Preparation method and application of magnetic nano tracer agent for tracing and monitoring oil gas well

Abstract

The invention relates to the technical field of oil gas well tracing monitoring, in particular to a preparation method and application of an oil gas well tracing monitoring magnetic nano tracer agent. Comprising the following steps: dissolving FeCl3, FeSO4. 7H2O and doped metal salt in water, and introducing N2 to remove oxygen; the initial reaction temperature is 85 DEG C, rapidly adding ammonia water, reacting to generate Fe3O4 nanoparticles, doping elements, reducing the temperature to 60 DEG C, and firstly adding sodium citrate for primary carboxyl modification; adding a mixed solution of oleic acid and PEG twice; the pH value of the reaction system is controlled to be 9.5-10.5 in the whole process. The method has the beneficial effects that the doping amount is remarkably increased, the doping amount of doped elements is multiple times of that in the prior art, and the detection sensitivity is remarkably improved; in addition, oleic acid / PEG composite modification is adopted instead of single citric acid modification, so that the tracer is kept stably dispersed in high-salinity formation water; the superparamagnetism facilitates magnetic separation and recovery, and is suitable for harsh formation conditions.

Description

Technical Field

[0001] This invention relates to the field of oil, gas and water well tracer monitoring technology, and in particular to a method for preparing and applying a magnetic nano-tracer for oil, gas and water well tracer monitoring. Background Technology

[0002] In oilfield extraction technology, traditional tracers such as fluorescent dyes and stable isotopes suffer from problems such as poor stability, limited quantity, and environmental pollution. Magnetic nanoparticles, as novel tracers, have advantages such as magnetic responsiveness, recyclability, and high stability. However, the doping amount of magnetic nanoparticle tracers in existing technologies is low, resulting in insufficient detection sensitivity, and their dispersion stability in highly salinized formation water is poor.

[0003] Chinese patent application number 202310183584.X, entitled "A Water-Based Magnetic Nanotracer and Its Preparation Method and Application," describes the synthesis of magnetic nanotracers doped with different metal elements using Fe3O4 as a matrix via a co-precipitation method. Surface modifiers with hydrophilic groups (e.g., trisodium citrate, ethylenediaminetetraacetic acid, ascorbic acid, etc.) are then added to the Fe3O4 matrix to construct a class of recyclable, sufficiently abundant water-based magnetic nanotracers. However, its problems include a doping ratio of 0.414%-4.466%, an emphasis on increasing the quantity and versatility of the tracer, a lack of adaptability to high mineralization environments, and a lack of specific optimization for high-mineralization environments.

[0004] Therefore, it is of great significance to develop a variety of magnetic nanotracers with high doping levels and high stability. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned deficiencies in existing technologies by providing a method for preparing and applying a magnetic nano-tracer for oil, gas, and water well tracking and monitoring. This magnetic nano-tracer features a wide variety of doped elements, high doping amounts, good dispersion stability in formation environments, and easy enrichment and detection. It overcomes the shortcomings of existing technologies, such as limited doping types, low doping amounts, insufficient detection sensitivity, easy aggregation and precipitation under high salinity conditions, and susceptibility to interference from formation ions.

[0006] The present invention discloses a method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring. The technical solution includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and doped metal salt in water at a molar ratio of iron ions to doped metal ions of 4:1-5:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, add ammonia water, react to generate Fe3O4 nanoparticles and dopants, stir the reaction for a period of time; Step 3: When the temperature drops to 60℃±1℃, sodium citrate is added for primary carboxyl modification. Step four: Add the mixture of oleic acid and polyethylene glycol in two separate additions, with a time interval between additions, to avoid competitive adsorption of the modifiers. Step 5: The pH of the reaction system is controlled between 9.5 and 10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol. The modified solution is then used to obtain the tracer solution.

[0007] Preferably, the doped metal salt mentioned above is LaCl3, which is dissolved in water at a Fe:La molar ratio of 4:1-5:1.

[0008] Preferably, the doped metal salt mentioned above is NdCl3, dissolved in water at a Fe:Nd molar ratio of 4:1-5:1.

[0009] Preferably, the doped metal salt mentioned above is ScCl3, which is dissolved in water at a Fe:Sc molar ratio of 4:1-5:1.

[0010] Preferably, the doped metal salt is MoCl6, dissolved in water at a Fe:Mo molar ratio of 4:1-5:1.

[0011] Preferably, in step four, oleic acid and polyethylene glycol are added in two portions at 20-minute intervals, with a mass ratio of 1:2.

[0012] Preferably, in step two, the stirring reaction time is 3 hours.

[0013] The present invention relates to the application of magnetic nano-tracers for oil, gas and water well tracking and monitoring, specifically the application of magnetic nano-tracer solutions for oil, gas and water well tracking and monitoring in segmented fracturing in oil and gas fields.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention significantly improves the doping amount, with the doping element reaching 10-15 wt%, which is a substantial improvement compared to previous technologies, thus significantly enhancing the detection sensitivity of ICP-MS. Furthermore, the use of oleic acid / polyethylene glycol (PEG) composite modification instead of single citric acid modification ensures that the tracer remains stably dispersed in formation water with a salinity of 200,000 mg / L for ≥24 hours. The superparamagnetic nature facilitates magnetic separation and recovery, resulting in a high recovery rate. Additionally, by optimizing the co-precipitation system and surface modification process, the present invention can be extended to trace doping of various lanthanide and transition metal elements, providing a richer fingerprint library for multi-well, multi-stage fracturing monitoring. Attached Figure Description

[0015] Figure 1 These are TEM images and particle size distribution diagrams of the tracers in Examples 1-3 of this invention; Figure 2This is a comparison chart of the dispersion stability of the tracers in Examples 1-4 of this invention in highly salinized water; Figure 3 This is a schematic diagram of the magnetic enrichment of the tracer in Embodiment 1 of the present invention: Figure 4 This is the dopant table of the present invention; Detailed Implementation

[0016] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0017] Example 1: A method for preparing a magnetic nano-tracer for oil, gas and water well tracking and monitoring, as mentioned in this invention, includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and the doped metal salt (LaCl3) in water at a Fe:La molar ratio of 4:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, ammonia water is added rapidly to generate Fe3O4 nanoparticles and dopants, accelerating nucleation, and the reaction time is stirred for 3 hours. Step 3: When the temperature drops to 60℃±1℃, add sodium citrate (0.5g) for primary carboxyl modification; Step four: Add the oleic acid / polyethylene glycol (PEG) mixture in two separate additions (20 minutes apart) to avoid competitive adsorption of the modifiers. The precise ratio of oleic acid to PEG is as follows: a composite modification of oleic acid (hydrophobic group) and PEG (hydrophilic group) is used, with the ratio optimized to 1:2 (mass ratio), that is, 0.1g of oleic acid and 0.2g of PEG are used per 100mg of nanoparticles. Step 5: The pH of the reaction system is controlled at 9.5~10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol (PEG). After modification, a stable tracer solution is obtained.

[0018] The magnetic nano-tracer solution for oil, gas and water well tracking and monitoring of the present invention is applied to the monitoring of staged fracturing in oil and gas fields.

[0019] Example 2, a method for preparing a magnetic nano-tracer for oil, gas and water well tracking and monitoring mentioned in this invention, includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and the doped metal salt (NdCl3) in water at a Fe:Nd molar ratio of 5:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, ammonia water is added rapidly to generate Fe3O4 nanoparticles and dopants, accelerating nucleation, and the reaction time is stirred for 3 hours. Step 3: When the temperature drops to 60℃±1℃, add sodium citrate (0.5g) for primary carboxyl modification; Step four: Add the oleic acid / polyethylene glycol (PEG) mixture in two separate additions (20 minutes apart) to avoid competitive adsorption of the modifiers. The precise ratio of oleic acid to PEG is as follows: a composite modification of oleic acid (hydrophobic group) and PEG (hydrophilic group) is used, with the ratio optimized to 1:2 (mass ratio), that is, 0.1g of oleic acid and 0.2g of PEG are used per 100mg of nanoparticles. Step 5: The pH of the reaction system is controlled at 9.5~10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol (PEG). After modification, a stable tracer solution is obtained.

[0020] The magnetic nano-tracer solution for oil, gas and water well tracking and monitoring of the present invention is applied to the monitoring of staged fracturing in oil and gas fields.

[0021] Example 3, a method for preparing a magnetic nano-tracer for oil, gas and water well tracking and monitoring mentioned in this invention, includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and doped metal salt (ScCl3) in water at a Fe:Sc molar ratio of 4.5:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, ammonia water is added rapidly to generate Fe3O4 nanoparticles and dopants, accelerating nucleation, and the reaction time is stirred for 3 hours. Step 3: When the temperature drops to 60℃±1℃, add sodium citrate (0.5g) for primary carboxyl modification; Step four: Add the oleic acid / polyethylene glycol (PEG) mixture in two separate additions (20 minutes apart) to avoid competitive adsorption of the modifiers. The precise ratio of oleic acid to PEG is as follows: a composite modification of oleic acid (hydrophobic group) and PEG (hydrophilic group) is used, with the ratio optimized to 1:2 (mass ratio), that is, 0.1g of oleic acid and 0.2g of PEG are used per 100mg of nanoparticles. Step 5: The pH of the reaction system is controlled at 9.5~10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol (PEG). After modification, a stable tracer solution is obtained.

[0022] The magnetic nano-tracer solution for oil, gas and water well tracking and monitoring of the present invention is applied to the monitoring of staged fracturing in oil and gas fields.

[0023] Example 4, a method for preparing a magnetic nano-tracer for oil, gas and water well tracking and monitoring mentioned in this invention, includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and the doped metal salt (MoCl6) in water at a Fe:Mo molar ratio of 4.7:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, ammonia water is added rapidly to generate Fe3O4 nanoparticles and dopants, accelerating nucleation, and the reaction time is stirred for 3 hours. Step 3: When the temperature drops to 60℃±1℃, add sodium citrate (0.5g) for primary carboxyl modification; Step four: Add the oleic acid / PEG mixture in two separate additions (20 minutes apart) to avoid competitive adsorption of the modifiers. The precise ratio of oleic acid to PEG is as follows: a composite modification of oleic acid (hydrophobic group) and PEG (hydrophilic group) is used, with the ratio optimized to 1:2 (mass ratio), that is, 0.1g of oleic acid and 0.2g of PEG are used per 100mg of nanoparticles. Step 5: The pH of the reaction system is controlled at 9.5~10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol (PEG). After modification, a stable tracer solution is obtained.

[0024] The magnetic nano-tracer solution for oil, gas and water well tracking and monitoring of the present invention is applied to the monitoring of staged fracturing in oil and gas fields.

[0025] The advantages of this invention are: 1. The doping amount of the doping element is as high as 10-15wt%, which is more than 10 times that of conventional methods, significantly improving the detection sensitivity of ICP-MS; 2. Oleic acid / polyethylene glycol (PEG) composite modification enables the tracer to maintain stable dispersion for ≥24 hours in formation water with a salinity of 200,000 mg / L; 3. Superparamagnetism facilitates magnetic separation and recovery, resulting in a high recovery rate.

[0026] in addition, Figure 1 These are electron microscope images and laser particle size distributions of the three nano-tracers synthesized in Examples 1-3, with particle size distributions ranging from 6 to 16 nm. Figure 2 The dispersion stability of the tracers in Examples 1-4 in highly salinized water was tested. No stratification or precipitation occurred when the tracers were dissolved in water with different salinities, indicating that the stability was excellent. Figure 3 The tracer can be attracted by a strong magnet, allowing for the magnetic enrichment of extremely low concentrations of tracer in later stages. (See reference...) Figure 4 This invention optimizes the co-precipitation system and surface modification process, and can be extended to trace doping of various lanthanide and transition metal elements, providing a richer fingerprint library for multi-well and multi-stage fracturing monitoring.

[0027] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a magnetic nano-tracer for oil, gas and water well tracking and monitoring, characterized in that: Includes the following steps: Step 1: Dissolve FeCl3, FeSO4·7H2O and doped metal salt in water at a molar ratio of iron ions to doped metal ions of 4:1-5:1, and then pass N2 through the solution to remove oxygen. Step 2: Initial reaction temperature 85℃±1℃, add ammonia water, react to generate Fe3O4 nanoparticles and dopants, stir the reaction for a period of time; Step 3: When the temperature drops to 60℃±1℃, sodium citrate is added for primary carboxyl modification. Step four: Add the mixture of oleic acid and polyethylene glycol in two separate additions, with a time interval between additions, to avoid competitive adsorption of the modifiers. Step 5: The pH of the reaction system is controlled between 9.5 and 10.5 throughout the process to avoid excessive alkalinity that could lead to the hydrolysis of polyethylene glycol. The modified solution is then used to obtain the tracer solution.

2. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 1, characterized in that: The doped metal salt is LaCl3, dissolved in water at a Fe:La molar ratio of 4:1-5:

1.

3. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 1, characterized in that: The doped metal salt is NdCl3, dissolved in water at a Fe:Nd molar ratio of 4:1-5:

1.

4. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 1, characterized in that: The doped metal salt is ScCl3, dissolved in water at a Fe:Sc molar ratio of 4:1-5:

1.

5. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 1, characterized in that: The doped metal salt is MoCl6, dissolved in water at a Fe:Mo molar ratio of 4:1-5:

1.

6. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 2, 3, 4 or 5, characterized in that: In step four, oleic acid and polyethylene glycol are mixed in a mass ratio of 1:2 and added in two portions, 20 minutes apart.

7. The method for preparing magnetic nano-tracers for oil, gas and water well tracking and monitoring according to claim 6, characterized in that: In step two, the stirring reaction time is 3 hours.

8. The application of the magnetic nano-tracer for oil, gas and water well tracking and monitoring according to claim 7, characterized in that: Magnetic nano-tracer solutions for oil, gas and water well tracking and monitoring are applied in segmented fracturing monitoring of oil and gas fields.

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