Composite long-acting-distance scale inhibitor for oilfield waterflooding development

Abstract

The invention discloses a composite long-acting-distance scale inhibitor for oilfield waterflooding development, and belongs to the field of oilfield chemistry application. The scale inhibitor is prepared from modified sodium polyepoxyadipate, a maleic anhydride-styrene copolymer and a diluent. The scale inhibitor disclosed by the invention belongs to a composite scale inhibitor, and has a very good scale inhibition effect on CaCO3 scale, BaSO4 scale and SiSO4 scale; compared with a conventional scale inhibitor, the scale inhibitor provided by the invention has the characteristic that the scale inhibitor is not easily adsorbed by stratum rocks, which shows that the acting distance is relatively long in actual water injection operation. The later-stage scale inhibitor supplementing procedure is reduced, and the construction frequency is reduced; the validity period of water injection operation is prolonged, and the purposes of reducing cost and improving efficiency are achieved.

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 application. Background Art

[0002] As the oil wells are produced, the formation energy gradually weakens or even exhausts. In order to increase the production capacity of the oil wells in the later stage, the usual method is to drill suitable water injection wells nearby and use water injection to increase the energy of the nearby oil wells. However, in the water injection operation, the water in the water usually contains certain scale-forming ions such as cations and anions. When 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 substances that are difficult to dissolve in water (commonly known as inorganic scale). As the water injection operation continues, more and more scale is formed. After these insoluble scale samples are squeezed into the formation, they will seriously block the formation, thereby causing the injection pressure to increase and reducing the injection volume. In severe cases, it will lead to the failure of the water injection operation or even the scrapping of the water injection well.

[0003] Scale inhibitors refer to a type of chemical agent that is added to the injected water in the oil field water injection operation to inhibit scale formation. After decades of development, scale inhibitors have experienced a development process from inorganic to organic, from small molecules to high molecular polymers. At present, organic phosphonic acid scale inhibitors and polymer scale inhibitors are used at home and abroad. Phosphate scale inhibitors mainly have a good ability to prevent carbonate scale (such as CaCO3), and polymer scale inhibitors mainly have a good ability to prevent sulfate scale (BaSO4, SiSO4), but polymer scale inhibitors are easily adsorbed by formation rocks, so the action distance is short. The ion composition of the injected water used in water injection development is complex, and carbonate scale and sulfate scale often occur at the same time. Therefore, the development of scale inhibitors with good ability to prevent both carbonate scale and sulfate scale for oil field water injection development is in line with the needs of oil and gas field development. Summary of the invention

[0004] The purpose of the present invention is to provide a composite scale inhibitor with a long action distance for oil field water injection development. The scale inhibitor of the present invention is a composite scale inhibitor, and the scale inhibition type is not single, and it has a good scale inhibition effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale. At the same time, compared with conventional scale inhibitors, the scale inhibitor of the present invention has the characteristic of not being easily adsorbed by formation rocks, and in actual water injection operations, the action distance is relatively long. Not only does it reduce the subsequent replenishment process of scale inhibitors and reduce the construction frequency; but it also increases the effective period of water injection operations, achieving the purpose 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 diluent;

[0006] Wherein, 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;

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

[0008] The molecular weight of 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, and then heating the mixed solution to temperature I, reacting under the action of a catalyst and a peroxide reagent; then adjusting the pH value with a sodium hydroxide solution, heating the mixed solution 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 poly(sodium epoxy 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 may be 28% to 35%, specifically 30%;

[0018] The proportions of adipic anhydride, modifier, sodium hydroxide aqueous solution, catalyst and peroxide reagent may 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, wherein temperature I 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 by 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 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 step 1) further comprises the steps of adding acetone to precipitate modified sodium epoxy adipate after the reaction is completed, filtering the solid to obtain modified sodium epoxy adipate, and drying the solid;

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

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

[0031] The 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 various scale types, and has a good scale inhibitor effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale; and it 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 belongs to a composite scale inhibitor, and the scale inhibition type is not single, and it has a good scale inhibition effect on CaCO3 scale, BaSO4 scale, and SiSO4 scale;

[0037] 2. Compared with conventional scale inhibitors, the scale inhibitor of the present invention is not easily adsorbed by formation rocks, which means that in actual water injection operations, the effective distance is relatively long. It not only reduces the subsequent replenishment process of scale inhibitors and reduces the construction frequency; but also increases the effective period of water injection operations, achieving the purpose of reducing costs and increasing efficiency. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0039] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0040] Example 1. Preparation of scale inhibitor

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

[0042] Install a thermometer, condenser, constant speed stirring device and constant pressure dropping funnel in a 250mL four-necked flask, add 21g of adipic anhydride, 16g of propylene oxide and 30g of distilled water, and heat until all are dissolved. Slowly drop 8.5g of 45% sodium hydroxide aqueous solution under constant stirring at 300-350r / min, heat, and react for 3.3h when the temperature rises to 75℃, add 0.035g of catalyst sodium molybdate, control the titration speed to drip 30mL of 30% hydrogen peroxide aqueous solution within 40min, and then adjust the pH value of the solution to 6 with 45% sodium hydroxide solution. Continue to heat to 95℃ and react for 2.5h. Add appropriate amount of acetone, stir for 1h, let stand, precipitate, filter, and vacuum dry to obtain 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 reacted for 1.5 hours to finally obtain a yellow liquid, which was precipitated by adding an appropriate amount of ethanol, filtered, and vacuum dried to obtain a white solid powder, which is modified sodium polyepoxy adipate (molecular weight 1286).

[0044] (2) Preparation of antiscalant solution

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

[0046] Example 2: Investigation of scale inhibition effect

[0047] 1. Use ion chromatograph to measure the Ca content of different simulated water samples before and after adding scale inhibitor. 2+ , Ba 2+ 、Si 2+ According to the changes in , the anti-scaling rate is calculated.

[0048] (1) Mix CaCl2 solution and Na2CO3 solution to simulate calcium carbonate scaling. Use ion chromatography to analyze the Ca 2+ The results of the investigation show that the scale inhibitor prepared in Example 1 has a scale prevention rate of more than 75% when the concentration is greater than 20 ppm at 60-140°C, and a scale prevention rate of more than 90% when the concentration is 30-35 ppm, and the scale prevention effect is not much different, indicating that the scale inhibitor prepared for oilfield water injection development has a good scale prevention ability. The test results are shown in Table 1.

[0049] Table 1 Evaluation of the effect of antiscalant prepared in Example 1 on preventing calcium carbonate scale

[0050]

[0051]

[0052] (2) Mix BaCl2, SiCl2 solution and Na2SO4 solution to simulate sulfate scaling. Use ion chromatography to analyze the BaCl2 in the mixed sample. 2+ 、Si 2+The results of the investigation show that the scale inhibitor prepared in the embodiment has a scale prevention rate of more than 75% when the concentration is greater than 20ppm at 60-140℃, and a scale prevention rate of more than 80% when the concentration is 30-35ppm, and the scale prevention effect is not much different, indicating that the scale inhibitor prepared for oilfield water injection development has a good scale prevention ability. The test results are shown in Table 2.

[0053] Table 2 Evaluation of the effect of the scale inhibitor 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 chromatograph to analyze the Ca in the mixed sample. 2+ , Ba 2+ 、Si 2+ The results of the investigation show that the scale inhibitor prepared in the embodiment has a scale prevention rate of more than 75% when the concentration is greater than 20ppm at 60-140℃, and a scale prevention rate of more than 90% when the concentration is 30-35ppm, and the scale prevention effect is not much different, indicating that the prepared scale inhibitor for oilfield water injection development has a good scale prevention ability. The test results are shown in Table 3.

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

[0057]

[0058]

[0059] Example 3: Investigation of adsorbed amount

[0060] The dynamic adsorption amount of the scale inhibitor solution for oilfield water injection development prepared in Example 1 was experimentally evaluated by the "dynamic core displacement method". Under the conditions of a temperature of 60°C and an initial scale inhibitor concentration of 100ppm, the concentration change after the scale inhibitor passed through the core was tested to evaluate the adsorption amount. If the concentration change is small, it means that the amount adsorbed by the rock mineral is small, and the longer the distance of action in the formation, the longer the scale prevention distance, thereby delaying the water injection operation cycle. The concentration change 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 the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with 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 ratios of modified sodium polyepoxy adipate, maleic anhydride-styrene copolymer and the diluent are 5.0-5.5:0.1-0.2:9.5-10 respectively; The molecular weight of the modified sodium polyoxyethylene 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.

2. The scale inhibitor according to claim 1, characterized in that 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, and then heating the mixed solution to temperature I, reacting under the action of a catalyst and a peroxide reagent; then adjusting the pH value with a sodium hydroxide solution, heating the mixed solution 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 poly(sodium epoxy adipate).

3. The scale inhibitor according to claim 2, characterized in that: In step 1), the modifier is propylene oxide; 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, alkali solution, catalyst and peroxide reagent is 20.8-21.4:15.7-16.9:8.0-8.7:0.03-0.04:32.0-35.

0.

4. The scale inhibitor according to claim 2, characterized in that: Raise the temperature to temperature I, wherein temperature I is 70-80°C, and the reaction time is 3.0-3.5h; Adjust the pH value to 5.5-6.5 with sodium hydroxide solution; The temperature is raised to temperature II, wherein temperature II is 90-98°C, and the reaction time is 2-2.5h.

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

2.

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

7. A method for preparing the scale inhibitor according to any one of claims 1 to 6, comprising 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.

8. Use of the scale inhibitor according to any one of claims 1 to 6 in oil field water injection development.

9. The use according to claim 8, characterized in that: The scale inhibitor is a composite scale inhibitor, which has a scale prevention effect on CaCO3 scale, BaSO4 scale and SiSO4 scale; it is not easily adsorbed by formation rocks and has a long action distance.

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