Compound scale inhibitor as well as preparation method and application thereof

Abstract

The invention relates to the technical field of preparation and compounding of scale inhibitors, in particular to a compound scale inhibitor as well as a preparation method and application thereof. The compound scale inhibitor is prepared from the following raw materials: polyvinyl phosphonate, sodium polysulfamate, sodium p-styrenesulfonate, acrylic acid-2-acrylic copolymer, polyvinyl alcohol and deionized water; the preparation method comprises the following steps: sequentially preparing the viscous PVA substrate solution, the first mixed solution, the second mixed solution, the third mixed solution and the fourth mixed solution from the raw materials, and then cooling, fixing the volume and filtering to obtain the compound scale inhibitor. The preparation process of the compound scale inhibitor is simple and easy to implement, the main components of the raw materials are water-soluble compounds, environmental protection requirements are met, the compound scale inhibitor not only can effectively inhibit formation of carbonate scale and sulfate scale at the same time, but also has excellent temperature tolerance and long-term stability, is good in scale inhibition effect and low in cost, and can adapt to different oilfield reinjection water environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of scale inhibitor preparation and compounding, and is a compounded scale inhibitor and a preparation method and application thereof. BACKGROUND

[0002] Pipeline scaling of oilfield reinjection water is a core bottleneck affecting injection-production balance stability and restricting efficient improvement of recovery rate, and control of carbonate and sulfate composite scale is a key technical problem. During reinjection, calcium and magnesium ions in produced water are easily crystallized and precipitated under the complex environment of high temperature and high pressure and pH value fluctuation in the pipeline. The scale formed not only tightly adheres to the inner wall of the pipeline, causing contraction of the pipeline path and a significant reduction in transportation efficiency, but also enters the oil reservoir formation with the injected water flow, plugging the reservoir pore channels, significantly weakening the effect of water injection development, and in severe cases, directly leading to paralysis of the injection-production well network, posing a great threat to continuous and stable production of oilfields. In view of such problems, adding a scale inhibitor is the most commonly used and most direct and effective technical means in current oilfield sites, and it is widely used due to its core advantages of convenient operation, rapid effect and wide adaptability.

[0003] The patent document with publication number CN118084220A discloses a compounded scale inhibitor and a preparation method thereof, which comprises the following raw materials by weight: 10-30 parts of hyperbranched polymer, 30-90 parts of synthetic scale inhibitor, 10-25 parts of organic phosphine scale inhibitor, 8-20 parts of modified carbon nanotube, 80-150 parts of deionized water and 10-30 parts of organic solvent; wherein the modified carbon nanotube is a carbon nanotube loaded with a modifier. The compounded scale inhibitor provided by the present application has strong functionality, has scale inhibition, corrosion inhibition and antibacterial effects, and is especially suitable for long-term and stable scale inhibition in high-temperature complex water systems.

[0004] The patent document with publication number CN119735313A discloses a green compounded scale inhibitor for geothermal fluid, which comprises modified polyaspartic acid, highly hydrolyzed polymaleic anhydride, polyepoxysuccinic acid and polyacrylic acid. The green compounded scale inhibitor for geothermal fluid disclosed by the present application compounds modified polyaspartic acid, highly hydrolyzed polymaleic anhydride, polyepoxysuccinic acid and polyacrylic acid, has good synergistic effect, realizes scale inhibition through chelation and solubilization and lattice distortion, has obvious advantages in scale inhibition in actual geothermal water, and has good practical promotion value.

[0005] The patent document with publication number CN114105322A discloses a scale inhibitor composition, a scale inhibitor and a preparation method thereof. The scale inhibitor composition includes 10-25 parts by weight of polyaspartate; 10-15 parts by weight of R1CH=CHC(O)NH2; 0.5-2 parts by weight of polyethylene glycol, 1-3 parts by weight of an initiator; and 50-80 parts by weight of water, wherein R1 is selected from any one of H, methyl and ethyl. The scale inhibitor composition has multiple characteristic functional groups for inhibiting the formation of silica scale and silicate scale, and the polyethylene glycol molecules can provide ether groups for the scale inhibitor molecules, thereby improving the water solubility of the polymer and preventing gel formation. The effects of the multiple characteristic groups can be synergistic, thereby enabling the scale inhibitor to have excellent silica scale inhibition capacity, and ultimately achieving the purpose of silica scale inhibition.

[0006] The patent document with publication number CN104211190A discloses a preparation method of hydroxyethylidene diphosphonic acid complex scale inhibitor. The product belongs to the field of chemical industry. The hydroxyethylidene diphosphonic acid complex scale inhibitor is prepared by using phosphorus trichloride, glacial acetic acid, phosphorous acid, polyacrylic acid, aminotri(methylphosphine) acid tetrasodium, and water-soluble benzotriazole sodium as raw materials, and using a phosphorus trichloride storage tank, a glacial acetic acid storage tank, a first chemical reaction kettle, a phosphorous acid storage tank, a stirring tank, and a second chemical reaction kettle as equipment. The production method has the advantages of simple process, mild and easy-to-control reaction conditions, easy batch production, no sewage and waste gas emission, etc.

[0007] The above-mentioned prior art solutions mainly use two to three simple complex scale inhibitors or single polymer scale inhibitors, but there are significant technical shortcomings: the single polymer scale inhibitor has weak functional targeting, the synergistic effect between the components of the two to three complex systems is insufficient, and some complex combinations even have antagonistic effects, resulting in large fluctuation range of scale inhibition rate under different working conditions.

[0008] Therefore, for the actual working conditions of high temperature, high pressure and high salinity of oilfield reinjection water, it is of great significance to develop a new complex scale inhibitor formula with multi-component synergistic optimization, strong targeting (simultaneous inhibition of carbonate and sulfate scale) and stability for solving the difficult problem of site scaling control, ensuring the long-term stable operation of injection-production system and reducing development cost. SUMMARY

[0009] The present application provides a complex scale inhibitor, a preparation method and application thereof, which overcomes the shortcomings of the prior art. It can effectively solve the problems of unsatisfactory scale inhibition effect, frequent addition of scale inhibitors, serious equipment pipeline blockage and high production cost.

[0010] One of the technical solutions of the present application is realized by the following measures: a compounded scale inhibitor, raw materials include, according to mass percentage, polyvinyl phosphonate 20-30%, sodium polyaminosulfonate 5-15%, styrene sodium sulfonate 5-10%, acrylic acid-2-acrylic acid copolymer 15-25%, polyvinyl alcohol 5-10%, and deionized water 40-55%.

[0011] The following is a further optimization or / and improvement of one of the above technical solutions of the application:

[0012] The above is obtained according to the following steps:

[0013] Step one, mix the required amount of polyvinyl alcohol with deionized water, heat and stir to dissolve uniformly, and obtain a viscous PVA base solution;

[0014] Step two, after the viscous PVA base solution is cooled, the required amount of polyvinyl phosphonate is added, stirred and dissolved uniformly to obtain a first mixed solution;

[0015] Step three, add the required amount of sodium polyaminosulfonate to the first mixed solution, stir and dissolve to mix uniformly to obtain a second mixed solution;

[0016] Step four, add the required amount of styrene sodium sulfonate to the second mixed solution, stir and dissolve uniformly to obtain a third mixed solution;

[0017] Step five, mix the required amount of acrylic acid-2-acrylic acid copolymer with deionized water to obtain a copolymer solution, then add the copolymer solution to the third mixed solution, stir and mix uniformly to obtain a fourth mixed solution;

[0018] Step six, cool the fourth mixed solution to constant volume, adjust the pH value of the fourth mixed solution, and filter to obtain the compounded scale inhibitor.

[0019] In step one, the amount of deionized water is 80% of the total mass of deionized water.

[0020] In step one, the specific process of heating and stirring to dissolve includes heating to 80-90°C at a heating rate of 2-3°C / min, and constant temperature stirring at a stirring speed of 120-150 r / min for 30-45 minutes.

[0021] In step two, the viscous PVA base solution is cooled to 45-55°C, and constant temperature stirring is carried out at a stirring speed of 150-180 r / min for 15-20 minutes.

[0022] In the third step, the specific process of stirring and dissolving includes: dissolving the mixture uniformly at 45-55 DEG C and 180-200 r / min, and then stirring for 20-25 minutes.

[0023] In the fourth step, the stirring speed is 180-200 r / min, and the stirring time is 10-20 minutes.

[0024] In the fifth step, the amount of deionized water is the mass of the remaining deionized water, the stirring speed is 180-200 r / min, and the stirring time is 25-35 minutes.

[0025] In the sixth step, the specific process of cooling to 25-30 DEG C, adjusting the pH value of the fourth mixture and filtering includes: adding citric acid solution or sodium hydroxide solution at a stirring speed of 100-120 r / min, adjusting the pH value of the fourth mixture to 4.0-6.0, and then filtering through a filter core with a pore size of 0.45 mu m.

[0026] The second technical solution of the application is realized by the following measures: a preparation method of a compounded scale inhibitor, which is performed according to the following steps:

[0027] In the first step, a required amount of polyvinyl alcohol is mixed with deionized water, heated and stirred to dissolve uniformly, and a viscous PVA base solution is obtained.

[0028] In the second step, the viscous PVA base solution is cooled, a required amount of polyvinyl phosphonate is added, stirred and dissolved uniformly, and a first mixture is obtained.

[0029] In the third step, a required amount of sodium polyaminosulfonate is added to the first mixture, stirred and dissolved uniformly, and a second mixture is obtained.

[0030] In the fourth step, a required amount of sodium styrene sulfonate is added to the second mixture, stirred and dissolved uniformly, and a third mixture is obtained.

[0031] In the fifth step, a required amount of acrylic acid-2-acrylic acid copolymer is mixed with deionized water to obtain a copolymer solution, and the copolymer solution is added to the third mixture, stirred and mixed uniformly, and a fourth mixture is obtained.

[0032] In the sixth step, the fourth mixture is cooled, adjusted to a constant volume, and filtered after adjusting the pH value, and a compounded scale inhibitor is obtained.

[0033] The third technical solution of the application is realized by the following measures: an application of a compounded scale inhibitor in an oilfield reinjection water system.

[0034] The preparation process of the compound scale inhibitor is simple and easy to implement, the main components of the raw materials are water-soluble compounds, meets the environmental protection requirements, can effectively inhibit the formation of carbonate scale and sulfate scale at the same time, has excellent temperature resistance and long-term stability, good scale inhibition effect, low cost, and can adapt to different oilfield reinjection water environments. DETAILED DESCRIPTION

[0035] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical scheme of the present application and the actual situation. The various chemical reagents and chemical supplies mentioned in the present application are well-known and commonly used chemical reagents and chemical supplies in the prior art unless otherwise specified; the percentages in the present application are mass percentages unless otherwise specified; the solution in the present application is a water solution with water as the solvent unless otherwise specified, for example, a hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present application generally refer to a temperature of 15-25℃, and is generally defined as 25℃.

[0036] The present application will be further described below in conjunction with examples:

[0037] Example 1: The compound scale inhibitor, the raw materials include, in terms of mass percentage: polyvinyl phosphonate (abbreviated as PVPA) 20-30%, polyaminosulfonic acid sodium (abbreviated as PAMPS) 5-15%, styrene sulfonic acid sodium (abbreviated as SSS) 5-10%, acrylic acid-2-acrylic acid copolymer (abbreviated as PAA) 15-25%, polyvinyl alcohol (abbreviated as PVA) 5-10%, and deionized water 40-55%.

[0038] In the present application, through the multi-component synergistic effect of polyvinyl phosphonate, polyaminosulfonic acid sodium, styrene sulfonic acid sodium, acrylic acid-2-acrylic acid copolymer, and polyvinyl alcohol, the obtained compound scale inhibitor can effectively inhibit the formation of carbonate scale and sulfate scale at the same time. The obtained compound scale inhibitor is suitable for various types of oilfield reinjection water systems, and is suitable for key links such as wellhead, ground gathering pipeline, and near-wellbore zone of injection wells, and can be targeted to cope with complex working conditions of high temperature, high pressure, high salinity, and pH value fluctuation.

[0039] PVPA is a common scale inhibitor, which can form stable complexes with metal ions in water through complexation and chemical adsorption, thereby inhibiting the crystallization and deposition of calcium carbonate. PVPA can effectively reduce the generation rate of carbonate scale by reducing the formation of scale nucleation, especially in hard water or high concentration environment.

[0040] Polyaminosulfonic acid sodium has strong amino sulfonic acid groups, which can form complexes with sulfate ions (SO4 2- ) to prevent the nucleation and growth of calcium sulfate (CaSO4) crystals. The mechanism of action is to adsorb and stabilize Ca 2+The ions inhibit the precipitation of CaSO4, effectively stopping the formation of sulfate scale. This makes the complex scale inhibitor have an advantage in dealing with carbonate and sulfate composite scale.

[0041] SSS, as a strong polar compound, can enhance the dispersion performance in the solution and improve its competitive adsorption capacity for various ions. In the process of scale inhibition, SSS helps to effectively disperse ions during the crystallization process, preventing crystal aggregation and deposition. By improving the dispersibility of the agent, SSS enhances the overall effect of the scale inhibitor, especially in high-concentration mineral water quality environments, with better inhibition of scale formation.

[0042] PAA binds to calcium ions in water through chelation, inhibiting the crystallization of calcium carbonate and calcium sulfate. It further enhances the scale inhibition effect of the complex scale inhibitor through synergistic action with other ingredients. AA copolymer can also form a film in the solution, reducing the deposition of scale crystals and delaying the scale formation process.

[0043] PVA, as a water-soluble polymer compound, can improve the stability and water solubility of the complex scale inhibitor. It helps to uniformly disperse other components, allowing each component to mix and distribute evenly in the solution, thereby enhancing the scale inhibition effect. PVA also has good temperature resistance and antioxidant properties, which helps to improve the stability of the scale inhibitor and prevent degradation during use.

[0044] Deionized water, as a solvent, mainly provides the required solution base, ensuring that other components can be uniformly dissolved and dispersed. The purity of deionized water ensures that there are no other impurities in the solution, avoiding fluctuations in the effect of the agent caused by minerals or ions in the water.

[0045] Example 2: As an optimization of the above examples, the following steps are taken:

[0046] Step one, mix the required amount of polyvinyl alcohol with deionized water, heat and stir to dissolve uniformly, and obtain a viscous PVA base solution;

[0047] Step two, after the viscous PVA base solution is cooled, the required amount of polyvinyl phosphonate is added, stirred and dissolved uniformly to obtain a first mixed solution;

[0048] Step three, add the required amount of sodium polyaminosulfonate to the first mixed solution, stir and dissolve to mix uniformly to obtain a second mixed solution;

[0049] Step four, add the required amount of sodium styrene sulfonate to the second mixed solution, stir and dissolve uniformly to obtain a third mixed solution;

[0050] Step 5: Mix the required amount of acrylic-2-acrylic copolymer with deionized water to obtain a copolymer solution. Then add the copolymer solution to the third mixture and stir to mix evenly to obtain the fourth mixture.

[0051] Step 6: After cooling the fourth mixture, bring it to a constant volume, adjust the pH value of the fourth mixture, and then filter it to obtain the compound scale inhibitor.

[0052] Example 3: As an optimization of the above example, in step one, the amount of deionized water used is 80% of the total mass of deionized water; the specific process of heating and stirring to dissolve in step one includes: heating to 80°C to 90°C at a heating rate of 2°C / min to 3°C / min, and stirring at a constant temperature of 120r / min to 150r / min for 30 to 45 minutes.

[0053] Example 4: As an optimization of the above example, in step two, the viscous PVA base liquid is cooled to 45°C to 55°C and stirred at a constant temperature of 150r / min to 180r / min for 15 to 20 minutes.

[0054] Example 5: As an optimization of the above example, in step three, the specific process of stirring and dissolving includes: dissolving and mixing evenly at a stirring speed of 180 r / min to 200 r / min at 45°C to 55°C, and then stirring for 20 to 25 minutes.

[0055] Example 6: As an optimization of the above example, in step four, the mixture is stirred at a stirring speed of 180 r / min to 200 r / min for 10 to 20 minutes.

[0056] Example 7: As an optimization of the above example, in step five, the amount of deionized water used is the mass of the remaining deionized water, and the mixture is stirred at a stirring speed of 180 r / min to 200 r / min for 25 to 35 minutes.

[0057] Example 8: As an optimization of the above example, in step six, the specific process of cooling to 25°C to 30°C and adjusting the pH value of the fourth mixture before filtration includes: adding citric acid solution or sodium hydroxide solution at a stirring speed of 100r / min to 120r / min, adjusting the pH value of the fourth mixture to 4.0 to 6.0, and then filtering through a 0.45μm filter element.

[0058] Example 9: The preparation method of this compound scale inhibitor is carried out according to the following steps:

[0059] Step 1: Mix the required amount of polyvinyl alcohol with deionized water, heat and stir to dissolve evenly to obtain a viscous PVA base liquid;

[0060] Step 2: After cooling the viscous PVA base liquid, add the required amount of polyvinyl phosphonate, stir and dissolve evenly to obtain the first mixture;

[0061] Step 3: Add the required amount of sodium polysulfamate to the first mixture, stir to dissolve and mix evenly to obtain the second mixture;

[0062] Step 4: Add the required amount of sodium styrene sulfonate to the second mixture, stir until dissolved and homogeneous, and obtain the third mixture.

[0063] Step 5: Mix the required amount of acrylic-2-acrylic copolymer with deionized water to obtain a copolymer solution. Then add the copolymer solution to the third mixture and stir to mix evenly to obtain the fourth mixture.

[0064] Step 6: After cooling the fourth mixture, bring it to a constant volume, adjust the pH value of the fourth mixture, and then filter it to obtain the compound scale inhibitor.

[0065] Example 10: Application of this compound scale inhibitor in oilfield reinjection water systems.

[0066] Example 11:

[0067] Operating conditions: High NaCl and CaCl2 concentrations, significant water quality variations, noticeable pH fluctuations, temperature ≥60℃, pressure ≥30MPa.

[0068] This compound scale inhibitor, by weight percentage, comprises: PVPA: 25%, PAMPS: 15%, SSS: 10%, PAA: 22%, PVA: 10%, and deionized water: 40%, and is obtained according to the following steps:

[0069] Step 1: Add deionized water to the reactor (use about 80% of the amount initially, reserving some for later adjustment), start stirring and control the speed at 120 r / min to form a stable vortex.

[0070] Next, PVA is slowly and evenly added to the reactor along the edge of the vortex. After mixing with deionized water, circulating hot water is introduced through the jacket and heated to 80°C at a heating rate of 2°C / min. The mixture is then stirred at a constant temperature of 120 r / min for 30 minutes to ensure complete and uniform dissolution, good particle dispersion, and no clumping or agglomeration, until the solution is completely transparent and free of any particulate matter, resulting in a uniform and stable viscous PVA base solution.

[0071] Step 2: Stop heating and cool the viscous PVA base liquid to 45°C using jacket cooling water or natural cooling (excessive temperature is not conducive to the stability of some polymers in the subsequent process). Then add PVPA and stir at a constant temperature of 150 r / min for 15 minutes until it is dissolved and uniformly dissolved to obtain the first mixture.

[0072] Step 3: Slowly add PAMPS to the first mixture, stir at 180 r / min at 45°C until dissolved and mixed evenly, then extend the stirring time for another 20 minutes to ensure complete dispersion and dissolution, to obtain the second mixture;

[0073] Step 4: Add PSS to the second mixture and stir at 180 r / min for 15 minutes to ensure complete dissolution and uniformity, thus obtaining the third mixture.

[0074] Step 5: Due to the high viscosity of the PAA component, the PAA needs to be diluted with the remaining deionized water to obtain a copolymer solution. The copolymer solution is then slowly added dropwise to the third mixture. The mixture is stirred at 180 r / min for 25 minutes to mix evenly (to avoid local over-viscosity leading to uneven mixing) to obtain the fourth mixture.

[0075] Step 6: After the fourth mixture is naturally cooled to 25°C, check the liquid level and make up the volume with the reserved deionized water to the final mass, ensuring accurate solid content. Then, with a stirring speed of 100 r / min, insert a calibrated pH meter, add citric acid solution, adjust the pH of the fourth mixture to 4.0, filter it through a 0.45 μm filter element to obtain the compound scale inhibitor, and fill it into a clean packaging container for later use.

[0076] Under these operating conditions, PVPA, as the main component, exhibits excellent stability at high temperatures and strongly inhibits the scaling of calcium carbonate and sulfate, preventing calcium salt precipitation. PAMPS enhances the agent's resistance to sulfate scaling at high temperatures and also strengthens its pressure resistance. PSS effectively improves the dispersibility of the formulation and inhibits crystal aggregation. PAA has a significant effect on calcium carbonate and sulfate formation. 2+ SO4 2- The binding of these compounds has a strong inhibitory effect, further enhancing the scale-reducing effect. PVA helps improve stability at high temperatures and prevents thermal degradation of the chemicals. Deionized water is used for dilution and to ensure uniformity throughout the system.

[0077] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0078] (1) The compound scale inhibitor of the present invention can effectively inhibit the formation of carbonate scale and sulfate scale at the same time. By utilizing the synergistic effect of each component, the scale inhibition effect is significantly improved. It can adapt to different oilfield reinjection water environments and shows strong versatility and high efficiency.

[0079] (2) By using highly stable components such as PVA, the scale inhibitor of the present invention has excellent temperature resistance and long-term stability, and can maintain the scale inhibition effect during long-term use, reduce frequent additions, and extend the service life of pipeline equipment.

[0080] (3) The compound scale inhibitor of the present invention is safe and environmentally friendly. Its main components are water-soluble compounds, which meet environmental protection requirements. At the same time, the high-efficiency scale inhibition characteristics of the compound formula reduce the cost of use and can bring higher economic benefits.

[0081] Example 12:

[0082] Operating conditions: High NaCl and KCl content, pH value fluctuates between 7 and 10, and CaSO4 and Mg(OH)2 are easily deposited.

[0083] The difference from Example 11 is that the raw materials, by mass percentage, include: PVPA: 28%, PAMPS: 15%, SSS: 7%, PAA: 22%, PVA: 10%, and deionized water: 40%, and the compound scale inhibitor is prepared according to the method described in Example 11.

[0084] Under these operating conditions, PVPA exhibits excellent resistance to CaSO4 / CaCO3 scaling and remains stable in environments with fluctuating pH levels. PAMPS plays a dual role in this formulation, inhibiting both sulfate and carbonate scaling. PSS improves the system's dispersibility and reduces salt aggregation. PAA effectively inhibits crystal formation in high pH environments. PVA is used in this formulation to stabilize the reagent structure and prevent reagent degradation, while deionized water ensures good dispersion of the system.

[0085] Example 13:

[0086] Operating conditions: Temperature ≥ 80℃, pressure ≥ 50MPa, pH value fluctuating between 7 and 11, Ca 2+ Mg 2+ SO4 2- High concentration.

[0087] The difference from Example 11 is that the raw materials, by mass percentage, include: PVPA: 28%, PAMPS: 15%, SSS: 7%, PAA: 20%, PVA: 10%, and deionized water: 45%, and the compound scale inhibitor is prepared according to the method described in Example 11.

[0088] Under these operating conditions, PVPA, as the main component, exhibits long-lasting anti-scaling capabilities and maintains strong inhibition under high temperature and pressure conditions. PAMPS enhances the control of calcium sulfate and strengthens the agent's pressure resistance. PSS effectively inhibits particle aggregation and enhances the system's dispersibility. PAA resists pH fluctuations and prevents crystal nucleation. PVA helps maintain the stability of the entire system, preventing failure caused by extreme temperature and pressure conditions. Deionized water is used to improve solubility and ensure formulation uniformity.

[0089] Example 14:

[0090] Operating conditions: The produced water from the oilfield contains a large amount of organic matter (asphaltite, gum, humic acid), and the total dissolved solids are >50g / L, with a temperature of approximately 70℃.

[0091] The difference from Example 11 is that the raw materials, by mass percentage, include: PVPA: 28%, PAMPS: 15%, SSS: 7%, PAA: 20%, PVA: 10%, and deionized water: 45%, and the compound scale inhibitor is prepared according to the method described in Example 11.

[0092] Under these operating conditions, PVPA effectively inhibits the scaling of CaCO3 and CaSO4 and resists interference from organic complexes. PAMPS enhances dispersibility in high-salt and organically contaminated environments and controls the formation of organic-inorganic complex scale. PSS effectively disperses organic particles, preventing their adhesion and agglomeration. PAA works synergistically with PVPA to inhibit inorganic scaling. PVA plays a stabilizing role in this formulation, reducing phase separation. Deionized water is used for dilution and to promote the uniform dissolution of the chemicals.

[0093] Example 15:

[0094] Operating conditions: The produced water from the oilfield contains a large amount of organic matter (asphaltite, gum, humic acid), and the total dissolved solids are >50g / L, with a temperature of approximately 70℃.

[0095] The difference from Example 11 is that the deep well water injection system (>4000m), temperature 40℃ to 50℃, pressure >60MPa, and Ca... 2 + Ba 2+ 、Sr 2+ At higher concentrations, BaSO4 and SrSO4 scale are easily formed. A compound scale inhibitor was prepared according to the method described in Example 11.

[0096] For the compound scale inhibitors obtained in Examples 11 to 15, their scale inhibition rates were determined using the following methods based on actual application conditions. The experimental conditions and simulated water ion composition are shown in Table 1, and the measurement results are shown in Table 2.

[0097] Using actual operating temperature and pressure as parameters, a static scale inhibition experiment was conducted in a high-temperature and high-pressure reactor. A corresponding simulated aqueous solution was prepared to simulate actual operating conditions. Static deposition experiments were performed with a blank group and a dosing group. The scale inhibition rate (denoted by η, unit: %) was calculated using the following formula:

[0098]

[0099] in,

[0100] C 初始 The experiment simulates the initial concentration of scale components and their corresponding ions in water.

[0101] C 空白 The remaining concentration of the corresponding ions in the filtrate of the blank group (without scale inhibitor) after standing;

[0102] C 加药 The remaining concentration of this ion in the filtrate after the dosing group (with scale inhibitor) has been allowed to stand.

[0103] Organic-inorganic complex scale is calculated using the weight gain method:

[0104]

[0105] m0: Initial mass of the hanging piece, g;

[0106] m 空白 : The total mass of the scale tablets and the composite scale after the experiment in the blank group (without scale inhibitor), in g;

[0107] m 加药 The total mass of scale inhibitor plus scale after the dosing group (with a specified concentration of scale inhibitor) experiment.

[0108] Table 1

[0109] Example 11 12 13 14 15 Temperature (°C) 60 70 80 70 45 Pressure (MPa) 30 0.1 50 0.1 60 Initial pH value 7.5 8.5 8.0 8.0 7.0 Na + / K + (mg / L)]]> 31956 21567 24270 19364 16256 Ca 2+ (mg / L) 5200 4800 3800 3600 1000 Ba 2+ (mg / L)]]> / / / / 850 Sr 2+ (mg / L)]]> / / / / 500 Mg 2+ (mg / L)]]> / 1500 1250 / / Cl - (mg / L)]]> 62437 41216 48746 33332 31528 SO4 2- (mg / L) 5100 4800 3850 1000 2400 HCO3 - (mg / L)]]> 6100 2440 3050 4210 1220 Asphaltene (mg / L) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 / / / 200 /

[0110] Table 2

[0111]

[0112] As shown in Table 2, this invention, through the scientific compounding of PVPA, PAMPS, SSS, PAA, and PVA, constructs a highly efficient compound scale inhibitor system applicable to extreme oilfield conditions such as high temperature, high pressure, high salinity, and wide pH fluctuations. It not only exhibits excellent broad-spectrum inhibition capabilities against common scales such as calcium carbonate and calcium sulfate, but also specifically addresses the deposition problems of extremely difficult-to-dissolve scales such as barium sulfate / strontium and organic-inorganic composite scales. It achieves high-efficiency scale inhibition with relatively low dosage, and the synergistic effect of each component, combined with excellent thermal stability, resistance to ionic interference, and dispersibility, provides a reliable and economical solution for scale control under complex water quality conditions.

[0113] In summary, the preparation process of the compound scale inhibitor of this invention is simple and easy to implement. The main components of the raw materials are all water-soluble compounds, which meet environmental protection requirements. It can not only effectively inhibit the formation of carbonate scale and sulfate scale at the same time, but also has excellent temperature resistance and long-term stability. It has good scale inhibition effect, low cost, and can adapt to different oilfield reinjection water environments.

[0114] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A compound scale inhibitor, characterized in that... The raw materials, by weight percentage, include: 20% to 30% polyvinyl phosphonate, 5% to 15% sodium polyaminosulfonate, 5% to 10% sodium styrene sulfonate, 15% to 25% acrylic acid-2-acrylic acid copolymer, 5% to 10% polyvinyl alcohol, and 40% to 55% deionized water.

2. The compound scale inhibitor according to claim 1, characterized in that... The following steps were followed to obtain: Step 1: Mix the required amount of polyvinyl alcohol with deionized water, heat and stir to dissolve evenly to obtain a viscous PVA base liquid; Step 2: After cooling the viscous PVA base liquid, add the required amount of polyvinyl phosphonate, stir and dissolve evenly to obtain the first mixture; Step 3: Add the required amount of sodium polysulfamate to the first mixture, stir to dissolve and mix evenly to obtain the second mixture; Step 4: Add the required amount of sodium styrene sulfonate to the second mixture, stir until dissolved and homogeneous, and obtain the third mixture. Step 5: Mix the required amount of acrylic-2-acrylic copolymer with deionized water to obtain a copolymer solution. Then add the copolymer solution to the third mixture and stir to mix evenly to obtain the fourth mixture. Step 6: After cooling the fourth mixture, bring it to a constant volume, adjust the pH value of the fourth mixture, and then filter it to obtain the compound scale inhibitor.

3. The compound scale inhibitor according to claim 2, characterized in that... In step one, the amount of deionized water used is 80% of the total mass of deionized water; Or / and, in step one, the specific process of heating and stirring to dissolve includes: heating to 80°C to 90°C at a heating rate of 2°C / min to 3°C / min, and stirring at a constant temperature for 30 to 45 minutes at a stirring speed of 120 r / min to 150 r / min.

4. The compound scale inhibitor according to claim 2 or 3, characterized in that... In step two, the viscous PVA base liquid is cooled to 45°C to 55°C and stirred at a constant temperature of 150r / min to 180r / min for 15 to 20 minutes.

5. The compound scale inhibitor according to any one of claims 2 to 4, characterized in that... In step three, the specific process of stirring and dissolving includes: dissolving and mixing evenly at a stirring speed of 180 r / min to 200 r / min at a temperature of 45°C to 55°C, and then stirring for another 20 to 25 minutes.

6. The compound scale inhibitor according to any one of claims 2 to 5, characterized in that... In step four, stir at a stirring speed of 180 r / min to 200 r / min for 10 to 20 minutes.

7. The compound scale inhibitor according to any one of claims 2 to 6, characterized in that... In step five, the amount of deionized water used is the same as the mass of the remaining deionized water, and the mixture is stirred at a stirring speed of 180 r / min to 200 r / min for 25 to 35 minutes.

8. The compound scale inhibitor according to any one of claims 2 to 7, characterized in that... In step six, the specific process of cooling to 25°C to 30°C and adjusting the pH value of the fourth mixture before filtration includes: adding citric acid solution or sodium hydroxide solution at a stirring speed of 100r / min to 120r / min, adjusting the pH value of the fourth mixture to 4.0 to 6.0, and then filtering through a 0.45μm filter cartridge.

9. A method for preparing a compound scale inhibitor according to any one of claims 1 or 3 to 8, characterized in that... Follow these steps: Step 1: Mix the required amount of polyvinyl alcohol with deionized water, heat and stir to dissolve evenly to obtain a viscous PVA base liquid; Step 2: After cooling the viscous PVA base liquid, add the required amount of polyvinyl phosphonate, stir and dissolve evenly to obtain the first mixture; Step 3: Add the required amount of sodium polysulfamate to the first mixture, stir to dissolve and mix evenly to obtain the second mixture; Step 4: Add the required amount of sodium styrene sulfonate to the second mixture, stir until dissolved and homogeneous, and obtain the third mixture. Step 5: Mix the required amount of acrylic-2-acrylic copolymer with deionized water to obtain a copolymer solution. Then add the copolymer solution to the third mixture and stir to mix evenly to obtain the fourth mixture. Step 6: After cooling the fourth mixture, bring it to a constant volume, adjust the pH value of the fourth mixture, and then filter it to obtain the compound scale inhibitor.

10. The application of a compound scale inhibitor according to any one of claims 1 to 8 in an oilfield reinjection water system.

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