Efficient neutral blocking remover

Abstract

The invention belongs to the technical field of oil and gas field chemistry, and particularly discloses an efficient neutral blocking remover. The neutral blocking remover comprises the following raw material components: 59%-67% of N-methyl pyrrolidone, 15%-19% of D-sodium erythorbate, 7%-9% of disodium ethylene diamine tetraacetate, 5%-6% of 8-(2-hydroxybenzamido) sodium caprylate, 4%-5% of sulfonated acetone formaldehyde polycondensate with the polymerization degree of 12-15, 1%-3% of sodium hydroxide, 1%-3% of sodium hydroxide, and the balance of water. And 2% of an amide propyl hydroxyl sulphobetaine viscoelastic surfactant, wherein the sum of the above components is 100%. The pH values of a stock solution and an aqueous solution of the neutral blocking remover are 6.0-8.0, the pH value is neutral when the neutral blocking remover is used, the neutral blocking remover is basically free of corrosion to oil well metal pipeline equipment, and the neutral blocking remover has an excellent scale dissolving effect on carbonate scale and sulfate scale.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field chemistry, and in particular relates to a highly efficient neutral plugging remover. Background Art

[0002] With the exploitation and water injection of oil fields, the output water of oil fields continues to increase. The calcium and magnesium ions carried in the output water of oil fields will produce a large amount of scale mainly composed of calcium carbonate, magnesium carbonate and calcium sulfate, which will block the channels and gaps of the oil layer, causing problems such as decreased oil well production and increased load on oil well equipment. To solve this problem, acidic unblocking agents are generally used for pickling and unblocking, which has good effects. However, acidic unblocking agents can also cause serious corrosion to metal pipeline equipment in oil wells, and acids are easy to react with oil in oil and gas layers to form acidic sludge precipitation to block oil and gas channels. Therefore, more and more oil fields around the world no longer allow the use of acidic unblocking agents with a pH value lower than 5.0, and the demand for neutral unblocking agents has emerged. However, the current neutral unblocking agent technology mainly adopts the invisible acid process: that is, the solution test on the ground is neutral, and the reaction underground generates an acid system with a pH value of 4.0-5.0, and unblocking is achieved through the reaction mechanism of acid and inorganic scale. This invisible acid process can reduce the corrosion of metal pipeline equipment, but it cannot solve the problem of acidic sludge, and methyl formate, which is the most commonly used in the invisible acid process, has a low flash point and is very dangerous, so its use is also hindered. If the invisible acid process is not adopted, the effect of authentic neutral unblocking agents is often much worse than that of acidic unblocking agents, and the oil well market is in urgent need of neutral unblocking agents with good scale dissolving effect. Summary of the invention

[0003] In view of the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide an efficient neutral plugging remover and a preparation method thereof. The neutral plugging remover of the present invention can dissolve and remove carbonate scale and sulfate scale in oil wells. The pH of the original solution and aqueous solution of the neutral plugging remover of the present invention are both 6.0-8.0. When it works in the oil well, it will not generate an acid system with a pH of 4.0-5.0 and can always maintain a pH of 6.0-8.0. After being diluted to a 4wt%-6wt% aqueous solution, the 60°C calcium carbonate scale dissolution rate is ≥60.0%, the 60°C magnesium carbonate scale dissolution rate is ≥50.0%, the 60°C calcium sulfate scale dissolution rate is ≥30.0%, and the 60°C barium sulfate scale dissolution rate is ≥25.0%.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] One of the technical solutions is a neutral unblocking agent. The raw materials of the unblocking agent include the following components by weight percentage: 59%-67% of N-methylpyrrolidone, 15%-19% of sodium D-isoascorbate, 7%-9% of disodium ethylenediaminetetraacetate, 5%-6% of sodium 8-(2-hydroxybenzamido)octanoate, 4%-5% of sulfonated acetone formaldehyde condensate, and 2% of amidopropyl hydroxysulfonobetaine viscoelastic surfactant, and the total of the above components is 100%.

[0006] Preferably, the raw materials of the blocking remover include the following components by weight percentage: 60%-63% N-methylpyrrolidone, 16%-18% sodium D-isoascorbate, 7%-9% disodium ethylenediaminetetraacetic acid, 5%-6% sodium 8-(2-hydroxybenzamido)octanoate, 4%-5% sulfonated acetone formaldehyde condensate, 2% amidopropyl hydroxysulfobetaine viscoelastic surfactant, and the total of the above components is 100%.

[0007] The invention comprises: N-methylpyrrolidone as a solvent, sodium D-isoascorbate and disodium ethylenediaminetetraacetate as chelating agent components, sodium 8-(2-hydroxybenzamido)octanoate as a chelating agent auxiliary synergistic component, sulfonated acetone formaldehyde condensation product as a dispersant, and amidopropyl hydroxysulfobetaine viscoelastic surfactant as an auxiliary dispersing component.

[0008] Wherein, the polymerization degree of the sulfonated acetone formaldehyde polycondensate is 12-15.

[0009] Furthermore, the solid content of the sulfonated acetone formaldehyde polycondensate is 30%-40%, preferably 35%.

[0010] Preferably, the amidopropyl hydroxysulfonyl betaine viscoelastic surfactant is selected from erucic acid amidopropyl hydroxysulfonyl betaine. The concentration of the erucic acid amidopropyl hydroxysulfonyl betaine is 40%.

[0011] Preferably, the viscosity of the neutral plugging remover diluted with water at 50°C-100°C 4wt%-6wt% aqueous solution is 125-180 mPa·s, preferably 130-170 mPa·s, and more preferably 135-160 mPa·s.

[0012] In the neutral unblocking agent of the present invention, the sulfonated acetone formaldehyde polycondensate with a degree of polymerization of 12-15 has a relatively high viscosity and a good dispersing effect, does not affect the dissolving effect of the chelating agent on the scale in the aqueous solution, and increases the contact area between the chelating agent and the scale by dispersing and suspending the chelating agent to improve the descaling efficiency. If the degree of polymerization of the sulfonated acetone formaldehyde polycondensate is less than 12, the viscosity of the unblocking agent aqueous solution is insufficient, and the effect of suspending and dispersing the scale particles cannot be achieved, so the synergistic effect of the chelating agent component cannot be achieved; if the degree of polymerization of the sulfonated acetone formaldehyde polycondensate is greater than 15, the viscosity of the unblocking agent aqueous solution is too high, the liquid fluidity is very poor, and the contact probability between the chelating agent and the scale is reduced. The effect after adding the component is worse than that without adding, which has a negative effect.

[0013] In the neutral plugging remover of the present invention, the amidopropyl hydroxysulfonyl betaine viscoelastic surfactant has good foaming property and high stability, does not affect the scale dissolving effect of the chelating agent on scale in the aqueous solution, and increases the contact area between the chelating agent and the scale through the foaming effect and the auxiliary suspension effect to improve the scale removal efficiency; in addition, the hydrogen bonding and micellization effect between the chelating agent and water will also increase the viscosity of the aqueous solution of the plugging remover to a certain extent.

[0014] The neutral plugging remover of the present invention is based on the combined use of sulfonated acetone formaldehyde condensation product and amidopropyl hydroxysulfonobetaine viscoelastic surfactant in addition to the chelating agent component, which greatly increases the contact area and probability between the chelating agent and the scale, and the scale dissolving performance of carbonate scale and sulfate scale is greatly improved.

[0015] Technical solution 2 is a method for preparing a neutral plugging remover, which is obtained by mixing the raw materials of the neutral plugging remover. More specifically, it comprises the following steps:

[0016] Weigh the raw materials according to the ratio, pour N-methylpyrrolidone into the reactor, start stirring at a speed of 120-150r / min, raise the temperature to 50℃-55℃, add sodium D-isoascorbate, stir to form a transparent liquid without solid phase, then add disodium ethylenediaminetetraacetate and sodium 8-(2-hydroxybenzamido)octanoate in sequence, keep the temperature at 50℃-55℃ and continue stirring for 0.5h-1.0h to obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed to 30-60r / min and add sulfonated acetone formaldehyde condensation product, stir for 0.5h, then cool to room temperature, add amidopropyl hydroxysulfobetaine viscoelastic surfactant, stir for 0.5h-1.0h, and obtain a uniform brown-red liquid, which is the neutral unblocking agent.

[0017] Technical solution three is the application of the neutral plugging remover in the field of oil field development, where it is used to remove carbonate scale and sulfate scale in oil wells at 50°C-100°C, and needs to be prepared into a 4wt%-6wt% aqueous solution when used.

[0018] It is precisely because of the adoption of the above scheme that the neutral plugging remover of the present invention has a neutral pH value when used, can withstand high temperatures of 100°C, has substantially no corrosion to metal pipeline equipment in oil wells, has excellent scale dissolving effect on carbonate scales such as calcium carbonate and magnesium carbonate, also has good scale dissolving effect on sulfate scales such as calcium sulfate and barium sulfate, and can inhibit the precipitation of iron ions, and can safely and efficiently perform plugging removal operations in a variety of oil wells. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The present invention provides a technical solution: a highly efficient neutral plugging remover.

[0021] The raw materials used in the embodiments not specifically introduced are as follows: sulfonated acetone formaldehyde condensation product was purchased from Shandong Juxin New Materials Co., Ltd., with a solid content of 35%, a degree of polymerization of 12-15, an average molecular weight of about 10,000, and a viscosity of about 450 mPa·s; EHSB-40 erucic acid amide propyl hydroxysulfonyl betaine was purchased from Shanghai Yincong New Materials Technology Co., Ltd., and the erucic acid amide propyl hydroxysulfonyl betaine content was 40%.

[0022] Embodiment 1:

[0023] The neutral plugging remover is composed of the following components: 60 kg of N-methylpyrrolidone, 19 kg of sodium D-isoascorbate, 9 kg of disodium ethylenediaminetetraacetate, 5 kg of sodium 8-(2-hydroxybenzamido)octanoate, 5 kg of sulfonated acetone formaldehyde polycondensate, and 2 kg of EHSB-40 erucamide propyl hydroxysulfobetaine, a total of 100 kg, and is obtained by the following method:

[0024] Weigh the raw materials according to the ratio, pour all 60kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50°C, add 19kg of D-sodium isoascorbate to the reactor, stir it into a transparent liquid without solid phase, then add 9kg of disodium ethylenediaminetetraacetate and 5kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, keep 50°C-54°C, continue stirring for 0.5h, and obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed of the reactor to 60r / min, add 5kg of sulfonated acetone formaldehyde condensate to the reactor, stir for 0.5h, then start cooling, when the temperature drops to room temperature (20°C), add 2kg of EHSB-40 erucamide propyl hydroxysulfobetaine, and continue stirring at room temperature for 1.0h. The obtained brown-red uniform liquid is the neutral unblocking agent stock solution sample.

[0025] Afterwards, the performance index test of the sample was carried out, and each embodiment was carried out according to the following test method:

[0026] (1) Scale dissolution rate test method: Take 5g of neutral plugging agent stock solution sample and add it to a 200ml beaker, then add 95g of deionized water and stir to prepare 100g of 5% plugging agent aqueous solution, a total of 4 portions; weigh 0.500g of 60-80 mesh calcium carbonate, magnesium carbonate, calcium sulfate, and barium sulfate respectively and add them to 1 portion of 100g Put 5% unblocking agent solution in a 200ml beaker, cover the beaker with two layers of plastic wrap to seal it; put the beaker into a water bath at 60℃ constant temperature for 8h; after 8h, filter the liquid in the beaker with quantitative filter paper, and then rinse the filter paper and residual scale sample repeatedly with distilled water to remove the complex product on the surface of the scale sample to obtain clean and moist residual calcium carbonate, magnesium carbonate, calcium sulfate and barium sulfate, and then put the calcium carbonate, magnesium carbonate, calcium sulfate and barium sulfate into a 105℃ oven for two hours, take them out and put them into a dryer, cool them at room temperature for another half an hour, weigh the remaining calcium carbonate, magnesium carbonate, calcium sulfate and barium sulfate respectively, and take the average value of the test twice. The reduced mass of calcium carbonate, magnesium carbonate, calcium sulfate and barium sulfate divided by the initial mass is the scale dissolution rate.

[0027] (2) pH test method: ① Use a temperature-controlled pH meter to test the pH value of the unblocking agent stock solution at 25°C for 3 times, take the average value, and obtain the pH value of the unblocking agent stock solution at 25°C; ② Use a temperature-controlled pH meter to test the pH value of the unblocking agent stock solution at 60°C for 3 times, take the average value, and obtain the pH value of the unblocking agent stock solution at 60°C; ③ Add 25°C deionized water to the unblocking agent stock solution and stir to prepare a 5% unblocking agent aqueous solution with a mass concentration of 5%, and the stirring time is 0.5h, and then use a temperature-controlled pH meter to test the pH value of the 5% unblocking agent aqueous solution at 25°C for 3 times, take the average value, and obtain the pH value of the 5% unblocking agent aqueous solution at 25°C; ④ Add 60°C deionized water to the unblocking agent stock solution and stir to prepare a 5% unblocking agent aqueous solution with a mass concentration of 5%, and the stirring time is 0.5h, and then use a temperature-controlled pH meter to test the pH value of the 5% unblocking agent aqueous solution at 60°C for 3 times, take the average value, and obtain the pH value of the 60°C 5% unblocking agent aqueous solution.

[0028] (3) Viscosity test: Use a high temperature rotation viscometer to test the viscosity of the 25°C unblocking agent original solution, the 25°C 5% unblocking agent aqueous solution, and the 60°C 5% unblocking agent aqueous solution.

[0029] The performance index test of the neutral plugging remover sample obtained in Example 1 is shown in Table 1 below:

[0030] Table 1

[0031] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 78.8 60℃ magnesium carbonate dissolution rate (%) ≥50.0 61.2 60℃ Calcium sulfate scaling rate (%) ≥30.0 44.2 60℃ Barium sulfate dissolution rate (%) ≥25.0 29.0 25℃ stock solution pH 6.0-8.0 7.0 60℃ stock solution pH 6.0-8.0 6.9 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.7 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.4 25℃ stock solution viscosity (mPa·s) --- 93 25℃ 5% aqueous solution viscosity (mPa·s) --- 196 60℃ 5% aqueous solution viscosity (mPa·s) --- 155

[0032] Embodiment 2:

[0033] The neutral plugging remover is composed of the following components: 63 kg of N-methylpyrrolidone, 15 kg of sodium D-isoascorbate, 9 kg of disodium ethylenediaminetetraacetate, 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, 5 kg of sulfonated acetone formaldehyde polycondensate, and 2 kg of EHSB-40 erucamide propyl hydroxysulfobetaine, a total of 100 kg, and is obtained by the following method:

[0034] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50°C, add 15kg of D-sodium isoascorbate to the reactor, stir it into a transparent liquid without solid phase, then add 9kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, keep 50°C-54°C, continue stirring for 0.5h, and obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed of the reactor to 60r / min, add 5kg of sulfonated acetone formaldehyde condensate to the reactor, stir for 0.5h, then start cooling, when the temperature drops to room temperature (20°C), add 2kg of EHSB-40 erucic acid amide propyl hydroxysulfonobetaine, and continue stirring at room temperature for 1.0h. The obtained brown-red uniform liquid is the neutral unblocking agent stock solution sample.

[0035] The performance index test of the blocking agent sample obtained in Example 2 is as follows in Table 2:

[0036] Table 2

[0037] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 80.4 60℃ magnesium carbonate dissolution rate (%) ≥50.0 62.4 60℃ Calcium sulfate scaling rate (%) ≥30.0 40.6 60℃ Barium sulfate dissolution rate (%) ≥25.0 26.4 25℃ stock solution pH 6.0-8.0 7.1 60℃ stock solution pH 6.0-8.0 7.0 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.8 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.5 25℃ stock solution viscosity (mPa·s) --- 96 25℃ 5% aqueous solution viscosity (mPa·s) --- 203 60℃ 5% aqueous solution viscosity (mPa·s) --- 159

[0038] Embodiment three:

[0039] The neutral plugging remover is composed of the following components: 63 kg of N-methylpyrrolidone, 17 kg of sodium D-isoascorbate, 8 kg of disodium ethylenediaminetetraacetate, 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, 4 kg of sulfonated acetone formaldehyde polycondensate, and 2 kg of EHSB-40 erucamide propyl hydroxysulfobetaine, a total of 100 kg, and is obtained by the following method:

[0040] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120 / min, and start heating. When the temperature reaches 50°C, add 17kg of D-sodium isoascorbate to the reactor, stir it into a transparent liquid without solid phase, then add 8kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, keep 50°C-54°C, continue stirring for 0.5h, and obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed of the reactor to 60r / min, add 4kg of sulfonated acetone formaldehyde condensate to the reactor, stir for 0.5h, then start cooling, when the temperature drops to room temperature (20°C), add 2kg of EHSB-40 erucamide propyl hydroxysulfobetaine, and continue stirring at room temperature for 1.0h. The obtained brown-red uniform liquid is the neutral unblocking agent stock solution sample.

[0041] The performance index test of the neutral plugging remover sample obtained in Example 3 is shown in Table 3 below:

[0042] Table 3

[0043] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 80.2 60℃ magnesium carbonate dissolution rate (%) ≥50.0 62.0 60℃ Calcium sulfate scaling rate (%) ≥30.0 44.2 60℃ Barium sulfate dissolution rate (%) ≥25.0 27.8 25℃ stock solution pH 6.0-8.0 7.3 60℃ stock solution pH 6.0-8.0 7.3 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.9 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.8 25℃ stock solution viscosity (mPa·s) --- 86 25℃ 5% aqueous solution viscosity (mPa·s) --- 181 60℃ 5% aqueous solution viscosity (mPa·s) --- 150

[0044] From the viscosity test results of Examples 1 to 3, it can be seen that the viscosity of the 5% blocking agent aqueous solution at 25°C is significantly higher than that of the blocking agent original solution at 25°C, which is due to the thickening effect of the sulfonated acetone formaldehyde polycondensate in water. The viscosity of the 5% blocking agent aqueous solution at 60°C is 150-160 mPa·s.

[0045] Embodiment 4:

[0046] The neutral plugging remover is composed of the following components: 63 kg of N-methylpyrrolidone, 17 kg of sodium D-isoascorbate, 8 kg of disodium ethylenediaminetetraacetate, 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, and 4 kg of sulfonated acetone formaldehyde polycondensate, a total of 98 kg, and is obtained by the following method:

[0047] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50°C, add 17kg of D-sodium isoascorbate into the reactor, stir it into a transparent liquid without solid phase, then add 8kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, maintain 50°C-54°C, continue stirring for 0.5h, and obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed of the reactor to 60r / min, add 4kg of sulfonated acetone formaldehyde condensate into the reactor, stir for 0.5h, cool to room temperature (20°C), and the obtained brown-red uniform liquid is the neutral unblocking agent stock solution sample.

[0048] The performance index test of the neutral plugging remover sample obtained in Example 4 is shown in Table 4 below:

[0049] Table 4

[0050] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 61.0 60℃ magnesium carbonate dissolution rate (%) ≥50.0 51.6 60℃ Calcium sulfate scaling rate (%) ≥30.0 28.6 60℃ Barium sulfate dissolution rate (%) ≥25.0 22.2 25℃ stock solution pH 6.0-8.0 7.1 60℃ stock solution pH 6.0-8.0 7.1 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.9 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.6 25℃ stock solution viscosity (mPa·s) --- 79 25℃ 5% aqueous solution viscosity (mPa·s) --- 148 60℃ 5% aqueous solution viscosity (mPa·s) --- 117

[0051] Compared with Example 3, the deblocking agent prepared in Example 4 does not add the EHSB-40 erucic acid amide propyl hydroxysulfonyl betaine component, and the test results show that its carbonate scale and sulfate scale dissolving performance is reduced. The viscosity test results show that the viscosity of the deblocking agent aqueous solution at 60°C in Example 4 is lower than that of the deblocking agent aqueous solution at 60°C in Example 3, and the viscosity is <125mPa·s; in addition, it was found during the test that the amount of bubbles generated by the deblocking agent aqueous solution in Example 4 in the scale dissolving rate test is significantly reduced compared with the amount of bubbles generated by the deblocking agent aqueous solution in Example 3, and the amount of suspended scale particles is also reduced. Therefore, it is speculated that the micellization effect of erucic acid amide propyl hydroxysulfonyl betaine and water can play the role of thickening the suspended scale particles, and its good foaming property increases the contact area and contact probability between the chelating agent and the scale, thereby improving the scale dissolving efficiency.

[0052] Embodiment five:

[0053] The blocking remover is composed of the following components: 63 kg of N-methylpyrrolidone, 17 kg of sodium D-isoascorbate, 8 kg of disodium ethylenediaminetetraacetate, 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, and 2 kg of EHSB-40 erucamidopropyl hydroxysulfobetaine, a total of 96 kg, and is obtained by the following method:

[0054] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50°C, add 17kg of D-sodium isoascorbate into the reactor, stir it into a transparent liquid without solid phase, then add 8kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, maintain 50°C-54°C, continue stirring for 0.5h, obtain a colorless slightly yellow transparent liquid, and start cooling; when the temperature drops to room temperature (20°C), add 2kg of EHSB-40 erucic acid amide propyl hydroxysulfonobetaine, and continue stirring at room temperature for 1.0h. The obtained light yellow transparent liquid is the neutral unblocking agent stock solution sample.

[0055] The performance index test of the blocking agent sample obtained in Example 5 is as follows in Table 5:

[0056] Table 5

[0057] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 57.8 60℃ magnesium carbonate dissolution rate (%) ≥50.0 51.6 60℃ Calcium sulfate scaling rate (%) ≥30.0 30.8 60℃ Barium sulfate dissolution rate (%) ≥25.0 22.2 25℃ stock solution pH 6.0-8.0 7.0 60℃ stock solution pH 6.0-8.0 6.9 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.7 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.5 25℃ stock solution viscosity (mPa·s) --- 28 25℃ 5% aqueous solution viscosity (mPa·s) --- 51 60℃ 5% aqueous solution viscosity (mPa·s) --- 33

[0058] Compared with Example 3, the unblocking agent prepared in Example 5 does not add sulfonated acetone formaldehyde condensation product. The test results show that its carbonate scale and sulfate scale dissolving performance are significantly reduced. During the scale dissolving rate test, it was found that the aqueous solution of the unblocking agent in Example 5 was basically unable to suspend scale particles. Combined with the viscosity test results, the viscosity of the aqueous solution of the unblocking agent in Example 5 at 60°C was relatively low, and the viscosity was significantly less than 125mPa·s. It can be seen that sulfonated acetone formaldehyde condensation product is a major component that affects the viscosity of the aqueous solution of the unblocking agent of the present application. In addition, the sulfonated acetone formaldehyde condensation product has outstanding dispersibility, and thus can effectively increase the contact area and contact probability between the chelating agent and the scale, thereby improving the scale dissolving efficiency.

[0059] Embodiment six:

[0060] The blocking remover is composed of the following components: 63 kg of N-methylpyrrolidone, 17 kg of sodium D-isoascorbate, 8 kg of disodium ethylenediaminetetraacetate, and 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, a total of 94 kg, and is obtained by the following method:

[0061] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50℃, add 17kg of D-sodium isoascorbate into the reactor, stir it into a transparent liquid without solid phase, then add 8kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, maintain 50℃-54℃, continue stirring for 0.5h, cool to room temperature (20℃), and obtain a colorless and slightly yellow transparent liquid, which is the neutral unblocking agent stock solution sample.

[0062] The performance index test of the blocking agent sample obtained in Example 6 is shown in Table 6 below:

[0063] Table 6

[0064] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 52.6 60℃ magnesium carbonate dissolution rate (%) ≥50.0 47.3 60℃ Calcium sulfate scaling rate (%) ≥30.0 27.6 60℃ Barium sulfate dissolution rate (%) ≥25.0 20.2 25℃ stock solution pH 6.0-8.0 6.8 60℃ stock solution pH 6.0-8.0 6.7 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.5 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.2 25℃ stock solution viscosity (mPa·s) --- 13 25℃ 5% aqueous solution viscosity (mPa·s) --- 8 60℃ 5% aqueous solution viscosity (mPa·s) --- 6

[0065] Compared with Example 3, the unblocking agent prepared in Example 6 does not add sulfonated acetone formaldehyde condensation product or EHSB-40 erucic acid amide propyl hydroxysulfonyl betaine. The test results show that its carbonate scale and sulfate scale dissolving performance are significantly reduced, and the dissolving performance is also worse than that of Example 4 and Example 5. During the scale dissolving rate test, it was found that there were basically no suspended scale particles in the unblocking agent aqueous solution in Example 6. Combined with the viscosity test results: the viscosity of the unblocking agent aqueous solution in Example 6 at 60°C is relatively low, and the viscosity is significantly less than 125mPa·s; in addition, the viscosity of the 5% unblocking agent aqueous solution at 25°C is lower than that of the unblocking agent stock solution at 25°C, which also shows that sodium D-isoascorbate, disodium ethylenediaminetetraacetate and sodium 8-(2-hydroxybenzamido)octanoate only have the effect of dissolving scale, and basically have no effect of thickening suspended scale particles. In addition, the scale dissolving effect of the plugging remover prepared in Example 6 is close to that of the common neutral plugging removers on the market. It can be seen that the combination of sulfonated acetone formaldehyde condensation product and EHSB-40 erucic acid amide propyl hydroxysulfonobetaine can strongly improve the scale dissolving performance of the plugging remover of the present application.

[0066] Embodiment seven:

[0067] The blocking agent is composed of the following components: 66 kg of N-methylpyrrolidone, 19 kg of sodium D-isoascorbate, and 9 kg of disodium ethylenediaminetetraacetate, a total of 94 kg, and is obtained by the following method:

[0068] Weigh the raw materials according to the ratio, pour all 66kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120r / min, and start heating. When the temperature reaches 50℃, add 19kg of D-sodium isoascorbate into the reactor, stir it into a transparent liquid without solid phase, then add 9kg of disodium ethylenediaminetetraacetate, maintain 50℃-54℃, continue stirring for 0.5h, cool to room temperature (20℃), and obtain a colorless and slightly yellow transparent liquid, which is the neutral unblocking agent stock solution sample.

[0069] The performance index test of the blocking agent sample obtained in Example 7 is as follows in Table 7:

[0070] Table 7

[0071] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 49.6 60℃ magnesium carbonate dissolution rate (%) ≥50.0 42.3 60℃ Calcium sulfate scaling rate (%) ≥30.0 25.3 60℃ Barium sulfate dissolution rate (%) ≥25.0 19.7 25℃ stock solution pH 6.0-8.0 6.7 %60℃ stock solution pH 6.0-8.0 6.7 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.4 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.1 25℃ stock solution viscosity (mPa·s) --- 12 25℃ 5% aqueous solution viscosity (mPa·s) --- 7 60℃ 5% aqueous solution viscosity (mPa·s) --- 6

[0072] The scale dissolving performance of Example 7 continued to decline compared with Example 6. The results show that sodium 8-(2-hydroxybenzamido)octanoate has an auxiliary enhancement effect on the scale dissolving performance of the chelating agent system of disodium ethylenediaminetetraacetate and sodium D-isoascorbate.

[0073] Embodiment eight:

[0074] The blocking remover is composed of the following components: 63 kg of N-methylpyrrolidone, 17 kg of sodium D-isoascorbate, 8 kg of disodium ethylenediaminetetraacetate, 6 kg of sodium 8-(2-hydroxybenzamido)octanoate, 4 kg of sulfonated acetone formaldehyde polycondensate (purchased from Shandong Juxin New Materials Co., Ltd., with a solid content of 35%, a degree of polymerization of 16-18, an average molecular weight of about 13,000, and a viscosity of about 550 mPa·s), and 2 kg of EHSB-40 erucamide propyl hydroxysulfobetaine, a total of 100 kg, which is obtained by the following method:

[0075] Weigh the raw materials according to the ratio, pour all 63kg of N-methylpyrrolidone into the reactor, start stirring at a speed of 120 / min, and start heating. When the temperature reaches 50°C, add 17kg of D-sodium isoascorbate to the reactor, stir it into a transparent liquid without solid phase, then add 8kg of disodium ethylenediaminetetraacetate and 6kg of sodium 8-(2-hydroxybenzamido)octanoate in sequence, keep 50°C-54°C, continue stirring for 0.5h, and obtain a colorless and slightly yellow transparent liquid; reduce the stirring speed of the reactor to 60r / min, add 4kg of sulfonated acetone formaldehyde condensate to the reactor, stir for 0.5h, then start cooling, when the temperature drops to room temperature (20°C), add 2kg of EHSB-40 erucamide propyl hydroxysulfobetaine, and continue stirring at room temperature for 1.0h. The obtained brown-red uniform liquid is the neutral unblocking agent stock solution sample.

[0076] The performance index test of the blocking agent sample obtained in Example 8 is as follows in Table 8:

[0077] Table 8

[0078] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 53.8 60℃ magnesium carbonate dissolution rate (%) ≥50.0 41.0 60℃ Calcium sulfate scaling rate (%) ≥30.0 25.5 60℃ Barium sulfate dissolution rate (%) ≥25.0 18.1 25℃ stock solution pH 6.0-8.0 6.9 60℃ stock solution pH 6.0-8.0 6.8 pH of 5% aqueous solution at 25℃ 6.0-8.0 6.6 pH of 5% aqueous solution at 60℃ 6.0-8.0 6.3 25℃ stock solution viscosity (mPa·s) --- 126 25℃ 5% aqueous solution viscosity (mPa·s) --- 283 60℃ 5% aqueous solution viscosity (mPa·s) --- 218

[0079] Compared with Example 3, the polymerization degree of the sulfonated acetone formaldehyde polycondensate added to the unblocking agent prepared in Example 8 is higher. It can be seen from the test results that the viscosity of the unblocking agent sample stock solution and the viscosity of the aqueous solution increased, but the scale dissolution rate decreased significantly. The decrease in scale dissolution rate is presumed to be mainly due to the increase in viscosity, the suspension of the unblocking agent is too good, which makes the fluidity and contact between particles worse, and it may also be related to the fact that the dispersibility of the sulfonated acetone formaldehyde polycondensate with a polymerization degree of 16-18 is not as good as that of the sulfonated acetone formaldehyde polycondensate with a polymerization degree of 12-15.

[0080] The inventors have also found through many tests that when the viscosity of the 4wt%-6wt% aqueous solution of the plugging remover diluted with water at 60°C is lower than 125mPa·s, the scale dissolving effect is limited. When it is higher than 180mPa·s, the scale dissolving rate will drop significantly. The aqueous solution of the plugging remover with a viscosity between 125-180mPa·s can achieve: 60°C calcium carbonate scale dissolving rate ≥60.0%, 60°C magnesium carbonate scale dissolving rate ≥50.0%, 60°C calcium sulfate scale dissolving rate ≥30.0%, 60°C barium sulfate scale dissolving rate ≥25.0%. Therefore, the suitable viscosity range of the 4wt%-6wt% aqueous solution of the plugging remover diluted with water at 50°C-100°C is 125-180mPa·s, preferably 130-170mPa·s, and more preferably 135-160mPa·s, and its effect of removing carbonate scale and sulfate scale is relatively excellent.

[0081] In addition, the inventors tested the scale cleaning agent PNT 470 of Shanghai Fengxin Environmental Protection Technology Co., Ltd. according to the scale dissolution rate, pH, and viscosity test methods in Example 1.

[0082] The performance index test of scale cleaning agent PNT 470 is shown in Table 9:

[0083] Table 9

[0084] Test items Recommended indicator requirements Test Results 60℃ Calcium carbonate dissolution rate (%) ≥60.0 49.6 60℃ magnesium carbonate dissolution rate (%) ≥50.0 42.3 60℃ Calcium sulfate scaling rate (%) ≥30.0 25.3 60℃ Barium sulfate dissolution rate (%) ≥25.0 19.7 25℃ stock solution pH 6.0-8.0 5.2 60℃ stock solution pH 6.0-8.0 5.0 pH of 5% aqueous solution at 25℃ 6.0-8.0 5.3 pH of 5% aqueous solution at 60℃ 6.0-8.0 5.0 25℃ stock solution viscosity (mPa·s) --- 6 25℃ 5% aqueous solution viscosity (mPa·s) --- 4 60℃ 5% aqueous solution viscosity (mPa·s) --- 3

[0085] The above description of the embodiments is to facilitate the understanding and use of the present invention by those of ordinary skill in the art. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A neutral plugging remover, characterized in that: The raw materials of the blocking remover include the following components by weight percentage: 59%-67% of N-methylpyrrolidone, 15%-19% of sodium D-isoascorbate, 7%-9% of disodium ethylenediaminetetraacetate, 5%-6% of sodium 8-(2-hydroxybenzamido)octanoate, 4%-5% of sulfonated acetone formaldehyde polycondensate with a polymerization degree of 12-15, and 2% of amidopropyl hydroxysulfobetaine viscoelastic surfactant, and the total of the above components is 100%.

2. The neutral plugging remover according to claim 1, characterized in that: The raw materials of the blocking remover include the following components by weight percentage: 60%-63% of N-methylpyrrolidone, 16%-18% of sodium D-isoascorbate, 7%-9% of disodium ethylenediaminetetraacetate, 5%-6% of sodium 8-(2-hydroxybenzamido)octanoate, 4%-5% of sulfonated acetone formaldehyde polycondensate with a polymerization degree of 12-15, and 2% of amidopropyl hydroxysulfobetaine viscoelastic surfactant, and the total of the above components is 100%.

3. The neutral plugging remover according to claim 1 or 2, characterized in that: The solid content of the sulfonated acetone formaldehyde polycondensate is 30%-40%.

4. The neutral plugging remover according to claim 3, characterized in that: The amidopropyl hydroxysulfonyl betaine viscoelastic surfactant is selected from erucic acid amidopropyl hydroxysulfonyl betaine.

5. The neutral plugging remover according to claim 4, characterized in that: The concentration of the erucamidopropyl hydroxysulfobetaine is 40%.

6. The neutral plugging remover according to any one of claims 1 to 5, characterized in that: The viscosity of the neutral plugging remover in a 4wt%-6wt% aqueous solution at 50°C-100°C diluted with water is 125-180 mPa·s, preferably 130-170 mPa·s, and more preferably 135-160 mPa·s.

7. A method for preparing a neutral plugging remover, characterized in that: The method is obtained by mixing the raw materials of the blocking remover according to any one of claims 1 to 6.

8. The preparation method according to claim 7, characterized in that: The method comprises the following steps: weighing raw materials according to a proportion, pouring N-methylpyrrolidone into a reaction kettle, stirring at a speed of 120-150 r / min, heating to 50-55°C, adding sodium D-isoascorbate, stirring to form a transparent liquid without a solid phase, and then sequentially adding disodium ethylenediaminetetraacetate and sodium 8-(2-hydroxybenzamido)octanoate, maintaining the temperature at 50-55°C and continuing to stir for 0.5h-1.0h to obtain a colorless and slightly yellow transparent liquid; reducing the stirring speed to 30-60 r / min, adding sulfonated acetone formaldehyde condensation product, stirring for 0.5h, cooling to room temperature, adding amidopropyl hydroxysulfonyl betaine viscoelastic surfactant, stirring for 0.5h-1.0h, and obtaining a uniform brown-red liquid, which is the neutral plugging remover.

9. Use of the plugging remover according to any one of claims 1 to 6 or the plugging remover prepared by the preparation method according to any one of claims 7 to 8 in the field of oil field development.

10. The use according to claim 9, characterized in that: Used for declogging carbonate scale and / or sulfate scale in oil wells.