An ultra-fine degradable solid tracer for oilfield logging and its preparation method

Abstract

The present invention discloses an ultra-fine degradable solid tracer for oilfield logging and its preparation method. The method uses natural degradable biomass materials as raw materials, through pretreatment, γ γ-ray irradiation, enzymatic hydrolysis with polysaccharide hydrolase and saccharifying enzyme, freeze-drying, radioactive isotope labeling, surface coating and antistatic treatment and other steps, to prepare a degradable solid tracer with a particle size less than 100 microns. In the coating process, a hydrophobic coating solution is used to coat the particles, and then antistatic treatment is carried out to improve the dispersibility and stability of the particles. By optimizing the processing technology of biomass materials, the present invention enhances the structural stability and processing adaptability of the tracer, and is especially suitable for oilfield logging in low-permeability formations and heterogeneous formations. The tracer has good radioactive labeling effect, particle size distribution and environmental protection characteristics, and at the same time meets the measurement accuracy requirements in the oilfield environment, and can be naturally degraded after use, reducing the negative impact on the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield logging, and relates to the preparation of radioactive isotope tracers. Specifically, it is an ultra-fine degradable solid tracer for oilfield logging and its preparation method. Background Technique

[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 positions and thicknesses of oil layers, gas layers and water layers can be determined, and the physical property parameters of reservoirs such as porosity, permeability and oil saturation can be evaluated, so as to provide 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 a specified 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 reach the water absorption layer and filters on its surface. The radiation intensity of the radioactive isotope carried by the tracer is proportional to the water absorption volume. By detecting and calculating the radiation intensity of the radioactive isotope, the water absorption conditions of each layer can be calculated, so as to judge the permeability of the formation and the water injection effect.

[0003] At present, the radioactive isotope tracers commonly used in oilfield logging mainly include solid tracers and liquid tracers. Solid tracers are generally made by combining radioactive isotopes with solid carrier materials. Its advantages are strong adaptability, that is, it can measure both vertical wells and horizontal wells, and can measure underground fluids with slow migration speeds and those with fast speeds. Liquid tracers are to disperse liquid radioactive isotope tracers in water, and after release, they flow with the water to log by relevant flow methods.

[0004] However, there are still some problems to be solved urgently in the actual application of existing radioactive isotope tracers. First of all, the particle size of the tracer directly affects its sedimentation speed and migration characteristics in water. The particle size of existing solid tracers is usually between 100 - 2000 μm. The tracer with a larger particle size has a faster sedimentation speed in the injected water and is difficult to reach the water absorption layer with the injected water flow. 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 deposit on the injection well string 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

[0008] 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.

[0009] (II) Technical solution

[0010] In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions:

[0011] 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:

[0012] 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;

[0013] SS2. Seal the initial biomass material particles obtained after pre-treatment in step SS1 in a vacuum heat-sealed bag and ensure there is no residual air in the bag, and then place it in γ a ray irradiation device for irradiation treatment;

[0014] SS3. Mix the irradiated biomass material particles with a buffer solution with a pH value of 4.5 - 5.5 according to a set mass ratio, then transfer the mixture to a constant temperature reactor and preheat it at 35 - 65 °C for 5 - 10 minutes. Subsequently, slowly add the pre-prepared polysaccharide hydrolase solution, and then add the saccharifying enzyme solution after stirring evenly, and continuously stir and react at 35 - 65 °C at a speed of 200 - 400 rpm for 0.5 - 4 hours;

[0015] SS4. After the enzymatic hydrolysis reaction ends, filter the biomass hydrolysis product at room temperature and rinse it with deionized water, and then place the washed product in a freeze-drying device for drying treatment;

[0016] SS5. Take an appropriate amount of freeze-dried biomass hydrolysis product 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;

[0017] SS6. Place the labeled biomass hydrolysis product particles in a fluidized bed coating device and coat the particles by spraying a hydrophobic coating solution. During the coating process, control the spraying speed of the coating solution at 20 - 30 ml / min, the coating temperature at 30 - 60 °C, and the relative humidity at 40 - 60%;

[0018] SS7. After completing the hydrophobic coating, use an antistatic agent solution to perform antistatic treatment on the particles for 20 - 40 minutes, control the spraying speed of the solution at 10 - 15 ml / min, and the temperature at 60 - 100 °C;

[0019] SS8. Screen the coated particle material to select the finished product of the ultra-fine particle size degradable solid tracer that meets the requirements, and ensure that its particle size meets the requirements of oilfield logging.

[0020] The second object of the present invention is to provide an ultra-fine degradable solid tracer for oilfield logging prepared based on the above method.

[0021] (III) Technical effects

[0022] Compared with the prior art, the ultra-fine degradable solid tracer for oilfield logging and its preparation method of the present invention have the following beneficial and remarkable technical effects:

[0023] (1) The present invention uses renewable biomass materials as raw materials, significantly improving the environmental friendliness and sustainability of the tracer. Compared with traditional chemically synthesized tracers, the tracer prepared by this method can naturally degrade after use, greatly reducing the long-term pollution risk to groundwater and soil.

[0024] (2) The present invention improves the reaction efficiency and the specific surface area of raw material particles through γ ray irradiation pretreatment and enzymatic reactions of polysaccharide hydrolase and saccharifying enzyme, realizing fine control of the particle size of the tracer. The particle size of the final product is less than 100 μm, and the particle size distribution is uniform, improving the distribution uniformity of the tracer on the surface of low-permeability layers and heterogeneous formations, thereby enhancing the accuracy and qualification rate of logging data.

[0025] (3) The present invention uses fluidized bed coating technology for hydrophobic coating and antistatic coating treatment, greatly improving the dispersibility and stability of the tracer. This not only helps the tracer maintain a good dispersed state during injection, preventing problems such as particle aggregation or uneven settlement in the oil well, but also ensures the stability of the tracer under complex formation conditions, improving the reliability and consistency of logging data.

[0026] (4) The ultra-fine degradable solid tracer prepared by the present invention is particularly suitable for the logging requirements of low-permeability layers and heterogeneous formations. Due to its ultra-fine particle size and excellent dispersibility, it can better match the tiny formation pores, providing more detailed and accurate formation information, significantly improving the logging accuracy and resolution under complex geological conditions. In addition, the tracer prepared by the present invention has controllable degradability, and its retention time in the formation can be adjusted according to actual logging requirements. This not only ensures an adequate logging cycle but also avoids the impact of long-term residues on subsequent oilfield development. Description of the Drawings

[0027] Figure 1 is a flow chart of the preparation method of the ultra-fine degradable solid tracer for oilfield logging of the present invention.

[0028] Figure 2 The SEM observation diagrams of starch particles before and after the enzymatic hydrolysis reaction are shown. (a) is the starch particle before the reaction, and (b) is the starch particle after 2 hours of enzymatic hydrolysis reaction.

[0029] Figure 3 The logging result diagram of the traditional tracer in low-permeability formation logging is shown.

[0030] Figure 4 The logging result diagram of the tracer of the present invention in low-permeability formation logging is shown. Detailed Embodiments

[0031] The materials involved in the present invention include, but are not limited to, the materials in the following embodiments, 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 herein have the same meaning as those familiar to persons skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or in accordance with the product instructions. In addition, any methods and materials similar or equivalent to the recorded content can be applied to the method of the present invention.

[0032] The present invention aims to provide a preparation method of an ultra-fine degradable solid tracer for oilfield logging. By using renewable biomass materials as raw materials and combining γ processes such as ray irradiation, enzymatic hydrolysis reaction, radioactive labeling, and fluidized coating, the particle size of the tracer is reduced, and its stability and antistatic performance are improved, ensuring its excellent performance under special conditions such as low-permeability layers, severely heterogeneous formations, and small water outlets. At the same time, it meets the environmental protection requirements and provides more reliable technical support for oilfield development. Examples

[0033] As a specific example, as Figure 1 shown, the preparation method of the ultra-fine degradable solid tracer for oilfield logging of the present invention mainly includes the following steps during implementation:

[0034] SS1. Pretreatment of biomass materials

[0035] Select natural degradable biomass materials. After preliminary screening of the selected materials, clean them to remove surface impurities, then perform a drying treatment, and finally crush the dried materials.

[0036] As a preference, the natural degradable biomass materials are selected from one or more of starch, cellulose, hemicellulose, and lignin; when drying the preliminarily screened biomass material particles, it should be ensured that the drying temperature is controlled at 40-60 °C, and the moisture content of the dried materials is reduced to less than 10% to avoid caking or deformation of the particles during subsequent crushing; when crushing the dried materials, the initial particle size should be controlled between 50-200 μm, and it should be ensured that they have a uniform particle size distribution to provide higher reaction efficiency and stability for subsequent reactions and treatments.

[0037] SS2. γ Ray irradiation treatment

[0038] Seal the initial biomass material particles obtained by the pretreatment in step SS1 in a vacuum heat-sealed bag and ensure that there is no residual air in the bag, and then place them in γ a ray irradiation device for irradiation treatment.

[0039] As a preference, during the irradiation treatment, the irradiation dose should be controlled within 0.5 - 3 KGy, the irradiation ambient temperature should be controlled within 10 - 30 °C, and the irradiation time should be controlled within 1 - 3 hours, so as to ensure that the molecular structure of the biomass material can be effectively changed, enhance the activity of its subsequent hydrolysis reaction, and at the same time avoid excessive degradation of the material or change of physical properties, and ensure the stability and repeatability of subsequent treatment.

[0040] SS3. Enzymatic hydrolysis reaction

[0041] Mix the irradiated biomass material particles with a buffer solution with a pH value of 4.5 - 5.5 according to a set mass ratio, then transfer the mixture to a constant-temperature reactor and preheat it at 35 - 65 °C for 5 - 10 minutes. Subsequently, slowly add the pre-prepared polysaccharide hydrolase solution, and then add the glucoamylase solution after stirring evenly, and continuously stir and react at 35 - 65 °C at a speed of 200 - 400 rpm for 0.5 - 4 hours.

[0042] As a preference, during the enzymatic hydrolysis reaction, choose the disodium hydrogen phosphate - citric acid solution as the buffer solution. The mass ratio of the irradiated biomass material particles to the buffer solution is controlled within 1:1 - 1:5, and the mass ratio of the irradiated biomass material particles to the polysaccharide hydrolase and glucoamylase is controlled between 100:1 and 1:1. And continuously detect the pH value during the reaction and adjust it when necessary to maintain the pH value within the optimal range of 4.5 - 5.5, so as to ensure the best activity of the enzyme and promote the full hydrolysis of the biomass material to form a uniform and fine porous particle structure.

[0043] SS4. Filtration and freeze-drying treatment

[0044] After the enzymatic hydrolysis reaction ends, filter the biomass hydrolysis product at room temperature and rinse it with deionized water, and then place the washed product in a freeze-drying device for drying treatment.

[0045] As a preference, after the enzymatic hydrolysis reaction ends, filter the biomass hydrolysis product at room temperature and rinse it with deionized water at least 3 times to remove the impurities generated during the reaction. Then, place the washed product in a freeze-drying device at -50 °C to -20 °C for drying for 12 - 24 hours to maintain the skeletal structure of the particles, prevent the particles from shrinking or collapsing, and at the same time reduce its water content.

[0046] SS5. Radioisotope labeling

[0047] Take an appropriate amount of freeze-dried biomass hydrolysis product particles, soak them in a radioactive isotope solution for 0.5 - 2 hours according to a set volume ratio, and then filter the soaked product at room temperature and dry it in a vacuum drying environment at 40 - 80 °C for 6 - 8 hours.

[0048] As a preference, select Na 131 I solution as the radioactive isotope solution, and the volume ratio of the biomass hydrolysis product particles to the Na 131 I solution is 5:1 - 1:2. During the soaking of the biomass hydrolysis product particles in the Na 131 I solution, the room temperature should be maintained at 20 - 25 °C and gently stirred to ensure that the isotope adheres evenly to the particle surface. After soaking, the product is filtered at room temperature and vacuum-dried at 40 - 80 °C for 6 - 8 hours to fix the radioactive isotope and make it stably adhere to the surface of the hydrolysis product particles.

[0049] SS6. Hydrophobic coating treatment

[0050] Place the labeled biomass hydrolysis product particles in a fluidized bed coating device, and coat the particles by spraying a hydrophobic coating solution. During the coating process, control the spraying speed of the coating solution at 20 - 30 ml / min, the coating temperature at 30 - 60 °C, and the relative humidity at 40 - 60%.

[0051] As a preference, place the labeled biomass hydrolysis product particles in a fluidized bed coating device, use a hydrophobic rosin ethanol solution as the coating material, with the concentration of the rosin ethanol solution being 0.1% - 1%, control the spraying speed at 20 - 30 ml / min, and control the coating thickness between 2 - 5 microns to ensure that the particle surface is evenly coated with a hydrophobic layer; and during the coating process, adjust the air flow speed 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, preventing uneven coating or adhesion between particles; after completing the hydrophobic coating, dry the particles in the fluidized bed 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.

[0052] SS7. Antistatic coating treatment

[0053] After completing the hydrophobic coating, conduct antistatic treatment on the particles with an antistatic agent solution for 20 - 40 minutes, control the spraying speed of the solution at 10 - 15 ml / min, and control the temperature between 60 - 100 °C.

[0054] As a preference, the particles after hydrophobic coating treatment are placed in a fluidized bed equipment and antistatic treatment is carried out using an antistatic agent solution. Octadecyl dimethyl hydroxyethyl ammonium nitrate with a concentration of 0.5% - 1% 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 at 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 dried in a fluidized coating equipment at 60 - 100 °C for 15 - 30 minutes to ensure that the antistatic agent is evenly attached to the particle surface and the residual moisture and solvent on the surface are completely removed, ensuring the stability and antistatic performance of the particles during use, while maintaining good fluidity and dispersibility.

[0055] SS8. Screening and finished product obtaining

[0056] The coated particle material is screened to obtain the finished product of the ultrafine particle size degradable solid tracer that meets the requirements, ensuring that its particle size meets the requirements of oilfield logging.

[0057] As a preference, the particles after antistatic treatment and drying are placed in a screening equipment for screening, and a sieve 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 screening, quality inspection is carried out on the finished product to ensure that its particle size is uniform, the dispersibility is good, it meets the application standards of oilfield logging, and meets the requirements of expected measurement accuracy and reliability.

[0058] 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 too large particle size, poor uniformity, and insufficient environmental protection performance in the prior art, and prepare a high - performance tracer suitable for various complex formation conditions, providing a new solution for oilfield logging.

[0059] Example 2

[0060] On the basis of the preparation method of the ultrafine degradable solid tracer for oilfield logging provided in the above Example 1, as a more specific example, this example selects potato starch as the natural degradable biomass material and strictly operates according to each specific preparation step defined in Example 1:

[0061] SS1. Pretreatment of biomass material

[0062] Potato starch was selected as the raw material. After preliminary screening, it was washed 3 times with deionized water 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, a grinding device was used to crush the potato starch granules to an initial particle size range of 50 - 100 microns, and ensure that its particle size distribution was uniform to facilitate subsequent reactions and processing.

[0063] SS2. γ Gamma irradiation treatment

[0064] 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 in 60 Co γ a gamma irradiation device for irradiation treatment. The irradiation dose was set at 2 KGy, the irradiation ambient temperature was 25 °C, and the irradiation time was 2 hours. The molecular structure of the potato starch was changed through irradiation treatment to enhance its activity in subsequent hydrolysis reactions.

[0065] SS3. Enzymatic hydrolysis reaction

[0066] A disodium hydrogen phosphate-citric acid buffer solution with a pH value of 5.0 was prepared and mixed with the irradiated potato starch granules at a mass ratio of 1:3. The mixture was transferred to a thermostatic reactor and preheated at 50 °C for 8 minutes. Subsequently, a pre-prepared α-amylase solution (the mass ratio of potato starch to α-amylase was 50:1) was added. After stirring evenly, a glucoamylase solution (the mass ratio of potato starch to glucoamylase was 50:1) was added. The reaction was continuously stirred at 50 °C at a speed of 300 rpm for 2 hours, and the pH value was continuously monitored and maintained within the range of 5.0 ± 0.2 to ensure the full hydrolysis of the starch.

[0067] To verify the effect of the enzymatic hydrolysis reaction, SEM (scanning electron microscopy) observations were made on the starch granules before and after the reaction. Figure 2 The scanning electron microscopy (SEM) images of the starch granules before and after the enzymatic hydrolysis reaction are shown, which can visually show the impact of the hydrolysis reaction on the surface structure of the granules. As Figure 2 shown in (a) below, the surface of the starch granules before hydrolysis was relatively smooth, with an obvious polygonal appearance and almost no pores or cracks on the surface. After 2 hours of enzymatic hydrolysis reaction (as Figure 2As shown in Figure 2(b), significant changes occurred on the surface of the starch granules, with obvious cracks and microporous structures appearing. The surface of the granules became rougher, showing a large number of pores, and the overall structure of the granules was also damaged to a certain extent. This indicates that enzymatic hydrolysis successfully changed the structure of the starch granules, which is beneficial for subsequent radiolabeling and coating treatments. In addition, the generation of these pores significantly increased the specific surface area of the granules, thus improving their performance in oilfield logging, especially in low-permeability formations.

[0068] SS4. Filtration and Freeze-Drying Treatment

[0069] After the reaction ended, the hydrolysis product was filtered at room temperature and rinsed 3 - 5 times with deionized water. The washed product was placed in a freeze-drying device at -30°C and dried for 18 hours to maintain the skeletal structure of the granules and avoid collapse or deformation of the granules.

[0070] SS5. Radioisotope Labeling

[0071] Take 10 g of the freeze-dried hydrolysis product granules and place them in 20 mL of Na 131 I solution (activity is 100 mCi / mL) and soak for 1.5 hours. During this period, maintain the room temperature at 23°C and stir gently to ensure that Na 131 I attaches evenly to the surface of the starch granules. Then filter at room temperature and dry in a vacuum drying environment at 60°C for 7 hours to fix the Na 131 I labeling and ensure its stable attachment.

[0072] SS6. Hydrophobic Coating Treatment

[0073] Place the labeled granules in a fluidized bed coating device and use a 0.5% hydrophobic rosin ethanol solution as the coating material. During the coating process, the solution spraying speed is 25 ml / min, the coating temperature is 45°C, and the relative humidity is 50%. The coating thickness is controlled at 3 microns, and the air flow rate is adjusted to make the granules rise to 3 / 4 of the height of the coating pan. After the coating is completed, dry in an environment at 45°C for 20 minutes.

[0074] To evaluate the coating effect, a contact angle test was conducted on the hydrolysis product granules before and after coating. The results showed that the contact angle of the granules before coating was 35°, belonging to a hydrophilic surface. After the hydrophobic coating treatment, the contact angle of the granules increased to 125°, showing obvious hydrophobicity, which proved that the coating treatment successfully formed a hydrophobic layer on the surface of the granules.

[0075] SS7. Antistatic Coating Treatment

[0076] 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.

[0077] 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.

[0078] SS8. Screening and finished product acquisition

[0079] 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.

[0080] 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.

[0081] 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.

[0082] Table 1 Performance comparison between the tracer prepared by the present invention and the traditional tracer

[0083] Test item The tracer prepared by the present invention Traditional tracer Particle size distribution (μm) 10-100 100-2000 Dispersibility (%) 98 95 Radioactive stability (%) 95 90

[0084] 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). Compared with traditional tracers (100 - 2000 μm), its particle size is significantly reduced, which enables the tracer to better adapt to low-permeability formations during oilfield logging, ensuring 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 that of traditional tracers, indicating that it can be more evenly distributed during use, reducing the possibility of sedimentation and blockage. In addition, the tracer of the present invention also has obvious advantages in terms of 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 result consistency.

[0085] Through the above embodiments, the object 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 content described in the accompanying drawings and the above specific embodiments. Although the present invention has been described with reference to the currently considered most practical and preferred embodiments, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A preparation method of an ultra-fine degradable solid tracer for oilfield logging, characterized in that, The method at least includes the following preparation steps: SS1. Select a natural degradable biomass material. After preliminary screening of the selected material, wash it to remove surface impurities, then perform a drying treatment, and finally crush the dried material; SS2. Seal the initial biomass material particles obtained from preprocessing in step SS1 in a vacuum heat-sealed bag and ensure there is no residual air in the bag, and then place it in γ a ray irradiation device for irradiation treatment; SS3. Mix the irradiated biomass material particles with a buffer solution having a pH value of 4.5 - 5.5 according to a set mass ratio. Then transfer the mixture to a constant temperature reactor and preheat it at 35 - 65°C for 5 - 10 minutes. Subsequently, slowly add a pre-prepared polysaccharide hydrolase solution, and after stirring evenly, add a saccharifying enzyme solution, and continuously stir and react at 35 - 65°C at a speed of 200 - 400 rpm for 0.5 - 4 hours; SS4. After the enzymatic hydrolysis reaction ends, filter the biomass hydrolysis product at room temperature and rinse it with deionized water. Then place the washed product in a freeze-drying device for drying treatment; SS5. Take an appropriate amount of freeze-dried biomass hydrolysis product 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 hydrolysis product particles in a fluidized bed coating device and coat the particles by spraying a hydrophobic coating solution. During the coating process, control the spraying speed of the coating solution at 20 - 30 ml / min, the coating temperature at 30 - 60°C, and the relative humidity at 40 - 60%; SS7. After completing the hydrophobic coating, perform an antistatic treatment on the particles with an antistatic agent solution for 20 - 40 minutes. Control the spraying speed of the solution at 10 - 15 ml / min and the temperature between 60 - 100°C; SS8. Screen the coated particulate material to select a finished product of a degradable solid tracer with an ultra-fine particle size that meets the requirements, ensuring that its particle size meets the requirements of oilfield logging.

2. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, wherein 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, ensure that the drying temperature is controlled at 40 - 60°C, and the moisture content of the dried material is reduced to less than 10% to avoid caking or deformation of the particles during subsequent crushing; when crushing the dried material, control its initial particle size between 50 - 200 μm and ensure that it has a uniform particle size distribution to provide higher reaction efficiency and stability for subsequent reactions and treatments.

3. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, wherein In the above step SS2, during the irradiation treatment, the irradiation dose should be controlled at 0.5 - 3 KGy, the irradiation environment temperature at 10 - 30°C, and the irradiation time at 1 - 3 hours to ensure that the molecular structure of the biomass material can be effectively changed, enhance its activity in subsequent hydrolysis reactions, and at the same time avoid excessive degradation of the material or changes in its physical properties, ensuring the stability and repeatability of subsequent treatments.

4. The preparation method of the ultra-fine degradable solid tracer for oilfield 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 the buffer. After irradiation, the mass ratio of the biomass material particles to the buffer is controlled within 1:1 - 1:5, and the mass ratio of the biomass material particles after irradiation to the polysaccharide hydrolase and glucoamylase is controlled between 100:1 and 1:

1. During the reaction process, the pH value is continuously detected 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 preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, characterized in that, In the above step SS4, after the enzymatic hydrolysis reaction ends, the biomass hydrolysis product is filtered at room temperature and rinsed with deionized water at least 3 times to remove the impurities generated during the reaction. Then, the washed product is placed in a freeze-drying device at -50°C to -20°C for 12 - 24 hours to maintain the skeletal structure of the particles, prevent particle shrinkage or collapse, and at the same time reduce its water content.

6. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, characterized in that, In the above step SS5, Na 131 I solution is selected as the radioactive isotope solution, and the volume ratio of the biomass hydrolysis product particles to the Na 131 I solution is 5:1 - 1:

2. During the immersion of the biomass hydrolysis product particles in the Na 131 I solution, the room temperature should be maintained at 20 - 25 °C and gently stirred to ensure that the isotope is evenly attached to the particle surface. The immersed product is filtered at room temperature and vacuum dried at 40 - 80 °C for 6 - 8 hours to fix the radioactive isotope and make it stably attached to the surface of the hydrolysis product particles.

7. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, characterized in that, In the above step SS6, the labeled biomass hydrolysis product particles are placed in a fluidized bed coating device, and a hydrophobic rosin ethanol solution is used as the coating material. The concentration of the rosin ethanol solution is 0.1% - 1%, the spraying speed is controlled at 20 - 30 ml / min, and the coating thickness is controlled between 2 - 5 microns to ensure a uniform hydrophobic layer is coated on the particle surface. During the coating process, the air flow speed 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, preventing uneven coating or adhesion between particles. After the hydrophobic coating is completed, the particles are dried in the fluidized bed coating device at 30 - 60°C for 15 - 30 minutes to remove the residual ethanol on the surface, while maintaining the physical integrity and functional stability of the particles.

8. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, wherein In the above step SS7, the particles treated with hydrophobic coating are placed in a fluidized bed device and antistatic treatment is carried out using an antistatic agent solution. Octadecyl dimethyl hydroxyethyl ammonium nitrate with a concentration of 0.5% - 1% is selected as the antistatic agent, and the mass ratio of the hydrophobic coated particles to the antistatic agent is controlled between 10000:1 - 100:

1. During the antistatic treatment process, the spraying speed of the antistatic agent solution is controlled at 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 dried in the fluidized bed at 60 - 100°C for 15 - 30 minutes to ensure that the antistatic agent is evenly attached to the particle surface and completely remove the residual moisture and solvent on the surface, ensuring the stability and antistatic performance of the particles during use, while maintaining good fluidity and dispersibility.

9. The preparation method of the ultra-fine degradable solid tracer for oilfield logging according to claim 1, characterized in that, In the above step SS8, the particles treated with antistatic treatment and dried are placed in a screening device for screening. A sieve 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 screening, quality inspection is carried out on the finished product to ensure that its particle size is uniform, its fluidity is good, it meets the application standards for oilfield logging, and meets the expected measurement accuracy and reliability requirements.

10. An ultra-fine degradable solid tracer for oilfield logging prepared by the preparation method of the ultra-fine degradable solid tracer for oilfield logging according to any one of claims 1 to 9 above.

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