A composite long-action distance scale inhibitor for oilfield water injection development

Abstract

The present invention discloses a composite scale inhibitor with a long action distance for oilfield water injection development, belonging to the field of oilfield chemical applications. The scale inhibitor is composed of modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer, and a diluent. The scale inhibitor of the present invention is a composite scale inhibitor, which has a good anti-scaling effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale. Compared with conventional scale inhibitors, the scale inhibitor of the present invention has the characteristic of not being easily adsorbed by formation rocks, indicating that in actual water injection operations, the action distance is relatively long. Not only does it reduce the need for the scale inhibitor to be replenished in the later stage and reduce the construction frequency, but it also increases the effective period of the water injection operation, achieving the purpose of reducing costs and increasing efficiency.

Description

Technical Field

[0001] The invention relates to a composite scale inhibitor with a long action distance for oil field water injection development, belonging to the field of oil field chemical applications. Background Art

[0002] As the oil wells produce, the energy of the formation gradually weakens or even depletes. To increase the production capacity of the oil wells in the later stages, a common method is to drill suitable water injection wells nearby and inject water to add energy to the nearby oil wells. However, during water injection operations, the water usually contains certain scale-forming ions such as cations and anions. As the injected water is injected from the ground into the formation, the temperature gradually rises, and the scale-forming ions in the water will form insoluble substances (commonly known as inorganic scale). As the water injection operation continues, more and more scale forms. These insoluble scales are squeezed into the formation and will seriously block the formation, causing the injection pressure to increase and the injection volume to decrease. In severe cases, this can lead to the failure of the water injection operation or even the scrapping of the injection well.

[0003] Scale inhibitors are a type of chemical agent added to the injected water during oilfield water injection operations to inhibit scale formation. After decades of development, scale inhibitors have evolved from inorganic to organic substances, and from small molecules to high molecular polymers. Currently, organic phosphonic acid-type scale inhibitors and polymer-type scale inhibitors are used both domestically and internationally. Phosphate-type scale inhibitors have a good ability to inhibit carbonate scale (such as CaCO3), while polymer-type scale inhibitors have a good ability to inhibit sulfate scale (BaSO4, SiSO4). However, polymer scale inhibitors are easily adsorbed by formation rocks, resulting in a shorter range of action. The injected water used in water injection development has a complex ion composition, and carbonate scale and sulfate scale often occur simultaneously. Therefore, the development of scale inhibitors with good ability to inhibit both carbonate scale and sulfate scale for oilfield water injection development is in line with the needs of oil and gas field development. Summary of the Invention

[0004] The present invention aims to provide a composite, long-range scale inhibitor for oilfield waterflooding. This scale inhibitor is a composite scale inhibitor that protects against a variety of scale types, including CaCO₃, BaSO₄, and SiSO₄. Furthermore, compared to conventional scale inhibitors, this scale inhibitor is less susceptible to adsorption by formation rock, resulting in a relatively long range of action during actual waterflooding operations. This not only reduces the need for subsequent scale inhibitor replenishment and the frequency of application, but also extends the effective life of waterflooding operations, thereby achieving the goal of reducing costs and increasing efficiency.

[0005] The scale inhibitor provided by the present invention is composed of modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and a diluent;

[0006] The mass ratio of modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and the diluent is 5.0-5.5:0.1-0.2:9.5-10.

[0007] The molecular weight of the modified sodium polyepoxy adipate may range from 1050 to 1400;

[0008] The molecular weight of the maleic anhydride-styrene copolymer is 769-955.

[0009] The modified polyepoxy sodium adipate is prepared by a method comprising the following steps:

[0010] 1) dissolving adipic anhydride and a modifier in a solvent to obtain a mixed solution, adding a sodium hydroxide aqueous solution to the mixed solution, then heating the mixture to temperature I, reacting in the presence of a catalyst and a peroxide reagent; then adjusting the pH value with sodium hydroxide solution, heating the mixture to temperature II, and reacting to obtain modified epoxy sodium adipate;

[0011] 2) preparing the modified sodium epoxy adipate into a modified sodium epoxy adipate aqueous solution, then mixing the modified sodium epoxy adipate aqueous solution and an initiator, and reacting them to obtain the modified polyepoxy sodium adipate.

[0012] In step 1) of the above method, the modifier may be propylene oxide;

[0013] The solvent may be distilled water;

[0014] The catalyst may be sodium molybdate;

[0015] The peroxide reagent may be an aqueous solution of hydrogen peroxide;

[0016] The mass concentration of the sodium hydroxide aqueous solution may be 40% to 50%, specifically 45%;

[0017] The mass concentration of the peroxide reagent can be 28% to 35%, specifically 30%;

[0018] The ratio of adipic anhydride, modifier, sodium hydroxide aqueous solution, catalyst and peroxide reagent can be 20.8-21.4:15.7-16.9:8.0-8.7:0.03-0.04:32.0-35.0, specifically 21.0:16.8; 8.5:0.035:33.3;

[0019] Raise the temperature to temperature I, which may be 70-80°C, specifically 75°C, and the reaction time may be 3.0-3.5h, specifically 3.3h;

[0020] The pH value can be adjusted to 5.5-6.5 using sodium hydroxide solution. Specifically, the sodium hydroxide solution can be slowly added dropwise within 50 minutes to adjust the pH value of the solution to 5.5-6.5.

[0021] Raise the temperature to temperature II, wherein the temperature II is 90-98°C, specifically 95°C, and the reaction time is 2-2.5h, specifically 2.5h;

[0022] The mass concentration of the sodium hydroxide solution may be 40% to 50%, specifically 45%;

[0023] In step 2), the mass concentration of the modified sodium epoxy adipate aqueous solution may be 62% to 67%, specifically 65%;

[0024] In step 2), the initiator may be an aqueous solution of calcium hydroxide;

[0025] The mass concentration of the initiator is 1.0% to 1.5%, specifically 1.2%;

[0026] The mass ratio of the modified sodium epoxy adipate aqueous solution to the initiator may be 52-58:0.8-1.2, specifically 54:1.

[0027] The reaction temperature may be 85-95° C., specifically 90° C., and the reaction time may be 1.0-2.0 h, specifically 1.5 h.

[0028] The method further comprises the steps of adding acetone to precipitate the modified sodium epoxy adipate after the reaction is completed, filtering the solid to obtain the modified sodium epoxy adipate, and drying the solid;

[0029] Step 2) further comprises the steps of adding ethanol to precipitate the modified sodium polyepoxy adipate after the reaction is completed, filtering the solid to obtain the modified sodium polyepoxy adipate, and drying the solid.

[0030] In the scale inhibitor, the diluent may be distilled water.

[0031] The present invention also provides a method for preparing the scale inhibitor.

[0032] The preparation method of the scale inhibitor provided by the present invention comprises the following steps: mixing the modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and a diluent, and stirring them uniformly to obtain the scale inhibitor.

[0033] The application of the above-mentioned scale inhibitor in oil field water injection development also falls within the protection scope of the present invention.

[0034] In the application, the scale inhibitor is a composite scale inhibitor with multiple scale types, and has a good scale inhibition effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale; and is not easily adsorbed by formation rocks, and has a long action distance.

[0035] The present invention has the following beneficial effects:

[0036] 1. The scale inhibitor of the present invention is a composite scale inhibitor, which has a wide range of scale types and has a good scale prevention effect on CaCO3 scale, BaSO4 scale and SiSO4 scale.

[0037] 2. Compared with conventional scale inhibitors, the scale inhibitor of this invention is less likely to be adsorbed by formation rocks, meaning it has a relatively long range of action during actual waterflooding operations. This not only reduces the need for subsequent scale inhibitor replenishment and reduces application frequency, but also extends the effective life of waterflooding operations, achieving the goal of reducing costs and increasing efficiency. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0039] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0040] Example 1. Preparation of scale inhibitor

[0041] (1) Preparation of modified polyepoxy sodium adipate

[0042] To a 250mL four-necked flask equipped with a thermometer, condenser, constant-speed stirring device, and constant-pressure dropping funnel, add 21g of adipic anhydride, 16g of propylene oxide, and 30g of distilled water and heat until completely dissolved. Slowly add 8.5g of a 45% aqueous sodium hydroxide solution dropwise while stirring at a constant speed of 300-350 r / min. Heat until the temperature reaches 75°C and react for 3.3 hours. Add 0.035g of the catalyst sodium molybdate and titrate 30mL of a 30% aqueous hydrogen peroxide solution over 40 minutes. Adjust the pH of the solution to 6 with 45% sodium hydroxide solution. Continue heating to 95°C and react for 2.5 hours. Add an appropriate amount of acetone and stir for 1 hour. Let the mixture stand for precipitation, filter, and vacuum dry to obtain a white powder, which is modified sodium epoxy adipate.

[0043] The prepared modified sodium epoxy adipate was prepared into a 65% aqueous solution, 100 mL was poured into a 250 mL four-necked flask equipped with a thermometer, a condenser, a constant speed stirring device and a constant pressure dropping funnel, and 2 g of a 1.2% mass concentration Ca(OH)2 solution as an initiator was added in batches under constant stirring. The temperature was raised to 90°C and the reaction was carried out for 1.5 hours to obtain a yellow liquid. An appropriate amount of ethanol was added for precipitation, filtered, and vacuum dried to obtain a white solid powder, which is the modified sodium epoxy adipate (molecular weight 1286).

[0044] (2) Preparation of scale inhibitor solution

[0045] Take 52 grams of the modified polyepoxy sodium adipate prepared above and add it to a beaker, weigh 1 gram of maleic anhydride-styrene copolymer (molecular weight 862) and 97 grams of distilled water, and stir with a glass rod until completely dissolved to obtain a scale inhibitor solution.

[0046] Example 2: Investigation of scale inhibition effect

[0047] 1. Using ion chromatography, the Ca content of different simulated water samples was measured before and after adding scale inhibitor. 2+ 、Ba 2+ 、Si 2+ According to the changes in , calculate the anti-scaling rate.

[0048] (1) Mix CaCl2 solution and Na2CO3 solution to simulate calcium carbonate scale. Use ion chromatography to analyze the Ca content in the mixed sample. 2+ The results of the experiment, conducted with varying amounts of scale inhibitor added and experimental temperatures, show that the scale inhibitor prepared in Example 1 achieved a scale prevention rate of over 75% at a concentration greater than 20 ppm between 60 and 140°C. At concentrations of 30 to 35 ppm, the scale prevention rate reached over 90%, with little difference in scale prevention effect. This demonstrates that the scale inhibitor prepared for oilfield water flooding has excellent scale prevention capabilities. The test results are shown in Table 1.

[0049] Table 1 Evaluation of the effectiveness of the scale inhibitors prepared in Example 1 in preventing calcium carbonate scale

[0050]

[0051]

[0052] (2) Mix BaCl2, SiCl2 solution and Na2SO4 solution to simulate sulfate scale. Use ion chromatography to analyze BaCl2 in the mixed sample. 2+ 、Si 2+The results of the experiments, conducted with varying amounts of scale inhibitor added and experimental temperatures, show that the scale inhibitor prepared in the example achieved a scale prevention rate of over 75% at a concentration greater than 20 ppm between 60 and 140°C. At concentrations of 30 to 35 ppm, the scale prevention rate reached over 80%, with little difference in scale prevention effect. This demonstrates that the scale inhibitor prepared for oilfield water flooding has excellent scale prevention capabilities. The test results are shown in Table 2.

[0053] Table 2 Evaluation of the effect of scale inhibitors prepared in Example 2 on preventing sulfate scale

[0054]

[0055] (3) Mix CaCl2, BaCl2, SiCl2 solution and Na2CO3, Na2SO4 solution to simulate the formation of mixed scale of carbonate scale and sulfate scale. Use ion chromatography to analyze the Ca content in the mixed sample. 2+ 、Ba 2+ 、Si 2+ The results of the experiment, conducted with varying the dosage of the scale inhibitor and the experimental temperature, show that the scale inhibitor prepared in the example can achieve a scale prevention rate of over 75% at a concentration greater than 20 ppm between 60 and 140°C. At a concentration of 30 to 35 ppm, the scale prevention rate can reach over 90%, with little difference in scale prevention effect. This demonstrates that the scale inhibitor prepared for oilfield water flooding has excellent scale prevention capabilities. The test results are shown in Table 3.

[0056] Table 3 Evaluation of the effect of antiscalant prepared in Example 3 on preventing mixed scale

[0057]

[0058]

[0059] Example 3: Investigation of adsorbed amount

[0060] The scale inhibitor solution prepared in Example 1 for oilfield waterflooding was subjected to a dynamic core flooding test to evaluate its dynamic adsorption capacity. Under conditions of a temperature of 60°C and an initial scale inhibitor concentration of 100 ppm, the concentration change after the scale inhibitor passed through the core was measured to assess adsorption. A small concentration change indicates low adsorption by rock minerals, and a longer effective distance in the formation indicates a longer scale prevention distance, thus prolonging the waterflooding cycle. The concentration change after passing through the core is shown in Table 4.

[0061] Table 4 Concentration changes of scale inhibitors prepared in Example after passing through long cores

[0062]

[0063] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that further improvements can be made to the present invention. In short, according to the principles of the present invention, this application is intended to include any changes, uses or improvements to the present invention, including changes that depart from the disclosed scope in this application and are made using conventional techniques known in the art.

Claims

1. A scale inhibitor, comprising modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and a diluent; in, The mass ratio of modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and the diluent is 5.0-5.5:0.1-0.2:9.5-10 respectively; The molecular weight of the modified sodium polyepoxy adipate is in the range of 1050 to 1400; The molecular weight of maleic anhydride-styrene copolymer is 769-955; The diluent is distilled water; The modified polyepoxy sodium adipate is prepared by a method comprising the following steps: 1) dissolving adipic anhydride and a modifier in a solvent to obtain a mixed solution, adding a sodium hydroxide aqueous solution to the mixed solution, then heating the mixture to temperature I, reacting in the presence of a catalyst and a peroxide reagent; then adjusting the pH value with sodium hydroxide solution, heating the mixture to temperature II, and reacting to obtain modified epoxy sodium adipate; 2) preparing the modified sodium epoxy adipate into a modified sodium epoxy adipate aqueous solution, then mixing the modified sodium epoxy adipate aqueous solution and an initiator, and reacting them to obtain the modified polyepoxy sodium adipate; In step 1), the modifier is propylene oxide; The catalyst is sodium molybdate; The temperature I is 70-80°C; Adjust the pH to 5.5-6.5 with sodium hydroxide solution; The temperature II is 90-98°C, In step 2), the initiator is an aqueous solution of calcium hydroxide.

2. The scale inhibitor according to claim 1, characterized in that In step 1), the solvent is distilled water; The catalyst is sodium molybdate; The peroxide reagent is an aqueous solution of hydrogen peroxide; The mass concentration of the sodium hydroxide aqueous solution is 40% to 50%; The mass concentration of the peroxide reagent is 28% to 35%; The mass ratio of adipic anhydride, modifier, catalyst and peroxide reagent is 20.8-21.4:15.7-16.9:0.03-0.04:32.0-35.

0.

3. The scale inhibitor according to claim 1, characterized in that Raise the temperature to temperature I, and the reaction time is 3.0 to 3.5 hours; Raise the temperature to temperature II, and the reaction time is 2 to 2.5 hours.

4. The scale inhibitor according to claim 1, characterized in that In step 2), the mass concentration of the modified sodium epoxy adipate aqueous solution is 62% to 67%; The mass concentration of the initiator is 1.0% to 1.5%; The mass ratio of the modified sodium epoxy adipate aqueous solution to the initiator is 52-58:0.8-1.

2.

5. The scale inhibitor according to claim 1, characterized in that In step 2), the reaction temperature is 85-95° C. and the reaction time is 1.0-2.0 h.

6. A method for preparing the scale inhibitor according to any one of claims 1 to 5, comprising the steps of: mixing the modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer, and a diluent, and stirring uniformly to obtain the scale inhibitor.

7. Use of the scale inhibitor according to any one of claims 1 to 5 in oil field water injection development.

8. The use according to claim 7, characterized in that The scale inhibitor is a composite scale inhibitor, which has an anti-scaling effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale; it is not easily adsorbed by formation rocks and has a long effective distance.

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