Squeezing anti-scaling agent as well as preparation method and application thereof

Abstract

The invention discloses a squeezing anti-scaling agent as well as a preparation method and application thereof. The squeezing anti-scaling agent comprises the following components in percentage by mass: 20-40% of an anti-scaling agent, 7-25% of a nonionic surfactant solution, 28-50% of a beta-cyclodextrin solution, 2-8% of a metal cation solution and 1-3% of a fluorescent marker. Beta-cyclodextrin is used as a host molecule, a nonionic surfactant is used as a guest molecule, supermolecules are self-assembled to construct hollow microspheres through recognition of the host molecule and the guest molecule under the action of hydrogen bonds, Van der Waals acting force, hydrophobic acting force and the like, and in the self-assembly process, a fluorescence-labeled metal-polymeric anti-scaling agent is wrapped in the hollow microspheres, so that the metal-polymeric anti-scaling agent is prepared. The squeezing anti-scaling agent is slowly dissolved and slowly released to the stratum after being squeezed into the stratum, the adsorption performance of the metal-anti-scaling agent chelate in the stratum is enhanced through active divalent metal ions, the retention performance of the anti-scaling agent in the stratum is improved, meanwhile, the concentration of the anti-scaling agent in produced liquid is monitored in real time through the added fluorescent marker, and the anti-scaling agent can be applied to the stratum. And judging whether the released anti-scaling agent can play an anti-scaling role or not.

Description

Technical Field

[0001] The invention belongs to the technical field of chemicals for petroleum industry, and in particular relates to a squeeze anti-scaling agent and a preparation method and application thereof. Background Art

[0002] With the continuous implementation of oilfield water injection development, the water content of the output fluid of major oilfields in my country is getting higher and higher, and the scaling problem of oil and water wells and pipeline systems is becoming more and more serious. Scaling causes production pipelines or equipment to be blocked, and the production volume to decrease. In severe cases, it causes the pumping rod to break, the oil well to be shut down, or even scrapped.

[0003] The chemical anti-scaling technology that is widely used in China is mainly the addition of anti-scaling agents, which include continuous injection at the wellhead, placement of solid anti-scaling blocks underground and squeeze treatment. Continuous injection at the wellhead has high requirements for pumps, complicated operation, and is prone to uneven dosing, large agent consumption, large workload and unstable effect. Solid anti-scaling blocks placed underground are easy to break at high temperatures, causing well blockage, and are difficult to promote and apply. These two methods are limited to preventing scaling in the wellbore and above, but have poor anti-scaling effects in the near-well formation. Squeeze treatment can not only prevent and slow down scaling and reservoir damage underground, but also play an anti-scaling role in the entire process above the wellhead and pipeline. However, in recent years, with the increasing number of deep and ultra-deep wells, as well as the requirements for safety and environmental protection, the original phosphorus-containing scale inhibitors can no longer fully meet the high temperature resistance, safety and environmental protection requirements of squeeze operations. Under high temperature conditions, scale inhibitors are prone to degradation, poor retention in the reservoir, and rapid release, resulting in a relatively short squeeze cycle, which limits the scope of application of this technology.

[0004] Existing technologies such as Chinese patent CN104046346B disclose a descaling agent and preparation method for oilfield water injection wells, and "Cleaning World" disclosed "Development of Two Sulfate Cleaning Agents" in June 2017. The sulfate scale dissolving agents involved in the above-mentioned publicly published documents are usually divided into three categories: acidic scale dissolving agents, neutral scale dissolving agents and alkaline scale dissolving agents. Neutral scale dissolving agents are the majority. The scale dissolving efficiency of acidic scale dissolving agents is lower than that of alkaline scale dissolving agents. The use temperature of all scale dissolving agents is lower than 100°C. After collecting a large number of domestic and foreign samples for actual testing, the results show that their sulfate scale dissolving rate is low (<50%) under conditions of ≥100°C. When mixed with displacement fluid at high temperature, incompatibility phenomena such as stratification and precipitation are prone to occur, which cannot achieve the effect described in the literature, and it is difficult to solve the scale deposition problem in the reservoir and wellbore, which greatly affects the release of oil and gas production capacity.

[0005] Chinese patent CN105949395B discloses a molecular cluster material of supramolecular polymer and its preparation method, which uses polystyrene microspheres as a substrate, grafts active groups containing a large number of carboxyl or sulfonic acid groups on the surface of polystyrene microspheres to synthesize molecular cluster materials. The preparation method of the invention is simple, low in cost, low in energy consumption, environmentally friendly and pollution-free, the product is efficient and stable, has a large amount of descaling, and has strong antioxidant properties, but it uses a multi-step synthesis process, has strict requirements on the synthesis conditions, and has no supporting monitoring method.

[0006] Therefore, in order to improve the temperature resistance and adsorption capacity of anti-scaling agent molecules in the formation, enhance the retention effect of anti-scaling agent, and achieve the purpose of continuous release in the formation and long-term anti-scaling, it is a good technical path to carry out research on squeezed anti-scaling agents and their preparation methods, but no related reports have been seen. Summary of the invention

[0007] The purpose of the present invention is to provide a squeeze injection anti-scaling agent and its preparation method and application to address the problems that the existing squeeze injection anti-scaling agents have poor anti-scaling effects on barium strontium scale, calcium scale and mixed scale of the two, poor high temperature resistance in reservoirs, weak adsorption, fast release rate and short effective period.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] The present invention first discloses a squeezing anti-scaling agent, which comprises the following components by mass percentage:

[0010]

[0011] As a preferred solution, the scale inhibitor is an anionic polycarboxylic acid scale inhibitor.

[0012] A further preferred embodiment is that the anionic polycarboxylic acid scale inhibitor is a polyacrylic acid scale inhibitor or a polymethacrylic acid scale inhibitor.

[0013] As another preferred embodiment of the present invention, the metal cation solution comprises a metal dissolved in an acid, and the acid comprises one or a mixture of acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, and nitric acid, and the metal comprises one or a mixture of zinc, calcium, magnesium, and aluminum.

[0014] As another preferred embodiment of the present invention, the metal cation solution comprises dissolving a metal salt in water, wherein the metal salt is one or a mixture of calcium salt, magnesium salt, manganese salt, nickel salt, aluminum salt and zinc salt.

[0015] Preferably, the nonionic surfactant solution is one of Pluronic (propylene glycol block polyether) F68 aqueous solution, Pluronic F88 aqueous solution or Pluronic F98 aqueous solution.

[0016] Preferably, the fluorescent marker is N-vinyl imidazole.

[0017] The present invention further discloses a method for preparing a squeezing anti-scaling agent, comprising the following steps:

[0018] S1. Preparation of metal-antiscalant chelates

[0019] The metal cation solution and the scale inhibitor are mixed in a mass ratio of 1:5-1:8 at a temperature of 50-70°C and a speed of 800-1200 r / min until they are fully mixed to form a stable metal-scale inhibitor chelate;

[0020] S2. Preparation of fluorescently labeled metal-antifouling agent chelates

[0021] Add water and the metal-antiscalant chelate prepared in step S1 to the reactor, raise the temperature to 80-90° C., and while stirring continuously, simultaneously drop a 20% aqueous solution of ammonium persulfate and a 3% aqueous solution of N-vinyl imidazole into the reactor. After the dropwise addition is completed, reflux the mixture at a constant temperature of 85-95° C. for 2-4 hours, cool the mixture to room temperature, and filter the mixture to obtain the fluorescently labeled metal-antiscalant chelate.

[0022] S3. Preparation of β-cyclodextrin solution

[0023] Dissolving β-cyclodextrin in water to prepare a β-cyclodextrin solution with a mass concentration of 2% to 3%;

[0024] S4. Preparation of nonionic surfactant solution

[0025] Dissolving a nonionic surfactant in water to prepare a nonionic surfactant aqueous solution with a mass concentration of 3% to 4%;

[0026] S5. Mix 200g-400g of fluorescent labeled metal-antiscalant chelate and 400-600mL of β-cyclodextrin solution to obtain mixed solution A, then add 100-300mL of non-ionic surfactant solution to the mixed solution A, stir at room temperature for 0.5-1.5h to obtain the target product.

[0027] As a further preferred embodiment, in step S2, the mass of the water is 3 times the mass of the metal-antiscalant chelate;

[0028] The mass of the ammonium persulfate aqueous solution is 0.02-0.04 times the mass of the metal-antiscalant chelate;

[0029] The mass of the N-vinylimidazole aqueous solution is 0.16-0.2 times the mass of the metal-antiscalant chelate.

[0030] Preferably, in step S2, the dropping time of the aqueous ammonium persulfate solution and the aqueous N-vinylimidazole solution should be controlled within 1.5-2.0 h.

[0031] As a further preferred embodiment, the method for preparing the nonionic surfactant solution is: dissolving 20-30 g of β-cyclodextrin in 1 L of water at 25° C.-30° C. to obtain a β-cyclodextrin solution with a mass concentration of 2%-3%.

[0032] As a further preferred embodiment, the method for preparing the non-ionic surfactant solution is: dissolving 30-40 g of the non-ionic surfactant in 1 L of water to prepare a non-ionic surfactant aqueous solution with a mass concentration of 3%-4%.

[0033] Preferably, in step S4, the nonionic surfactant is slowly added dropwise at a rate of 100 to 150 drops per minute.

[0034] The present invention further discloses the application of any one of the above squeeze-in anti-scaling agents or the squeeze-in anti-scaling agent prepared by the above method in downhole near-wellbore areas and formation scaling.

[0035] The reaction mechanism of the present invention is:

[0036] With β-cyclodextrin as the main molecule and nonionic surfactant as the guest molecule, the supramolecular self-assembly constructs hollow microspheres through host-guest molecule recognition, under the action of hydrogen bonds, van der Waals forces, hydrophobic forces, etc., and in the process of self-assembly, the metal-polymer antiscalant is wrapped inside the hollow microspheres. Then, after the squeezed antiscalant is squeezed into the formation, the formation polymer is slowly dissolved, and then the internal antiscalant is slowly released into the formation, and then the metal-antiscalant chelate enhances its adsorption performance in the formation through active divalent metal ions, thereby improving the retention performance of the antiscalant in the formation.

[0037] By adopting the above technical solution, the present invention has the following beneficial effects:

[0038] 1. The present invention uses β-cyclodextrin as the main molecule and nonionic surfactant as the guest molecule, and performs supramolecular self-assembly through host-guest molecule recognition under the action of hydrophobic interaction, hydrogen bonding, van der Waals force, etc. At the same time, adjacent β-cyclodextrins form hydrogen bonds through the hydroxyl groups outside the cavity and are connected together. In the process of multi-layer self-assembly, the fluorescently labeled metal-antiscalant is coated in the hollow microspheres, achieving the effect of dual controlled release of antiscalant by β-cyclodextrin and metal ions. At the same time, by adding fluorescent markers to the antiscalant, the concentration of the antiscalant in the produced fluid can be monitored in real time to determine whether the released antiscalant can play an antiscaling role.

[0039] 2. After the squeezed scale inhibitor provided by the present invention is squeezed into the formation, the formation polymer is slowly dissolved, so that the internal scale inhibitor is slowly released into the formation, and the metal-scale inhibitor chelate enhances its adsorption performance in the formation through active divalent metal ions, thereby improving the retention performance of the scale inhibitor in the formation.

[0040] 3. The present invention improves the temperature resistance and adsorption capacity of the anti-scaling agent molecules in the formation, enhances the retention effect of the anti-scaling agent, can protect the entire well section, and at the same time meet the safety and environmental protection requirements, achieving the purpose of continuous release in the formation and long-term anti-scaling, providing technical support for stable production of oil wells.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other design solutions and drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 This is the molecular formula structure and cavity structure diagram of β-cyclodextrin.

[0044] Figure 2 This is a graph showing the results of measuring the minimum effective concentration (MIC value) of the squeeze scale inhibitor in Example 2.

[0045] Figure 3 It is the desorption curve of squeezing antiscalant with different concentrations.

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0047] The content of the present invention can be further understood by combining the following detailed description of the preferred implementation method of the present invention and the embodiments included. Unless otherwise specified, all technical and scientific terms used in this article have the same meaning as those of ordinary skill in the art to which the present invention belongs. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in the present invention, the definition of the term provided in the present invention shall prevail.

[0048] In a typical embodiment of the present application, a squeeze-in anti-scaling agent is provided, which comprises the following components by mass percentage: 20%-40% anti-scaling agent, 7%-25% non-ionic surfactant solution, 28%-50% β-cyclodextrin solution, 2%-8% metal cation solution, and 1%-3% fluorescent marker.

[0049] As a preferred embodiment, the scale inhibitor is an anionic polycarboxylic acid scale inhibitor.

[0050] A further preferred solution is that the anionic polycarboxylic acid scale inhibitor is an environmentally friendly polyacrylic acid scale inhibitor or a polymethacrylic acid scale inhibitor.

[0051] In a preferred embodiment of the present invention, the metal cation solution comprises a metal dissolved in an acid, and the acid comprises one or a mixture of acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, and nitric acid, and the metal comprises one or a mixture of zinc, calcium, magnesium, and aluminum.

[0052] In another preferred embodiment of the present invention, the metal cation solution comprises a metal salt dissolved in water, wherein the metal salt is one or a mixture of calcium salt, magnesium salt, manganese salt, nickel salt, aluminum salt and zinc salt.

[0053] In the present invention, metal cations and scale inhibitors rely on chemical construction to form a stable metal-scale inhibitor chelate, which further enhances the adsorption performance of the scale inhibitor in the reservoir.

[0054] As a further preferred embodiment, the nonionic surfactant solution is one of Pluronic (propylene glycol block polyether) F68 aqueous solution, Pluronic F88 aqueous solution or Pluronic F98 aqueous solution.

[0055] As a further preferred embodiment, the fluorescent marker is N-vinyl imidazole.

[0056] The present invention uses β-cyclodextrin as the main molecule (the molecular formula structure and cavity structure of β-cyclodextrin are as follows Figure 1 As shown), nonionic surfactants are guest molecules, and supramolecular self-assembly is carried out through host-guest molecule recognition under the action of hydrogen bonds, van der Waals forces, hydrophobic forces, etc. Figure 1Adjacent β-cyclodextrins are connected together by forming hydrogen bonds through the outer hydroxyl groups of the cavity. In the process of multilayer self-assembly, the fluorescently labeled metal-polymer antiscalant is wrapped inside the hollow microspheres, so that after the squeezed antiscalant is squeezed into the formation, the formation polymer is slowly dissolved, and then the internal antiscalant is slowly released into the formation. The metal-antiscalant chelate enhances its adsorption performance in the formation through active divalent metal ions, thereby improving the retention performance of the antiscalant in the formation. At the same time, by adding fluorescent markers to the metal-antiscalant chelate, the concentration of the antiscalant in the produced fluid can be monitored in real time to determine whether the released antiscalant can play an antiscaling role.

[0057] In a second typical embodiment of the present invention, a method for preparing a squeezing anti-scaling agent is provided, comprising the following steps:

[0058] S1. Preparation of metal-antiscalant chelates

[0059] The metal cation solution and the scale inhibitor are mixed in a mass ratio of 1:5-1:8 at a temperature of 50-70°C and a speed of 800-1200 r / min until they are fully mixed to form a stable metal-scale inhibitor chelate;

[0060] S2. Preparation of fluorescently labeled metal-antifouling agent chelates

[0061] Add water and the metal-antiscalant chelate prepared in step S1 to the reactor, raise the temperature to 80-90° C., and while stirring continuously, simultaneously drop a 20% aqueous solution of ammonium persulfate and a 3% aqueous solution of N-vinyl imidazole into the reactor. After the dropwise addition is completed, reflux the mixture at a constant temperature of 85-95° C. for 2-4 hours, cool the mixture to room temperature, and filter the mixture to obtain the fluorescently labeled metal-antiscalant chelate.

[0062] S3. Preparation of β-cyclodextrin solution

[0063] Dissolving β-cyclodextrin in water to prepare a β-cyclodextrin solution with a mass concentration of 2% to 3%;

[0064] S4. Preparation of nonionic surfactant solution

[0065] Dissolving a nonionic surfactant in water to prepare a nonionic surfactant solution with a mass concentration of 3% to 4%;

[0066] S5. Mix 200g-400g of fluorescent labeled metal-antiscalant chelate and 400-600mL of β-cyclodextrin solution to obtain mixed solution A, then add 100-300mL of non-ionic surfactant solution to the mixed solution A, stir at room temperature for 0.5-1.5h to obtain the target product.

[0067] As a further preferred embodiment, in step S2, the mass of the water is 3 times the mass of the metal-antiscalant chelate;

[0068] The mass of the ammonium persulfate aqueous solution is 0.02-0.04 times the mass of the metal-antiscalant chelate;

[0069] The mass of the N-vinylimidazole aqueous solution is 0.16-0.2 times the mass of the metal-antiscalant chelate.

[0070] As a further preferred embodiment, in step S2, the dropping time of the aqueous ammonium persulfate solution and the aqueous N-vinylimidazole solution should be controlled within 1.5-2.0 hours.

[0071] As a further preferred embodiment, the method for preparing the β-cyclodextrin solution is: dissolving 20-30 g of β-cyclodextrin in 1 L of water at 25° C.-30° C. to obtain a β-cyclodextrin solution with a mass concentration of 2%-3%.

[0072] As a further preferred embodiment, the method for preparing the non-ionic surfactant solution is: dissolving 30-40 g of the non-ionic surfactant in 1 L of water to prepare a non-ionic surfactant aqueous solution with a mass concentration of 3%-4%.

[0073] Preferably, in step S4, the nonionic surfactant is slowly added dropwise at a rate of 100 to 150 drops per minute.

[0074] In a third typical embodiment of the present invention, there is provided the use of any one of the above-mentioned squeezing anti-scaling agents or the squeezing anti-scaling agent prepared by the above-mentioned method in scaling of formations in downhole and near-wellbore areas.

[0075] The present invention will be further described below in conjunction with embodiments:

[0076] Example 1

[0077] This embodiment relates to a method for preparing a squeeze anti-scaling agent, comprising the following steps:

[0078] (1) Active divalent Zn 2+ The metal cation and the polyacrylic acid scale inhibitor are stirred and fully mixed in a high temperature and high pressure autoclave at a ratio of 1:6.5 at 60°C and a speed of 1000r / min. The metal cation and the scale inhibitor form a stable metal-scale inhibitor chelate by chemical construction.

[0079] (2) Add water and metal-scale inhibitor chelate to a reactor equipped with a reflux condenser and a thermometer, the mass of water is 3 times the mass of the metal-scale inhibitor chelate, and the temperature is raised to 85° C. Under constant stirring, use a dropping funnel to simultaneously drop a 20% ammonium persulfate aqueous solution and a 3% N-vinyl imidazole aqueous solution into the reactor, the mass of the ammonium persulfate aqueous solution is 0.04 times the mass of the metal-scale inhibitor chelate, and the mass of the N-vinyl imidazole aqueous solution is 0.2 times the mass of the metal-scale inhibitor chelate, and the dripping is controlled within 1.5-2.0 hours. After the dripping is completed, the reaction is refluxed at 85° C. for 4 hours, cooled to room temperature, and filtered to obtain a fluorescently labeled metal-polymer scale inhibitor;

[0080] (3) Prepare 1 L of 2.5% β-cyclodextrin solution;

[0081] (4) Prepare 1 L of 3.5% nonionic surfactant (Pluronic F68) solution;

[0082] (5) Weigh 300 g of the fluorescently labeled metal-antiscalant chelate prepared in (2) and 500 mL of β-cyclodextrin solution, stir them at room temperature 25°C for 30 min in a high-temperature autoclave, then slowly add 200 mL of non-ionic surfactant solution to the mixed solution of the metal-antiscalant chelate and β-cyclodextrin solution, and stir at room temperature 25°C for 1 h to obtain the target product.

[0083] Example 2

[0084] This embodiment relates to a method for preparing a squeeze anti-scaling agent, comprising the following steps:

[0085] (1) Active divalent Ca 2+ The metal cation and the polymethacrylic acid scale inhibitor are stirred and fully mixed in a synthesis reactor at a ratio of 1:5 at 60°C and a speed of 1000r / min. The metal cation and the scale inhibitor form a stable metal-scale inhibitor chelate by chemical construction;

[0086] (2) adding water and a metal-antiscalant chelate to a reactor equipped with a reflux condenser and a thermometer, wherein the mass of the water is 3 times the mass of the metal-antiscalant chelate, raising the temperature to 80° C., and under constant stirring, using a dropping funnel to simultaneously add a 20% ammonium persulfate aqueous solution and a 3% N-vinyl imidazole aqueous solution to the reactor, wherein the mass of the ammonium persulfate aqueous solution is 0.03 times the mass of the metal-antiscalant chelate, and the mass of the N-vinyl imidazole aqueous solution is 0.18 times the mass of the metal-antiscalant chelate, and the dripping is controlled within 1.5-2.0 hours. After the dripping is completed, the reaction is carried out at a constant temperature reflux reaction at 90° C. for 3 hours, cooled to room temperature, and filtered to obtain a fluorescently labeled metal-antiscalant chelate;

[0087] (3) Prepare 1 L of 2% β-cyclodextrin solution;

[0088] (4) Prepare 1 L of 3% nonionic surfactant (Pluronic F88) solution;

[0089] (5) Weigh 200 g of the metal-antiscalant chelate prepared in (2) and 400 mL of β-cyclodextrin solution, stir them at room temperature 25°C for 30 min in a high-temperature autoclave, then slowly add 100 mL of non-ionic surfactant solution to the mixed solution of the metal-antiscalant chelate and β-cyclodextrin solution, and stir at room temperature 25°C for 1 h to obtain the target product.

[0090] Example 3

[0091] This embodiment relates to a method for preparing a squeeze anti-scaling agent, comprising the following steps:

[0092] (1) Active divalent Mg 2+ The metal cation and the scale inhibitor are stirred and fully mixed in a synthesis reactor at a ratio of 1:8 at 60°C and a speed of 1000r / min. The metal cation and the scale inhibitor form a stable metal-scale inhibitor chelate by chemical construction;

[0093] (2) Add water and metal-antiscalant chelate to a reactor equipped with a reflux condenser and a thermometer, the mass of water being 3 times the mass of the metal-antiscalant chelate, raise the temperature to 90° C., and under constant stirring, use a dropping funnel to simultaneously add 20% ammonium persulfate aqueous solution and 3% N-vinyl imidazole aqueous solution to the reactor, the mass of the ammonium persulfate aqueous solution being 0.02 times the mass of the metal-antiscalant chelate, and the mass of the N-vinyl imidazole aqueous solution being 0.16 times the mass of the metal-antiscalant chelate, and control the dripping to be completed within 1.5-2.0 hours. After the dripping is completed, reflux at 95° C. for 2 hours, cool to room temperature, and filter to obtain the fluorescently labeled metal-antiscalant chelate;

[0094] (3) Prepare 1 L of 3% β-cyclodextrin solution;

[0095] (4) Prepare 1 L of 4% nonionic surfactant (Pluronic F98) solution;

[0096] (5) Weigh 400 g of the metal-antiscalant chelate prepared in (2) and 600 mL of β-cyclodextrin solution, stir them at room temperature 25°C for 30 min in a high-temperature autoclave, then slowly add 300 mL of non-ionic surfactant solution to the mixed solution of the metal-antiscalant chelate and β-cyclodextrin solution, and stir at room temperature 25°C for 1 h to obtain the target product.

[0097] The following performance tests were performed on the squeeze scale inhibitor obtained in Example 2:

[0098] 1. Determination of minimum effective concentration (MIC value)

[0099] The purpose of this test is to give the minimum concentration value for the antiscalant to take effect, and to provide a standard for real-time monitoring of the antiscalant in the produced fluid in the later stage. If the concentration is greater than this value, the antiscalant will continue to be effective. If the concentration is less than this value, the agent needs to be added in time. The test uses a fluorescently labeled metal-antiscalant chelate.

[0100] The experimental process is as follows:

[0101] The actual formation temperature of the simulated oil field (70°C) and the water quality parameters of the simulated injected water are shown in Table 1. The dynamic loop evaluation device is used to inject the simulated injected water anion solution (with different concentrations of 35 mg / L, 40 mg / L, 45 mg / L, and 50 mg / L of fluorescent labeled metal-antiscalant chelate) and cationic solution into the mixed pipeline at a slower rate of 1:1 from different pipelines using two constant flow pumps. The pressure changes at both ends of the mixed pipeline are recorded and observed with the help of pressure sensors. The increase in the pressure difference of the mixed pipeline indicates that scale has formed in the pipeline.

[0102] Table 1 Simulated injection water quality

[0103]

[0104] Before adding the anti-scaling agent, a set of blank tests is performed first, and then the anti-scaling agents with different mass concentrations from high to low are added to the anionic solution of the formation water, and then injected into the mixed pipeline with the cationic solution at a slower rate of 1:1 from different pipelines using two constant flow pumps. Generally, the concentration corresponding to the scaling time reaching 2.5 to 3 times of the blank time after adding a certain mass concentration of anti-scaling agent is taken as the MIC value of the anti-scaling agent (refer to Figure 2 ). The experimental results show that the minimum effective anti-scaling concentration is 45 mg / L.

[0105] 2. Dynamic adsorption / desorption evaluation

[0106] First, simulated formation water was injected into the core to saturate the core, and then a certain amount of brine was injected at a formation temperature of 70°C to pre-treat the reservoir core fracture. Table 2 reflects the actual permeability of the reservoir after on-site fracturing. Therefore, the core after fracture was selected for the dynamic adsorption and desorption experiment of the anti-scaling agent.

[0107] Table 2 Physical parameters of reservoir core after fracture creation

[0108]

[0109] Then, different concentrations of 50000mg / L and 100000mg / L squeezing anti-scaling agent solutions were pumped in. During the injection process, the mass concentration of the anti-scaling agent in the discharged liquid was recorded at different PV numbers (1PV, 2PV, 5PV, 8PV, 10PV, 12PV), and the relationship curve between the backflow mass concentration and the cumulative injection volume was made to detect the adsorption performance of the anti-scaling agent. When the mass concentration no longer changes, it can be considered that the adsorption amount of the anti-scaling agent in the core has reached saturation; stop the injection and simulate the well shut-in for 6 hours.

[0110] Finally, the injected aqueous solution was used to reversely displace the anti-scaling agent with different concentrations of 50000mg / L and 100000mg / L in the core, and the dynamic core displacement experimental device was used to simulate the production process. The anti-scaling agent mass concentration in the return solution was detected by fluorescence at any time, and the anti-scaling agent mass concentration in the discharged liquid under different PV numbers (0.5PV, 1PV, 2PV, 3PV, 5PV, 10PV, 20PV, 50PV, 100PV, 150PV, 200PV) was recorded. The relationship curve between the return mass concentration and the cumulative volume of the discharged liquid was drawn, such as Figure 3 As shown, the desorption performance of the antifouling agent was studied.

[0111] The results show that the concentration of the antiscalant drops very quickly in the early stage of flowback, and slowly drops in the later stage. The prepared squeeze antiscalant has better dynamic desorption performance and slow release. The concentration of the antiscalant is higher during the flowback process, and the effective antiscaling time is longer.

[0112] 3. Temperature resistance evaluation

[0113] A 50000 mg / L squeezed antiscalant solution was added to the formation water cationic solution (100 mL) and stirred thoroughly. The high temperature resistant container containing the experimental solution was placed in an insulated box and kept warm for 48 hours (the set temperatures were 70°C, 90°C, 110°C, 130°C, and 150°C, respectively). The solution was shaken and stirred 2-4 times in the middle. After the experiment was completed, the concentration of the antiscalant in the solution was detected by fluorescence method. The concentration change was used to determine whether the squeezed antiscalant had temperature resistance. The evaluation results are shown in Table 3.

[0114] From the results in Table 3, it can be seen that the temperature resistance is good and the release rate of the squeezed antiscalant is relatively stable.

[0115] Table 3 Temperature resistance evaluation results

[0116] Solution No. Temperature(℃) Antiscalant concentration (mg / L) 1 70 480 2 90 483 3 110 486 4 130 506 5 150 513

[0117] The above description is only a preferred embodiment of the present invention, which is merely illustrative of the present invention and does not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A squeeze scale inhibitor, characterized in that: The squeezing anti-scaling agent comprises the following components by mass percentage:

2. The squeezing anti-scaling agent according to claim 1, characterized in that: The scale inhibitor is an anionic polycarboxylic acid scale inhibitor, and the anionic polycarboxylic acid scale inhibitor is a polyacrylic acid scale inhibitor or a polymethacrylic acid scale inhibitor.

3. The squeezing anti-scaling agent according to claim 1, characterized in that: The nonionic surfactant solution is one of a Pluronic F68 aqueous solution, a Pluronic F88 aqueous solution or a Pluronic F98 aqueous solution.

4. The squeezing anti-scaling agent according to claim 1, characterized in that: The metal cation solution comprises a metal dissolved in an acid, wherein the acid comprises one or a mixture of acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, and nitric acid, and the metal comprises one or a mixture of zinc, calcium, magnesium, and aluminum.

5. The squeezing anti-scaling agent according to claim 1, characterized in that: The metal cation solution comprises a metal salt dissolved in water, wherein the metal salt is one or a mixture of calcium salt, magnesium salt, manganese salt, nickel salt, aluminum salt and zinc salt.

6. The squeezing anti-scaling agent according to claim 1, characterized in that: The fluorescent marker is N-vinyl imidazole.

7. A method for preparing a squeeze anti-scaling agent, characterized in that: The following steps are involved: S1. Preparation of metal-antiscalant chelates The metal cation solution and the scale inhibitor are mixed in a mass ratio of 1:5-1:8, at a temperature of 50-70°C and a speed of 800-1200 r / min until fully mixed to form a stable metal-scale inhibitor chelate; S2. Preparation of fluorescently labeled metal-antifouling agent chelates Add water and the metal-antiscalant chelate prepared in step S1 to the reactor, raise the temperature to 80-90° C., and simultaneously drop a 20% ammonium persulfate aqueous solution and a 3% N-vinyl imidazole aqueous solution into the reactor under continuous stirring, and control the dropping time to be within 1.5-2.0 h. After the dropping is completed, reflux at a constant temperature of 85-95° C. for 2-4 h, cool to room temperature, and filter to obtain the fluorescently labeled metal-antiscalant chelate; S3. Preparation of β-cyclodextrin solution Dissolving β-cyclodextrin in water to prepare a β-cyclodextrin solution with a mass concentration of 2%-3%; S4. Preparation of nonionic surfactant solution Dissolving a nonionic surfactant in water to prepare a nonionic surfactant aqueous solution with a mass concentration of 3% to 4%; S5. Mix 200g-400g of fluorescent labeled metal-antiscalant chelate and 400-600mL of β-cyclodextrin solution to obtain mixed solution A, then add 100-300mL of non-ionic surfactant solution to the mixed solution A, stir at room temperature for 0.5-1.5h to obtain the target product.

8. The method for preparing the squeezing anti-scaling agent according to claim 6, characterized in that: The method for preparing the β-cyclodextrin solution in step S3 is: dissolving 20-30 g of β-cyclodextrin in 1 L of water at 25° C.-30° C. to obtain a β-cyclodextrin solution with a mass concentration of 20%-30%; Step S4: The method for preparing the non-ionic surfactant solution is as follows: 30-40 g of the non-ionic surfactant is dissolved in 1 L of water to prepare a non-ionic surfactant aqueous solution with a mass concentration of 3%-4%.

9. The method for preparing the squeezing anti-scaling agent according to claim 6, characterized in that: In step S2, the mass of the water is 3 times the mass of the metal-antiscalant chelate; The mass of the ammonium persulfate aqueous solution is 0.02-0.04 times the mass of the metal-antiscalant chelate; The mass of the N-vinylimidazole aqueous solution is 0.16-0.2 times the mass of the metal-antiscalant chelate.

10. Use of the squeeze anti-scaling agent according to any one of claims 1 to 7 or the squeeze anti-scaling agent prepared by the preparation method according to any one of claims 8 to 9 in downhole near-wellbore areas and formation scaling.

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