A technetium tracer for oilfield logging and a method for preparing the same

Abstract

This invention discloses a technetium tracer for oilfield logging and its preparation method, belonging to the technical field of isotope tracer logging and radioactive tracer material preparation for oilfield water injection development. The method involves constructing composite particles from chitosan and nano-hydroxyapatite, and then combining them with a polyacrylic acid / acrylic acid system to form a gel precursor. This precursor is then subjected to irradiation crosslinking, freeze-drying to create pores, and pulverization and sieving to obtain porous composite carrier particles. Subsequently, the particles are leached with sodium chloride solution. 99 Mo- 99m Tc generator obtains Na 99m The TcO4 eluent was mixed with the carrier at a predetermined volume ratio, loaded, dried, and sieved to obtain technetium (TcO4). 99m Tc) tracer finished product. This tracer has a half-life of approximately 6.02 hours. 99m Tc balances well logging detectability and operational timeliness, reduces the duration of radioactive contamination of wellbore and instruments and environmental risks, improves the stability and repeatability of water injection profile tracer logging results, and is suitable for stratified water absorption evaluation and dynamic monitoring of water injection wells.

Description

Technical Field

[0001] This invention belongs to the technical field of isotope tracer logging and radioactive tracer material preparation for oilfield water injection development. It relates to the carrier construction, loading solidification, and particle forming process of short-half-life radioactive isotope tracers, specifically a technetium (Tt) tracer for oilfield logging. 99m Tc tracers and their preparation methods. Background Technology

[0002] In oilfield water injection development, the water absorption capacity of the wellbore and formation, as well as the effectiveness of stratified injection, directly affect displacement efficiency and recovery rate. To obtain the water absorption of each layer and its variation over time, tracer logging technology is widely used in engineering. Among them, isotope tracer logging utilizes tracers to enter the formation with the injected water and form a detectable gamma radiation distribution. By measuring the count rate curve during well operation, information such as water injection profile and inter-layer flow can be inverted, making it a common method for stratified water injection and dynamic monitoring.

[0003] Existing isotope tracer systems mostly use gamma-emitting nuclides and prepare them into solutions or solid-phase carrier particles to balance injectability and detectability. To meet operational cycle requirements, nuclides with longer half-lives are often selected, such as barium-131 ​​isotopes (half-life 11.7 days) or iodine-131 isotopes (half-life 8.02 days), to ensure sufficient activity from preparation and transportation to downhole measurement. However, in complex wellbore environments, tracers are prone to adsorption or mechanical retention with oil, wax deposits, corrosion products, and downhole tool surfaces, leading to radioactive contamination. In engineering practice, this type of contamination is more common in water injection wells. In severe cases, it can cause abnormally high counts in localized areas of the wellbore, resulting in profile interpretation errors and potentially contaminating logging instruments and surface processes, raising instrument background, generating crosstalk, and increasing decontamination and maintenance costs.

[0004] Furthermore, when the injected water has high salinity and contains polyvalent ions and fine-grained solids, the chemical form of the tracer may undergo hydrolysis, complexation, or precipitation transformation, leading to carrier aggregation, pore throat blockage, or activity loss, thus reducing tracer efficiency and repeatability. Downhole temperature, shear, and pressure fluctuations can also accelerate tracer migration to interfaces or deposition in non-target areas, causing significant dispersion of the same formulation in different well areas. For shallow injection wells, if there is a potential connection path to near-surface aquifers, long-half-life radioactive tracers are unlikely to decay to background levels in a short time, further increasing environmental compliance pressure and risk management difficulties.

[0005] In summary, although isotope tracer logging has developed into a relatively mature application system, it still suffers from problems such as tracer contamination leading to data distortion, high operation and maintenance costs, and difficulty in simultaneously addressing environmental risks. Therefore, how to reduce contamination and residue risks while ensuring logging detectability, and improve downhole stability and result consistency, is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0006] (a) Purpose of the invention To address the shortcomings of existing oilfield water injection profile isotope tracer logging, which commonly uses long-half-life radionuclide tracers that are easily adsorbed and retained on wellbore oil and downhole tool surfaces, leading to radioactive contamination, data distortion, increased instrument background, and long maintenance waiting times, as well as environmental risks posed by radioactive residues under shallow water injection well conditions, this invention aims to provide a technetium (Tt) tracer for oilfield logging. 99m Tc tracers and their preparation methods, using a half-life as short as 6.02 hours 99m Using Tc as the core marker nuclide, combined with key technologies such as the construction of chitosan-hydroxyapatite composite carriers (including ultrasonic dispersion, glutaraldehyde crosslinking and dialysis purification), polyacrylic acid-acrylic acid system polymerization, and irradiation crosslinking, the radioactive risk of the tracer is significantly reduced (including reducing the incidence of contamination, shortening instrument maintenance and settling time, and mitigating environmental pollution). At the same time, its stability, dispersibility, and adsorption in the downhole environment are ensured to meet the accuracy and practicality requirements of water injection profile logging.

[0007] (II) Technical Solution To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution: The first objective of this invention is to provide a technetium (Turbidium) for oilfield logging. 99m The preparation method of Tc tracers, with an isotopic half-life as short as 6.02 hours, meets the requirements of oilfield tracer logging while reducing radioactive risks, and includes at least the following steps: S100. Preparation of chitosan solution: Chitosan with a viscosity of 80-120 Pa·s is dissolved in an aqueous acetic acid solution with a volume fraction of 1.5-2.5% at 55-65 ℃ to prepare a chitosan solution A with a mass fraction of 0.5-2.0% and which is basically transparent. S200. Preparation of hydroxyapatite dispersion: Hydroxyapatite with a particle size of 60~80 nm was added to solution A and ultrasonically dispersed at 50~70 ℃ for 2~6 h to obtain hydroxyapatite dispersion B; S300. Preparation of composite particles: At a mass ratio of chitosan to hydroxyapatite of 0.8~1.2:1, a 45~55% glutaraldehyde solution was added dropwise to dispersion B at 25~35℃ to make the mass ratio of glutaraldehyde to hydroxyapatite 1.3~1.9:1. The mixture was stirred for 5~7 h. The reaction product was loaded into a semi-permeable membrane, dialyzed with deionized water for 2~4 days, and then spray-dried to obtain chitosan / hydroxyapatite composite particle product C. S400. Preparation of polyacrylic acid dispersion: 10-30 g of polyacrylic acid with a weight average molecular weight of 15000-25000 g / mol and 0.5-2.0 g of anhydrous calcium chloride are added to 65-90 g of deionized water and stirred at 10-40 °C until completely dissolved to obtain polyacrylic acid dispersion D; S500. Preparation of acrylic acid system dispersion: 0.2~1.0 g of product C, 2~10 g of acrylic acid, 2~10 g of sodium acrylate and 0.5~2.5 g of anhydrous sodium carbonate are added to 80~100 g of deionized water and stirred evenly at 10~40 ℃ to obtain acrylic acid system dispersion E; S600. Formation of composite gel carrier precursor: Add dispersion E to dispersion D and stir for 3-10 min and let stand for 2-4 h to settle. Pour off the supernatant and wash the obtained wet solid with deionized water to obtain composite gel carrier precursor product F. S700. Formation of composite porous carrier particles: Product F is poured into a mold with a thickness of 2-4 mm, subjected to irradiation crosslinking treatment with an irradiation dose of 8-12 kGy, and then freeze-dried, pulverized and sieved to obtain porous composite carrier particle product G with a predetermined particle size range. S800. 99m Tc loading: rinsing with a sodium chloride solution with a mass fraction of 0.5~1.0% 99 Mo- 99m Tc generator, to obtain Na with an activity of 37~3700 MBq. 99m TcO4 eluent; the eluent was diluted and mixed with product G at a volume ratio of 0.8~1.2:1 and stirred for 20~40 min, dried at 70~90 ℃ for 20~40 min and sieved to obtain technetium (TcO4) in the target particle size range. 99m Tc tracer finished product.

[0008] The second aspect of this invention aims to provide a technetium (Turbidium) for oilfield logging. 99m Tc tracers, including porous composite support particles and Na supported thereon. 99m TcO4, where The porous composite carrier particles are particulate solids with a particle size in the range of 50~2000 μm, including a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein. The cross-linked polymer network backbone comprises polyacrylic acid segments, acrylic acid segments, and sodium acrylate segments, and contains ionic cross-linking points composed of calcium ions and carboxyl groups, forming an interconnected porous structure within the network backbone; and the surface of the porous composite carrier particles has a hydrophilic hydration layer formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments, Na99m TcO4 is distributed within the pore structure and / or adsorbed on the surface of the hydrophilic hydration layer for use in oilfield tracer logging.

[0009] A third aspect of this invention aims to provide a porous composite carrier particle for oilfield logging. The porous composite carrier particle is a particulate solid with a particle size of 50-2000 μm, comprising a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein. The chitosan / hydroxyapatite composite particles are formed by cross-linking chitosan (viscosity 80-120 Pa·s) and hydroxyapatite (particle size 60-80 nm) with glutaraldehyde. The cross-linked polymer network framework comprises polyacrylic acid segments, acrylic acid segments, and sodium acrylate segments, and contains ionic cross-linking points formed by calcium ions and carboxyl groups, creating an interconnected porous structure within the cross-linked polymer network framework. The surface of the porous composite carrier particle has a hydrophilic hydration layer enriched with polyacrylic acid segments and / or sodium acrylate segments, serving as a loading carrier for isotope tracer components in oilfield tracking logging.

[0010] (III) Technical Effects Compared with the prior art, the technetium (Turpentine) for oilfield logging of the present invention... 99m The Tc tracer and its preparation method have the following beneficial and significant technical effects: (1) The present invention selects a half-life of 6.02 hours. 99m Tc and Na 99m TcO4 is loaded onto a particulate carrier to achieve a balance between the detectability of gamma radiation required for tracer logging and the timeliness of operations. After logging is completed, the radioactivity can decay to a low level in a short time, thereby significantly reducing the duration of radioactive contamination and maintenance waiting costs caused by contact adsorption of the wellbore, surface process and logging instruments, and reducing environmental compliance risks in the event of potential interconnection in shallow water injection wells.

[0011] (2) This invention employs a carrier construction route of chitosan / hydroxyapatite composite particles—polyacrylic acid / acrylic acid system composite—irradiation crosslinking—freeze-drying pore formation, enabling the carrier to simultaneously possess the adsorption anchoring provided by the inorganic phase and the morphological stability provided by the polymer network, forming a connected pore structure to facilitate the entry and distribution of the eluent; thereby improving… 99m The uniformity and retention of Tc loading reduce the risk of activity loss and morphological drift during injection and migration, and reduce non-targeted perturbations in the count rate curve.

[0012] (3) This invention implements parameterized control over key steps such as dissolution, dispersion, crosslinking, dialysis, irradiation, freeze drying, sieving and load drying, so that the particle size range and pore structure of the carrier can be obtained stably according to the process, taking into account the injectability, anti-settling and agglomeration and downhole transport adaptability; at the same time, the generator eluent is used as the radiation source input, combined with mixing, drying and sieving, to achieve the reproducibility and batch consistency of the tracer preparation process, which is convenient for the formation of controlled addition and quality traceability engineering applications in oilfield. Attached Figure Description

[0013] Figure 1 Flowchart of a method for preparing technetium tracers for oilfield logging; Figure 2 The diagram shows a cross-sectional structure of technetium (99mTc) tracer particles used in oilfield logging.

[0014] Figure reference numerals: 1-hydrophilic hydration layer, 2-crosslinked polymer network framework, 3-chitosan / hydroxyapatite composite particles, 4-interconnected pore structure, 5-Na 99m TcO4 pore wall adsorption (shown by ● in the figure), 6-Na 99m TcO4 hydration layer adsorption (shown as ○ in the figure), 7-ion crosslinking sites (Ca) 2+ -COO - wait). Detailed Implementation

[0015] This invention aims to provide a technetium (Turpentine) for oilfield logging. 99m Tc) tracers and their preparation methods: To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, embodiments of this invention, and are exemplary and intended to explain the invention, but should not be construed as limiting the invention.

[0016] Example 1: Technetium tracer preparation method As a specific example, the technetium (Turpentine) provided in the embodiments of the present invention 99m The preparation method of the Tc tracer has an isotopic half-life as short as 6.02 hours, which not only meets the requirements of detectability and operational timeliness for oilfield tracer logging, but also helps to reduce the maintenance and environmental risks caused by radioactive residues. The method includes at least the following steps: Figure 1 As shown: S100. Preparation of chitosan solution: Chitosan with a viscosity of 80-120 Pa·s was dissolved in an aqueous acetic acid solution with a volume fraction of 1.5-2.5% at 55-65 °C to prepare a chitosan solution A with a mass fraction of 0.5-2.0% and which is basically transparent. Preferably, the chitosan has a degree of deacetylation of 75-95% and a molecular weight of 100,000-500,000 Da. Before dissolution, the chitosan is sieved through an 80-120 mesh screen and vacuum-dried at 40-60 °C for 2-6 h to reduce adsorbed water content and increase the dissolution rate. During dissolution, an inert gas is introduced for protection to prevent oxidative degradation. A combination of mechanical stirring (300-800 rpm) and intermittent ultrasonic assistance (100-300 W ultrasonic power, 5-15 min intervals, 10-20 min intervals) is used to control the dissolution time of chitosan in acetic acid aqueous solution to 1-3 h. After dissolution, undissolved impurities are removed by filtration through a 0.45-1.0 μm microporous membrane, and degassing treatment is performed to ensure no visible bubble layer after standing, guaranteeing the transmittance of solution A (wavelength 550 nm, optical path 1). The viscosity (cm) reached over 95%, ultimately resulting in a homogeneous chitosan solution system with stable viscosity and transmittance, a pH value of 4.0~5.5, suitable for subsequent loading of radionuclides.

[0017] Preparation of S200. Hydroxyapatite dispersion: Hydroxyapatite with a particle size of 60-80 nm was added to solution A and ultrasonically dispersed at 50-70 °C for 2-6 h to obtain hydroxyapatite dispersion B. Preferably, the hydroxyapatite was nano-sized hydroxyapatite powder with the chemical formula Ca. 10 (PO4)6(OH)2, calcium-to-phosphorus molar ratio 1.60-1.70:1, hexagonal crystal system, specific surface area 50-150 m² 2 / g;; During the ultrasonic dispersion process, the ultrasonic power is controlled at 200~600 W, the ultrasonic frequency is 20~40 kHz, and the ultrasonic mode combines pulsed operation (5~10 s operation, 3~8 s interval) with intermittent cooling cycle (cooling for 10~20 min every 30~60 min operation). This breaks up particle agglomeration through cavitation, ensuring uniform dispersion in the chitosan solution to form a stable suspension system. Simultaneously, it prevents local overheating that could damage the hydroxyapatite crystal form. Furthermore, the solid content of hydroxyapatite in dispersion B is controlled at 0.1~5.0%, ensuring a concentrated particle size distribution (polydispersity index PDI < 0.3), low agglomeration (average agglomerated particle size < 200 nm), and high dispersion stability (Zeta potential absolute value > 25 mV) in chitosan solution A. The nanoscale effect and high specific surface area of ​​hydroxyapatite result in abundant calcium ion sites and phosphate sites on its surface, enabling it to interact with the chitosan through multiple mechanisms such as electrostatic adsorption, coordination, and ion exchange. 99m TcO4⁻ exhibits strong adsorption, with an adsorption capacity of 50~200 mg / g, thus improving the tracer loading efficiency.

[0018] S300. Preparation of composite particles: At a mass ratio of chitosan to hydroxyapatite of 0.8–1.2:1, a 45–55% glutaraldehyde solution was added dropwise to dispersion B at 25–35°C to achieve a mass ratio of glutaraldehyde to hydroxyapatite of 1.3–1.9:1. The mixture was stirred for 5–7 hours. The reaction product was then placed in a semi-permeable membrane, dialyzed with deionized water for 2–4 days, and spray-dried to obtain chitosan / hydroxyapatite composite particle product C.

[0019] Preferably, the dropping rate of the glutaraldehyde solution is 0.5–2.0 mL / min, and the dispersion B is continuously stirred during the dropping process at a stirring speed of 200–500 rpm to reduce the risk of agglomeration caused by excessive local cross-linking. Furthermore, the mass ratio of glutaraldehyde to hydroxyapatite is linked to the reaction time to achieve synergistic optimization of the degree of cross-linking and pore structure in the composite particles. Specifically, when the mass ratio of glutaraldehyde to hydroxyapatite is 1.5–1.8:1, the reaction time is controlled at 5.5–6.5 h. During the dialysis process, a continuous flow deionized water dialysis device is used, with deionized water replaced every 8–12 h to maintain the conductivity of the dialysis solution stably below 10 μS / cm, effectively removing free glutaraldehyde and small molecule impurities and reducing non-specific adsorption during subsequent radiolabeling. The inlet air temperature of the spray dryer is 150–180 ℃, the outlet air temperature is 80–100 ℃, and the feed rate is 5–15 mL / min, thereby obtaining an average particle size of 1–20 μm. Chitosan / hydroxyapatite composite particles with a pore size distribution concentrated in the range of 10~200 nm.

[0020] S400. Preparation of polyacrylic acid dispersion: 10–30 g of polyacrylic acid with a weight average molecular weight of 15,000–25,000 g / mol and 0.5–2.0 g of anhydrous calcium chloride were added to 65–90 g of deionized water and stirred at 10–40 °C until completely dissolved to obtain polyacrylic acid dispersion D. Preferably, the polyacrylic acid is partially neutralized, with a degree of neutralization controlled at 30–70%, and the alkali used for neutralization is an aqueous solution of sodium hydroxide and / or potassium hydroxide. After adding polyacrylic acid and anhydrous calcium chloride to deionized water, the mixture was first dissolved at a low speed of 300–800 r / min for 10–30 min, and then stirred at a high speed of 800–1500 r / min for another 10–40 min to ensure uniform complexation distribution of calcium ions in the polyacrylic acid segments. The pH value of the final polyacrylic acid dispersion D was controlled at 5.0–7.5 to balance polymer stability and subsequent gel network formation ability.

[0021] S500. Preparation of acrylic acid dispersion: 0.2–1.0 g of product C, 2–10 g of acrylic acid, 2–10 g of sodium acrylate, and 0.5–2.5 g of anhydrous sodium carbonate were added to 80–100 g of deionized water and stirred evenly at 10–40 °C to obtain an acrylic acid dispersion E. Preferably, the molar ratio of acrylic acid to sodium acrylate was controlled at 0.5–2.0:1, and the degree of neutralization of acrylic acid was controlled at 20–60% by adjusting the amount of anhydrous sodium carbonate added, so as to obtain an acrylic acid dispersion E with both sufficient crosslinkable double bond content and suitable hydrophilicity. During the stirring process, the stirring speed was controlled at 500–1200 r / min, and the stirring was carried out under an inert atmosphere (nitrogen or argon) or under conditions of limited oxygen contact to reduce spontaneous polymerization and oxidation of acrylic acid in solution, maintain the reactivity and stability of dispersion E (stable for 3–7 days when sealed at 4 °C), and provide a uniform distribution of crosslinkable monomers and a stable pH environment (pH 6.0–8.0) for subsequent irradiation crosslinking.

[0022] S600. Formation of the composite gel carrier precursor: Add dispersion E to dispersion D and stir for 3-10 min, then let it stand for 2-4 h to settle. Discard the supernatant and wash the resulting wet solid with deionized water to obtain the composite gel carrier precursor product F. Preferably, dispersion E is added to dispersion D dropwise at a rate of 1–5 mL / min. Dispersion D is continuously stirred (200–600 rpm) during the addition process to reduce local concentration gradients and avoid the formation of uneven gel clumps. Immediately after mixing the two dispersions, a significant increase in viscosity and gradual gel formation are observed. At this point, the stirring speed is reduced to 100–300 rpm and stirring continues for 3–10 min to allow the gelation reaction to proceed fully. During the settling period after mixing, the system temperature is controlled at 15–30 °C, and the settling container should be protected from vibration. After 2–4 h of settling, a clear liquid-solid separation is observed, with the supernatant being essentially transparent and the lower layer being a wet gel solid. The supernatant is removed by slow pouring or siphoning to minimize disturbance to the settling structure and prevent gel particle loss. The resulting wet solid is washed at least 2–5 times with deionized water, with each wash allowing it to stand for 10–30 min, ensuring the supernatant conductivity after washing does not exceed 200. The endpoint criteria were μS / cm and pH 6.0-8.0, in order to fully remove unreacted free small molecule electrolytes (such as unreacted sodium carbonate, excess calcium ions, etc.) and soluble oligomers, thereby obtaining a composite gel carrier precursor product F with uniform structure, low ion residue, and water content of 75-90%.

[0023] S700. Formation of composite porous carrier particles: Product F is poured into a mold with a thickness of 2-4 mm and subjected to irradiation crosslinking treatment with an irradiation dose of 8-12 kGy. Subsequently, it is freeze-dried, pulverized, and sieved to obtain porous composite carrier particles G with a predetermined particle size range. Preferably, the irradiation crosslinking treatment uses... 60Irradiation with Co-γ rays or electron beams under sealed conditions, with an oxygen volume fraction in the irradiation environment not exceeding 5% (achieved by vacuuming and purging with nitrogen or direct irradiation in a nitrogen atmosphere), to reduce the impact of oxygen inhibition on crosslinking uniformity and improve irradiation crosslinking efficiency. After irradiation crosslinking, the product is washed with deionized water (soaking for 1–3 hours each time and replacing with fresh deionized water) until the washing solution is free of visible turbidity and has a conductivity below 50 μS / cm, to remove soluble degradation products and uncrosslinked oligomers generated during irradiation, before proceeding to lyophilization. The lyophilization process includes a pre-freezing stage and a sublimation drying stage. The pre-freezing temperature is controlled at -60 to -40 °C, and the pre-freezing time is 2–72 h, allowing the internal moisture of product F to form uniform ice crystals. The sublimation drying stage is carried out at -60 to 0 °C and a vacuum of 5–200 Pa for 10–72 hours. h allows ice crystals to sublimate directly into water vapor while preserving their original porous structure; the pulverization process employs low-temperature mechanical pulverization (sample pre-cooled to below -20℃) or air jet milling to avoid pore structure collapse caused by room-temperature pulverization; sieving uses sieves of different aperture sizes (e.g., 100 μm, 200 μm, 300 μm) for stepwise sieving, resulting in particle sizes ranging from 50 to 2000 μm, internal interconnected porosity greater than 50%, and specific surface area of ​​50 to 150 m². 2 / g porous composite carrier particle product G.

[0024] S800. 99m Tc's load: Rinse with a sodium chloride solution with a mass fraction of 0.5-1.0%. 99 Mo- 99m Tc generator, to obtain Na with an activity of 37~3700 MBq. 99m TcO4 eluent; the eluent was diluted and mixed with product G at a volume ratio of 0.8~1.2:1 and stirred for 20~40 min, dried at 70~90 ℃ for 20~40 min and sieved to obtain technetium (TcO4) in the target particle size range. 99m Tc tracer finished product.

[0025] Preferably, the rinsing flow rate of the sodium chloride solution is 0.5~2.0 mL / min, and the single rinsing volume is 1~10 mL; Na 99m The TcO4 eluent is diluted 1 to 1000 times, and the diluent is physiological saline or deionized water; Na 99m The TcO4 eluent was filtered through a 0.22 μm filter membrane and its pH was adjusted with a buffer solution of pH 6.0–8.0 before being mixed with product G to reduce the formation of radioactive impurities and colloidal technetium. During loading, the temperature of the mixing system was controlled at 20–40 °C, and uniform contact was achieved using a shaking table or magnetic stirring to ensure proper contact of the TcO4 eluent. 99mTechnetium tracers undergo physical adsorption and weak coordination binding on the surface and within the pores of porous carrier particles; after drying, the resulting technetium tracers are sieved to obtain particles with a particle size range of 50~2000 μm, a specific activity of 1~100 MBq / g, and a radiochemical purity of not less than 90%.

[0026] In some preferred embodiments, after obtaining the finished technetium tracer, the present invention performs an anti-fouling directional surface hydration treatment: the finished product is contacted with a hydrophilic polymer solution with a mass fraction of 0.01-0.2% for 10-60 minutes and then dried and solidified, so that a continuous hydration layer is formed on the particle surface, thereby reducing its adhesion tendency on oily metal surfaces and organic deposit surfaces, and improving the interpretability and repeatability of the count rate curve during tracer logging.

[0027] It should be noted that this invention achieves synergistic effects by constructing a core-shell-network three-level composite structure of chitosan / hydroxyapatite composite core and polyacrylic acid gel network. 99m TcO4 - The tracer utilizes multiple immobilization mechanisms, including electrostatic adsorption, coordination fixation, and physical retention, to achieve high labeling efficiency, low leaching rate, and anti-fouling properties. Key technical features include hydroxyapatite nanoparticles providing high-density adsorption sites, glutaraldehyde cross-linking chitosan forming a stable framework, calcium-polyacrylic acid complex gel constructing a sustained-release control layer, irradiated cross-linked polyacrylic acid network providing mechanical support, and a hierarchical porous structure ensuring... 99m The rapid loading and controllable release of Tc ultimately achieved the technical goals of short half-life, strong logging signal, and low environmental risk.

[0028] Example 2: Technetium for oilfield logging ( 99m Tc tracer Based on the above embodiment 1, this embodiment 2 further provides technetium for oilfield logging (… 99m Tc) tracer, the tracer being prepared based on the preparation method of the present invention, comprising porous composite support particles and Na supported thereon. 99m TcO4, wherein the porous composite carrier particles are particulate solids with a particle size ranging from 50 to 2000 μm, comprising a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein; the cross-linked polymer network framework contains polyacrylic acid segments, acrylic acid segments, and sodium acrylate segments, and contains ionic cross-linking points composed of calcium ions and carboxyl groups, forming an interconnected porous structure within the network framework; and the surface of the porous composite carrier particles has a hydrophilic hydration layer formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments, Na 99m TcO4 is distributed within the pore structure and / or adsorbed on the surface of the hydrophilic hydration layer for use in oilfield tracer logging.

[0029] Figure 2 The image shows technetium (Turpentine) used for oilfield logging. 99m (Tc) Schematic diagram of the cross-sectional structure of the tracer particles. The tracer consists of porous composite carrier particles and Na supported on them. 99m The porous composite carrier particles, composed of TcO4, include a cross-linked polymer network framework 2 and chitosan / hydroxyapatite composite particles 3 dispersed and embedded within it. The network framework 2 forms an interconnected pore structure 4 with a porosity of 40–85%, and the pore size is mainly distributed in the range of 10–200 nm. It also contains calcium ions (Ca). 2+ ) and carboxyl groups (-COO) - The network framework is composed of ionic crosslinking points 7, which endow the network framework with pH responsiveness and ionic strength sensitivity; chitosan / hydroxyapatite composite particles 3 are dispersed and embedded in the network framework 2, wherein chitosan is crosslinked with glutaraldehyde to form a stable three-dimensional framework, and hydroxyapatite nanoparticles (particle size 60~80 nm) are crosslinked with Ca2+. 10 (PO4)6(OH)2 is dispersed in it in crystalline form, and 99m TcO4 - Ions provide high-density adsorption active sites; the particle surface has a hydrophilic hydration layer 1 with a thickness of 0.1~1 μm, which is formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments on the surface, carrying a large number of hydrophilic carboxyl and carboxylate groups, which can form a stable hydration film in aqueous solution, effectively reducing the adhesion of particles to oily metal surfaces and organic deposits; Na 99m Part of the TcO4 is adsorbed on the pore walls of the pore structure 4 (see reference numeral 5 in the figure, indicated by ●), and another part is adsorbed on the surface of the hydrophilic hydration layer 1 (see reference numeral 6 in the figure, indicated by ○). The synergistic effect of the two adsorption modes enables the tracer to achieve a radioactivity specific activity of 100~1000 MBq / g, a radiochemical purity of not less than 90%, and a radioactive leaching rate of not more than 20% after soaking in 0.9% sodium chloride solution for 28 h, ensuring that the tracer has high labeling efficiency, low leaching loss, and stable signal output characteristics in oilfield logging applications.

[0030] It should be noted that the core innovation of the tracer in this embodiment lies in the establishment of a three-level fixation mechanism: surface hydration, network interception, and core anchoring. The hydrophilic hydration layer 1 achieves the dual functions of rapid adsorption and anti-fouling. The interconnected pore structure 4 of the cross-linked polymer network skeleton 2 provides physical interception and diffusion slow-release channels. The nano-active sites of the chitosan / hydroxyapatite composite particles 3 achieve strong anchoring. The introduction of ionic cross-linking points 7 not only enhances the mechanical strength and structural stability of the network skeleton, but also endows the carrier with pH and ionic strength responsiveness, enabling it to maintain structural integrity when formation conditions change. 99mThe dual-site distribution of Tc (pore wall adsorption and hydration layer adsorption) achieves a balance between immediate signal response and continuous signal output, adapting to the complex working conditions of different flow rates and salinity in oilfield logging. The tracer has a half-life of only 6.02 hours, which not only meets the logging efficiency requirements but also significantly reduces the risk of long-term radioactive contamination. The radioactivity decays to the background level 24 to 48 hours after injection, achieving a balance between efficient logging and environmental friendliness.

[0031] Example 3: Porous composite carrier particles for oilfield logging Based on Examples 1 and 2 above, Example 3 further provides porous composite carrier particles for oilfield logging, which have the synergistic advantages of high specific surface area, interconnected pore structure, and hydrophilic surface properties. The porous composite carrier particles are particulate solids with a particle size of 50-2000 μm, comprising a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein. The chitosan / hydroxyapatite composite particles are formed by cross-linking chitosan (viscosity 80-120 Pa·s) and hydroxyapatite (particle size 60-80 nm) with glutaraldehyde. The chitosan forms a three-dimensional network framework through a Schiff base reaction at its amino sites with glutaraldehyde. Hydroxyapatite nanoparticles are uniformly embedded and anchored within the chitosan network, forming micron-sized composite particles with a particle size of 1-20 μm, providing high-density adsorption sites for subsequent radionuclides. The cross-linked polymer network framework includes polyacrylic acid segments, acrylic acid segments, and sodium acrylate segments, which are irradiated with an electron beam or gamma rays (irradiation dose 8-12). The free radical copolymerization reaction induced by (kGy) forms a covalent cross-linked network containing ionic cross-linking points formed by calcium ions and carboxyl groups. This creates an interconnected porous structure within the cross-linked polymer network framework, with pore sizes mainly distributed in the range of 10–200 nm. The pores exhibit good connectivity, providing physical channels and chemisorption sites for the rapid adsorption and stable fixation of radionuclides. The surface of the porous composite carrier particles has a hydrophilic hydration layer formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments. This hydration layer is rich in carboxyl groups (-COOH) and carboxyl groups (-COO). - The group forms a stable hydrophilic interface in aqueous solution through electrostatic repulsion and hydration, which effectively reduces the adhesion tendency of particles on oily metal surfaces, organic sediment surfaces and formation rock surfaces, and improves the migration stability and signal reliability of tracers in complex oilfield environments, so as to serve as an efficient loading carrier for isotopic tracer components used in oilfield tracer logging.

[0032] Preferably, the pore structure formed by the cross-linked polymer network skeleton is a connected pore structure, and the open porosity of the porous composite carrier particles accounts for no less than 70% of the total porosity. This ensures that the radionuclide solution can quickly penetrate into the interior of the particles and fully contact the active adsorption sites. The total porosity is 40-85%, which balances high adsorption capacity and structural mechanical strength. The total porosity is obtained by measuring the true density using the helium specific gravity method and the apparent density using the liquid drainage method. The open porosity is determined by the volume fraction of accessible pores obtained by the mercury indentation method. This connected pore structure feature increases the adsorption rate of the carrier particles when loaded with radionuclides by 30-80% and shortens the adsorption equilibrium time to 20-40 min.

[0033] Preferably, the particle size distribution of the porous composite carrier particles meets the narrow distribution characteristics: D10 is 100~400 μm (indicating that 10% of the particles are smaller than this particle size, controlling the content of fine powder), D50 is 900~1200 μm (median particle size, determining the size of the main particles), and D90 is 1700~2000 μm (indicating that 90% of the particles are smaller than this particle size, controlling the content of coarse particles), and the mass fraction of fine powder with a particle size of less than 50 μm is not higher than 5%, and the mass fraction of coarse particles with a particle size of greater than 2000 μm is not higher than 5%. D10, D50 and D90 are determined by laser particle size analysis, and the mass fraction of fine powder and coarse particles is obtained by sieving.

[0034] Preferably, the hydrophilic hydration layer is formed through post-treatment: the sieved porous composite carrier particles are contacted with a hydrophilic polymer aqueous solution with a mass fraction of 0.01~0.20% for 10~60 min and then separated, and dried to constant weight at 40~80℃. The porous composite carrier particles after post-treatment meet the requirement that the liquid absorption ratio after soaking in a sodium chloride aqueous solution with a mass fraction of 0.5%~1.0% at 25℃ for 24 h is not less than 0.5 g / g, so as to characterize the formation effect of the hydrophilic hydration layer and the wetting stability in the injectable system.

[0035] Example 4: Tracers with highly porous interconnected structures and moderately cross-linked supports Based on Example 1 above, Example 4, without changing the process route (S100~S800), selects the following parameters to prepare the tracer: In S100, the chitosan mass fraction is 1.5%, the acetic acid volume fraction is 2.0%, and the dissolution temperature is 60℃; in S200, the hydroxyapatite particle size is approximately 70 nm, and it is ultrasonically dispersed at 60℃ for 4 h; in S300, the mass ratio of chitosan to hydroxyapatite is 1.0:1, the mass ratio of glutaraldehyde to hydroxyapatite is 1.6:1, the reaction temperature is 30℃, the reaction time is 6 h, and after dialysis for 3 days, it is spray-dried to obtain product C; in S400, the polyacrylic acid weight-average molecular weight is approximately 2.0 × 10⁻⁶. 4g / mol, add 20 g of polyacrylic acid and 1.0 g of anhydrous calcium chloride; in S500, add 0.6 g of product C, 6 g of acrylic acid, 6 g of sodium acrylate, and 1.5 g of anhydrous sodium carbonate; in S700, irradiate with a dose of 10 kGy and freeze-dry to form porous particulate product G; in S800, elute with 0.8% sodium chloride solution to obtain Na. 99m The TcO4 eluent was mixed with the product G at a volume ratio of 1.0:1 and stirred for 30 min, then dried. The finished product was then subjected to surface hydration treatment: it was contacted with a 0.1% polyvinyl alcohol solution for 30 min and dried and cured to form a stable hydrophilic hydration layer.

[0036] Example 5: Tracers with high specific surface area and rapid adsorption orientation supports Based on Example 1 above, Example 5 selects parameters that favor increasing the adsorption rate and specific surface area: In S100, the chitosan mass fraction is 1.2%, the acetic acid volume fraction is 1.8%, and the dissolution temperature is 58℃; in S200, the hydroxyapatite particle size is approximately 65nm, and it is ultrasonically dispersed at 65℃ for 5 hours; in S300, the chitosan to hydroxyapatite mass ratio is 0.9:1, the glutaraldehyde to hydroxyapatite mass ratio is 1.7:1, the reaction temperature is 28℃, and the reaction time is 6.5 hours; in S400, the polyacrylic acid weight-average molecular weight is approximately 1.8 × 10⁻⁶. 4 In step S500, the concentration of product C was increased to 0.8 g, along with 7 g of acrylic acid, 8 g of sodium acrylate, and 1.8 g of anhydrous sodium carbonate. In step S700, the irradiation dose was 11 kGy. In step S800, the mixture was stirred for 25 min at a volume ratio of 1.1:1. The finished product was then hydrated with a 0.08% sodium carboxymethyl cellulose solution for 40 min and dried to achieve better anti-fouling properties.

[0037] Example 6: Tracers for Oriented Carriers with High Structural Stability and Low Eluting Rate Based on Example 1 above, Example 6 selects parameters that prioritize improving structural stability and reducing leaching rate: In S100, the chitosan mass fraction is 1.8%, the acetic acid volume fraction is 2.2%, and the dissolution temperature is 62℃; in S200, the hydroxyapatite particle size is approximately 75nm, and it is ultrasonically dispersed at 55℃ for 3.5h; in S300, the chitosan to hydroxyapatite mass ratio is 1.1:1, the glutaraldehyde to hydroxyapatite mass ratio is 1.5:1, the reaction temperature is 32℃, and the reaction time is 5.5h; in S400, the polyacrylic acid weight-average molecular weight is approximately 2.2×10⁻⁶. 4In step S500, 18g of polyacrylic acid and 0.8g of anhydrous calcium chloride were added at a concentration of g / mol. In step S700, 0.5g of product C, 5g of acrylic acid, 5g of sodium acrylate, and 1.2g of anhydrous sodium carbonate were added. In step S700, an irradiation dose of 9kGy was applied, followed by enhanced freeze-drying to form a stable porous structure. In step S800, the mixture was stirred for 35 minutes at a volume ratio of 0.9:1. The finished product was then hydrated with a 0.12% polyethylene glycol solution for 25 minutes and dried to form a highly stable hydrophilic hydration layer.

[0038] Comparative Example 1: Technetium tracer with a single chitosan carrier Comparative Example 1 used a traditional single chitosan carrier to prepare technetium tracers without adding hydroxyapatite and polyacrylic acid systems. Chitosan with a viscosity of 100 Pa·s was dissolved in a 2.0% (v / v) aqueous acetic acid solution to prepare a 1.5% chitosan solution. A 50% glutaraldehyde solution was then added dropwise for cross-linking (glutaraldehyde to chitosan mass ratio 1.6:1), and the reaction was carried out at 25°C for 4 h. The reaction product was dialyzed, freeze-dried, pulverized, and sieved to obtain chitosan carrier particles with a particle size of 100–2000 μm. Na₂O₃ with an activity of 1850 MBq was then added... 99m The TcO4 eluent was mixed with the carrier particles, stirred at 30°C for 30 min, and then dried at 80°C for 30 min to obtain the technetium tracer product.

[0039] Comparative Example 2: Technetium tracer with polyacrylic acid carrier without hydroxyapatite Comparative Example 2 used a polyacrylic acid-acrylic acid system carrier without hydroxyapatite to prepare technetium tracers. 20 g of polyacrylic acid and 1.0 g of anhydrous calcium chloride were added to 80 g of deionized water and stirred until dissolved. 6 g of acrylic acid, 6 g of sodium acrylate, and 1.5 g of anhydrous sodium carbonate were added to 90 g of deionized water and stirred until homogeneous. After mixing, standing, and washing, the mixture was subjected to irradiation crosslinking (10 kGy), freeze-drying, pulverizing, and sieving to obtain polyacrylic acid carrier particles with a particle size of 100–2000 μm. Na₂O₃ with an activity of 1850 MBq was then used as a carrier. 99m The TcO4 eluent was mixed with the carrier particles, stirred at 30°C for 30 min, and then dried at 80°C for 30 min to obtain the technetium tracer product.

[0040] Comparative Example 3: Commercial resin-carrier technetium tracer This comparative example uses commercial anion exchange resin as a carrier to prepare technetium tracers. A strongly basic quaternary ammonium anion exchange resin was selected, and the resin was washed with deionized water, converted to its chloride form, and vacuum dried before use. Na₂O₃ with an activity of 1850 MBq was used... 99m The TcO4 eluent was mixed with resin particles, statically adsorbed at room temperature for 60 min, then filtered and separated, and dried at 80℃ for 30 min to obtain the technetium tracer product.

[0041] Performance testing and comparative analysis: The following performance tests were performed on the technetium tracer samples prepared in Examples 4-6 and Comparative Examples 1-3: Radioactivity specific activity determination: The specific activity of the sample is determined using a radionuclide activity meter. 99m Tc radioactivity activity, combined with sample mass, is used to calculate specific radioactivity (MBq / g).

[0042] Radiochemical purity determination: The radiochemical purity was determined by instantaneous thin-layer chromatography (ITLC) with acetone as the developing solvent. Radiochemical purity = loaded technetium activity / (total activity - free technetium activity - colloidal technetium activity) × 100%.

[0043] Adsorption rate determination: Under the same conditions (25℃, solid-liquid ratio 1:20), samples were taken at 5, 10, 15, 20 and 30 min to determine the adsorption rate, and the time (min) required to reach 90% adsorption equilibrium was calculated.

[0044] Rinsing stability test: The sample was placed in a 0.9% sodium chloride solution (solid-liquid ratio 1:50) and shaken and soaked at 25℃ for 4 h. The radioactivity in the solution was measured and the radioactivity rinsing rate was calculated as (solution activity / sample instantaneous activity) × 100%.

[0045] Anti-fouling performance test: The sample was suspended in simulated oilfield water (mineralization 50 g / L, containing 20 mg / L crude oil) and left to stand in contact with the surface of N80 steel sheet for 24 h. The steel sheet was then cleaned and its surface radioactivity was measured. The surface adhesion rate was calculated as (surface activity of steel sheet / initial activity of sample) × 100%.

[0046] Particle size stability determination: The sample was placed under simulated formation conditions (80℃, pressure 10 MPa, mineralization 80 g / L) for 24 h, and the changes in particle size distribution before and after aging were measured. The particle size retention rate was calculated as (D50 after treatment / D50 before treatment) × 100%.

[0047] Specific surface area determination: The specific surface area (m²) of the samples was determined using the BET nitrogen adsorption method. 2 / g).

[0048] Connectivity porosity determination: The open porosity was determined by mercury indentation method, and the total porosity was determined by helium specific gravity method and liquid drainage method. Connectivity porosity was calculated as (open porosity / total porosity) × 100%.

[0049] Table 1 Comparison of Test Results The comparison shows that the technetium tracers prepared by the porous composite carriers constructed by the chitosan / hydroxyapatite composite particles and cross-linked polymer network skeleton of the present invention in Examples 4-6 are significantly better than those in Comparative Examples 1-3 in terms of key performance indicators such as radioactivity, radiochemical purity, adsorption rate, leaching stability, antifouling performance, particle size stability, specific surface area and interconnected porosity.

[0050] Specifically, the radioactivity specific activity of Examples 4-6 was 580-720 MBq / g, which was 107-157% higher than that of Comparative Example 1, 53-89% higher than that of Comparative Example 2, and 38-71% higher than that of Comparative Example 3; the adsorption rate (time to reach 90% equilibrium) was 20-30 min, which was 54-69% shorter than that of Comparative Example 1; the leaching stability (4-hour leaching rate) was 9-15%, which was much lower than that of Comparative Example 13 (28-38%); the anti-fouling performance (surface adhesion rate) was 2.8-4.1%, which was 78-85% lower than that of Comparative Example 1; and the specific surface area was 85-120 m². 2 / g, which is 240-380% higher than that of Comparative Example 1; the interconnected porosity is 58-72%, while Comparative Example 1 has no interconnected pore structure. In summary, this invention achieves synergistic optimization of high specific activity, high purity, rapid adsorption, low leaching, low contamination, and high stability through a three-level composite structure design of chitosan / hydroxyapatite composite particles, cross-linked polymer network framework, and hydrophilic hydration layer.

[0051] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A method for preparing a technetium tracer for oilfield logging, characterized in that, At least including: S100. Dissolve chitosan with a viscosity of 80~120 Pa·s in an aqueous solution of acetic acid with a volume fraction of 1.5~2.5% at 55~65 ℃ to prepare a transparent solution A with a mass fraction of 0.5~2.0%; S200. Hydroxyapatite with a particle size of 60~80 nm is added to solution A and ultrasonically dispersed at 50~70 °C for 2~6 h to obtain dispersion B; S300. Add a 45-55% glutaraldehyde solution dropwise to dispersion B at a chitosan to hydroxyapatite mass ratio of 0.8-1.2:1, making the glutaraldehyde to hydroxyapatite mass ratio 1.3-1.9:

1. Stir the reaction for 5-7 hours. Pack the reaction product into a semi-permeable membrane, dialyze with deionized water for 2-4 days, and then spray dry to obtain product C. S400. Add 10-30 g of polyacrylic acid with a weight average molecular weight of 15,000-25,000 g / mol and 0.5-2.0 g of anhydrous calcium chloride to 65-90 g of deionized water and stir at 10-40 °C to obtain dispersion D; S500. Add 0.2~1.0 g of product C, 2~10 g of acrylic acid, 2~10 g of sodium acrylate and 0.5~2.5 g of anhydrous sodium carbonate to 80~100 g of deionized water and stir at 10~40 °C to obtain dispersion E; S600. Add dispersion E to dispersion D and stir for 3-10 min. Let it stand for 2-4 h to settle. Pour off the supernatant and wash the wet solid with deionized water to obtain product F. S700. Pour product F into a mold with a thickness of 2-4 mm, apply irradiation crosslinking treatment with an irradiation dose of 8-12 kGy, and then freeze-dry, pulverize and sieve to obtain product G; S800. Rinse with a sodium chloride solution with a mass fraction of 0.5~1.0%. 99 Mo- 99m Tc generator, to obtain Na with an activity of 37~3700 MBq. 99m TcO4 eluent; after diluting the eluent, mix it with product G at a volume ratio of 0.8~1.2:1 and stir for 20~40 min, dry at 70~90 ℃ for 20~40 min and sieve to obtain the target particle size range. 99m Tc tracer finished product.

2. The method according to claim 1, characterized in that, In step S100, the degree of deacetylation of chitosan is 75-95%, and the chitosan is sieved through an 80-120 mesh and vacuum dried at 40-60 °C for 2-6 h before dissolution. During the dissolution process, an inert gas is introduced for protection, and a combination of mechanical stirring and intermittent ultrasonic assistance is used. The dissolution time is controlled within 1-3 h. After dissolution, undissolved impurities are removed by filtration through a 0.45-1.0 μm microporous membrane, and degassing treatment is performed so that there is no visible bubble layer after standing, ensuring that the transmittance of solution A reaches more than 95%.

3. The method according to claim 1, characterized in that, In step S200, the hydroxyapatite is nano-sized hydroxyapatite powder with the chemical formula Ca. 10 (PO4)6(OH)2, with a calcium-to-phosphorus molar ratio of 1.60–1.70:1, a hexagonal crystal system, and a surface area of ​​20–80 m². 2 The specific surface area is controlled at / g; during the ultrasonic dispersion process, the ultrasonic power is controlled at 200~600W, the ultrasonic frequency is 20~40 kHz, the ultrasonic mode is a combination of pulse operation and intermittent cooling cycle, and the solid content of hydroxyapatite in dispersion B is controlled at 0.1~5.0%.

4. The method according to claim 1, characterized in that, In step S300, the dropping rate of the glutaraldehyde solution is 0.5~2.0 mL / min. During the dropping process, the dispersion B is kept under continuous stirring at a speed of 200~500 rpm. A continuous flow deionized water dialysis device is used during the dialysis process, and the deionized water is replaced every 8~12 h to keep the conductivity of the dialysis solution stable below 10 μS / cm. The inlet air temperature of the spray drying is 150~180 ℃, the outlet air temperature is 80~100 ℃, and the feed rate is 5~15 mL / min, to obtain chitosan / hydroxyapatite composite particles with an average particle size of 1~20 μm and a pore size distribution concentrated in 10~200 nm.

5. The method according to claim 1, characterized in that, In step S400, the polyacrylic acid is a partially neutralized polyacrylic acid with a degree of neutralization controlled at 30-70%. The alkali used for neutralization is an aqueous solution of sodium hydroxide and / or potassium hydroxide. After adding deionized water to the polyacrylic acid and anhydrous calcium chloride, the mixture is first dissolved at a low speed of 300-800 r / min for 10-30 min, and then stirred at a high speed of 800-1500 r / min for 10-40 min. The pH value of the final polyacrylic acid dispersion D is controlled at 5.0-7.

5.

6. The method according to claim 1, characterized in that, In step S500, the molar ratio of acrylic acid to sodium acrylate is controlled at 0.5~2.0:1, and the degree of neutralization of acrylic acid is controlled at 20~60% by adjusting the amount of anhydrous sodium carbonate added. During the stirring process, the stirring speed is controlled at 500~1200 r / min, and the process is carried out under an inert atmosphere or under conditions of limited oxygen contact.

7. The method according to claim 1, characterized in that, In step S600, dispersion E is added to dispersion D dropwise at a rate of 1-5 mL / min. During the settling period after mixing, the system temperature is controlled at 15-30℃, and the supernatant is removed by slow pouring or siphoning. The resulting wet solid is washed at least 2-5 times with deionized water, and each wash is allowed to stand for 10-30 min. The endpoint is determined by the conductivity of the supernatant after washing not exceeding 200 μS / cm and the pH being between 6.0 and 8.

0.

8. The method according to claim 1, characterized in that, In step S700, the irradiation crosslinking treatment uses 60 Irradiation with Co-γ rays or electron beams under sealed conditions, with an oxygen volume fraction in the irradiation environment not exceeding 5%; after irradiation crosslinking, the product is washed with deionized water until the washing liquid is free of visible turbidity, and then subjected to freeze-drying; the freeze-drying process includes a pre-freezing stage and a sublimation drying stage. The pre-freezing temperature is controlled at -60 to -40 ℃, and the pre-freezing time is 2 to 72 h, so that the internal water of the product F forms uniform ice crystals. The sublimation drying stage is carried out at -60 to 0 ℃ and a vacuum degree of 5 to 200 Pa for 10 to 72 h; the pulverization process uses low-temperature mechanical pulverization or air jet milling, and after sieving, the particle size range is 50 to 2000 μm, the internal interconnected porosity is greater than 50%, and the specific surface area is 50 to 150 m². 2 / g porous composite carrier particle product G.

9. The method according to claim 1, characterized in that, In step S800, the rinsing flow rate of the sodium chloride solution is 0.5~2.0 mL / min, and the single rinsing volume is 1~10 mL; Na 99m The TcO4 eluent is diluted 1 to 1000 times, and the diluent is physiological saline or deionized water; Na 99m The TcO4 eluent was filtered through a 0.22 μm filter membrane and its pH was adjusted with a buffer solution of pH 6.0–8.0 before being mixed with product G. During the loading process, the temperature of the mixing system is controlled at 20~40 ℃, and uniform contact is achieved by shaking or magnetic stirring to ensure that technetium ( 99m Technetium tracers undergo physical adsorption and weak coordination binding on the surface and within the pores of porous carrier particles; after drying, the resulting technetium tracers are sieved to obtain particles with a particle size range of 50~2000 μm, a specific activity of 1~100 MBq / g, and a radiochemical purity of not less than 90%.

10. The method according to claim 1, characterized in that, After obtaining the finished technetium tracer, an anti-fouling oriented surface hydration treatment is performed: the finished product is contacted with a hydrophilic polymer solution with a mass fraction of 0.01-0.2% for 10-60 minutes and then dried and cured to form a continuous hydration layer on the particle surface.

11. A technetium tracer for oilfield logging, characterized in that, Including porous composite support particles and Na supported thereon 99m TcO4, wherein the porous composite carrier particles are particulate solids with a particle size ranging from 50 to 2000 μm, comprising a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein; the cross-linked polymer network framework comprises polyacrylic acid segments, acrylic acid segments, and sodium acrylate segments, and contains ionic cross-linking points composed of calcium ions and carboxyl groups, forming an interconnected porous structure within the network framework; and the surface of the porous composite carrier particles has a hydrophilic hydration layer formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments, Na 99m TcO4 is distributed within the porous structure and / or adsorbed on the surface of the hydrophilic hydration layer.

12. A porous composite carrier particle for oilfield logging, characterized in that, The porous composite carrier particles are particulate solids with a particle size of 50-2000 μm, comprising a cross-linked polymer network framework and chitosan / hydroxyapatite composite particles dispersed and embedded therein; the chitosan / hydroxyapatite composite particles are formed by chitosan with a viscosity of 80-120 Pa·s and hydroxyapatite with a particle size of 60-80 nm under the cross-linking action of glutaraldehyde; the cross-linked polymer network framework contains polyacrylic acid segments, acrylic acid segments and sodium acrylate segments, and contains ionic cross-linking points formed by calcium ions and carboxyl groups, so that the cross-linked polymer network framework forms an interconnected porous structure; the surface of the porous composite carrier particles has a hydrophilic hydration layer formed by the enrichment of polyacrylic acid segments and / or sodium acrylate segments.

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