Calcium carbonate scale inhibitor for oil and gas field injection and production and preparation method thereof

Abstract

The invention discloses a calcium carbonate scale inhibitor for oil and gas field injection and production and a preparation method thereof, and belongs to the technical field of scale inhibitors. The raw materials adopted by the invention comprise maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine, wherein the molar ratio of the maleic anhydride to the sodium hypophosphite to the 2-acrylamide-2-methylpropanesulfonic acid to the methacryloylethyl sulfobetaine is (100-300): (100-300): (5-15): (50-150). The scale inhibitor provided by the invention is used in the injection-production process of oil and gas fields, a sulfo betaine monomer is introduced into the scale inhibitor, the monomer has positive ions and negative ions, the positive ions and the negative ions have the same isoelectric point and do not influence the whole charge performance, and meanwhile, a sulfonic acid strong polar group is introduced into the negative ions, so that the temperature resistance and salt resistance of the scale inhibitor are improved; the cationic charges can improve the dispersing capacity of the scale inhibitor, so that the scale inhibition effect of the scale inhibitor is improved, the scale inhibitor provided by the invention has a relatively good scale inhibition effect on CaCO3, and the scale inhibition rate can reach 90% or above.

Description

Technical Field

[0001] The invention relates to the technical field of scale inhibitors, in particular to a calcium carbonate scale inhibitor for oil and gas field injection and a preparation method thereof. Background Art

[0002] At present, the main method for improving crude oil recovery in my country is chemical flooding, while foreign countries mainly use gas miscible flooding. However, with the development of technology for improving crude oil recovery, CO2 flooding technology has received attention and research. Studies have found that when CO2 gas is injected into the oil field by a certain technology, the entry of CO2 gas effectively reduces the viscosity of crude oil, while reducing the interfacial tension of the formation oil-water interface and increasing the crude oil recovery rate. CO2 flooding technology has become one of the main methods for improving crude oil recovery (EOR) due to its low cost and green environmental protection. Although CO2 flooding technology has entered a relatively mature stage today, there are still many problems that need to be solved in the process of using CO2 flooding technology for oil production, and scaling and corrosion problems are the main difficulties facing CO2 flooding technology now. In the process of CO2 flooding, CO2 is easily soluble in water, so it dissolves in water to form CO2 solution to form carbonic acid, and carbonic acid will form a primary cell with the iron inside the pipeline to undergo an electrochemical reaction, which will cause serious corrosion to the pipeline and oil production tools. At the same time, HCO3 in the water during the flooding process - 、CO3 2- The anions will react with the scaling cations contained in the formation water or oil layer under various factors such as temperature, pH value and pressure to produce scaling. Scaling phenomenon will directly lead to pipeline blockage when the scaling phenomenon is serious, resulting in a significant reduction in crude oil recovery rate. Subsequent descaling work increases the cost of oil production and causes a lot of economic losses. The main component of scale is calcium carbonate scale, so how to inhibit the formation of calcium carbonate scale is currently the key to solving the structural phenomenon.

[0003] The current challenge facing oil production is how to increase production under high temperature, high pressure and saline conditions. Specifically, in order to ensure flow, the injection of scale inhibitors plays a key role in controlling scaling.

[0004] Polycarboxylic acid scale inhibitors are one of the most commonly used scale inhibitors in oilfield water injection and water treatment industries. The scale inhibition mechanism is that the synthesized polymer contains a large number of carboxylic acid functional groups, which can form water-soluble complexes with metal cations in the solution through chelation. The synthesis of polycarboxylic acid scale inhibitors is mainly based on maleic anhydride and acrylic acid, which can be copolymerized or homopolymerized with other monomers. Carboxylic acid scale inhibitors can interfere with the normal arrangement of crystals and hinder crystal growth by adsorbing on the active sites of crystals, and generate electrostatic repulsion through the action of the double electric layer, interfering with the formation and growth of calcium carbonate and calcium sulfate crystals. In addition, this type of scale inhibitor can also disperse and resist the solid impurities contained in the solution, such as dust, soil and some pipeline corrosion products, as well as microbial excrement or corpses.

[0005] However, the existing scale inhibitors for oil and gas field injection have certain defects, such as poor scale inhibition effect on CaCO3 and low scale inhibition rate. Therefore, how to provide a scale inhibitor for oil and gas field injection with high scale inhibition efficiency and good effect and its preparation method is a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0006] In view of this, in order to solve the problem that the existing scale inhibitors used for oil and gas field injection have poor scale inhibition effect on CaCO3 and low scale inhibition rate, the present invention provides a scale inhibitor for calcium carbonate used for oil and gas field injection and a preparation method thereof.

[0007] To achieve the above purpose, the present invention adopts the following technical scheme: a calcium carbonate scale inhibitor for oil and gas field injection, comprising the following raw materials: maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid and methacryloylethyl sulfobetaine.

[0008] The present invention selects four monomers, namely maleic anhydride, sodium hypophosphite, 2-acrylamido-2-methyl-1-propanesulfonic acid and methacryloylethyl sulfobetaine, to polymerize into a novel polymer scale inhibitor. A sulfobetaine monomer is introduced into the scale inhibitor. The monomer has cations and anions, and the two have the same isoelectric point and will not affect the overall charge performance. At the same time, the anion introduces a sulfonic acid strong polar group to improve the temperature and salt resistance of the scale inhibitor. The cationic charge can improve the dispersibility of the scale inhibitor and can effectively inhibit the formation of calcium scale, so that the scale inhibitor of the present invention has a better scale inhibition effect on CaCO3 and a higher scale inhibition rate, and can effectively solve the problem that the existing scale inhibitor has a poor scale inhibition effect on CaCO3 and a low scale inhibition rate.

[0009] Furthermore, the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine is 100-300:100-300:5-15:50-150.

[0010] Preferably, the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine is 300:300:10:100.

[0011] Furthermore, the calcium carbonate scale inhibitor used for oil and gas field injection also includes an initiator.

[0012] Furthermore, the initiator is 2,2'-azobisisobutylamidine hydrochloride.

[0013] Furthermore, the amount of the initiator used is 0.5%-2.5% of the total mass of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine.

[0014] The present invention also provides a method for preparing the above-mentioned calcium carbonate scale inhibitor for oil and gas field injection, comprising the following steps: (1) weighing each raw material according to the above-mentioned raw material dosage; (2) uniformly mixing maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, methyl acryloylethyl sulfobetaine and deionized water to fully dissolve and form a reaction system; (3) placing the reaction system in a water bath at a preset temperature, reacting at a constant temperature for a preset time, cooling to room temperature to obtain a synthetic polymer, purifying the synthetic polymer, and drying to obtain the calcium carbonate scale inhibitor for oil and gas field injection.

[0015] Furthermore, in step (2), the combined mass ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine to deionized water is 1:3.

[0016] Furthermore, the step (2) of fully dissolving to form a reaction system is to dissolve a mixture of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, methacryloylethyl sulfobetaine and deionized water at 55-65° C. for 1-1.5 hours.

[0017] Furthermore, in step (3), the water bath temperature is 55-65°C, and the water bath time is 5-7h.

[0018] Furthermore, the step (3) further includes adding an initiator before the water bath.

[0019] The beneficial effects of the present invention are as follows: the present invention provides a scale inhibitor for use in the injection and production process of oil and gas fields, a sulfonic acid betaine monomer is introduced into the scale inhibitor, the monomer has a cation and an anion, and the two have the same isoelectric point and will not affect the overall charge performance, and at the same time, the anion introduces a sulfonic acid strong polar group to improve the temperature and salt resistance of the scale inhibitor, and the cationic charge can improve the dispersion ability of the scale inhibitor, thereby improving the scale inhibition effect of the scale inhibitor, and the scale inhibitor is a novel betaine-containing calcium carbonate scale inhibitor.

[0020] The present invention adopts maleic anhydride monomer and sodium hypophosphite monomer, 2-acrylamide-2-methylpropanesulfonic acid, methacryloylethyl sulfobetaine monomer, and free radical polymerization occurs between the monomers under the action of initiator 2,2'-azobisisobutylamidine hydrochloride and suitable temperature to generate an oil and gas field injection scale inhibitor. The oil and gas field injection scale inhibitor prepared by the present invention has an obvious scale inhibition effect on CaCO3, with a scale inhibition rate of more than 95%, can be used as an oil and gas field injection scale inhibitor, and the method is simple and easy to operate.

[0021] The scale inhibitor used in oil and gas field injection disclosed by the invention has a wide range of applications and great advantages due to the superior performance of the prepared scale inhibitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a reaction flow chart of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine.

[0023] Figure 2 This is an infrared spectrum characterization diagram of the calcium carbonate scale inhibitor synthesized by the present invention for use in oil and gas field injection. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1 A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection.

[0026] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 300:300:10:100.

[0027] (2) The reaction system was placed in a 60 ℃ water bath, and the initiator 2,2'-azobisisobutylamidine hydrochloride was added. After the reaction was carried out at a constant temperature for 6 hours, the system was cooled to room temperature, and the synthesized polymer was purified with ethanol. After purification, the system was placed in an oven and dried at 70 ℃ for use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added was 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, was 25% of the total mass of the reaction system.

[0028] Example 2 A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection.

[0029] (1) Take raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, methacryloylethyl sulfobetaine and deionized water evenly, and place them at 60°C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine is 300:300:5:100.

[0030] (2) The reaction system was placed in a 60°C water bath, and the initiator 2,2'-azobisisobutylamidine hydrochloride was added. After the reaction was carried out at a constant temperature for 6 hours, the system was cooled to room temperature, and the synthesized polymer was purified with ethanol. After purification, the system was placed in an oven and dried at 70°C for use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added was 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, was 25% of the total mass of the reaction system.

[0031] Example 3 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0032] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 300:300:15:100.

[0033] (2) The reaction system is placed in a 60°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After constant temperature reaction for 6 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for standby use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0034] Example 4 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0035] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfonyl betaine is 200:300:10:100.

[0036] (2) The reaction system is placed in a 60°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After constant temperature reaction for 6 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for standby use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0037] Example 5 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0038] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 100:300:10:100.

[0039] (2) The reaction system is placed in a 60°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After the reaction is carried out at a constant temperature for 7 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0040] Example 6 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0041] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 300:300:10:100.

[0042] (2) The reaction system is placed in a 60°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After constant temperature reaction for 5 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for standby use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0043] Example 7 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0044] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 300:300:10:100.

[0045] (2) The reaction system is placed in a 55°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After constant temperature reaction for 6 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for standby use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0046] Example 8 Preparation method of calcium carbonate scale inhibitor for oil and gas field injection.

[0047] (1) Take the raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, methacryloylethyl sulfonyl betaine and deionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropane sulfonic acid, and methacryloylethyl sulfonyl betaine is 300:300:10:100.

[0048] (2) The reaction system is placed in a 65°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After constant temperature reaction for 6 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the four monomers, maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloylethyl sulfobetaine, is 25% of the total mass of the reaction system.

[0049] Comparative Example 1 A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection.

[0050] (1) Take raw materials in molar ratio, mix maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and ionized water evenly, and place them at 60 °C to fully dissolve for 0.5 h to form a reaction system; wherein the molar ratio of maleic anhydride, sodium hypophosphite and 2-acrylamide-2-methylpropanesulfonic acid is 300:300:10.

[0051] (2) The reaction system is placed in a 65°C water bath, and an initiator 2,2'-azobisisobutylamidine hydrochloride is added. After the reaction is carried out at a constant temperature for 6 hours, the system is cooled to room temperature, and the synthesized polymer is purified with ethanol. After purification, the system is placed in an oven and dried at 70°C for use to obtain a scale inhibitor for oil and gas field injection. The amount of the initiator 2,2'-azobisisobutylamidine hydrochloride added is 1.0% of the total mass of the reaction monomers; the total mass of the three monomers, maleic anhydride, sodium hypophosphite, and 2-acrylamide-2-methylpropanesulfonic acid, is 25% of the total mass of the reaction system.

[0052] Experimental Example 1, step 1: Prepare the scale inhibitor for oil and gas field injection according to the methods of Examples 1-8 and Comparative Example 1 and set aside.

[0053] Step 2: Prepare the simulated saline solution required for the evaluation experiment.

[0054] Preparation of brine A: Accurately weigh 11.46 ± 0.01 g of anhydrous CaCl2, 41.25 ± 0.01 g of NaCl, and 4.60 ± 0.01 g of MgCl2·6H2O, dissolve and dilute them with deionized water to make a volume of 1000 mL to prepare a CaCl2 solution.

[0055] Preparation of brine B: Accurately weigh NaHCO3 9.20 ± 0.01 g, NaCl 41.25 ± 0.01 g, and NaSO4 0.04 g, dissolve and dilute them with deionized water to make a volume of 1000 mL to prepare NaHCO3 solution.

[0056] Preparation of antiscalant solution: 5.00±0.01 g of the antiscalants prepared in Examples 1-8 and Comparative Example 1 were accurately weighed, dissolved and diluted with deionized water, and the volume was fixed to 1000 mL to prepare antiscalant solution.

[0057] Step 3: Prepare the experimental group and blank group solutions required for the evaluation experiment.

[0058] Preparation of the blank group: Measure 100 mL of deionized water into a 250 mL volumetric flask, add 50.00 mL of brine A (CaCl2 solution), shake the volumetric flask slowly to mix it evenly and let it stand for 10 min, then slowly add 50.00 mL of brine B (NaCO3 solution), make up the solution volume to 250 mL with deionized water, mix the solution evenly and transfer it to a 250 mL silk-mouth bottle for use.

[0059] Preparation of the scale inhibitor experimental group: Measure 100 mL of deionized water into a 250 mL volumetric flask, add 50.00 mL of brine A (CaCl2 solution) and 2.50 mL of scale inhibitor solution, slowly shake the volumetric flask to mix evenly and let it stand for 10 min, then slowly add 50.00 mL of brine B (NaHCO3 solution), make up the solution volume to 250 mL with deionized water, mix the solution evenly and transfer it to a 250 mL silk-mouth bottle for standby use.

[0060] Step 4: Place the thread-capped bottle containing the experimental group and blank group solutions in a 70 ± 0.5°C constant temperature water bath for 30 min, open the bottle cap to release the gas, and then cover the bottle cap and continue to place for 16 hours. After the end, take out the thread-capped bottle and cool it to room temperature.

[0061] Step 5: Use medium-speed qualitative filter paper to pour and filter the upper clear liquid in the thread-mouth bottle, collect the filtrate in a clean and dry conical flask, and titrate with 10 mmol / L EDTA standard solution according to GB / T 7476. EDTA standard solution (10 mmol / L) is prepared and calibrated according to the method specified in GB / T 7476.

[0062] The scale inhibition rate η (%) of the CaCO3 scale inhibitor is evaluated according to the formula (1) according to the scale inhibition performance of the scale inhibitor in accordance with the Petroleum and Natural Gas Standard of the People's Republic of China SY / T5673-2020 "General Technical Conditions for Scale Inhibitors for Oil Fields".

[0063] calculate: (1).

[0064] Where: M1 is one fifth of the concentration of calcium ions in salt water solution a, mg / L.

[0065] M2——The concentration of calcium ions in the mixed solution after constant temperature with antiscalant added, mg / L.

[0066] M0 - the concentration of calcium ions in the blank mixed solution (mixed solution without scale inhibitor) after constant temperature, mg / L.

[0067] The results of the experimental evaluation of the scale inhibition rate of CaCO3 obtained by the preparation methods provided in Examples 1-8 of the present invention and Comparative Example 1 using the scale inhibitor for oil and gas field injection are shown in Table 1.

[0068] Table 1: .

[0069] Experimental Example 2: Infrared spectroscopy was performed on synthetic oil and gas field injection using anti-scaling agents. The characterization results are shown in Figure 2 shown.

[0070] according to Figure 2As shown, 1190cm -1 is the stretching vibration absorption peak of sulfur-oxygen double bond (S=O); 1050cm -1 The peak at 3500cm is the stretching vibration peak of the P=O double bond; -1 The peak at 1550cm is the stretching absorption vibration peak of hydroxyl (-OH); -1 is the stretching vibration peak of carbonyl (-C=O); 680cm -1 It is the stretching vibration peak of the amide group; thus, the successful synthesis of the antifouling agent can be confirmed.

[0071] In summary, after verification by Experimental Examples 1 and 2, the preparation method of the present invention can prepare a scale inhibitor with excellent scale removal effect, and the scale inhibitor provided by the present invention can effectively prevent and destroy the aggregation and growth of calcium carbonate crystals, can effectively inhibit the formation of calcium scale, and can also adsorb calcium scale that has not been successfully inhibited. The scale inhibitor of the present invention has a good scale inhibition effect on CaCO3 and a high scale inhibition rate. It can effectively solve the problem that the existing scale inhibitors have a poor scale inhibition effect on CaCO3 and a low scale inhibition rate, and has superiority.

[0072] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A calcium carbonate scale inhibitor for oil and gas field injection, It is characterized in that The invention comprises the following raw materials: maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethylsulfobetaine.

2. According to claim 1, a calcium carbonate scale inhibitor is used for oil and gas field injection, It is characterized in that The molar ratio of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine is 100-300:100-300:5-15:50-150.

3. According to claim 1, a calcium carbonate scale inhibitor for oil and gas field injection, It is characterized in that Also included are initiators.

4. According to claim 3, a calcium carbonate scale inhibitor is used for oil and gas field injection, It is characterized in that The initiator is 2,2'-azobisisobutylamidine hydrochloride.

5. According to claim 4, a calcium carbonate scale inhibitor is used for oil and gas field injection, It is characterized in that The amount of the initiator used is 0.5%-2.5% of the total mass of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine.

6. A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection, It is characterized in that The following steps are involved: (1) Weighing each raw material according to the amount of raw materials described in any one of claims 1 to 5; (2) mixing maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid, methacryloylethyl sulfobetaine and deionized water uniformly and fully dissolving them to form a reaction system; (3) placing the reaction system in a water bath at a preset temperature, reacting at a constant temperature for a preset time, cooling to room temperature to obtain a synthetic polymer, purifying the synthetic polymer, and drying to obtain a calcium carbonate scale inhibitor for oil and gas field injection.

7. A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection according to claim 6, It is characterized in that The step (2) of fully dissolving to form a reaction system is to dissolve a mixture of maleic anhydride, sodium hypophosphite, 2-acrylamide-2-methylpropanesulfonic acid and methacryloylethyl sulfobetaine with deionized water at 55-65° C. for 1-1.5 hours.

8. A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection according to claim 6, It is characterized in that The water bath temperature in step (3) is 55-65°C, and the water bath time is 5-7h.

9. A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection according to claim 6, It is characterized in that The step (3) also includes adding an initiator before the water bath.

10. A method for preparing a calcium carbonate scale inhibitor for oil and gas field injection according to claim 6, It is characterized in that The purification in step (3) is as follows: ethanol is poured into the synthetic polymer and mixed to precipitate a white precipitate, the white precipitate is separated from the liquid by filtration, and then the white precipitate is washed with ethanol to complete the purification.

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