Magnetic logging tracer agent and preparation method and application thereof

Abstract

The invention discloses a magnetic well logging tracer agent and a preparation method and application thereof. The preparation method comprises the following steps that 1, 1-20 parts of an iron-cobalt-nickel magnetic material, 70-90 parts of light material powder and 1-10 parts of filler are added into a high-speed mixer according to the proportion to be mixed for use; weighing the mixture, adding the mixture into a mixing granulator, starting stirring, adding 5-30 parts of a binder solution, and continuing stirring until the magnetic microsphere particles grow to the required size; 2, spraying and adhering a low-density light material with strong adhesion to one end of the magnetic microsphere through a microsphere single-side exposure spraying technology, and fusing the low-density light material with the magnetic microsphere; and step 3, after the single-side exposure spraying of the microspheres, carrying out magnetization treatment on the magnetic microspheres in the single-side exposure spraying device of the microspheres. The technical problems that magnetic domains of magnetic microspheres in underground fluid are disordered and signals are mutually counteracted are effectively solved, the magnetic field signal intensity is amplified, the signal-to-noise ratio is improved, and real-time, high-precision and environment-friendly monitoring of oil and gas underground fluid migration is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield logging, and in particular to a magnetic tracer for oilfield water injection and liquid production profile monitoring, and a preparation method and application thereof. Background Art

[0002] During oilfield development, accurate monitoring of water injection and production profiles is crucial for understanding reservoir dynamics and optimizing recovery plans. Existing technologies for oilfield water injection development and production profile monitoring still have numerous shortcomings. Radioisotope water injection profile logging technology poses environmental risks. Mechanical limitations make turbine flowmeters difficult to start in low-fluid-volume horizontal wells (<50 m³ / d). They are also prone to plugging due to sand and polymer residue, impacting logging success rates. Well temperature logging can only qualitatively identify water-absorbing strata but cannot provide data on stratified water absorption. Furthermore, it is significantly affected by water injection from adjacent wells, resulting in a high rate of false positives. Chemical tracers are susceptible to adsorption or biodegradation by formation water, requiring complex pre-processing, which is time-consuming and costly. Fiber optic sensing technology requires customized downhole tools, and the high cost of single-well conversions limits its widespread adoption. Magnetic signals offer advantages such as strong penetration, low cost, and environmental friendliness, making them an important complement to existing technologies. Therefore, the development of a magnetic tracer and related technologies that can accurately monitor downhole fluid migration information is of great practical significance. Summary of the Invention

[0003] The present invention addresses the shortcomings of existing technologies by providing a magnetic well logging tracer, its preparation method, and its application. By adding a lightweight material to one end of the microspheres and using a specific device to align and magnetize the microspheres, the magnetic field's N-slope poles of all microspheres are aligned. Influenced by buoyancy, this innovative design achieves a uniform N-slope pole orientation for all magnetic microspheres during downhole fluid monitoring, amplifying the magnetic signal and improving the signal-to-noise ratio. This avoids the clutter and mutual cancellation of magnetic domains among the microspheres, which could affect monitoring effectiveness, significantly improving the sensitivity, accuracy, and precision of downhole fluid migration monitoring.

[0004] The technical solutions of the present invention are as follows: A method for preparing a magnetic logging tracer comprises the following steps: Step 1: 1-20 parts of iron-cobalt-nickel magnetic material, 70-90 parts of lightweight material powder, and 1-10 parts of filler are added to a high-speed mixer in proportion and mixed for later use; 100 parts of the mixture are weighed and added to a mixing granulator, stirring is started, 5-30 parts of the binder solution is added, and stirring is continued until the magnetic microsphere particles grow to the desired size; Step 2: Using the microsphere single-side exposure spraying technology, a low-density lightweight material with strong adhesion and cohesion is sprayed and adhered to one end of the magnetic microsphere, and integrated with the magnetic microsphere; Step 3: After the microspheres are sprayed on one side, the magnetic microspheres are magnetized in the microsphere spraying device so that the magnetic field of each magnetic microsphere is aligned under the action of an external magnetic field, and the magnetic field is directed toward the side of the magnetic microspheres on which the low-density lightweight material is sprayed; Step 4: Coating the carrier surface with resin glue, antistatic agent, heat-resistant agent, and surfactant, and drying; after the above coating treatment, the dispersibility can be improved, the specific gravity can be adjusted, and the adaptability to the underground environment can be enhanced.

[0005] The coated magnetic tracer is screened through liquid sorting to produce magnetic microspheres that can be suspended in the downhole fluid according to the downhole fluid density requirements of the oil field user.

[0006] In the method, in step 1, the particle size of the magnetic microspheres is 100-5000 μm, preferably 200-400 μm.

[0007] The method, in step 1, the sieving is placed in an oven and dried for 2 hours, and the drying temperature is 100-300°C.

[0008] In the method, in step 1, the lightweight material powder includes carbon powder, resin powder or floating beads. The filler includes calcium carbonate, kaolin, fiber, glass powder, etc.

[0009] In the method, in step 1, the binder is phenolic resin or epoxy resin.

[0010] In the method, in step 1, the specific gravity of the magnetic microspheres finally obtained is 1.0-1.08 g / cm³, and the specific gravity of the tracer is adjusted by adjusting the amount of lightweight material powder.

[0011] In the method, in step 2, the low-density lightweight material is SiO2 aerogel, boron nitride (BN), or polyimide.

[0012] The method described above, in step 2, the single-side exposure spraying method of the microspheres is: using a single-side exposure spraying device for microspheres, the device is divided into two layers, the upper layer is a cover plate with holes, and the lower layer is a bottom plate with pits, the magnetic microspheres are placed on the bottom plate with pits, and covered with a cover plate with holes, the top part of the magnetic microspheres is exposed outside the cover plate with holes, and the exposed part is less than half the diameter of the magnetic microspheres; a low-density lightweight material is plasma or atomized sprayed on the single-side exposed part of the magnetic microspheres, so that the low-density lightweight material is fused to one end of the magnetic microspheres.

[0013] A magnetic logging tracer prepared according to any of the methods described.

[0014] The application of the magnetic logging tracer comprises the following steps: Step 1: Magnetic microspheres are injected into the target layer fluid through a downhole release device, and they are synchronized with the downhole fluid. Due to the buoyancy, the low-density lightweight material end of all magnetic microspheres is uniformly facing upward, and the magnetic field direction of each microsphere is consistent and points to the lightweight material end; Step 2: In the vertical section of the injection or production well, a logging tool equipped with a magnetic sensor is lowered into the well using a cable to continuously track the magnetic tracer and record changes in magnetic field intensity. Alternatively, a magnetic sensor can be installed at a certain distance. After injecting the tracer, the downhole magnetic sensor and surface processing software can be immediately started to monitor the magnetic field changes in real time. The magnetic field strength can be recorded at regular intervals. When the peak of the magnetic field intensity is detected, it corresponds to the time when the tracer reaches the sensor, and the migration rate is calculated: rate = magnetic sensor spacing / time. Since the tubing diameter remains constant, the change in the fluid production profile rate can be used to map the oil-water production profile curves of different fractured layers downhole. The magnetic field intensity distribution of sensors at different depths is used to invert the water absorption or liquid production profile of each layer; when monitoring the water injection profile, the water absorption is inversely proportional to the magnetic field intensity; Step 3: Data acquisition and transmission: The magnetic field signal data collected by the sensor is collected in real time and transmitted to the ground monitoring system via cables or wireless transmission; Step 4: The ground monitoring system processes and analyzes the received data to obtain the vertical magnetic field intensity change curve in real time; uses wavelet transform to remove noise and sets abnormal warnings; Step 5: Data processing and inversion: Use algorithms to invert downhole fluid migration information, including flow rate, water absorption profile or liquid production profile; use numerical simulation and mathematical modeling methods to process and invert data to improve the accuracy of monitoring results.

[0015] The present invention has the following beneficial effects: Through the asymmetric structural design of microspheres and lightweight materials, a special magnetization process is used to ensure that the NS pole directions of all microspheres are consistent and point to the lightweight end, forming a cooperative magnetic matrix column; the buoyancy-magnetic moment coupling effect is used to make the microsphere group naturally maintain the same magnetic moment arrangement in the well, effectively solving the technical problems of chaotic magnetic domains and mutual cancellation of signals of magnetic microspheres in the well fluid, amplifying the magnetic field signal intensity, improving the signal-to-noise ratio, and realizing real-time, high-precision, and environmentally friendly monitoring of oil and gas well fluid migration, effectively solving the pain points of traditional tracers (chemical / radioactive) of "poor real-time performance and high environmental risks", and can be widely used in fluid migration monitoring, residual oil potential tapping, and water injection scheme optimization in water injection development oil fields. Magnetic tracers are non-radioactive and non-toxic. Compared with traditional tracers (chemical / radioactive) that have "poor real-time performance and high environmental risks", they enable real-time, high-precision, and environmentally friendly monitoring of fluid migration in oil and gas wells. They can be widely used in fluid migration monitoring, residual oil potential development, and water injection scheme optimization in water injection oilfields, providing key technical support for the efficient development of oil and gas fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a schematic structural diagram of the microsphere single-side exposed spraying device used in the present invention; Figure 3 The magnetic domain changes of magnetic materials before and after magnetization, a before magnetization, b after magnetization; 1. Tracer carrier; 2. Low-density material; 3. Magnetic material; 4. Coating layer; DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to specific embodiments.

[0018] refer to Figure 1 This embodiment provides a preparation method and application of a magnetic logging tracer, the specific steps of which are: Step 1: Add 4.5 parts of iron-cobalt-nickel magnetic material, lightweight material powder (including 50 parts of carbon powder, 20 parts of phenolic resin powder, and 20 parts of floating beads), and 5 parts of calcium carbonate as filler into a high-speed mixer in proportion and mix for 10 minutes, and set aside; weigh 100 parts of the mixture, add it to the Eirich mixer granulator, start stirring, add 10 parts of the binder solution (epoxy resin ethanol solution, concentration is 20%), continue stirring until the magnetic microsphere particles grow to 400 μm, sieve, and place them in an oven to dry for 2 hours, and the drying temperature is 180°C.

[0019] The final specific gravity of the obtained magnetic microspheres is 1.0-1.08 g / cm³. The specific gravity of the tracer can be adjusted by adjusting the amount of lightweight material powder.

[0020] Step 2: Use the microsphere single-side exposure spraying technology to spray and adhere a low-density lightweight material with strong adhesion and cohesion to one end of the magnetic microsphere and integrate it with the magnetic microsphere.

[0021] The low-density and lightweight materials are SiO2 aerogel, boron nitride (BN), and polyimide.

[0022] The microsphere single-side exposure spraying technology is as follows: Figure 2As shown, the device consists of two layers: an upper perforated cover plate and a lower recessed base plate. Magnetic microspheres are placed on the recessed base plate and covered with the perforated cover plate. The tops of the microspheres are exposed outside the perforated cover plate, with the exposed portion being less than half the diameter of the microspheres. A low-density, lightweight material is plasma- or atom-sprayed onto the exposed portion on one side of the magnetic microspheres, fusing the material to one end of the magnetic microspheres.

[0023] Step 3: After the microspheres are sprayed on one side, the magnetic microspheres are magnetized in the microsphere spraying device so that the magnetic field directions of the magnetic microspheres are consistent under the action of an external magnetic field, and the magnetic field direction is toward the side of the magnetic microspheres where the low-density lightweight material is sprayed.

[0024] The magnetic saturation intensity of the magnetic microspheres is ≥150 emu / g, ensuring detectability under weak magnetic fields.

[0025] Step 4: Coat the magnetic microspheres with resin glue, antistatic agent, heat-resistant agent, and surfactant, and then dry them. This coating treatment improves dispersibility, adjusts specific gravity, and enhances adaptability to underground environments.

[0026] For example: take 500g asymmetric magnetic microspheres, add 450ml resin glue, 1.2g antistatic agent, 500ml heat-resistant resin, 65ml surfactant, stir and dry at 85℃ and 25r / min for 6h.

[0027] The coated magnetic tracer is screened through liquid sorting to produce magnetic microspheres that can be suspended in the downhole fluid according to the downhole fluid density requirements of the oil field user.

[0028] Step 5: Magnetic microspheres (specific gravity 1.0-1.08 g / cm³) are injected into the target fluid zone via a downhole release device. These microspheres align with the downhole fluid. Buoyancy forces the low-density, lightweight end of each microsphere upward, aligning the magnetic field of each microsphere toward the lightweight end.

[0029] Step 6: In the vertical well section of the injection well or production well, a logging tool equipped with a magnetic sensor is lowered into the well using a cable to continuously track the magnetic tracer and record the changes in the magnetic field strength.

[0030] Alternatively, magnetic sensors can be installed at regular intervals (e.g., 50 meters). These sensors, such as fluxgate sensors (high sensitivity, suitable for weak magnetic fields) or giant magnetoresistive (GMR) sensors (small size, fast response), can be used. After tracer injection, the downhole magnetic sensors and surface processing software are immediately activated to monitor magnetic field changes in real time. The magnetic field strength is recorded at regular intervals, such as 10 minutes.

[0031] Giant magnetoresistance (GMR) sensors (such as NVE's AA002-02) are used, with a sensitivity of ≥1 nT and a response time of ≤1ms, making them suitable for monitoring weak magnetic fields (tracer magnetic field ≤100 nT). They are also small in size (2×2×0.5 mm) and easy to arrange in arrays.

[0032] When the peak magnetic field intensity is detected, it corresponds to the time when the tracer reaches the sensor, allowing the migration rate to be calculated: rate = magnetic sensor spacing / time. Since the tubing diameter remains constant, changes in the fluid production profile rate can be used to map the oil-water production profile curves for different fractured layers downhole.

[0033] The magnetic field intensity distribution of sensors at different depths can be used to invert the water absorption or liquid production profile of each layer. When monitoring the water injection profile, the water absorption is inversely proportional to the magnetic field intensity (high tracer concentration).

[0034] Shield the magnetic sensor: Wrap the sensor with a Permalloy shield (thickness ≥ 0.5 mm) to reduce the impact of the formation magnetic field (≤ 50,000 nT) and electromagnetic interference (≤ 100 nT) from downhole equipment (pumps, cables). At the same time, use digital filtering (such as wavelet transform) to remove noise during data processing.

[0035] Step 7: Data acquisition and transmission: The magnetic field signal data collected by the sensor is collected in real time and transmitted to the ground monitoring system via cables or wireless transmission.

[0036] Step 8: The ground monitoring system processes and analyzes the received data, obtaining a real-time curve of vertical magnetic field intensity changes. Wavelet transforms are used to remove noise and anomaly warnings are set, such as sudden changes in magnetic field peaks, indicating the arrival of the tracer.

[0037] Data processing and inversion: Specific algorithms are used to invert downhole fluid migration information, including flow rate, water absorption profile, or liquid production profile. Numerical simulation and mathematical modeling can be used to process and invert data to improve the accuracy of monitoring results.

[0038] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a magnetic logging tracer, characterized in that: The method comprises the following steps: step 1: adding 1-20 parts of iron-cobalt-nickel magnetic material, 70-90 parts of lightweight material powder, and 1-10 parts of filler to a high-speed mixer in proportion and mixing for later use; weighing 100 parts of the mixture, adding it to a mixing granulator, starting stirring, adding 5-30 parts of a binder solution, and continuing stirring until the magnetic microsphere particles grow to a desired size; step 2: using a microsphere single-side exposure spraying device to perform microsphere single-side exposure spraying, spraying and adhering a low-density lightweight material with strong adhesion and adhesiveness to one end of the magnetic microsphere through the microsphere single-side exposure spraying technology, and adhering it to the magnetic microsphere, and adhering it to the magnetic microsphere. The magnetic microspheres are integrated into one; step 3: after the microspheres are exposed and sprayed on one side, the magnetic microspheres are magnetized in the microsphere single-side exposure spraying device, so that the magnetic microspheres can achieve the purpose of consistent magnetic field directions under the action of an external magnetic field, and the magnetic field direction is toward the side of the magnetic microspheres sprayed with low-density lightweight material; step 4: coating the carrier surface with resin glue, antistatic agent, heat-resistant agent, and surfactant, and drying; the coated magnetic tracer is screened out by liquid sorting to obtain magnetic microspheres that can be suspended in the downhole fluid according to the downhole fluid specific gravity requirements of oil field users.

2. The method according to claim 1, characterized in that In the step 1, the particle size of the magnetic microspheres is 100-5000 μm, preferably 200-400 μm.

3. The method according to claim 1, characterized in that In the step 1, the sieved product is placed in an oven and dried for 2 hours, and the drying temperature is 100-300°C.

4. The method according to claim 1, wherein In step 1, the lightweight material powder includes one of carbon powder, resin powder, and floating beads, or any combination thereof; the filler includes one of calcium carbonate, kaolin, fiber, and glass powder, or any combination thereof.

5. The method according to claim 1, wherein In the step 1, the binder is phenolic resin or epoxy resin.

6. The method according to claim 1, characterized in that In step 1, the specific gravity of the magnetic microspheres finally obtained is 1.0-1.08 g / cm³, and the specific gravity of the tracer is adjusted by adjusting the amount of lightweight material powder.

7. The method according to claim 1, characterized in that In step 2, the low-density lightweight material is SiO2 aerogel, boron nitride (BN), or polyimide.

8. The method according to claim 1, characterized in that In step 2, the single-side exposure spraying method of the microspheres is as follows: a single-side exposure spraying device for microspheres is used, the device being divided into two layers, the upper layer being a cover plate with holes, and the lower layer being a bottom plate with pits, the magnetic microspheres being placed on the bottom plate with pits and covered with the cover plate with holes, the top portion of the magnetic microspheres being exposed outside the cover plate with holes, and the exposed portion being less than half the diameter of the magnetic microspheres; a low-density lightweight material being plasma or atomized sprayed on the single-side exposed portion of the magnetic microspheres, so that the low-density lightweight material is fused to one end of the magnetic microspheres.

9. A magnetic logging tracer prepared according to the method of any one of claims 1 to 8.

10. The use of the magnetic logging tracer according to claim 9, characterized in that: The method comprises the following steps: Step 1: Magnetic microspheres are injected into the target layer fluid through a downhole release device, and are synchronized with the downhole fluid; under the action of buoyancy, the low-density lightweight material ends of all magnetic microspheres are uniformly directed upward, and the magnetic field directions of each microsphere are consistent and point to the lightweight material end; Step 2: In the vertical well section of the water injection well or production well, a logging instrument equipped with a magnetic sensor is lowered into the well with a cable to continuously track the magnetic tracer and record the change in magnetic field intensity; or a magnetic sensor is installed at a certain interval, and after the tracer is injected, the downhole magnetic sensor and ground processing software are immediately started to monitor the magnetic field changes in real time; and the magnetic field intensity is recorded at regular intervals. When the peak value of the magnetic field intensity is detected, it corresponds to the time when the tracer reaches the sensor, and the migration rate is calculated: rate = magnetic sensor spacing / time; since the tubing diameter remains constant, the change in the production profile rate can be used to map the oil-water production profile curves of different fractured layers downhole; the magnetic field intensity distribution of sensors at different depths is used to invert the water absorption or production profile of each layer; when monitoring the water injection profile, the water absorption is inversely proportional to the magnetic field intensity; Step 3: Data acquisition and transmission: The magnetic field signal data collected by the sensor is collected in real time and transmitted to the ground monitoring system via cable or wireless transmission; Step 4: The ground monitoring system processes and analyzes the received data to obtain the vertical magnetic field intensity change curve in real time; wavelet transform is used to remove noise and set abnormal warnings; Step 5: Data processing and inversion: The migration information of the downhole fluid, including flow rate, water absorption profile or liquid production profile, is inverted through algorithms; numerical simulation and mathematical modeling methods are used to process and invert the data to improve the accuracy of the monitoring results.

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