Superfine degradable solid tracer agent for oil field logging and preparation method of superfine degradable solid tracer agent

Abstract

The invention discloses a superfine degradable solid tracer agent for oil field logging and a preparation method of the superfine degradable solid tracer agent. According to the method, a natural degradable biomass material is used as a raw material, and the degradable solid tracer agent with the particle size smaller than 100 micrometers is prepared through the steps of pretreatment, gamma-ray irradiation, enzymatic hydrolysis of polysaccharide hydrolase and saccharifying enzyme, freeze drying, radioisotope labeling, surface coating, antistatic treatment and the like. In the coating process, particles are coated with a hydrophobic coating solution, and then antistatic treatment is performed to improve the dispersity and stability of the particles. By optimizing the treatment process of the biomass material, the structural stability and processing adaptability of the tracer agent are enhanced, and the tracer agent is particularly suitable for oil field logging of low-permeability strata and heterogeneous strata. The tracer agent has a good radioactive labeling effect, particle size distribution and environmental protection characteristics, meets the measurement precision requirement in an oil field environment, can be naturally degraded after being used, and reduces negative effects on the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield logging and relates to the preparation of a radioactive isotope tracer, in particular to an ultrafine degradable solid tracer for oilfield logging and a preparation method thereof. Background Art

[0002] Oilfield logging is an important technical means in the process of oilfield development, which is used to obtain physical and chemical property data of underground formations. Through logging technology, the location and thickness of oil layers, gas layers and water layers can be determined, and the physical parameters of reservoirs such as porosity, permeability and oil saturation can be evaluated, thereby providing a scientific basis for oilfield development. Among them, radioactive isotope tracer logging technology is widely used in injection profile logging due to its high sensitivity and accuracy. The basic principle of this technology is to inject the tracer into the designated position of the oil well. The tracer is mixed with the injected water to form a stable suspension. The tracer moves with the water to the water-absorbing layer and accumulates on its surface. The radiation intensity of the radioactive isotope carried by the tracer is proportional to the amount of water absorbed. By detecting and calculating the radiation intensity of the radioactive isotope, the water absorption of each layer can be calculated, thereby judging the permeability of the formation and the effect of water injection.

[0003] At present, the radioactive isotope tracers commonly used in oilfield logging mainly include solid tracers and liquid tracers. Solid tracers are generally made of radioactive isotopes combined with solid carrier materials. Their advantages are strong adaptability, which can measure both vertical wells and horizontal wells, and can measure both slow-migrating underground fluids and fast-migrating ones. Liquid tracers are liquid radioactive isotope tracers dispersed in water, which flow with the water after release, and are logged using the related flow method.

[0004] However, there are still some urgent problems to be solved in the practical application of existing radioactive isotope tracers. First, the particle size of the tracer directly affects its sedimentation velocity and migration characteristics in water. The particle size of existing solid tracers is usually between 100-2000 μm. Tracers with larger particle sizes settle faster in the injected water and are difficult to reach the water-absorbing layer with the flow of injected water. Especially when measuring low-permeability layers with small pore diameters and severely heterogeneous formations, the particle size of the solid tracer does not match the formation pores, resulting in inaccurate logging results. In addition, larger tracers are prone to deposition on the injection well tubing and downhole tools, increasing the risk of equipment contamination and affecting the water injection effect.

[0005] Secondly, most of the existing tracers use chemical synthetic materials as carriers, which may produce harmful substances and pollute the environment during the preparation process. At the same time, the degradation performance of tracers in underground fluids is poor. If they exist underground for a long time, they may pollute groundwater resources and do not meet environmental protection requirements. It should also be pointed out that the existing tracer preparation process is complicated, requires multiple steps, has high production costs, and is difficult to apply on a large scale. In addition, there are technical difficulties in the radioactive isotope labeling process of tracers, and the operating conditions need to be strictly controlled to ensure the radioactivity and stability of the tracer, which increases the difficulty of preparation.

[0006] In summary, the existing radioisotope tracers for oilfield logging have many technical difficulties and challenges in terms of particle size control, material selection, preparation process, etc. Therefore, developing an oilfield logging tracer with smaller particle size, better performance and environmental protection requirements is a technical problem that needs to be solved urgently. Summary of the invention

[0007] 1. Purpose of the invention Aiming at the defects and shortcomings of the existing tracer used for oilfield logging, such as the large particle size, fast sedimentation speed, high risk of contamination of downhole tools, and inability to adapt to low permeability layers and serious heterogeneous formations, the present invention aims to provide an ultrafine degradable solid tracer for oilfield logging and a preparation method thereof, by using renewable biomass materials as raw materials, combined with γ Through processes such as irradiation, enzymatic reaction, radioactive labeling and fluidized coating, the tracer particle size can be miniaturized, and stability and antistatic performance can be improved, ensuring its excellent performance under special conditions such as low permeability layers, severely heterogeneous formations and small water outlets, while meeting environmental protection requirements and providing more reliable technical support for oilfield development.

[0008] (II) Technical solution In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions: The first object of the present invention is to provide a method for preparing an ultrafine degradable solid tracer for oilfield logging, which is used to prepare a radioactive isotope tracer with a small, uniform particle size and environmentally friendly degradable, and the method comprises at least the following preparation steps: SS1. Select natural biodegradable biomass materials, perform preliminary screening on the selected materials, wash them to remove surface impurities, dry them, and finally crush the dried materials; SS2. The initial biomass material particles obtained by pretreatment in step SS1 are sealed in a vacuum heat-sealed bag and no residual air is left in the bag. γ Carry out irradiation treatment in a ray irradiation device; SS3. The irradiated biomass material particles are mixed with a buffer solution having a pH value of 4.5-5.5 at a set mass ratio, and then the mixture is transferred to a constant temperature reactor and preheated at 35-65°C for 5-10 minutes, and then the pre-prepared polysaccharide hydrolase solution is slowly added and the saccharification enzyme solution is added after stirring evenly, and the reaction is continuously stirred at 35-65°C at a speed of 200-400 rpm for 0.5-4 hours; SS4. After the enzymatic hydrolysis reaction is completed, the biomass hydrolysate is filtered at room temperature and rinsed with deionized water, and then the washed product is placed in a freeze drying device for drying; SS5. Take an appropriate amount of freeze-dried biomass hydrolysate particles, soak them in a radioactive isotope solution according to a set volume ratio for 0.5-2 hours, then filter the soaked product at room temperature and dry it in a vacuum drying environment at 40-80°C for 6-8 hours; SS6. Place the labeled biomass hydrolysate particles in a fluidized coating device and coat the particles by spraying a hydrophobic coating solution. During the coating process, the spraying rate of the coating solution is controlled at 20-30 ml / min, the coating temperature is controlled at 30-60°C, and the relative humidity is maintained at 40-60%; SS7. After the hydrophobic coating is completed, the particles are treated with an antistatic agent solution for 20-40 minutes. The spraying rate of the solution is controlled at 10-15 ml / min and the temperature is controlled between 60-100°C. SS8. Screen the coated granular materials to select the ultra-fine particle size biodegradable solid tracer products that meet the requirements, ensuring that their particle size meets the requirements of oil field logging.

[0009] The second object of the present invention is to provide an ultrafine degradable solid tracer for oil field logging prepared based on the above method.

[0010] (III) Technical Effect Compared with the prior art, the ultrafine degradable solid tracer for oil field logging and the preparation method thereof of the present invention have the following beneficial and significant technical effects: (1) The present invention uses renewable biomass materials as raw materials, which significantly improves the environmental friendliness and sustainability of the tracer. Compared with traditional chemically synthesized tracers, the tracer prepared by this method can be naturally degraded after use, greatly reducing the risk of long-term pollution to groundwater and soil.

[0011] (2) The present invention is γRadiation pretreatment and enzymatic reactions of polysaccharide hydrolases and saccharifying enzymes improve the reaction efficiency and specific surface area of ​​raw material particles, and achieve fine control of tracer particle size. The final product has a particle size of less than 100 μm and a uniform particle size distribution, which improves the uniformity of tracer distribution on the surface of low permeability layers and heterogeneous formations, thereby improving the accuracy and pass rate of logging data.

[0012] (3) The present invention uses fluidized coating technology to perform hydrophobic coating and antistatic coating treatment, which greatly improves the dispersion and stability of the tracer. This not only helps the tracer to maintain a good dispersion state during the injection process and prevents the particles from aggregating or settling unevenly in the oil well, but also ensures that the tracer remains stable under complex formation conditions, thereby improving the reliability and consistency of logging data.

[0013] (4) The ultrafine degradable solid tracer prepared by the present invention is particularly suitable for logging needs in low permeability layers and heterogeneous formations. Due to its ultrafine particle size and excellent dispersibility, it can better match the tiny formation pores, provide more detailed and accurate formation information, and significantly improve the logging accuracy and resolution under complex geological conditions. In addition, the tracer prepared by the present invention has controllable degradability, and its residence time in the formation can be adjusted according to actual logging needs. This not only ensures sufficient logging cycles, but also avoids the impact of long-term residues on subsequent oil field development. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of a method for preparing an ultrafine degradable solid tracer for oil field logging.

[0015] Figure 2 Shown are SEM observation images of starch granules before and after enzymatic hydrolysis reaction, (a) is the starch granules before the reaction, and (b) is the starch granules after 2 hours of enzymatic hydrolysis reaction.

[0016] Figure 3 Shown is the logging results of traditional tracers in low permeability formation logging.

[0017] Figure 4 Shown is a diagram of the logging results of the tracer of the present invention in low permeability formation logging. DETAILED DESCRIPTION

[0018] The materials involved in the present invention include but are not limited to the materials in the following examples, and the preparation methods involved include but are not limited to the preparation methods used in the following examples. Unless otherwise defined, all professional and scientific terms used in the text have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. If there are no special instructions, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar to or equal to the recorded content can be applied to the method of the present invention.

[0019] The present invention aims to provide a method for preparing an ultrafine degradable solid tracer for oil field logging, by using renewable biomass materials as raw materials, combining γ Through processes such as irradiation, enzymatic reaction, radioactive labeling and fluidized coating, the tracer particle size can be miniaturized, and stability and antistatic performance can be improved, ensuring its excellent performance under special conditions such as low permeability layers, severely heterogeneous formations and small water outlets, while meeting environmental protection requirements and providing more reliable technical support for oilfield development. Example

[0020] As a specific example, Figure 1 As shown, the preparation method of the ultrafine degradable solid tracer for oil field logging of the present invention mainly comprises the following steps during implementation: SS1. Biomass material pretreatment Natural degradable biomass materials are selected, the selected materials are preliminarily screened, cleaned to remove surface impurities, then dried, and finally the dried materials are crushed.

[0021] Preferably, the natural degradable biomass material is selected from one or more of starch, cellulose, hemicellulose, and lignin; when drying the preliminarily screened biomass material particles, the drying temperature should be controlled at 40-60°C, and the moisture content of the material after drying should be reduced to below 10% to avoid agglomeration or deformation of the particles during subsequent crushing; when crushing the dried material, the initial particle size should be controlled between 50-200 μm, and a uniform particle size distribution should be ensured to provide higher reaction efficiency and stability for subsequent reactions and treatments.

[0022] SS2. γ Radiation treatment The initial biomass material particles obtained by pretreatment in step SS1 are sealed in a vacuum heat-sealed bag and no residual air is left in the bag. γ The irradiation treatment is carried out in a ray irradiation device.

[0023] As a preferred embodiment, during irradiation treatment, the irradiation dose should be controlled at 0.5-3 KGy, the irradiation environment temperature should be controlled at 10-30°C, and the irradiation time should be controlled at 1-3 hours to ensure that the molecular structure of the biomass material can be effectively changed and the activity of its subsequent hydrolysis reaction can be enhanced, while avoiding excessive degradation of the material or changes in physical properties, and ensuring the stability and repeatability of subsequent treatment.

[0024] SS3. Enzymatic hydrolysis The irradiated biomass material particles are mixed with a buffer solution with a pH value of 4.5-5.5 at a set mass ratio, and then the mixture is transferred to a constant temperature reactor and preheated at 35-65°C for 5-10 minutes, followed by slowly adding the pre-prepared polysaccharide hydrolase solution and adding the saccharification enzyme solution after stirring evenly, and continuously stirring the reaction at 35-65°C at a speed of 200-400rpm for 0.5-4 hours.

[0025] As a preferred embodiment, during the enzymatic hydrolysis reaction, disodium hydrogen phosphate-citric acid solution is selected as a buffer solution, the mass ratio of the irradiated biomass material particles to the buffer solution is controlled at 1:1-1:5, the mass ratio of the irradiated biomass material particles to the polysaccharide hydrolase and saccharification enzyme is controlled at between 100:1 and 1:1, and the pH value is continuously detected during the reaction and adjusted when necessary to maintain the pH value within the optimal range of 4.5-5.5, thereby ensuring the optimal activity of the enzyme and promoting the full hydrolysis of the biomass material to form a uniform and fine porous particle structure.

[0026] SS4. Filtration and freeze drying After the enzymatic hydrolysis reaction is completed, the biomass hydrolysate is filtered at room temperature and rinsed with deionized water, and then the washed product is placed in a freeze-drying device for drying.

[0027] Preferably, after the enzymatic hydrolysis reaction is completed, the biomass hydrolysate is filtered at room temperature and rinsed with deionized water at least 3 times to remove impurities generated in the reaction. Then, the washed product is placed in a freeze-drying device at -50°C to -20°C and dried for 12-24 hours to maintain the skeleton structure of the particles, prevent the particles from shrinking or collapsing, and reduce their water content.

[0028] SS5. Radioisotope labeling Take an appropriate amount of freeze-dried biomass hydrolysate particles, soak them in a radioactive isotope solution according to a set volume ratio for 0.5-2 hours, then filter the soaked product at room temperature and dry it in a vacuum drying environment at 40-80°C for 6-8 hours.

[0029] As a preferred method, Na 131I solution was used as radioisotope solution, and biomass hydrolysate particles were mixed with Na 131 The volume ratio of I solution is 5:1-1:2, and the biomass hydrolysate particles are in Na 131 During the soaking period of I solution, the room temperature should be maintained at 20-25°C and slightly stirred to ensure that the isotope is evenly attached to the surface of the particles. The soaked product is filtered at room temperature and vacuum dried at 40-80°C for 6-8 hours to fix the radioactive isotope and stably attach it to the surface of the hydrolyzate particles.

[0030] SS6. Hydrophobic coating treatment The labeled biomass hydrolysate particles are placed in a fluidized coating device and coated by spraying a hydrophobic coating solution. During the coating process, the spraying rate of the coating solution is controlled at 20-30 ml / min, the coating temperature is controlled at 30-60°C, and the relative humidity is maintained at 40-60%.

[0031] As a preferred embodiment, the labeled biomass hydrolysate particles are placed in a fluidized coating device, and a hydrophobic rosin ethanol solution is used as a coating material. The concentration of the rosin ethanol solution is 0.1%-1%, the spraying speed is controlled at 20-30ml / min, and the coating thickness is controlled between 2-5 microns to ensure that the surface of the particles is evenly coated with a hydrophobic layer; and during the coating process, the air flow rate should be adjusted to make the particles rise to 2 / 3 to 4 / 5 of the height of the coating pan to ensure that the particles are always in a uniform air flow during the coating process to prevent uneven coating or adhesion between particles; after completing the hydrophobic coating, the particles are dried in a fluidized coating device at 30-60°C for 15-30 minutes to remove the residual ethanol solution on the surface while maintaining the physical integrity and functional stability of the particles.

[0032] SS7. Antistatic coating treatment After the hydrophobic coating is completed, the particles are treated with an antistatic agent solution for 20-40 minutes, the spraying speed of the solution is controlled at 10-15 ml / min, and the temperature is controlled between 60-100°C.

[0033] As a preferred embodiment, the particles after the hydrophobic coating are placed in a fluidized bed device, and an antistatic agent solution is used for antistatic treatment, and 0.5%-1% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate is selected as the antistatic agent, and the mass ratio of the hydrophobic coated particles to the antistatic agent is controlled at 10000:1-100:1; during the antistatic treatment, the spraying speed of the antistatic agent solution is controlled to be 10-15 ml / min, the temperature is controlled to be between 60-100°C, and the treatment time is 20-40 minutes; after the antistatic coating is completed, the particles are dried in a fluidized coating device at 60-100°C for 15-30 minutes to ensure that the antistatic agent is evenly attached to the surface of the particles, and completely remove the moisture and solvent remaining on the surface, to ensure the stability and antistatic performance of the particles in use, while maintaining good fluidity and dispersibility.

[0034] SS8. Screening and finished product acquisition The coated granular material is screened to select the ultra-fine particle size degradable solid tracer finished product that meets the requirements, ensuring that its particle size meets the requirements of oil field logging.

[0035] As a preferred method, the particles that have been antistatically treated and dried are placed in a screening device for screening, and a screen with a mesh size of 10-100 microns is used for step-by-step screening to ensure that the particle size is controlled within a specific range; after the screening is completed, the finished product is quality tested to ensure that its particle size is uniform and has good dispersion, meets the application standards of oilfield logging, and meets the expected measurement accuracy and reliability requirements.

[0036] Through the above steps, the preparation method of the ultrafine degradable solid tracer for oilfield logging provided by the present invention can effectively solve the problems of excessively large tracer particle size, poor uniformity, insufficient environmental performance, etc. in the prior art, and prepare high-performance tracers suitable for various complex formation conditions, providing a new solution for oilfield logging.

[0037] Example 2 Based on the preparation method of the ultrafine degradable solid tracer for oil field logging provided in the above Example 1, as a more specific example, this example selects potato starch as the natural degradable biomass material, and operates strictly according to the specific preparation steps specified in Example 1: SS1. Biomass material pretreatment Potato starch was selected as the raw material. After preliminary screening, it was washed with deionized water three times to remove surface impurities. The washed potato starch was placed in an oven at 50°C and dried for 24 hours to reduce its moisture content to 8%. After drying, the potato starch particles were crushed to an initial particle size range of 50-100 microns using a grinding device, and its particle size distribution was ensured to be uniform to facilitate subsequent reactions and treatments.

[0038] SS2. γ Radiation treatment The pretreated potato starch granules were sealed in a vacuum heat-sealed bag to ensure that there was no residual air in the bag and then placed 60 Co γ The potato starch was irradiated in a X-ray irradiation device. The irradiation dose was set to 2 KGy, the irradiation environment temperature was 25°C, and the irradiation time was 2 hours. The molecular structure of potato starch was changed by irradiation treatment to enhance its subsequent hydrolysis reaction activity.

[0039] SS3. Enzymatic hydrolysis Prepare a sodium dihydrogen phosphate-citric acid buffer with a pH value of 5.0 and mix it with the irradiated potato starch granules at a mass ratio of 1:3. Transfer the mixture to a constant temperature reactor and preheat it at 50°C for 8 minutes. Then add the pre-prepared α-amylase solution (the mass ratio of potato starch to α-amylase is 50:1), stir well, and then add the saccharifying enzyme solution (the mass ratio of potato starch to saccharifying enzyme is 50:1). Stir the reaction at 50°C at a speed of 300rpm for 2 hours, during which the pH value is continuously monitored and maintained within the range of 5.0±0.2 to ensure sufficient hydrolysis of starch.

[0040] In order to verify the effect of the enzymatic hydrolysis reaction, SEM (scanning electron microscopy) observations were performed on the starch granules before and after the reaction. Figure 2 Scanning electron microscope (SEM) images of starch granules before and after enzymatic hydrolysis are shown, which can intuitively show the effect of hydrolysis on the surface structure of granules. Figure 2 As shown in (a), the surface of starch granules before hydrolysis is relatively smooth, with a distinct polygonal appearance and almost no pores or cracks on the surface. Figure 2 (b) shows that the surface of the starch granules has changed significantly, with obvious cracks and microporous structures. The surface of the granules has become rougher, showing a large number of holes, and the overall structure of the granules has also been damaged to a certain extent. This shows that enzymatic hydrolysis has successfully changed the structure of the starch granules, which is beneficial for subsequent radioactive labeling and coating treatment. In addition, the generation of these pores has greatly increased the specific surface area of ​​the granules, thereby improving their performance in oilfield logging, especially in low permeability formations.

[0041] SS4. Filtration and freeze drying After the reaction is completed, the hydrolyzate is filtered at room temperature and rinsed with deionized water for 3-5 times. The washed product is placed in a freeze drying device at -30°C and dried for 18 hours to maintain the skeleton structure of the particles and avoid collapse or deformation of the particles.

[0042] SS5. Radioisotope labeling Take 10g of freeze-dried hydrolyzate granules and place them in 20mL Na 131 I solution (activity 100 mCi / mL) for 1.5 hours, maintained at 23°C and stirred gently to ensure that Na 131 I was uniformly attached to the surface of starch particles. It was then filtered at room temperature and dried in a vacuum drying environment at 60°C for 7 hours to fix Na 131 I mark and ensure its stable attachment.

[0043] SS6. Hydrophobic coating treatment The marked particles were placed in a fluidized coating device and a 0.5% hydrophobic rosin ethanol solution was used as the coating material. During the coating process, the solution spray rate was 25 ml / min, the coating temperature was 45°C, and the relative humidity was 50%. The coating thickness was controlled at 3 microns, and the air flow rate was adjusted to make the particles rise to 3 / 4 of the height of the coating pan. After the coating was completed, it was dried at 45°C for 20 minutes.

[0044] In order to evaluate the coating effect, the contact angle test of the hydrolyzate particles before and after coating was carried out. The results showed that the contact angle of the particles before coating was 35°, which was a hydrophilic surface. After the hydrophobic coating treatment, the contact angle of the particles increased to 125°, showing obvious hydrophobicity, proving that the coating treatment successfully formed a hydrophobic layer on the surface of the particles.

[0045] SS7. Antistatic coating treatment After the hydrophobic coating is completed, an antistatic treatment is performed using a 0.8% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate solution for 30 minutes. The solution spray rate is 12 ml / min and the temperature is controlled at 80°C. The mass ratio of the hydrophobic coated particles to the antistatic agent is 1000:1. After the treatment is completed, dry at 80°C for 20 minutes.

[0046] In order to verify the effect of antistatic coating, the hydrolyzate particles before and after coating were tested for electrostatic charge. The results showed that the electrostatic charge of the particles before coating was -20 mV, while after antistatic coating, the electrostatic charge was reduced to -5 mV. This indicates that the antistatic coating successfully reduced the electrostatic repulsion of the particles, which is beneficial to the dispersion and stability of the particles in water.

[0047] SS8. Screening and finished product acquisition The dried granular material is placed in a screening device and screened using a 100-micron screen to ensure that the finished product particle size is less than 100 microns. The final product is tested for quality and has a uniform particle size distribution and good dispersion, meeting the application standards for oilfield logging.

[0048] Figure 3 The figure shows the results of oilfield logging using traditional tracers in low permeability formations. The logging results show that due to the large particle size of traditional tracers, the suspension of tracers in low permeability formations is poor, resulting in uneven distribution during the logging process. The tracers fail to diffuse effectively, and the logging results show more local deposition, which greatly reduces the measurement accuracy and effect.

[0049] Figure 4 The well logging results of the ultrafine degradable solid tracer prepared by the present invention in low permeability formations are shown. Compared with traditional tracers, the tracer of the present invention has a moderate particle size (less than 100 microns) and good suspension and fluidity, which enables it to diffuse evenly in low permeability formations and form a stable suspension. The tracer has both a release reaction and an accumulation reaction, and can be evenly distributed in the perforation layer. The logging results show that the radioactive signal intensity of the tracer matches well with the water absorption of the water-absorbing layer, and its distribution is highly consistent with the temperature curve and flow curve. This shows that the tracer of the present invention has significant technical advantages in complex formations and can effectively improve the logging accuracy and consistency of the results.

[0050] Table 1 Performance comparison between the tracer prepared by the present invention and the traditional tracer Test items Tracer prepared by the present invention Traditional tracers Particle size distribution (μm) 10-100 100-2000 Dispersibility(%) 98 95 Radioactive stability (%) 95 90 Table 1 shows the particle size distribution, dispersibility and radioactive labeling stability of the tracer of the present invention and its comparison with traditional tracers. As can be seen from Table 1, the tracer of the present invention has an obvious small particle size distribution (10-100 μm), and its particle size is significantly reduced compared with traditional tracers (100-2000 μm), which enables the tracer to better adapt to low permeability formations during oil field logging and ensure its effective diffusion under complex formation conditions. At the same time, the dispersibility of the tracer of the present invention is as high as 98%, which is better than traditional tracers, indicating that it can be more evenly distributed during use, reducing the possibility of sedimentation and clogging. In addition, the tracer of the present invention also has obvious advantages in radioactive stability, with a stability of 95%, which is better than 90% of traditional tracers, further verifying the significant technical advantages of the present invention in improving logging accuracy and consistency of results.

[0051] Through the above embodiments, the purpose of the present invention is fully and effectively achieved. Those skilled in the art can understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Although the present invention has been described with respect to the most practical and preferred embodiments currently considered, it should be understood that the present invention is not limited to the disclosed embodiments, and any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for preparing an ultrafine degradable solid tracer for oilfield logging, characterized in that: The method comprises at least the following preparation steps: SS1. Select natural biodegradable biomass materials, perform preliminary screening on the selected materials, wash them to remove surface impurities, dry them, and finally crush the dried materials; SS2. The initial biomass material particles obtained by pretreatment in step SS1 are sealed in a vacuum heat-sealed bag and no residual air is left in the bag. γ Irradiation treatment is carried out in a ray irradiation device; SS3. The irradiated biomass material particles are mixed with a buffer solution having a pH value of 4.5-5.5 at a set mass ratio, and then the mixture is transferred to a constant temperature reactor and preheated at 35-65°C for 5-10 minutes, and then the pre-prepared polysaccharide hydrolase solution is slowly added and the saccharification enzyme solution is added after stirring evenly, and the reaction is continuously stirred at 35-65°C at a speed of 200-400 rpm for 0.5-4 hours; SS4. After the enzymatic hydrolysis reaction is completed, the biomass hydrolysate is filtered at room temperature and rinsed with deionized water, and then the washed product is placed in a freeze drying device for drying; SS5. Take an appropriate amount of freeze-dried biomass hydrolysate particles, soak them in a radioactive isotope solution according to a set volume ratio for 0.5-2 hours, then filter the soaked product at room temperature and dry it in a vacuum drying environment at 40-80°C for 6-8 hours; SS6. Place the labeled biomass hydrolysate particles in a fluidized coating device and coat the particles by spraying a hydrophobic coating solution. During the coating process, the spraying rate of the coating solution is controlled at 20-30 ml / min, the coating temperature is controlled at 30-60°C, and the relative humidity is maintained at 40-60%; SS7. After the hydrophobic coating is completed, the particles are treated with an antistatic agent solution for 20-40 minutes. The spraying rate of the solution is controlled at 10-15 ml / min and the temperature is controlled between 60-100°C. SS8. Screen the coated granular materials to select the ultra-fine particle size biodegradable solid tracer products that meet the requirements, ensuring that their particle size meets the requirements of oil field logging.

2. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS1, the natural degradable biomass material is selected from one or more of starch, cellulose, hemicellulose, and lignin; when drying the preliminarily screened biomass material particles, the drying temperature should be controlled at 40-60°C, and the moisture content of the material after drying should be reduced to below 10% to avoid agglomeration or deformation of the particles during the subsequent crushing process; when crushing the dried material, the initial particle size should be controlled between 50-200 μm, and it should be ensured that it has a uniform particle size distribution to provide higher reaction efficiency and stability for subsequent reactions and treatments.

3. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS2, during the irradiation treatment, the irradiation dose should be controlled at 0.5-3 KGy, the irradiation environment temperature should be controlled at 10-30°C, and the irradiation time should be controlled at 1-3 hours to ensure that the molecular structure of the biomass material can be effectively changed and the activity of its subsequent hydrolysis reaction can be enhanced, while avoiding excessive degradation of the material or changes in physical properties, and ensuring the stability and repeatability of subsequent treatment.

4. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS3, during the enzymatic hydrolysis reaction, disodium hydrogen phosphate-citric acid solution is selected as a buffer solution, the mass ratio of the irradiated biomass material particles to the buffer solution is controlled at 1:1-1:5, the mass ratio of the irradiated biomass material particles to the polysaccharide hydrolase and saccharification enzyme is controlled between 100:1 and 1:1, and the pH value is continuously detected during the reaction and adjusted when necessary to maintain the pH value within the optimal range of 4.5-5.5, thereby ensuring the optimal activity of the enzyme and promoting the full hydrolysis of the biomass material to form a uniform and fine particle structure.

5. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS4, after the enzymatic hydrolysis reaction is completed, the biomass hydrolysate is filtered at room temperature and rinsed with deionized water at least 3 times to remove impurities generated in the reaction. Then, the washed product is placed in a freeze-drying device at -50°C to -20°C and dried for 12-24 hours to maintain the skeleton structure of the particles, prevent the particles from shrinking or collapsing, and reduce their water content.

6. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS5, select Na 131 I solution was used as radioisotope solution, and biomass hydrolysate particles were mixed with Na 131 The volume ratio of I solution is 5:1-1:2, and the biomass hydrolysate particles are in Na 131 During the soaking period of I solution, the room temperature should be maintained at 20-25°C and slightly stirred to ensure that the isotope is evenly attached to the surface of the particles. The soaked product is filtered at room temperature and vacuum dried at 40-80°C for 6-8 hours to fix the radioactive isotope and stably attach it to the surface of the hydrolyzate particles.

7. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS6, the labeled biomass hydrolysate particles are placed in a fluidized coating device, and a hydrophobic rosin ethanol solution is used as a coating material. The concentration of the rosin ethanol solution is 0.1%-1%, the spray speed is controlled at 20-30 ml / min, and the coating thickness is controlled between 2-5 microns to ensure that the surface of the particles is evenly coated with a hydrophobic layer; and during the coating process, the air flow rate should be adjusted to make the particles rise to 2 / 3 to 4 / 5 of the height of the coating pan to ensure that the particles are always in a uniform air flow during the coating process to prevent uneven coating or adhesion between particles; after completing the hydrophobic coating, the particles are dried in a fluidized coating device at 30-60°C for 15-30 minutes to remove residual ethanol on the surface while maintaining the physical integrity and functional stability of the particles.

8. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS7, the particles after the hydrophobic coating are placed in a fluidized bed device, and an antistatic agent solution is used for antistatic treatment, and 0.5%-1% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate is selected as the antistatic agent, and the mass ratio of the hydrophobic coated particles to the antistatic agent is controlled at 10000:1-100:1; during the antistatic treatment process, the spraying speed of the antistatic agent solution is controlled to be 10-15 ml / min, the temperature is controlled between 60-100°C, and the treatment time is 20-40 minutes; after the antistatic coating is completed, the particles are placed in a fluidized bed at 60-100°C and dried for 15-30 minutes to ensure that the antistatic agent is evenly attached to the surface of the particles, and completely remove the residual moisture and solvent on the surface, to ensure the stability and antistatic performance of the particles in use, while maintaining good fluidity and dispersibility.

9. The method for preparing the ultrafine degradable solid tracer for oil field logging according to claim 1, characterized in that: In the above step SS8, the particles that have been antistatically treated and dried are placed in a screening device for screening, and a screen with a mesh size of 10-100 microns is used for step-by-step screening to ensure that the particle size is controlled within a specific range; after the screening is completed, the finished product is quality inspected to ensure that its particle size is uniform and has good fluidity, meets the application standards of oilfield logging, and meets the expected measurement accuracy and reliability requirements.

10. An ultrafine degradable solid tracer for oilfield logging prepared by the method for preparing an ultrafine degradable solid tracer for oilfield logging according to any one of claims 1 to 9.

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