Stratum tracing detection method based on < 19 > F NMR and fluorine-containing compound

Abstract

The invention discloses a stratum tracing detection method based on < 19 > F NMR (nuclear magnetic resonance) and a fluorine-containing compound. According to the method, tracing detection of underground water or oil reservoir fluid in a stratum is achieved by selecting the appropriate fluorine-containing compound as the tracer and combining the 19F NMR technology, accurate quantitative analysis of the trace tracer is achieved while the detection cost is greatly reduced, meanwhile, the lower detection limit of the tracer can be reduced to 10 <-6 >-10 <-9 > or a lower concentration range, and the detection accuracy of the tracer is improved. And relatively high quantitative accuracy is kept. Wherein the fluorine-containing compound is slightly influenced by environmental factors, and can maintain chemical and biological stability under extreme formation conditions; a water-based sample is concentrated by adopting a rotary evaporation method, so that the reagent dosage and the detection cost can be further reduced; the 19F NMR technology can provide better signal resolution and effectively avoid interference of environmental background impurities. The method has the advantages of high sensitivity, strong anti-interference capability, quantitative analysis and the like, and an efficient, accurate and environment-friendly connectivity measurement method is provided for oilfield waterflooding development.

Description

Technical Field

[0001] The present invention belongs to the field of formation tracing and detection technology, and in particular relates to a method based on 19 F NMR and formation tracer detection methods for fluorine-containing compounds. Background Art

[0002] Currently, tracer technology is mainly divided into three categories: chemical tracers, radioisotope tracers and non-radioisotope tracers.

[0003] As the earliest technology, chemical tracers are considered the first generation of tracers, including inorganic salts, dyes, halogenated hydrocarbons and alcohols. Traditional detection methods such as spectrophotometers can only achieve 10 -4 to 10 -6 The lack of precision at this level limits chemical tracers in terms of adaptability, dosage, cost-effectiveness, and test accuracy. This can also affect subsequent crude oil processing, leading to uncertainty in interpreting results. Consequently, these tracers are gradually being phased out of the market.

[0004] Second-generation tracers—radioisotope tracers, represented by tritiated water, tritiated alkanes, and tritiated alcohols—can achieve extremely high sensitivity when detected using precision equipment such as liquid scintillometers. Radioisotope tracers are widely used in various fields due to their advantages, such as trace usage, ease of addition and detection, and high cost-effectiveness. However, their use requires strict compliance with national regulations on the management of radioactive materials and the supervision of specialized personnel and institutions to ensure safety and compliance.

[0005] The third generation of tracer technology, namely non-radioactive isotope (or stable isotope) tracers, represents the latest progress in this field. This type of tracer covers activatable non-radioactive isotopes present in various reagents, which can also provide high-precision results when detected by advanced methods such as neutron activation analysis and liquid scintillation counting. Non-radioactive isotope tracers not only inherit the advantages of radioactive isotopes, but also eliminate the complexity and risks of the latter in addition, sampling and management, showing broad application prospects. However, since these isotopes usually need to be activated by reactors, they still rely on professional facilities and technicians for effective detection. Nevertheless, with the development of technology, the degree of dependence on professional departments is expected to gradually decrease, thereby promoting the wider adoption and application of this technology.

[0006] Organofluorine compounds possess unique properties that make them potentially suitable as chemical tracers. The carbon-fluorine bond is one of the strongest bonds in organic chemistry, resulting in high thermal and chemical stability. This stability ensures that tracers remain intact under the harsh conditions encountered in oil reservoirs. Their low intermolecular forces make them relatively oleophobic. This property is crucial for tracers, as it allows them to flow with the traced fluid without significant retention in the reservoir rock. Furthermore, the presence of fluorine in organic compounds can significantly alter their physical and chemical properties, including their reactivity and solubility. This tunability allows the design of tracers with specific properties tailored to reservoir conditions and the desired tracer target. In addition to organofluorine compounds, inorganic fluorine-containing salts, such as potassium hexafluorophosphate, also offer significant potential as tracers in various fields, such as geology, hydrology, environmental science, and industrial process monitoring, due to their high chemical stability, low toxicity, minimal environmental signal interference, and relatively low preparation and use costs. Summary of the Invention

[0007] In view of the problems existing in the background technology, the purpose of the present invention is to provide two 19 F NMR (nuclear magnetic resonance) and fluorine-containing compound formation tracer detection method, specifically using fluorine-containing compounds as tracers and combining 19 F NMR (nuclear magnetic resonance) technology is used to trace groundwater or reservoir fluids, aiming to provide a highly sensitive, low-cost, environmentally friendly detection method that is not affected by formation sand adsorption for formation fluid tracking, technology evaluation, and related applications.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a 19 The method for detecting formation tracers using F NMR and fluorine-containing compounds comprises the following steps:

[0010] S1. Dissolve the fluorine-containing compound in water to obtain a fluorine-containing compound mother solution, then add alkali to the fluorine-containing compound mother solution to adjust the pH of the solution to 8.8-9.2 to obtain a standard alkaline tracer solution:

[0011] S2. Conduct formation sand simulation adsorption experiment: Mix the standard alkaline tracer solution and formation sand, place at 80-90℃ for 60-72h to obtain a water-based sample; 19 F NMR uses sodium trifluoromethanesulfonate as an internal standard to test the concentration of fluorinated compounds in the solution before and after the adsorption experiment. 19 The characteristic peaks of fluorinated compounds on the F NMR spectrum were integrated to achieve quantitative analysis of the concentration of fluorinated compounds in the water-based samples obtained after the adsorption experiment.

[0012] The second aspect of the present invention provides another method based on 19 The method for detecting formation tracers using F NMR and fluorine-containing compounds comprises the following steps:

[0013] A1. Dissolve the fluorine-containing compound in water to obtain a fluorine-containing compound mother solution, dilute the fluorine-containing compound solution to 10-30 times, and then add alkali to the diluted fluorine-containing compound solution to adjust the pH of the solution to 8.8-9.2 to obtain a standard alkaline tracer solution:

[0014] A2. Conduct formation sand simulation adsorption experiment: Mix the standard alkaline tracer solution with formation sand and place it at 80-90℃ for 60-72h to obtain a water-based sample; concentrate the water-based sample obtained after the adsorption experiment and use 19 F NMR was used to test and compare the concentrated water-based sample with the fluorinated compound mother liquor using sodium trifluoromethanesulfonate as the internal standard to quantitatively analyze the concentration of fluorinated compounds in the concentrated water-based sample.

[0015] Preferably, the standard alkaline tracer solution is mixed with formation sand in a material-liquid mass ratio ranging from 1 to 10.

[0016] Preferably, the concentration of the fluorine-containing compound mother solution is 1-3 ppm.

[0017] Preferably, the base is sodium hydroxide or potassium hydroxide.

[0018] Preferably, in order to ensure good applicability in various formation environments, the fluorine-containing compound is an aliphatic fluorine-containing sodium carboxylate, an aromatic fluorine-containing sodium carboxylate or a fluorine-containing inorganic salt.

[0019] Preferably, the sodium aliphatic fluorine-containing carboxylate is one or a combination of two or more of sodium trifluoroacetate, sodium pentafluoropropionate, sodium 2,2-difluoropropionate, sodium 3,3,3-trifluoropropionate, and sodium 4,4,4-trifluorobutyrate; the sodium aromatic fluorine-containing carboxylate is one or a combination of two or more of sodium 2-(trifluoromethyl)benzoate, sodium 4-trifluoromethylbenzoate, sodium 2,4-difluorobenzoate, sodium p-fluorobenzoate, sodium 3-fluorobenzoate, sodium o-fluorobenzoate, sodium 2,4,5-trifluorobenzoate, sodium p-fluorophenylacetate, sodium 2,3,4-trifluorobenzoate, sodium 3,4,5-trifluorobenzoate, sodium 3,4-difluorobenzoate, sodium tetrafluoroterephthalate, and sodium 2,3,4,5,6-pentafluorobenzoate; and the fluorine-containing inorganic salt is potassium hexafluorophosphate. The present invention selects the above-mentioned fluorine-containing compounds as tracers because such compounds have the advantages of low cost and environmental friendliness, and are not affected by formation sand adsorption. At the same time, they can also overcome the lower limit problem of nuclear magnetic resonance detection by concentrating the solvent through rotary evaporation, further reducing the reagent dosage and detection cost.

[0020] Preferably, the use19 F NMR was used to test and compare the concentrated water-based sample with the mother liquor of fluorinated compounds using sodium trifluoromethanesulfonate as the internal standard, and the concentration of fluorinated compounds in the concentrated water-based sample was quantitatively analyzed. The specific steps were as follows: (1) sodium trifluoromethanesulfonate aqueous solution was used as the internal standard solution during the test, and standardized quantification was achieved through its clear marker peak; (2) the concentrated water-based sample was mixed with sodium trifluoromethanesulfonate aqueous solution and deuterated water, and the deuterated water was used for nuclear magnetic locking; (3) the concentration of fluorinated compounds in the concentrated water-based sample was determined by the following methods: 19 The characteristic peaks of fluorinated compounds on the F NMR spectrum are integrated to achieve quantitative analysis of the concentration of fluorinated compounds in the concentrated water-based sample.

[0021] Preferably, the volume ratio of the concentrated water-based sample to the sodium trifluoromethanesulfonate aqueous solution is in the range of 0.1 to 10:1; the volume ratio of the sum of the volumes of the concentrated water-based sample and the sodium trifluoromethanesulfonate aqueous solution to deuterated water is in the range of 0.1 to 10:1.

[0022] Preferably, in order to further reduce the detection limit and save testing costs, the water-based sample is concentrated by rotary evaporation to reduce the solvent volume and increase the nuclear magnetic resonance signal intensity, thereby improving the detection sensitivity.

[0023] Technical effect:

[0024] (1) The present invention selects a suitable fluorine-containing compound as a tracer and combines 19 F NMR (nuclear magnetic resonance) technology has realized the tracer detection of groundwater or reservoir fluid in the formation, which can not only significantly reduce the detection cost but also realize the accurate quantitative analysis of trace tracers and reduce the detection limit of tracers to 10 -6 ~10 -9 , or even lower concentration ranges, while maintaining high quantitative accuracy, sensitivity, and selectivity. This high sensitivity and selectivity has important practical value in formation environment monitoring, oilfield water flooding / chemical flooding effect evaluation, and groundwater flow research.

[0025] (2) In the present invention, sodium fluorinated carboxylates (including aliphatic sodium fluorinated carboxylates and aromatic sodium fluorinated carboxylates) or fluorinated inorganic salts are used as tracers. These compounds are not only abundant in variety but also have the advantages of low cost, environmental friendliness, and ease of preparation. Due to their stable chemical properties, they remain stable in different water systems and formation environments, are not easily adsorbed or decomposed, and maintain good stability in formation sand adsorption experiments without causing additional interference to the formation environment.

[0026] (3) In the present invention, the steps of alkalization treatment of the fluorine-containing compound (tracer) mother liquor and rotary evaporation concentration are performed, which not only effectively improves the 19F NMR detection signal intensity can also effectively reduce the cost of instruments and reagents, while also achieving a wider concentration range of detection (the lower limit of detection can reach 10 -6 ~10 -9 , or even lower);

[0027] (4) In the present invention, the concentrated water-based sample is compared with the fluorine-containing compound (tracer) mother solution, and the 19 The characteristic peak signal of fluorine-containing compounds is integrated on the F NMR spectrum to quantitatively analyze the concentration of fluorine-containing compounds in the concentrated water-based sample. This operation not only reduces the overall detection cost, but also simplifies the sample preparation process, providing great convenience for on-site and laboratory testing. In addition, by using 19 F NMR technology (given that nuclear magnetic resonance technology can still provide good signal resolution in a complex matrix background, effectively avoiding the interference of environmental background impurities) performs quantitative analysis on the characteristic peak integration of fluorine-containing compounds, which can effectively reduce the interference caused by environmental impurities or background signals, making the detection accuracy and sensitivity better than traditional chromatographic methods.

[0028] (5) The fluorine-containing compound selected as the tracer in the present invention can maintain chemical and biological stability under extreme formation conditions. Even under extreme formation conditions (groundwater or reservoir fluid) placed at high temperature (up to 90°C) and for a long time (up to 72 hours), it can still be stable and not decay, and maintain good chemical and biological stability. Therefore, it is particularly suitable for fluid tracking or monitoring in harsh environments.

[0029] (6) The present invention has the advantages of high sensitivity, strong anti-interference ability, and quantitative analysis. It provides an efficient, accurate, and environmentally friendly connectivity measurement method for oil field water injection development. It can be widely used in the fields of oil exploration, environmental testing, etc., and is suitable for various scenarios such as oil extraction, formation flow research, and environmental monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 is the value before adsorption experiment in Example 1 19 F NMR spectrum;

[0032] Figure 2 After the adsorption experiment in Example 1 19 F NMR spectrum;

[0033] Figure 3 is the value before adsorption experiment in Example 2 19 F NMR spectrum;

[0034] Figure 4 The adsorption experiment in Example 2 was concentrated 19 F NMR spectrum; DETAILED DESCRIPTION

[0035] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may also be implemented in other embodiments without these specific details.

[0036] Example 1

[0037] A kind of 19 The method for detecting formation tracers using F NMR and fluorine-containing compounds comprises the following steps:

[0038] S1. Prepare a standard alkaline tracer solution: dissolve the fluorine-containing compound (see Table 1) in deionized water to obtain 100 mL of a fluorine-containing compound mother solution with a mass concentration of 1 ppm; then slowly add concentrated NaOH solution to the fluorine-containing compound mother solution to adjust the pH to 9;

[0039] S2. Conduct formation sand simulation adsorption experiment: take appropriate amount of standard alkaline fluorine-containing tracer solution and record its initial concentration, then add 20g formation sand to every 100g standard alkaline tracer solution, mix, seal and place in a 90℃ water bath for 72h to obtain water-based solution. 19 F NMR uses sodium trifluoromethanesulfonate as the internal standard to test the changes in the concentration of fluorinated compounds in the solution before and after the adsorption experiment. The specific steps are as follows: take samples before and after the adsorption experiment, and use 19 The concentration changes of fluorinated compounds were determined by F NMR. Sodium trifluoromethanesulfonate was used as the internal standard. The influence of formation sand on fluorinated compounds was evaluated by measuring the signal integral value before and after adsorption of fluorinated compounds. The results are shown in Table 1 and Table 2. Figure 1-2 shown.

[0040] The results show that the fluorinated compounds provided by the present invention are minimally affected by adsorption under high-temperature (90°C) water bath conditions, and the actual loss of the fluorinated compounds in solution is extremely low, demonstrating their excellent anti-adsorption and stability as tracers. Simulation experiments using groundwater and reservoir fluids for tracing also demonstrate that the fluorinated compounds remain stable and unattenuated even under extreme formation conditions, such as high temperatures and prolonged exposure, making them particularly suitable for fluid tracking or monitoring in harsh environments.

[0041] Table 1

[0042]

[0043]

[0044] Example 2

[0045] S1. Prepare a standard alkaline tracer solution: Dissolve the fluorinated compound (see Table 2) in deionized water to obtain a fluorinated compound mother solution with a mass concentration of 1 ppm. Dilute this solution to prepare 100 mL of an aqueous solution with a mass concentration of approximately 50 ppb. Slowly add concentrated NaOH solution to the aqueous solution to adjust the pH to 9.

[0046] S2. Conducting a simulated adsorption experiment of formation sand: adding 20 g of formation sand to a solution with a concentration of 50 ppb, mixing evenly, sealing the solution and placing it in a 90°C water bath for 72 hours to obtain a water-based sample;

[0047] S3, concentration and testing: After the adsorption experiment, take 20 mL of the obtained water-based sample and concentrate it to 1 mL using a rotary evaporator; 19 The concentrated solution was tested and compared with the original 1 ppm mother solution by F NMR using sodium trifluoromethanesulfonate as the internal standard. The concentration of the fluorinated compound (tracer) was calculated by integrating the characteristic NMR peaks of the fluorinated compound. The relative concentration of the target compound in the sample was increased by rotary evaporation, which significantly improved the detection sensitivity. The results are shown in Tables 2 and 3. Figure 3-4 shown.

[0048] Table 2

[0049]

[0050] The results show that the changes of fluorine-containing compounds can be accurately quantified even at a low initial concentration (50 ppb), and the fluorine-containing compounds used for tracing still show good stability under the combined effects of high temperature and formation sand.

[0051] The above results show that the concentration of the fluorine-containing compound selected as the tracer in the present invention does not change significantly before and after the experiment, indicating that it is less affected by environmental factors and has good adaptability to complex formation environments.

[0052] In summary, the present invention utilizes the adjustability and 19 The high sensitivity of F NMR detection technology provides a simple, efficient and widely applicable water-based tracer and its application method, which can better meet the needs of multiple scenarios such as reservoir dynamic monitoring, groundwater tracing, oilfield water injection and chemical flooding tracing. Its innovation lies in combining the low cost and environmental friendliness of the tracer with 19The high precision and high sensitivity of the F NMR method can overcome the interference of environmental factors such as formation sand, and it has broad application prospects in geological exploration and energy development.

[0053] The present invention is not limited to the above-mentioned specific implementation methods. Various changes made by ordinary technicians in this field based on the above-mentioned concept without creative work are all within the scope of protection of the present invention.

Claims

1. A method based on 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The following steps are involved: S1. Dissolve the fluorine-containing compound in water to obtain a fluorine-containing compound mother solution, then add alkali to the fluorine-containing compound mother solution to adjust the pH of the solution to 8.8-9.2 to obtain a standard alkaline tracer solution: S2. Conduct formation sand simulation adsorption experiment: Mix the standard alkaline tracer solution and formation sand, place at 80-90℃ for 60-72h to obtain a water-based sample; 19 F NMR uses sodium trifluoromethanesulfonate as an internal standard to test the concentration of fluorinated compounds in the solution before and after the adsorption experiment. 19 The characteristic peaks of fluorinated compounds on the F NMR spectrum were integrated to achieve quantitative analysis of the concentration of fluorinated compounds in the water-based samples obtained after the adsorption experiment.

2. A method based on 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The following steps are involved: A1. Dissolve the fluorine-containing compound in water to obtain a fluorine-containing compound mother solution, dilute the fluorine-containing compound solution to 10-30 times, and then add alkali to the diluted fluorine-containing compound solution to adjust the pH of the solution to 8.8-9.2 to obtain a standard alkaline tracer solution: A2. Conduct formation sand simulation adsorption experiment: Mix the standard alkaline tracer solution with formation sand and place it at 80-90℃ for 60-72h to obtain a water-based sample; concentrate the water-based sample obtained after the adsorption experiment and use 19 F NMR was used to test and compare the concentrated water-based sample with the fluorinated compound mother liquor using sodium trifluoromethanesulfonate as the internal standard to quantitatively analyze the concentration of fluorinated compounds in the concentrated water-based sample.

3. The method according to claim 1 or 2 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The standard alkaline tracer solution is mixed with formation sand in a material-to-liquid mass ratio ranging from 1 to 10.

4. The method according to claim 1 or 2 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The fluorine-containing compound is an aliphatic fluorine-containing sodium carboxylate, an aromatic fluorine-containing sodium carboxylate or a fluorine-containing inorganic salt; and the base is sodium hydroxide or potassium hydroxide.

5. The method according to claim 1 or 2 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The aliphatic sodium fluorine-containing carboxylate is one or a combination of two or more of sodium trifluoroacetate, sodium pentafluoropropionate, sodium 2,2-difluoropropionate, sodium 3,3,3-trifluoropropionate, and sodium 4,4,4-trifluorobutyrate; the aromatic sodium fluorine-containing carboxylate is one or a combination of two or more of sodium 2-(trifluoromethyl)benzoate, sodium 4-trifluoromethylbenzoate, sodium 2,4-difluorobenzoate, sodium p-fluorobenzoate, sodium 3-fluorobenzoate, sodium o-fluorobenzoate, sodium 2,4,5-trifluorobenzoate, sodium p-fluorophenylacetate, sodium 2,3,4-trifluorobenzoate, sodium 3,4,5-trifluorobenzoate, sodium 3,4-difluorobenzoate, sodium tetrafluoroterephthalate, and sodium 2,3,4,5,6-pentafluorobenzoate; and the fluorine-containing inorganic salt is potassium hexafluorophosphate.

6. The method according to claim 2 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: In step A2, the use 19 F NMR uses sodium trifluoromethanesulfonate as an internal standard to compare the concentrated water-based sample with the mother liquor of fluorine-containing compounds, and quantitatively analyzes the concentration of fluorine-containing compounds in the concentrated water-based sample; the specific steps are: (1) using sodium trifluoromethanesulfonate aqueous solution as the internal standard solution during the test, and achieving standardized quantification through its clear marker peak; (2) mixing the concentrated water-based sample with sodium trifluoromethanesulfonate aqueous solution and deuterated water, and using deuterated water for nuclear magnetic locking; (3) 19 The characteristic peaks of fluorinated compounds on the F NMR spectrum are integrated to achieve quantitative analysis of the concentration of fluorinated compounds in the concentrated water-based sample.

7. The method according to claim 6 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The volume ratio of the concentrated water-based sample to the sodium trifluoromethanesulfonate aqueous solution is in the range of 0.1 to 10:1; the volume ratio of the sum of the volumes of the concentrated water-based sample and the sodium trifluoromethanesulfonate aqueous solution to deuterated water is in the range of 0.1 to 10:

1.

8. The method according to claim 6 19 The formation tracing detection method using F NMR and fluorine-containing compounds is characterized by: The concentration treatment of the water-based sample adopts a rotary evaporation method.

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