A copolymer antiscaling agent and preparation method thereof

Abstract

The present invention discloses a copolymer antiscalant and a preparation method thereof, belonging to the field of oil and gas field development. The technical scheme is as follows: maleic anhydride monomer is added to a three-necked flask, heated to dissolve, and then acrylamide and hydroxypropyl acrylate are added, with the monomer mass concentration being 20-40%. When the temperature rises to 60°C, 0.1-1% of an initiator, potassium persulfate, is added, and the mixture is stirred and reacted in constant temperature water at 70-90°C for 8-5 hours. After the reaction is completed, a light yellow transparent liquid is obtained, thereby obtaining a copolymer antiscalant. The copolymer antiscalant of the present invention can affect the formation process of calcium carbonate crystals, causing the calcium carbonate crystal form to change from a stable calcite crystal form to an unstable aragonite and aragonite crystal form, which is then washed away by water flow, thereby preventing the calcium carbonate from agglomerating on the inner wall of the pipeline and having a good antiscaling effect.

Description

Technical Field

[0001] The present invention relates to the field of oilfield chemical applications, and in particular to a copolymer-type antiscalant and a preparation method thereof, which uses maleic anhydride, acrylamide and hydroxypropyl acrylate as monomers for ternary copolymerization and potassium persulfate as an initiator. Background Art

[0002] my country's economy has developed rapidly in recent years, and demand for oil and natural gas has continued to grow. Most onshore oil and gas fields have entered the middle or late stages of development, and formation energy is continuously depleting. To replenish formation energy, oil and gas fields generally use water injection. However, due to water scarcity, oily wastewater is often used for water injection, causing oil and gas fields to enter a high water-cut stage. The poor compatibility of injected water with formation water can easily undermine reservoir stability and cause scale deposition, especially in low-permeability reservoirs, which can easily clog pores and reduce permeability and recovery. Furthermore, high temperature, high pressure, pH fluctuations, and high concentrations of calcium and bicarbonate ions in oilfield wastewater all accelerate the formation of calcium carbonate scale.

[0003] Existing oilfield anti-scaling technologies primarily rely on chemical anti-scaling, which is low-cost and easy to use. These anti-scaling agents primarily include phosphate, natural, copolymer, and green anti-scaling agents. Phosphate anti-scaling agents are highly effective but can cause eutrophication; natural anti-scaling agents are widely available but have limited effectiveness and require modification; green anti-scaling agents are environmentally friendly but complex to synthesize and hinder large-scale application; and copolymer anti-scaling agents work by influencing the normal formation of scale crystals through chelation and lattice distortion by the anionic groups on their molecular chains. This alters the crystal structure of the scale, reducing its accumulation volume and preventing it from agglomerating, allowing the scale to be carried away by the water. This more effectively prevents scale formation. Summary of the Invention

[0004] The present invention primarily addresses the problem of poor effectiveness and high dosage requirements of existing antiscalants. This polymer antiscalant is obtained by polymerizing acrylamide, maleic anhydride, and hydroxypropyl acrylate in water. The ester groups introduced into the polymer enhance the copolymer's ability to complex scale-forming metal ions through their hydrophobic properties and steric hindrance. The introduced amide groups also allow the molecules to adsorb on the surface of calcium carbonate crystal nuclei, hindering their growth. Compared to existing antiscalants, this polymer antiscalant offers advantages such as high effective concentration, low viscosity, low dosage, and excellent scale inhibition.

[0005] The present invention provides a method for preparing a polymer antiscalant. The preparation process is simple and the structural formula is as follows:

[0006]

[0007] The specific preparation method of the present invention is as follows:

[0008] (1) Maleic anhydride (MA) monomer was added to a three-necked flask, heated to 50°C, and after it was completely dissolved in distilled water, acrylamide (AM) and hydroxypropyl acrylate (HPA) were added to a monomer concentration of 20-40%;

[0009] (2) When the temperature rises to 60°C, add 0.1-1% of potassium persulfate as an initiator, and stir the reaction in a constant temperature water bath at 70-90°C for 5-8 hours. After the reaction is completed, a light yellow transparent solution is obtained, thereby obtaining a copolymer anti-scaling agent.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] (1) The present invention can effectively inhibit the deposition of calcium carbonate scale in the formation and the inner wall of the pipeline, disrupt the normal formation process of calcium carbonate crystals, prevent the aggregation and growth of calcium carbonate crystals, and allow tiny calcium carbonate crystal nuclei to be carried away by water flow;

[0012] (2) The copolymer antiscalant of the present invention has a good antiscaling effect and requires a small amount of addition during application. Compared with conventional antiscalants, it can effectively inhibit the formation of calcium carbonate scale, greatly reducing the blockage of scale on the formation and gathering and transportation pipelines. It also requires low cost and simple on-site construction process.

[0013] (3) The copolymer antiscalant prepared by the present invention is weakly acidic and will not corrode the oil casing. It is stable in storage, simple to prepare, and easy to use.

[0014] (4) The raw materials of the composite inhibitor of the present invention are easily available and have a wide range of sources. DETAILED DESCRIPTION

[0015] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all public chemical reagents and chemicals disclosed in the prior art.

[0016] Example 1

[0017] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 3:2:1, with a monomer mass concentration of 20%. When the temperature was raised to 60°C, 0.1% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 80°C for 6 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was recorded as FG1.

[0018] Example 2

[0019] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 4:2:1, and the monomer mass concentration was 25%. When the temperature was raised to 60°C, 0.2% of the initiator potassium persulfate was added. The mixture was stirred in a constant temperature water bath at 75°C for 6 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was recorded as FG2.

[0020] Example 3

[0021] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 5:2:2, with a monomer mass concentration of 25%. When the temperature was raised to 60°C, 0.2% of the initiator potassium persulfate was added. The mixture was stirred in a constant temperature water bath at 75°C for 6 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was recorded as FG3.

[0022] Example 4

[0023] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 5:3:2, with a monomer mass concentration of 30%. When the temperature was raised to 60°C, 0.4% of the initiator potassium persulfate was added. The mixture was stirred in a constant temperature water bath at 85°C for 6 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was recorded as FG4.

[0024] Example 5

[0025] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 6:2:1, with a monomer mass concentration of 30%. When the temperature was raised to 60°C, 0.6% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 85°C for 6 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was recorded as FG5.

[0026] Example 6

[0027] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 7:4:2, with a monomer mass concentration of 30%. When the temperature was raised to 60°C, 0.4% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 90°C for 6 hours. After the reaction, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, designated as FG6.

[0028] Example 7

[0029] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 7:1:1, with a monomer mass concentration of 30%. When the temperature was raised to 60°C, 1.0% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 90°C for 7 hours. After the reaction, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, designated FG7.

[0030] Example 8

[0031] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and hydroxypropyl acrylate were added in a ratio of MA:AM:HPA = 3:1:1, with a monomer mass concentration of 30%. When the temperature was raised to 60°C, 0.8% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 90°C for 8 hours. After the reaction was completed, a light yellow transparent solution was obtained, thereby obtaining a copolymer anti-scaling agent, which was designated as FG8.

[0032] Comparative Example 1

[0033] Maleic anhydride monomer was added to a three-necked flask and the temperature was raised to 50°C. After it was completely dissolved in distilled water, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid were added in a ratio of MA:AM:AMPS = 3:1:1, with a monomer mass concentration of 30%. When the temperature reached 60°C, 0.8% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 90°C for 8 hours. After the reaction, a light yellow transparent solution was obtained, thereby obtaining a copolymer antiscalant, designated DB1.

[0034] Comparative Example 2

[0035] Maleic anhydride monomer was added to a three-necked flask and heated to 50°C. After it was completely dissolved in distilled water, acrylic acid and hydroxypropyl acrylate were added in a ratio of MA:AA:HPA = 3:1:1, with a monomer concentration of 30%. When the temperature reached 60°C, 0.8% of potassium persulfate as an initiator was added. The mixture was stirred in a constant temperature water bath at 90°C for 8 hours. After the reaction, a light yellow transparent solution was obtained, resulting in a copolymer antiscalant, designated DB2. The antiscaling efficiency of the copolymers of Examples 1-8 and Comparative Examples 1 and 2 was measured. The antiscaling efficiency evaluation criteria for the antiscalant was referenced to GB / T 16632-2008, "Determination of Antiscaling Performance of Water Treatment Agents: Calcium Carbonate Precipitation Method," for solution preparation and antiscaling performance evaluation. The test results are as follows:

[0036] Table 1 Anti-scaling rate of anti-scaling agent

[0037]

[0038] Experiments have shown that the copolymer anti-scaling agent of the present invention has a good anti-scaling effect on calcium carbonate scale. At an addition amount of 25 ppm, the anti-scaling rate can reach up to 99%.

Claims

1. A copolymer antiscalant, the structural formula of which is as follows: in: x, y, and z are the molar ratios of monomers; The preparation of the copolymer antiscalant comprises the following steps: (1) Add maleic anhydride monomer to a three-necked flask, heat to 50°C, and after it is completely dissolved in distilled water, add acrylamide and hydroxypropyl acrylate. The monomer concentration is 20-40%, and the ratio of maleic anhydride, hydroxypropyl acrylate and acrylamide is 3:1:1; (2) When the temperature rises to 60°C, add 0.1-1% of potassium persulfate as an initiator, and stir the reaction in a constant temperature water bath at 70-90°C for 5-8 hours. After the reaction is completed, a light yellow transparent solution is obtained, thereby obtaining a copolymer anti-scaling agent.

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