenly, add 20 g of epoxidized soybean oil. Reflux at a rotation speed of 240 r / min and a temperature of 70 °C for 6 h. After the reaction is completed, add an aqueous solution of sodium bicarbonate with a mass fraction of 15% to adjust the pH of the system to neutral. Extract with ethyl acetate and water, concentrate the organic phase, and dry to obtain sodium alkenylsulfonate - modified soybean oil.

[0052] (2) Pass nitrogen into a reaction flask equipped with a reflux condenser, add 80 g of styrene and 960 mL of an aqueous ethanol solution with a volume fraction of 80%. After dispersing evenly, add 40 g of sodium alkenylsulfonate - modified soybean oil, heat up to 50 °C, stir to dissolve, add 0.96 g of initiator azobisisobutyronitrile, react at 75 °C for 7 h, then cool and filter, wash with ethanol, and dry to obtain a novel wax crystal modifier.

[0053] (3) Add 10 g of alkylphenol polyoxyethylene polyoxypropylene ether, 6 g of sodium lauryl sulfate, and 3 g of limonene to a reaction flask. After stirring evenly, add 1.2 g of alkyl glycoside and mix at 55 °C for 4 h to obtain a compound surfactant.

[0054] (4) Add 25 g of the compound surfactant, 30 g of ethylene glycol monobutyl ether, 1.5 g of sodium phosphate, and 33 g of water to a reaction flask. Stir at a temperature of 30 °C and a rotation speed of 350 r / min for 20 min. After dispersing evenly, add 5 g of ethylene glycol and 0.4 g of sodium 5 - sulfophthalate, continue to stir for 15 min, then add 10 g of the novel wax crystal modifier and stir evenly to obtain a paraffin inhibitor and de - waxing agent for oil well boreholes.

[0055] Comparative Example 1

[0056] Add 10 g of the compound surfactant (prepared in Example 1), 25 g of diethylene glycol ethyl ether, 1 g of sodium hydroxide, and 58 g of water to a reaction flask. Stir at a temperature of 25 °C and a rotation speed of 400 r / min for 15 min. After dispersing evenly, add 6 g of ethylene glycol and 0.4 g of sodium 5 - sulfophthalate, stir evenly to obtain a paraffin inhibitor and de - waxing agent for oil well boreholes.

[0057] Comparative Example 2

[0058] Add 25 g of diethylene glycol ethyl ether, 1 g of sodium hydroxide, and 58 g of water to a reaction flask. Stir at a temperature of 25 °C and a rotation speed of 400 r / min for 15 min. After dispersing evenly, add 6 g of ethylene glycol and 0.4 g of sodium 5 - sulfophthalate, continue to stir for 10 min, then add 1 g of the novel wax crystal modifier (prepared in Example 1), stir evenly to obtain a paraffin inhibitor and de - waxing agent for oil well boreholes.

[0059] Wax Dissolution Rate Test: Refer to the standard SY / T6300-2009 "Technical Conditions for Paraffin Removers and Inhibitors for Oil Production" to conduct the wax dissolution rate test. Add 15 mL of the synthesized paraffin remover and inhibitor for oil well boreholes into the wax dissolution test device, with the water bath temperature at 45°C. After the solution reaches a constant temperature, place the wax ball into the paraffin remover and inhibitor solution, and record the time t required for the wax ball to completely dissolve at different temperatures. The calculation formula for the wax dissolution rate V is: V = m / t, where V is the wax dissolution rate (g / min), m is the mass of the wax ball (g), and t is the time required for the wax ball to completely dissolve (min).

[0060] Paraffin Inhibition Rate Test: Refer to the standard SY / T6300-2009 "Technical Conditions for Paraffin Removers and Inhibitors for Oil Production", and use the circulating wax deposition tube method to test the paraffin inhibition rate of the paraffin remover and inhibitor at different temperatures. The calculation formula for the paraffin inhibition rate E is E = (m1 - m0) / m1, where E is the paraffin inhibition rate (%), m1 is the wax deposition amount of the oil sample without adding the paraffin remover and inhibitor (g), and m0 is the wax deposition amount of the oil sample with the paraffin remover and inhibitor added (g).

[0061] Table 1 Wax Dissolution Rate and Paraffin Inhibition Rate Tests

[0062]

[0063] From the test results in the above table, it can be seen that as the content of the compounded surfactant and the new wax crystal improver in the paraffin remover and inhibitor for oil well boreholes increases, its wax dissolution rate is significantly improved. At the same time, the temperature has a great influence on the wax dissolution rate. At 30°C, the wax dissolution rate of the paraffin remover and inhibitor in Example 5 is 0.0801 g / min. After the temperature rises to 60°C, the wax dissolution rate reaches 0.1395 g / min, indicating that the higher the temperature, the faster the movement of the molecules on the wax crystal surface. According to the "like dissolves like" principle, the wax crystal can dissolve in the new wax crystal improver, and the compounded surfactant has a solubilization effect, further improving the wax crystal dissolution rate.

[0064] Temperature is the main factor affecting paraffin deposition. The higher the temperature, the less likely paraffin will form and wax crystals will grow. However, when the temperature drops, wax crystals begin to precipitate from the crude oil. From the test results in the table above, it can be seen that even at a relatively low temperature of 30°C, the paraffin prevention rate of the paraffin prevention and removal agent prepared for oil well casings is above 60%, reaching a maximum of 75.4%, showing good paraffin prevention effect. This is because the new wax crystal improver has a branched structure with long epoxy soybean oil branches, which can better adsorb onto the solid-liquid interface and play a wetting inversion role. The more the branched chain content, the larger the proportion of non-polar segments in the polymer molecule, which plays a eutectic role in the paraffin prevention process, increasing its compatibility with the oil sample and enhancing the paraffin prevention effect. At the same time, its structure contains strongly polar sodium sulfonate groups. After copolymerization with styrene, the polar groups enter the molecular chain. Its strong polarity can change the polarity of the paraffin prevention agent molecules, regulate the crystallinity of the paraffin prevention agent molecules, and at the same time can synergize with asphaltenes, resins, etc. in the crude oil, thereby enhancing the paraffin prevention effect of the paraffin prevention agent. Sodium sulfonate, as a hydrophilic group, can greatly reduce the surface tension of water, has good wetting properties, and can also adsorb on the surface of wax crystals, making the wax crystals form a polar surface that is not conducive to continued growth, thus remaining in a fine state and achieving the purpose of wax removal.

[0065] In Comparative Example 1, there is no paraffin prevention and removal agent for oil well casings, and its wax dissolving ability only depends on additives such as mutual solvents, resulting in a poor paraffin prevention effect. In Comparative Example 2, there is no compound surfactant, and it does not have a wetting inversion effect, with poor wax dissolving performance.

[0066] Crude oil viscosity test: Weigh 100 g of crude oil, heat the crude oil until it is completely melted, add 0.5 mL of the paraffin prevention and removal agent prepared in the examples and comparative examples respectively, stir well for 20 min, seal the crude oil added with the water-based paraffin prevention and removal agent, heat it at 80°C for 1 h, draw 10 mL with a syringe and add it to the sample cylinder, start the rotational viscometer, set the rotation speed to 50 r / min, and record the viscosity value after the measured value displayed by the instrument is basically stable. Measure 5 times and take the average value. The measurement temperatures are 20°C, 30°C, and 40°C respectively.

[0067] Table 2 Crude oil viscosity test

[0068]

[0069] As can be seen from the test results in the above table, the lower the temperature, the higher the viscosity of the crude oil. The viscosity of the crude oil with the paraffin inhibitor is much lower than that of the crude oil without the paraffin inhibitor, and the difference between the two increases with the continuous decrease of the temperature. When the temperature is 20 °C, the viscosity of the crude oil in Example 4 drops to 870.3 mP·s. In Comparative Example 1, no paraffin inhibitor was added, and the viscosity of its crude oil was 1961.2 mP·s, indicating that the addition of the paraffin inhibitor effectively reduces the viscosity of the crude oil. This is because the compounded surfactant and the novel wax crystal improver in the paraffin inhibitor have good penetration and dispersion properties, enabling the paraffin inhibitor to penetrate into the gaps of the loosely structured wax crystals, weakening the binding force between wax molecules, hindering the formation of wax crystals and the growth of large wax blocks, and weakening the binding force between wax molecules, thus reducing the viscosity of the crude oil. However, when the temperature is higher than the pour point temperature of the crude oil, the viscosity difference between the two rapidly decreases at 40 °C. This is because at this time, the influence of temperature on the viscosity of the crude oil plays a major role. It can be seen that the paraffin inhibitor prepared by the present invention has good paraffin prevention and removal performance, improving the low-temperature fluidity of the crude oil.

[0070] Surface tension test: The test was carried out with reference to the standard SY / T5370-2018 "Determination Method for Surface and Interfacial Tension".

[0071] Table 3 Surface tension test

[0072]

[0073] As can be seen from the test results in the above table, as the content of the compounded surfactant in the paraffin inhibitor for oil well boreholes increases, its surface tension value gradually decreases. After the surfactant is adsorbed on the surface of the wax crystals, the oriented adsorption layer is covered with hydrophilic groups such as sodium sulfate and sodium sulfonate, making the surface hydrophilic. The wax crystals precipitated from the crude oil are not easily adsorbed and deposited, thus achieving the purpose of wax prevention. The compounded surfactant has the functions of reducing surface tension and wetting reversal, can promote emulsification, reduce the wax deposition tendency, and can well strip the wax from the oil pipe, thereby improving the wax dissolution rate. In Comparative Example 2, no compounded surfactant is contained, and its surface tension value is relatively high, with poor wetting reversal effect, resulting in poor wax dissolution effect.

[0074] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A paraffin removal and prevention agent for oil well casings, characterized in that, The paraffin removal and prevention agent for oil well boreholes comprises the following components in parts by weight: 10-25 parts of compound surfactant, 15-30 parts of mutual solvent, 5-10 parts of stabilizer, 1-10 parts of novel wax crystal improver, 0.2-0.5 part of rapid penetrant, 0.5-1.5 parts of alkali, and 25-70 parts of water; The preparation process of the novel wax crystal improver is carried out according to the following steps: (1) Add an aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate, tetrafluoroboric acid and tetrahydrofuran into a reaction flask. After mixing evenly, add epoxidized soybean oil. Carry out a reflux reaction at a rotation speed of 150-300 r / min. After the reaction is completed, add an aqueous solution of sodium bicarbonate to adjust the pH of the system to neutral. Extract with ethyl acetate and water, concentrate the organic phase, and obtain sodium alkenylsulfonate modified soybean oil after drying; (2) Pass nitrogen into a reaction flask equipped with a reflux condenser. Add styrene and an aqueous ethanol solution. After dispersing evenly, add sodium alkenylsulfonate modified soybean oil. Heat up to 45-55 °C, stir and dissolve. Add the initiator azobisisobutyronitrile, stir and react. After the reaction is completed, cool and filter, wash with ethanol, and obtain the novel wax crystal improver after drying; The preparation process of the compound surfactant is carried out according to the following steps: Add 30-60 parts of alkylphenol polyoxyethylene polyoxypropylene ether, 25-40 parts of sodium lauryl sulfate and 10-20 parts of limonene by weight into a reaction flask. After stirring evenly, add 5-10 parts of alkyl glycoside, and mix at 50-70 °C for 2-4 h to obtain the compound surfactant; The mutual solvent is any one of isopropanol, ethylene glycol monobutyl ether, and diethylene glycol monoethyl ether; The stabilizer is ethylene glycol; the rapid penetrant is sodium 5-sulfophthalate; In the step (1), by weight, the sodium 3-allyloxy-2-hydroxy-1-propanesulfonate solution is 6-15 parts, tetrafluoroboric acid is 0.8-1.3 parts, and epoxidized soybean oil is 100 parts; the mass fraction of the aqueous solution of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate is 40%; In the step (2), by weight, styrene is 100 parts, sodium alkenylsulfonate modified soybean oil is 15-70 parts, and azobisisobutyronitrile is 1-1.5 parts.

2. The paraffin removal and prevention agent for oil well boreholes according to claim 1, wherein In the step (1), the reflux reaction temperature is 65-75 °C and the reflux reaction time is 3-8 h.

3. The paraffin removal and prevention agent for oil well boreholes according to claim 1, wherein In the step (2), the reaction temperature is 70-85 °C and the reaction time is 5-8 h.

4. The paraffin control and prevention agent for oil well boreholes according to claim 1, wherein The alkali is any one of sodium hydroxide, sodium orthosilicate, sodium phosphate, and sodium hexametaphosphate.

5. A preparation process of a paraffin removal and prevention agent for oil well boreholes according to any one of claims 1-4, characterized in that, The preparation process is carried out according to the following steps: Add the compound surfactant, mutual solvent, alkali and water into a reaction bottle. Stir at a temperature of 20-35 °C and a rotation speed of 300-500 r / min for 10-20 min. After dispersing evenly, add the stabilizer and rapid penetrant, continue to stir for 5-15 min, then add the novel wax crystal improver, and stir and mix evenly to obtain the paraffin removal and prevention agent for oil well boreholes.

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