A water-soluble viscosity reducer and its preparation method

Abstract

This invention relates to a water-soluble viscosity reducer and its preparation method, belonging to the field of water-soluble viscosity reducers for low-temperature heavy oil. The water-soluble viscosity reducer has the following structural formula: where n is 10,000 to 40,000, and x is 5 to 85. The polyoxyethylene ether chain end [OCH2(OCH2CH2)] of the water-soluble viscosity reducer molecular chain of this invention... X [OCH2CH3] is a flexible ethylene oxide (EO) chain that forms an interfacial sublayer at the oil-water interface, enhancing the elasticity of the interfacial film and thus forming a stable O / W emulsion. This reduces the interaction between heavy oil droplets and prevents droplet aggregation, thereby achieving the purpose of viscosity reduction.

Description

Technical Field

[0001] This invention relates to a water-soluble viscosity reducer and its preparation method, belonging to the field of water-soluble viscosity reducers for low-temperature heavy oil. Background Technology

[0002] Heavy oil is an important component of global petroleum resources, typically more than 10 times the amount of conventional oil. Heavy oil is a product of the biodegradation and oxidation of organic matter after thermal evolution into hydrocarbons, and belongs to the category of naphthenic crude oil composed of high-molecular-weight hydrocarbons and heteroatom components.

[0003] As one of China's important oil-producing areas, Inner Mongolia Oilfield currently reports a cumulative reserve of 14.2867 million tons of ordinary heavy oil, mainly distributed in the Mao 1, Mao 8, and Yi 16 blocks, possessing significant development potential. The ordinary heavy oil in Inner Mongolia contains 6.5%–12.9% gum and 1.1%–3.5% asphaltene. Due to the high gum and asphaltene content, the viscosity of the degassed crude oil at 50℃ reaches as high as 2500–5100 mPa·s, which reduces the fluidity of the crude oil in the reservoir and wellbore. Furthermore, the reservoir temperature of Inner Mongolia heavy oil ranges from 27 to 47.5℃, making conventional extraction processes more difficult under low-temperature conditions.

[0004] Currently, heavy oil development technologies are mainly divided into two categories: thermal recovery and cold recovery. Thermal recovery uses artificial heating to reduce the viscosity of difficult-to-extract oil reservoirs, i.e., heavy oil, increasing its fluidity and thus improving recovery rates. Cold recovery, as a traditional heavy oil extraction technology, involves contacting a viscosity reducer with the heavy oil to form an oil-in-water emulsion. This disperses the heavy oil in the aqueous phase, significantly reducing flow resistance and thus achieving emulsification and viscosity reduction, thereby improving heavy oil recovery rates. Compared to thermal recovery, cold recovery offers advantages for Inner Mongolia heavy oil, including strong on-site operability, technical flexibility, and strong environmental adaptability.

[0005] Chinese invention patent application CN110396401A discloses an emulsified viscosity reducer, which is formulated from anionic-nonionic surfactants, anionic surfactants, alkalis, and additives. This viscosity-reducing system has strong hydrophilic groups and can form an oil-in-water emulsion system with water (dispersed phase) at temperatures above 50°C, significantly reducing the viscosity of heavy oil. However, in the low-temperature conditions of the Inner Mongolia heavy oil reservoirs, it either does not emulsify or exhibits poor emulsion stability.

[0006] Chinese invention patent application CN110627930A discloses a polymer viscosity reducer for heavy oil, which is a hydrophobically modified polyacrylamide polymerized from acrylamide and sodium α-olefin sulfonate. This viscosity reducer exhibits strong affinity and penetration ability for heavy oil, effectively differentiating and dismantling the supramolecular structure of heavy oil, thus reducing viscosity while simultaneously improving the stability of heavy oil emulsions. However, this viscosity reducer is suitable for formation temperatures of 50–70℃. Under the low-temperature conditions of 27–47.5℃ in the Inner Mongolia heavy oil reservoir, the crude oil emulsification effect is poor, failing to meet the extraction requirements of low-temperature heavy oil. Summary of the Invention

[0007] The purpose of this invention is to provide a water-soluble viscosity reducer to solve the problem of poor emulsification and viscosity reduction effect of existing viscosity reducers on low-temperature heavy oil reservoirs.

[0008] The second objective of this invention is to provide a method for preparing a water-soluble viscosity reducer, in order to solve the problem that the existing viscosity reducers have poor emulsification and viscosity reduction effects on low-temperature heavy oil reservoirs.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A water-soluble viscosity reducer has the following structural formula:

[0011]

[0012] Where n ranges from 10,000 to 40,000, and x ranges from 5 to 85.

[0013] The water-soluble viscosity reducer of this invention is a pioneering invention. The polyoxyethylene ether chain end [OCH2(OCH2CH2)] of the water-soluble viscosity reducer molecular chain of this invention... X [OCH2CH3] is a flexible ethylene oxide (EO) chain that forms an interfacial sublayer at the oil-water interface, enhancing the elasticity of the interfacial film and thus forming a stable O / W emulsion. This reduces the interaction between heavy oil droplets and prevents droplet aggregation, thereby achieving the purpose of viscosity reduction.

[0014] The water-soluble viscosity reducer of the present invention achieves a viscosity reduction rate of over 93% for heavy oil at a low temperature of 40-50°C. When the temperature is further lowered to 30-35°C, the viscosity reduction rate for heavy oil can reach over 95%, indicating that the water-soluble viscosity reducer of the present invention has a good viscosity reduction effect on heavy oil at low temperatures.

[0015] More preferably, x is 30–85. The molecular weight of the water-soluble viscosity reducer is 4–10 × 10⁻⁶. 5 .

[0016] The second technical solution of the present invention is:

[0017] A method for preparing a water-soluble viscosity reducer includes the following steps: oxidized polyethylene glycol monoethyl ether undergoes an acid chlorination reaction with oxaloyl chloride to obtain an acid-chlorinated product; the acid-chlorinated product is then subjected to an ammonolysis reaction with polyacrylamide to obtain the water-soluble viscosity reducer.

[0018] This invention provides a water-soluble viscosity reducer by sequentially subjecting oxidized polyethylene glycol monoethyl ether to acid chlorination and ammonolysis. This preparation method is simple, easy to operate, and suitable for large-scale production.

[0019] To improve preparation efficiency, preferably, the mass ratio of the oxidized polyethylene glycol monoethyl ether to oxaloyl chloride is 1:(1.9-2); the mass ratio of the acid chlorination product to polyacrylamide is 1:(1-1.2); and the molecular weight of the polyacrylamide is (4-10)×10⁻⁶. 5 .

[0020] To ensure the reaction proceeds fully, preferably, the temperature of the polyethylene glycol monoethyl ether oxidation treatment is 120–140°C and the time is 10–12 h; the acid chlorination reaction is carried out at room temperature and the reaction time is 10–12 h; and the ammonolysis reaction is carried out at 70–90°C and the time is 6–10 h.

[0021] Preferably, the polyethylene glycol monoethyl ether is obtained by etherification of polyethylene glycol with ethanol.

[0022] Preferably, the mass-to-volume ratio of polyethylene glycol to ethanol is 1:(40-45), and the molecular weight of polyethylene glycol is (1.0-6.0)×10⁻⁶. 3 Under these reaction conditions, the reaction efficiency is high, and polyethylene glycol and ethanol can be fully utilized.

[0023] Preferably, the etherification reaction is carried out at a temperature of 200–240°C for 2–2.5 hours.

[0024] Preferably, the catalyst for the oxidation treatment is any one of palladium, rhodium, and silver. Under the catalysis of the catalyst, the hydroxyl groups in polyethylene glycol monoethyl ether are oxidized to carboxylic acids.

[0025] Preferably, the catalyst for the etherification reaction is an acidic catalyst, wherein the silicon-to-aluminum ratio in the acidic catalyst is 11 to 25.

[0026] Preferably, the acidic catalyst is any one of HY, H-beta, and HZSM-5 catalysts. HY, H-beta, and HZSM-5 catalysts are commercially available products. Attached Figure Description

[0027] Figure 1 This is an interfacial tension diagram of the viscosity reducer solution in Example 4;

[0028] Figure 2 This is an interfacial tension diagram of a comparative viscosity reducer solution. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0030] Existing hydrophobically modified polyacrylamides exhibit poor emulsification effects on Inner Mongolia heavy oil at low temperatures (27–47.5°C). In contrast, the viscosity reducer of this invention possesses lipophilic long alkyl chains, a polyether structure, and polyacrylamide molecular chains. It can spontaneously react with gums and asphaltenes in crude oil, emulsifying them into small particles. Furthermore, it can adsorb onto the oil-water interface at low temperatures to form an interfacial sublayer, creating a stable O / W emulsion. It also reduces the interfacial tension between oil and water, ultimately improving the viscosity-reducing effect on low-temperature heavy oil.

[0031] The H-beta catalyst used in the following examples was purchased from Raodong New Materials Co., Ltd., catalog number BETA-25; the HZSM-5 catalyst was purchased from Shanghai Zhenzhun Biotechnology Co., Ltd., catalog number Z31; and the HY catalyst was purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., catalog number 32.

[0032] The method for preparing the water-soluble viscosity reducer of the present invention includes the following steps:

[0033] (1) Polyethylene glycol and ethanol undergo an etherification reaction under the action of an acidic catalyst to produce polyethylene glycol monoethyl ether, i.e., compound A. The reaction formula for the etherification reaction is shown below:

[0034]

[0035] (2) Polyethylene glycol monoethyl ether (compound A) undergoes an oxidation reaction under the action of a metal catalyst, which oxidizes the alcohol hydroxyl group to a carboxylic acid to give compound B; the specific reaction formula is shown below:

[0036]

[0037] (3) Compound B undergoes an acid chlorination reaction with oxalyl chloride to give compound C; the specific reaction formula is shown below:

[0038]

[0039] (4) Compound C undergoes an ammonolysis reaction with polyacrylamide to yield compound D, which is a water-soluble viscosity reducer; the specific reaction formula is shown below:

[0040]

[0041] I. Specific embodiments of the water-soluble viscosity reducer of the present invention are as follows:

[0042] Example 1

[0043] The water-soluble viscosity reducer of this embodiment has the following structural formula:

[0044]

[0045] Where n is 18,000, x is 30, and the molecular weight is 4.8 × 10⁻⁶. 5 .

[0046] Example 2

[0047] The water-soluble viscosity reducer of this embodiment has the following structural formula:

[0048]

[0049] Where n is 25,000, x is 50, and the molecular weight is 6.7 × 10⁻⁶. 5 .

[0050] Example 3

[0051] The water-soluble viscosity reducer of this embodiment has the following structural formula:

[0052]

[0053] Where n is 38,000, x is 80, and the molecular weight is 1.0 × 10⁻⁶. 6 .

[0054] II. Specific embodiments of the preparation method of the water-soluble viscosity reducer of the present invention are as follows:

[0055] Example 4

[0056] This embodiment describes the preparation method of the water-soluble viscosity reducer from Example 1, and includes the following steps:

[0057] (1) In a high-pressure reactor, add 5g of a material with a molecular weight of 1.3×10⁻⁶. 3 Polyethylene glycol and 200 mL of ethanol were mixed evenly, and then 0.3 g of H-beta catalyst (silicon-to-aluminum ratio of 25) was added. The mixture was stirred evenly at room temperature and then sealed. The air was replaced with nitrogen five times, and the reaction was carried out at 220 °C for 2 hours under nitrogen atmosphere. After the reaction was completed, the reaction vessel was cooled to room temperature, filtered, and then distilled under reduced pressure using a rotary evaporator (temperature: 50-55 °C, pressure: <20 kPa). The mixture was then purified by column chromatography with petroleum ether and ethyl acetate as the mobile phase in the silica gel column, with a volume ratio of petroleum ether to ethyl acetate of 1:2, to obtain compound A (i.e., polyethylene glycol monoethyl ether).

[0058] (2) At room temperature, 3.5g of compound A, 50mg of palladium catalyst and 100mL of tetrahydrofuran were added to the reactor and heated to 140℃ for 10h. After the reaction was completed, compound B 3.2g was obtained by filtration purification.

[0059] (3) At room temperature, 3.2 g of compound B, 6.4 g of oxalyl chloride and 200 mL of solvent benzene were added to a round-bottom flask. The mixture was stirred for a period of time, and then 10 mL of DMF (N,N-dimethylformamide) was added to the mixture. The reaction mixture was stirred at room temperature for 10 h, and the oxalyl chloride and benzene were evaporated to obtain compound C.

[0060] (4) Under N2 protection, add 3g of a material with a molecular weight of 4.86×10⁻⁶ to a reactor equipped with a stirrer, condenser, and thermometer. 5 A mixture of polyacrylamide, 500 mL of water and ethanol (volume ratio 1:2) was prepared, and then 2.5 g of compound C synthesized in step (3) and 0.15 g of basic acid-binding agent triethylamine were added. The mixture was heated to 70 °C and reacted for 6 h. The resulting material was subjected to vacuum distillation (temperature: 60 °C, pressure: <15 KPa) to remove the solvent, followed by crystallization, filtration, washing, drying and pulverization to obtain 4.8 g of water-soluble heavy oil viscosity reducer product.

[0061] Example 5

[0062] This embodiment describes the preparation method of the water-soluble viscosity reducer in Example 2, and includes the following steps:

[0063] (1) In a high-pressure reactor, add 5g of a material with a molecular weight of 2.2×10⁻⁶. 3 Polyethylene glycol and 200 mL of ethanol were mixed evenly, and then 0.2 g of HZSM-5 catalyst (silicon-to-aluminum ratio of 25) was added. The mixture was stirred evenly at room temperature and then sealed. The air was replaced with nitrogen five times, and the reaction was carried out at 220 °C for 2 h under nitrogen atmosphere. After the reaction was completed, the reaction vessel was cooled to room temperature, filtered, and then distilled under reduced pressure using a rotary evaporator (temperature: 50-55 °C, pressure: <20 kPa). The mixture was purified by column chromatography with petroleum ether and ethyl acetate as the mobile phase in the silica gel column, with a volume ratio of petroleum ether to ethyl acetate of 1:2, to obtain compound A.

[0064] (2) At room temperature, 3.3g of compound A, 50mg of rhodium catalyst and 100mL of tetrahydrofuran were added to the reactor and heated to 120℃ for 10h. After the reaction was completed, 2.9g of compound B was obtained by filtration purification.

[0065] (3) At room temperature, 3.5 g of compound B, 6.8 g of oxalyl chloride and 200 mL of solvent benzene were added to a round-bottom flask and the mixture was stirred for a period of time. Then, 10 mL of DMF was added to the mixture and the reaction mixture was stirred at room temperature for 12 h. Oxaloyl chloride and benzene were evaporated to obtain compound C.

[0066] (4) Under N2 protection, add 3g of a material with a molecular weight of 6.75×10⁻⁶ to a reactor equipped with a stirrer, condenser, and thermometer. 5 A mixed solvent of polyacrylamide, 500 mL of water and ethanol (volume ratio 1:2) was prepared, and then 3 g of compound C and 0.15 g of basic acid-binding agent triethylamine were added. The mixture was heated to 80 °C and reacted for 8 h. The resulting material was subjected to vacuum distillation (temperature: 60 °C, pressure: <15 kPa) in a rotary evaporator to remove the solvent, followed by crystallization, filtration, washing, drying and pulverization to obtain 4.4 g of water-soluble heavy oil viscosity reducer product.

[0067] Example 6

[0068] This embodiment describes the preparation method of the water-soluble viscosity reducer in Example 3, and includes the following steps:

[0069] (1) In a high-pressure reactor, add 5g of a material with a molecular weight of 5.2×10⁻⁶. 3 Polyethylene glycol and 200 mL of ethanol were mixed evenly, and then 0.8 g of HY catalyst (silicon-to-aluminum ratio of 1:1) was added. The mixture was stirred evenly at room temperature and then sealed. The air was replaced with nitrogen five times, and the reaction was carried out at 220 °C for 2 hours under nitrogen atmosphere. After the reaction was completed, the reaction vessel was cooled to room temperature, filtered, and then distilled under reduced pressure using a rotary evaporator (temperature: 50-55 °C, pressure: <20 kPa). The mixture was purified by column chromatography with petroleum ether and ethyl acetate as the mobile phase in the silica gel column, with a volume ratio of petroleum ether to ethyl acetate of 1:2, to obtain compound A.

[0070] (2) At room temperature, 3.3g of compound A, 50mg of metallic silver catalyst and 100mL of toluene were added to the reactor and heated to 140℃ for 10h. After the reaction was completed, 2.7g of compound B was obtained by filtration purification.

[0071] (3) At room temperature, 2.7 g of compound B, 5.4 g of oxalyl chloride and 200 mL of solvent toluene were added to a round-bottom flask. The mixture was stirred for a period of time, and then 10 mL of DMF was added to the mixture. The reaction mixture was stirred at room temperature for 10 h. Oxaloyl chloride and benzene were evaporated to obtain compound C.

[0072] (4) Under N2 protection, add 5g of a molecular weight of 1.0×10⁻⁶ to a reactor equipped with a stirrer, condenser, and thermometer. 6A mixed solvent of polyacrylamide, 500 ml of water and ethanol (volume ratio 1:2) was prepared, and then 5 g of compound C and 0.25 g of basic acid-binding agent triethylamine were added. The mixture was heated to 90 °C and reacted for 10 h. The resulting material was subjected to vacuum distillation (temperature: 60 °C, pressure: <15 kPa) in a rotary evaporator to remove the solvent, followed by crystallization, filtration, washing, drying and pulverization to obtain 6.1 g of water-soluble heavy oil viscosity reducer product.

[0073] III. Comparative Example

[0074] The preparation method of the viscosity reducer in this comparative example refers to the preparation method of the viscosity reducer for heavy oil in Chinese invention patent application CN110627930A, and specifically adopts the following steps:

[0075] (1) Add 20g of acrylamide and 10g of sodium α-olefin sulfonate to 100g of deionized water, and heat the resulting solution to 60℃ in a water bath.

[0076] (2) Add 0.4g Na2S2O8 and 0.2g Na2SO3 to the above aqueous solution in sequence, and stir at 300rpm for 14h.

[0077] (3) Take 70 mL of the solution obtained in (2) above, add 20 mL of 0.1 wt% NaOH-Na2CO3 (mass ratio 1:1), place it in an 80℃ oven for 5 h of hydrolysis, and obtain the viscosity reducer of the comparative example.

[0078] IV. Experimental Examples

[0079] This experimental example measures the viscosity-reducing performance and oil-water interfacial tension of the water-soluble viscosity reducers prepared in the comparative examples and Examples 4-6. The experimental methods are as follows:

[0080] Preparation of test solutions: Take four 500mL beakers, add 2.4g of the comparative example and the water-soluble viscosity reducer from Examples 4-6 to each beaker, and add 397.6g of block-produced water to each beaker. Then place the beakers in a constant temperature water bath at 40℃ and stir for 40-60min at a speed of 200-300rpm / min until the viscosity reducer is completely dissolved in the water, thus obtaining four viscosity reducer solutions.

[0081] Viscosity Reduction Performance: The viscosity reduction rate was determined according to Q / SH0055-2007 "Technical Requirements for Heavy Oil Viscosity Reducers". The specific method was as follows: 12g of the four prepared viscosity reducer solutions were added to each of four test cups containing 28g of crude oil. The cups were then incubated in a constant temperature water bath at 30℃ for 30min. After thorough stirring with a glass rod, the viscosity data were rapidly measured using a Brookfield RV DV-Ⅲ rotational viscometer. Viscosity data were measured under the same conditions at water bath temperatures of 35℃, 40℃, 45℃, and 50℃. The results are shown in Table 1.

[0082] Table 1 Viscosity performance results

[0083]

[0084] As shown in Table 1, when the temperature is 50℃, the viscosity reduction rate of the comparative viscosity reducer reaches 96%, demonstrating a good viscosity reduction effect on heavy oil. However, as the temperature decreases, the viscosity reduction rate of the comparative viscosity reducer gradually declines. At 35℃, the viscosity reduction effect of the comparative viscosity reducer is only partial emulsification, failing to achieve effective viscosity reduction. In contrast, the water-soluble viscosity reducer of this invention exhibits a high viscosity reduction rate for heavy oil at temperatures ranging from 30℃ to 50℃. Especially when the temperature drops to 35℃, the viscosity reduction effect on heavy oil can still reach over 95%. Therefore, the viscosity reducer of this invention has a better viscosity reduction effect on heavy oil at low temperatures than the comparative viscosity reducer.

[0085] Compared with the comparative heavy oil polymer viscosity reducer (i.e., the patent with publication number CN110627930A), the water-soluble viscosity reducer of the present invention has high hydrophilicity of polyoxyethylene ether chains on its molecular chain, and therefore still maintains good interfacial emulsification and dispersion ability at low temperature (<50°C). In contrast, the penetration and diffusion activity of long alkyl chains on the molecular chain of the comparative heavy oil polymer viscosity reducer is greatly affected by temperature. At low temperature, the penetration and diffusion ability of long alkyl chains decreases, and the viscosity reducing ability weakens.

[0086] Oil-water interfacial tension measurement: The oil-water interfacial tension of the viscosity reducer solutions of the comparative example and Example 4 at 30°C was measured using a rotating ultra-low interfacial analyzer (Kno, USA, model TX500).

[0087] The interfacial tension measurement process was as follows: oil droplets were suspended in a viscosity reducer solution, and the tensile properties of the oil droplets were observed when they rotated at high speed (6000 rpm) around a horizontal axis. The interfacial tension value was read after 1-1.5 hours. At a test temperature of 30℃, the interfacial tension value of the 0.3% solution in Example 4 was 0.030451 mN / m. The test interface is shown below. Figure 1 The interfacial tension value for the comparative example was 1.730391 mN / m. The test interface is shown below. Figure 2 Therefore, compared with the comparative example, the viscosity reducer solution of Example 4 has a lower interfacial tension value, the oil-water interface is more easily expanded, and crude oil is more easily emulsified in the viscosity reducer solution of Example 4.

Claims

1. A water-soluble viscosity reducer, characterized in that, It has the following structural formula: Where n ranges from 10,000 to 40,000, and x ranges from 5 to 85.

2. A method for preparing the water-soluble viscosity reducer as described in claim 1, characterized in that, The process includes the following steps: oxidized polyethylene glycol monoethyl ether undergoes an acid chlorination reaction with oxaloyl chloride to obtain an acid-chlorinated product; the acid-chlorinated product is then subjected to an ammonolysis reaction with polyacrylamide to obtain a water-soluble viscosity reducer.

3. The method for preparing the water-soluble viscosity reducer according to claim 2, characterized in that, The mass ratio of the oxidized polyethylene glycol monoethyl ether to oxaloyl chloride is 1:(1.9-2); the mass ratio of the acid chlorination product to polyacrylamide is 1:(1-1.2); and the molecular weight of the polyacrylamide is (4-10)×10⁻⁶. 5 .

4. The method for preparing the water-soluble viscosity reducer according to claim 2 or 3, characterized in that, The polyethylene glycol monoethyl ether oxidation treatment is carried out at a temperature of 120–140°C for 10–12 h; the acid chlorination reaction is carried out at room temperature for 10–12 h; and the ammonolysis reaction is carried out at a temperature of 70–90°C for 6–10 h.

5. The method for preparing the water-soluble viscosity reducer according to claim 2, characterized in that, The polyethylene glycol monoethyl ether is obtained by etherification of polyethylene glycol with ethanol.

6. The method for preparing the water-soluble viscosity reducer according to claim 5, characterized in that, The mass-to-volume ratio of polyethylene glycol to ethanol is 1:(40-45), and the molecular weight of polyethylene glycol is (1.0-6.0)×10⁻⁶. 3 .

7. The method for preparing the water-soluble viscosity reducer according to claim 5 or 6, characterized in that, The etherification reaction is carried out at a temperature of 200–240°C for 2–2.5 hours.

8. The method for preparing the water-soluble viscosity reducer according to claim 4, characterized in that, The catalyst for the oxidation treatment is any one of palladium, rhodium, and silver.

9. The method for preparing the water-soluble viscosity reducer according to claim 5 or 6, characterized in that, The catalyst for the etherification reaction is an acidic catalyst, and the silicon-to-aluminum ratio in the acidic catalyst is 11 to 25.

10. The method for preparing the water-soluble viscosity reducer according to claim 9, characterized in that, The acidic catalyst is any one of HY, H-beta, or HZSM-5 catalyst.

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