Scale inhibitor for oilfield produced water and preparation method thereof

Abstract

The present invention relates to the field of oil production, and more particularly to a scale inhibitor for oilfield produced water and a preparation method thereof. Specifically, the invention relates to an epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer having a structure represented by formula (I) or a salt thereof. The terpolymer exhibits strong scale inhibition capabilities, achieving a scale inhibition rate exceeding 95% at an addition level of 8 ppm. Furthermore, while maintaining scale inhibition capabilities, the terpolymer also exhibits good biodegradability, with a 28-day degradation rate exceeding 80% in biodegradation experiments.

Description

Technical Field

[0001] The present invention relates to the field of petroleum extraction, and in particular to a scale inhibitor for oilfield produced water and a preparation method thereof. Background Art

[0002] In the mid-to-late stages of oilfield development, water injection is often used to maintain reservoir pressure to increase oil recovery. Due to constant fluctuations in temperature, pressure, and the oil-gas-water phase equilibrium, large amounts of scale accumulate in the formations near production wells, in the wellbore, and on surface pipelines. This scale adheres to reservoirs, formations, and pipelines. This accumulation of scale can damage production equipment and, in severe cases, even cause pump rod breakage, rendering the well useless. Therefore, adding scale inhibitors to the produced water generated during the production process is one method to prevent scale accumulation in pipelines.

[0003] Common scale inhibitors include organic phosphoric acids, multi-component copolymers, etc.

[0004] Chinese patent invention CN101870758A discloses a polyether phosphate scale inhibitor with a long polyethoxy chain and a preparation method thereof. The scale inhibitor can be monitored by ultraviolet tracing to achieve online detection and automatic dosing of the scale inhibitor. It is suitable for scale inhibition of calcium phosphate and calcium carbonate in industrial circulating cooling water systems. It is obtained by free radical polymerization of a polyether phosphate monomer with a long polyethoxy chain containing an unsaturated double bond, an unsaturated carboxylic acid monomer, and an unsaturated aromatic compound monomer. Its general structural formula is as follows: Wherein: E is a repeating structural unit obtained by free radical copolymerization of unsaturated aromatic compound monomers; R1 is -H or -COOH; R2 and R3 are -H or C1-C4 low carbon alkyl; R4 and R5 are one of C1-C4 alkyl, -H, and -M, and M is H + or K + Or Na + ; The number of repeating units m is 1 to 100, the number of repeating units n is 0 to 100, the degree of polymerization x is 1 to 5000, the degree of polymerization y is 1 to 5000, and the degree of polymerization z is 1 to 5000.

[0005] Chinese patent invention CN108291136A discloses a thermally stable polymeric scale inhibitor composition and its uses. The polymeric scale inhibitor is preferably a polycarboxylic acid copolymer comprising acrylic acid, methacrylic acid, and styrenesulfonic acid. The polymeric scale inhibitor composition is particularly suitable for high-pressure / high-temperature scale inhibition in oil, gas, and geothermal production wells and / or underground formations.

[0006] Chinese patent invention CN110921857A discloses a scale inhibitor specifically designed for MVR systems. The scale inhibitor is composed of the following ingredients: acrylic acid-styrene sulfonate copolymer, organic phosphonic acid, allyl polyoxyethylene polycarboxylic acid scale inhibitor, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-tert-butylacrylamide terpolymer, adipic acid-terminated amino polyether-diethylenetriamine copolymer, epoxysuccinic acid derivative, phosphorus-containing polymer, phosphate starch, and pure water. This invention addresses the high-temperature, high-silicon, and high-sulfate water conditions of MVR systems, resulting in the development of a scale inhibitor specifically designed for MVR systems. This scale inhibitor exhibits excellent scale inhibition and dispersibility for sulfates, silicates, and carbonates, while not affecting subsequent crystallization and salt separation. This scale inhibitor offers excellent application effectiveness and production value, contributing to energy conservation and emission reduction, waste salt utilization, and zero-emission development for enterprises.

[0007] However, the use of organophosphate scale inhibitors may lead to eutrophication of water bodies and is not recommended for large-scale use. While multi-polymer scale inhibitors have good scale inhibition effects, they are generally poorly degradable and can also cause pollution when discharged into water bodies. Summary of the Invention

[0008] The purpose of the present invention is to address the water pollution problem caused by phosphorus-containing scale inhibitors and copolymer scale inhibitors in the related art, and to develop a polymer scale inhibitor that has good scale inhibition effect and can be effectively degraded.

[0009] The purpose of the present invention is achieved through the following technical solutions.

[0010] In one aspect, the present invention provides an epoxysuccinic acid-carboxyl terminated allyl polyether-styrene sulfonic acid terpolymer having a structure of formula (I) or a salt thereof

[0011]

[0012] Furthermore, wherein x is 1-4000; y is 1-4000; z is 1-4000; and n is 1-100.

[0013] Furthermore, the terpolymer is obtained by free radical polymerization of epoxysuccinic acid, allyl polyether and styrene sulfonic acid;

[0014] Furthermore, the molar ratio of the epoxysuccinic acid, allyl polyether and styrene sulfonic acid is 1:0.2-0.3:0.3-0.5.

[0015] On the other hand, the present invention provides a method for preparing an epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer, comprising the following steps:

[0016] S1: epoxysuccinic acid or its salt, carboxyl-terminated allyl polyether or its salt and styrenesulfonic acid or its salt are mixed in a solvent, and a free radical initiator is added to react to obtain the product.

[0017] Furthermore, the epoxysuccinic acid has the structure of formula (Ia)

[0018]

[0019] The present invention does not require the configuration of epoxysuccinic acid.

[0020] Furthermore, the carboxyl-terminated allyl polyether has a structure of formula (Ib):

[0021]

[0022] Where n is 1-100.

[0023] Formula (Ib) of the present invention is prepared by reacting the corresponding allyl polyether (APEG) and oxalic acid at 70-90° C. for 2-4 hours, with specific reference to the operating steps disclosed in Preparation of a low-phosphorous terpolymer as a scale, corrosion inhibitor, and dispersant for ferric oxide. (Chen Y, Zhou Y, Yao Q, et al. Journal of Applied Polymer Science, 2015, 132(6).).

[0024] Furthermore, the styrene sulfonic acid has the structure of formula (Ic)

[0025]

[0026] The present invention does not require the configuration of styrenesulfonic acid.

[0027] Furthermore, the molar ratio of epoxysuccinic acid or its salt, carboxyl-terminated allyl polyether or its salt and styrenesulfonic acid or its salt is 1:0.2-0.3:0.3-0.5.

[0028] Furthermore, in S1, the solvent is water.

[0029] Furthermore, in S1, the free radical initiator is selected from at least one of hydrogen peroxide and persulfate.

[0030] Furthermore, in S1, the persulfate is selected from at least one of K2S2O8, Na2S2O8 or (NH4)2S2O8, preferably (NH4)2S2O8.

[0031] Furthermore, the amount of the initiator used is 5-10% of the total amount of monomers used.

[0032] Furthermore, the reaction temperature is 60-80° C., and the reaction time is 3-6 hours.

[0033] In one aspect, the present invention provides an application of the terpolymer, wherein the application is an application as a scale inhibitor in the transportation or treatment of produced water in oil fields.

[0034] The advantages of the present invention are:

[0035] 1. The epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer of the present invention has a strong scale inhibition ability. When the addition amount is 8 ppm, the scale inhibition rate can reach more than 95%.

[0036] 2. The terpolymer of the present invention adopts a suitable main chain and side chain structure, which ensures the scale inhibition ability while having good biodegradability. In the biodegradation experiment, the degradation rate in 28 days is more than 80%.

[0037] 3. The terpolymer of the present invention can be prepared by free radical polymerization in aqueous solution using a free radical initiator. The preparation method is simple and rapid, and is suitable for large-scale production. DETAILED DESCRIPTION

[0038] Example 1

[0039] An epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer is prepared by the following method:

[0040] Carboxyl-terminated allyl polyether was prepared by reacting allyl polyethylene glycol 300 (APEG-300) with oxalic acid.

[0041] Weigh 1 mol of epoxy succinate, add 2 mol of deionized water, and dissolve in a 40-50°C water bath. After the solution cools, pour it into a three-necked reactor equipped with an electric stirrer, a condenser reflux device, a dropping funnel, and a thermometer. Then add 0.2 mol of carboxyl-terminated allyl polyether and 0.5 mol of styrene sulfonic acid, and start electric stirring to ensure uniform dissolution. Then, dissolve 10% of the total monomer mass of ammonium persulfate in 1 mol of deionized water and place it in a dropping funnel. Arrange the reaction apparatus. Heat slowly and introduce nitrogen for 15 minutes. Raise the temperature to 70°C and maintain it stable. Add the ammonium persulfate aqueous solution dropwise, paying attention to the dropwise addition rate. The ammonium persulfate addition time is controlled to control the dropwise addition time. After the addition is complete, continue the reaction for 3.0-4.0 hours to obtain a yellow, transparent, viscous liquid. The product is poured into ethanol, and the product will precipitate from the solution. It is then vacuum filtered, washed with ethanol 3-6 times, and vacuum dried at 60° C. to a constant weight to obtain the terpolymer.

[0042] Example 2

[0043] An epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer is prepared by the following method:

[0044] Carboxyl-terminated allyl polyether was prepared by reacting allyl polyethylene glycol 300 (APEG-3000) with oxalic acid.

[0045] Weigh 1 mol of epoxy succinate, add 3 mol of deionized water, and dissolve in a 40-50°C water bath. After the solution cools, pour it into a three-necked reactor equipped with an electric stirrer, reflux device, dropping funnel, and thermometer. Then add 0.25 mol of carboxyl-terminated allyl polyether and 0.4 mol of styrene sulfonic acid, and start electric stirring to ensure uniform dissolution. Then, dissolve 8% of the total monomer weight of ammonium persulfate in 1 mol of deionized water and place it in the dropping funnel. Arrange the reaction apparatus. Heat slowly and introduce nitrogen for 15 minutes. Raise the temperature to 70°C and maintain it stable. Add the ammonium persulfate aqueous solution dropwise, paying attention to the dropwise addition rate. Keep the ammonium persulfate addition time at approximately 1.0 hour. After the addition is complete, continue the reaction for 3.0-4.0 hours to obtain a yellow, transparent, viscous liquid. The product is poured into ethanol, and the product will precipitate from the solution. It is then vacuum filtered, washed with ethanol 3-6 times, and vacuum dried at 60° C. to a constant weight to obtain the terpolymer.

[0046] Example 3

[0047] An epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer is prepared by the following method:

[0048] Carboxyl-terminated allyl polyether was prepared by reacting allyl polyethylene glycol 300 (APEG-4500) with oxalic acid.

[0049] Weigh 1 mol of epoxy succinate, add 1.5 mol of deionized water, and dissolve in a 40-50°C water bath. After the solution cools, pour it into a three-necked reactor equipped with an electric stirrer, a condenser reflux device, a dropping funnel, and a thermometer. Then add 0.3 mol of carboxyl-terminated allyl polyether and 0.35 mol of styrene sulfonic acid, and start electric stirring to ensure uniform dissolution. Then, dissolve 5% of the total monomer weight of ammonium persulfate in 1 mol of deionized water and place it in a dropping funnel. Arrange the reaction apparatus. Heat slowly and introduce nitrogen for 15 minutes. Raise the temperature to 70°C and maintain it stable. Add the ammonium persulfate aqueous solution dropwise, paying attention to controlling the dropwise addition rate. The ammonium persulfate addition time is controlled to control the dropwise addition time to about 1.0 hour. After the addition is complete, continue the reaction for 3.0-4.0 hours to obtain a yellow, transparent, viscous liquid. The product is poured into ethanol, and the product will precipitate from the solution. It is then vacuum filtered, washed with ethanol 3-6 times, and vacuum dried at 60° C. to a constant weight to obtain the terpolymer.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that the amounts of the three monomers are different. If the molar ratio of epoxysuccinic acid or its salt, carboxyl-terminated allyl polyether or its salt, and styrenesulfonic acid or its salt is 1:0.4:0.2, a terpolymer is obtained by the reaction.

[0052] Comparative Example 2

[0053] The difference from Example 1 is that acrylic acid is used instead of the carboxyl-terminated allyl polyether to obtain a terpolymer.

[0054] The scale inhibition evaluation method of the products obtained in each embodiment and comparative example is based on GB / T16632-2008 "Determination of scale inhibition performance of water treatment agents - Calcium carbonate precipitation method". 2+ The concentration is 240 mg / L, HCO 3- Concentration 732 mg / L, temperature 80℃, time 16h.

[0055] Table 1 Scale inhibition performance evaluation results

[0056]

[0057] The biodegradability evaluation of the products obtained in each embodiment and comparative example is as follows:

[0058] Phosphate buffer, calcium chloride solution, magnesium sulfate solution, ferric chloride solution, ammonium sulfate solution, and water treatment agent solution were added. Then, 2 mL of calcium chloride solution, 2 mL of magnesium sulfate solution, 2 mL of ammonium sulfate solution, 4 mL of ferric chloride solution, and 2 mL of phosphate buffer were added to each liter of the test solution, controlling the solution's ρ(CODMn) between 10 and 20 mg / L. Finally, 20 mg of the inoculum was added. Mix thoroughly and dispense into 100 mL Erlenmeyer flasks. Add 50 mL of the mixed solution to each flask, seal with cotton plugs, cover with plastic wrap, tie tightly, and place in a waterbath in a constant-temperature oscillator. Separately, distilled water was used as the test solution, to which the nutrient solution and inoculum were added sequentially, for a blank control experiment. The waterbath temperature was adjusted to 30°C, the oscillation frequency was set at 120 rpm, and incubation began. On days 4, 10, 16, 20, and 28, a set of Erlenmeyer flasks (test solution and blank) was removed each time, filtered, and the ρ(CODMn) value of the filtrate was determined. The net ρ(CODMn) is obtained by subtracting the ρ(CODMn) value of the blank from the ρ(CODMn) value of the test solution. The entire experimental period is controlled within 10-28 days. The degradation rate is calculated as follows:

[0059]

[0060] Where: ρ(CODMn n )-net potassium permanganate index of the sample filtrate on day n;

[0061] ρ(CODMn 0 )-the net potassium permanganate index of the sample filtrate at the beginning.

[0062] The biodegradability results are shown in Table 2.

[0063] Table 2 Biodegradability evaluation

[0064]

[0065] It can be seen from the results in Table 1 and Table 2 that the epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer provided by the present invention has good scale inhibition performance and biodegradation effect.

[0066] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. An epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer having a structure of formula (I) or a salt thereof, The terpolymer is obtained by free radical polymerization of epoxysuccinic acid, allyl polyether and styrene sulfonic acid; The molar ratio of the epoxysuccinic acid, the allyl polyether and the styrene sulfonic acid is 1:0.2-0.3:0.3-0.

5.

2. The terpolymer according to claim 1, characterized in that in, x is 1-4000; y is 1-4000; z is 1-4000; n is 1-100.

3. A method for preparing an epoxysuccinic acid-carboxyl-terminated allyl polyether-styrenesulfonic acid terpolymer or its salt, comprising the following steps: S1: mixing epoxy succinic acid or its salt, carboxyl terminated allyl polyether or its salt, and styrene sulfonic acid or its salt in a solvent, and adding a free radical initiator for reaction; the molar ratio of epoxy succinic acid or its salt, carboxyl terminated allyl polyether or its salt, and styrene sulfonic acid or its salt is 1:0.2-0.3:0.3-0.5; The carboxyl-terminated allyl polyether has a structure of formula (Ib) The styrene sulfonic acid has the structure of formula (Ic) 4. The preparation method according to claim 3, characterized in that n is 1-100.

5. The preparation method according to claim 4, characterized in that In S1, the free radical initiator is selected from at least one of hydrogen peroxide and persulfate, and the amount used is 5-10% of the total weight of the monomers.

6. The preparation method according to claim 5, characterized in that In S1, the persulfate is selected from at least one of K2S2O8, Na2S2O8 or (NH4)2S2O8.

7. Use of the terpolymer according to any one of claims 1 to 2 or the terpolymer prepared by the preparation method according to any one of claims 3 to 6, wherein the use is as a scale inhibitor in the transportation or treatment of oilfield produced water.

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