A method for determining the initial filling time of oil and gas using carbonate cluster isotopes

Abstract

The application discloses a method for determining initial oil and gas charging time by using carbonate cluster isotopes. 18 O and carbonate cluster isotope Δ 47 Test analysis, calculate the cluster isotope temperature T-Δ 47 of the carbonate rock sample; test the maximum burial temperature of the oil and gas reservoir where the carbonate rock sample is located, evaluate the solid state resetting effect on T-Δ 47 , and quantitatively restore the influence of the solid state resetting effect on T-Δ 47 by using the kinetics model of the solid state resetting, so that the T-Δ 47‑R of the sample before the solid state resetting is obtained; evaluate whether the recrystallization of the carbonate rock sample occurs, and determine the temperature of the initial oil and gas charging by using the maximum T-Δ 47‑R of the sample which has recrystallized; combine the burial temperature evolution history of the oil and gas reservoir where the carbonate rock sample is located, and the time when the temperature of the oil and gas reservoir reaches the oil and gas charging temperature is the initial oil and gas charging time.

Description

Technical Field

[0001] This invention belongs to the field of petroleum and natural gas geological exploration technology, and relates to a method for determining the initial charging time of oil and gas using carbonate cluster isotopes. Background Technology

[0002] The charging time of oil and gas (referred to as "oil and gas") is the "critical moment" when oil and gas enter the trap from the source rock and form an oil and gas reservoir. Determining this critical moment is essential for studying the formation and evolution of oil and gas reservoirs, elucidating their distribution patterns, and reducing exploration risks. It has also been a long-standing focus for oil and gas geologists. Previous researchers have proposed various methods for determining the "oil and gas charging time," including: trap development history, hydrocarbon generation and expulsion periods of the source rock, homogenization temperature of fluid inclusions, and authigenic illite geochronology. The trap development history and source rock hydrocarbon generation and expulsion period methods both infer the earliest time of hydrocarbon charging and reservoir formation, but do not directly determine the key moment of hydrocarbon charging. The reservoir authigenic illite geochronology method is based on the cessation of authigenic illite growth after hydrocarbon charging. The earliest time of hydrocarbon charging is represented by the K / Ar age of the smallest authigenic illite. However, this method requires the separation of fine illite (generally less than 10 micrometers) from the reservoir rock, which is very difficult and time-consuming. The fluid inclusion homogenization temperature method is currently a widely used method. Its principle is based on the homogenization temperature of brine inclusions associated with hydrocarbons representing the temperature of hydrocarbon charging. Then, the time of hydrocarbon charging is determined by combining the burial thermal history of the reservoir. This method requires strong practical experience to conduct detailed petrographic observations of fluid inclusions in the mineral grains and cement of the reservoir rock, and to analyze the phases and types of fluid inclusions before the homogenization temperature of the fluid inclusions can be determined.

[0003] carbonate cluster isotopes (Δ 47 Carbonate cluster isotope temperatures (T-ΔT) can directly determine the formation or equilibrium temperature of minerals and are currently widely used in paleoclimate, uplift and erosion history, diagenetic sequences, and reconstruction of diagenetic fluid properties. 47 The main influences are recrystallization and high-temperature solid-state resetting. A kinetic model of high-temperature solid-state resetting has been established. Based on the temperature evolution history, the influence of solid-state resetting on the mineral equilibrium temperature can be accurately recovered. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the initial charging time of oil and gas using carbonate cluster isotopes.

[0005] This invention provides a method for determining the initial charging time of oil and gas using carbonate cluster isotopes, comprising the following steps: S1. Collect carbonate rock samples from the oil and gas reservoir section for petrological analysis; S2. Perform oxygen isotope δ¹⁴ analysis on the carbonate rock sample. 18 O and carbonate cluster isotopes Δ 47 Test analysis was conducted, and the cluster isotope temperature T-Δ of the carbonate rock sample was calculated based on the test analysis results. 47 ; S3. Test to determine the maximum burial temperature of the oil and gas reservoir where the carbonate rock sample is located; S4. Based on the maximum burial temperature, determine the cluster isotope temperature T- of the carbonate rock sample. 47 The solid-state relocation effect was assessed, and the effect of the solid-state relocation effect on the cluster isotope temperature T- of the carbonate rock sample was quantitatively recovered using a kinetic model of solid-state relocation. 47 The influence of the solid-state resetting of the carbonate rock sample was investigated to obtain the T-value before solid-state resetting. 47-R ; S5. Based on the cluster isotope temperature T- of the carbonate rock sample before solid-state resetting. 47-R To assess whether the carbonate rock sample has undergone recrystallization; S6. Based on the confirmation of recrystallization in the carbonate rock samples, utilize the maximum T- of the recrystallized samples. 47-R The initial oil and gas injection temperature of the carbonate rock sample was determined. S7. Based on the initial charging temperature of the oil and gas, and combined with the burial temperature evolution history of the oil and gas reservoir where the carbonate rock sample is located, the time when the temperature of the oil and gas reservoir reaches the charging temperature is the initial charging time of the oil and gas in the oil and gas reservoir where the carbonate rock sample is located.

[0006] In the above method, the carbonate rock sample in step S1 is selected from limestone or dolomite; The steps for collecting and analyzing carbonate rock samples from the oil and gas reservoir are as follows: S11, X-ray diffraction analysis is performed on the powder sample of the carbonate rock to obtain its mineral composition, and samples are selected. S12. Grind the selected samples into thin castings, and then use a polarizing microscope to observe the petrological aspects of the thin castings to select qualified samples. S13. Using the microscopic image of the rock thin section of the qualified sample, determine the grain size of calcite or dolomite crystals in the rock, calculate the average value, and obtain the average grain size of the entire carbonate rock sample.

[0007] In this invention, in step S13, the selected samples are specifically measured for the particle size of 30-50 crystals in each sample, and the average particle size of the sample is calculated. This is because selecting samples with different particle sizes is to determine the degree of recrystallization and ensure that all particle sizes are counted.

[0008] In the above method, in step S11, the standard for selecting the sample is: the relative content of dolomite or calcite is greater than 95%; In step S12, the selection criteria for qualified samples are: samples that are mainly composed of matrix particles or grains and have no significant late cementing.

[0009] In the above method, step S5, the step of evaluating whether the carbonate rock sample has undergone recrystallization is as follows: S51, using the oxygen isotope δ of the sample... 18 O and T- before solid-state resetting of the carbonate rock sample 47-R Data, combined with oxygen isotope thermometer readings, were used to calculate the oxygen isotope δ0.05 of the fluid in equilibrium with the mineral. 18 Of; S52: Plot the oxygen isotope δ of the sample. 18 O, T- of the carbonate rock sample before solid-state resetting 47-R and the oxygen isotope δ of the mineral equilibrium fluid 18 Of's plate, with the carbonate rock sample before solid-state resetting T- 47-R Increase, mineral oxygen isotope δ 18 O continuously decreases, but the oxygen isotope δ of the mineral equilibrium fluid remains constant. 18 If the 'O' value remains essentially unchanged, then the sample has undergone significant recrystallization.

[0010] In the above method, the oxygen isotope δ of the mineral equilibrium fluid is calculated according to formula I or formula II. 18 Of:

[0011] In Equation I, T is the temperature at which dolomite forms, in K; α dolomite-fluid The oxygen isotope fractionation coefficient between dolomite and the fluid; Formula II 1000lnα calcite-fluid =18.03×10 3 / T-32.42 In Equation II, T is the temperature at which calcite forms, in K; α calcite-fluid The oxygen isotope fractionation coefficient between calcite and the fluid is given.

[0012] In the above method, in step S2, oxygen isotope δ¹⁴O₂ analysis is performed on the carbonate rock sample. 18 O and carbonate cluster isotopes Δ 47 The test analysis was conducted as follows: S21. Remove any residual soluble organic matter from the qualified sample to avoid contamination of the cluster isotope test. S22. Based on the sample obtained in step S21, react the powder with H2O2 to remove residual organic matter and clay minerals, and then dry it (specifically, it can be dried at low temperature, or more specifically, dried at 40°C). S23. Take the dried sample and react it with phosphoric acid to produce CO2. Use an isotope mass spectrometer to test the purified CO2 and obtain the relative abundance of CO2 molecules with a mass number of 44-47. S24. Calculate the oxygen isotope δ of the sample based on the relative abundance of the CO2 molecules. 18 O and the original Δ 47 value; In this invention, in step S22, the reaction is processed as follows: during the reaction, ultrasonic oscillation is applied, and then the upper suspension is poured off. This process is repeated multiple times until no more bubbles are generated. In step S23, the specific operation is as follows: Weigh about 10 mg of the dried sample, react it with 103% phosphoric acid to produce CO2, and then purify it in a series of steps. Then, use an isotope mass spectrometer to test the purified CO2 and obtain the relative abundance of CO2 molecules with a mass number of 44-47.

[0013] In the above method, in step S2, the cluster isotope temperature T-Δ of the carbonate rock sample is calculated according to the following operation. 47 : S25. Using solid carbonate standards ETH1~ETH4 and laboratory carbonate rock sample standards, the original Δ of the sample was determined. 47 Value converted to Δ in an absolute reference system 47 value; S26. Δ based on the aforementioned absolute reference system 47 The value was used to calculate the cluster isotope temperature T of the sample. 47 .

[0014] In the above method, in step S2, the cluster isotope temperature T-Δ of the carbonate rock sample is calculated according to the following formula III. 47 (Specifically, the temperature calibration equation established by Bonifacie et al. (2017)):

[0015] In Formula III, 47 This represents the Δ of the absolute reference system of the sample at CDES90℃. 47 Value, T-Δ 47 This indicates the cluster isotope temperature of the sample.

[0016] In the above method, step S3, the test is performed as follows: S31. If the oil and gas reservoir only undergoes a continuous burial process, then the current burial temperature is the maximum burial temperature, wherein the current burial temperature is obtained based on the geothermal gradient determined by the burial depth and the temperature test of the well. S32. If the oil and gas reservoir undergoes late-stage uplift and the current formation temperature cannot represent the maximum burial temperature, the maximum burial temperature can be determined using the vitrinite reflectance Ro and EasyRo model of the mudstone in the adjacent reservoir; or the maximum burial temperature can be determined using the cluster isotopes of micritic limestone or dolomite (see ZL202411492554.8 for details).

[0017] In the above method, in step S4, the T-phase of the carbonate rock sample before solid-state resetting is obtained. 47-R Process according to any of the following methods S41~S43: S41. When the maximum burial temperature is lower than the solid-state reset threshold temperature of calcite or dolomite (specifically, 100°C for calcite and 150°C for dolomite), the T-Δ of the sample... 47 Without being affected by solid-state resetting, the cluster isotope temperature T-Δ of the carbonate rock sample is... 47 The temperature of cluster isotopes affected only by recrystallization; S42. When the maximum burial temperature is higher than the solid-state relocation threshold temperature of calcite or dolomite but lower than the threshold temperature for complete relocation (specifically, 175-100℃ for calcite and 250℃ for dolomite), the sample has undergone partial solid-state relocation. A solid-state relocation model is needed to determine the temperature rise t caused by this relocation, and then the cluster isotope temperature T-Δ of the carbonate rock sample is calculated. 47 Subtracting this increase, we obtain the cluster isotope temperature affected only by recrystallization; S43. When the maximum burial temperature is higher than the threshold temperature for complete resetting of calcite or dolomite, the sample undergoes complete solid-state resetting, and the cluster isotope temperature T-Δ of the carbonate rock sample... 47 When the temperature reaches equilibrium with the burial temperature of the formation, and the increase in cluster isotope temperature cannot be determined using the solid-state reset model, nor can the cluster isotope temperature affected only by recrystallization be obtained, the experiment is terminated.

[0018] In this invention, the solid-state reset model is based on the literature Stolper and Eiler, 2015; Lloyd et al., 2018.

[0019] The present invention has the following beneficial effects: 1. This invention utilizes the basic principle that the recrystallization of carbonate minerals ceases when oil and gas enter the reservoir, causing formation water to be discharged (significantly reducing the water-to-rock ratio). This is achieved by measuring the cluster isotope temperatures (T-ΔT) of a series of carbonate minerals. 47 This can effectively constrain the temperature at which oil and gas enter the reservoir. Then, by combining the burial and temperature evolution history of the reservoir, the time when oil and gas enter the reservoir can be finally determined.

[0020] 2. Unlike traditional methods, this invention only requires measuring the cluster isotopes of carbonate minerals with different degrees of crystallinity to obtain the cluster isotope temperature (T-ΔT). 47 The highest cluster isotope temperature can represent the temperature of oil and gas injection; while the traditional method is based on the homogenization temperature of fluid inclusions inside the mineral grains of the reservoir rock, combined with the burial and temperature evolution history to obtain the time of oil and gas injection. This method requires detailed petrographic observation of inclusions of different stages and occurrences inside the mineral grains. Attached Figure Description

[0021] Figure 1 Dolomite plates of different grain sizes in the reservoir section of the study area provided as examples of this invention; wherein Figure 1 a: Muddy-crystalline dolomite; b: Microcrystalline dolomite; c: Fine-crystalline dolomite; d: Fine-to-medium-crystalline dolomite.

[0022] Figure 2 The solid-state reset recovery δ provided in the example of the present invention 18 O and T- 47 Relationship diagram; its Figure 2 The dashed line represents the oxygen isotope value of the mineral equilibrium fluid obtained using a dolomite oxygen isotope thermometer.

[0023] Figure 3 Solid-state resetting evaluation diagram of carbonate sample cluster isotope temperature provided for an example of the present invention.

[0024] Figure 4 δ after solid-state reset provided as an example of the present invention 18 O and T- 47 Relationship diagram, its Figure 4 The dashed line represents the oxygen isotope value of the mineral equilibrium fluid obtained using a dolomite oxygen isotope thermometer.

[0025] Figure 5 This invention provides a burial history map based on the evolution of reservoir burial temperature in the study area to determine the charging time, which is an example of the invention. Detailed Implementation

[0026] To provide a clearer understanding of the technical features and beneficial effects of the present invention, preferred embodiments of the present invention will now be described in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0028] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0029] This invention provides a method for determining the initial charging time of oil and gas using carbonate cluster isotope temperatures, specifically comprising the following steps: S1: Collect carbonate rock samples (limestone or dolomite) from the oil and gas reservoir area for petrological analysis, and select qualified samples, including the following 3 steps: S11: Collect carbonate rock samples from the reservoir section, perform X-ray diffraction analysis (XRD) on the powder samples to obtain the mineral composition of the samples, and select samples with a relative content of dolomite or calcite greater than 95%. S12: Grind the selected samples into thin sections of casting, and then use a polarizing microscope to conduct petrological observations on the thin sections of casting. Select samples that are mainly composed of matrix particles or grains and have no significant late cementation as qualified samples. S13: Then, using the microscopic images of the rock thin sections of the qualified sample, the grain size of calcite or dolomite in the rock is determined, and the average value is calculated to represent the average grain size of the entire sample. S2: Oxygen isotope (δ¹⁸O) analysis of qualified samples. 18 O) and cluster isotopes (Δ) 47 The analysis includes the following 6 steps: S21: Remove residual soluble organic matter from qualified samples with different average particle sizes to avoid contamination of cluster isotope testing. S22: Based on the sample obtained by the above treatment, the powder is reacted with H2O2. During the reaction, ultrasonic vibration is applied, and then the upper suspension is poured off. This process is repeated several times until no more bubbles are generated, removing any possible residual organic matter and clay minerals. The sample is then dried at low temperature. S23: Weigh approximately 10 mg of the dried sample and react it with 103% phosphoric acid to produce CO2. After a series of purifications, the purified CO2 is then tested using an isotope mass spectrometer to obtain the relative abundance of CO2 molecules with a mass number of 44-47. S24: Calculate the δ of the sample according to the method provided by Huntington et al. (2009). 18 O and the original Δ 47 value; S25: Then, using solid carbonate standards (ETH1~ETH4) and internal laboratory standards, the original Δ of the sample was determined. 47 Values ​​converted to an absolute reference frame (Δ) 47 CDES90℃). S26: Δ based on an absolute reference system 47 The cluster isotope temperature (T-) of the sample was calculated using the temperature calibration equation established by Bonifacie et al. (2017). 47 ); S3: Determine the maximum burial temperature of the reservoir, specifically in the following cases: S31: If the reservoir only undergoes a continuous burial process, the current burial temperature is the maximum burial temperature. The current burial temperature of the reservoir can be obtained from the geothermal gradient determined by the burial depth and the temperature test of the well. S32: If the reservoir has undergone late uplift, the current formation temperature cannot represent the maximum burial temperature. The maximum burial temperature needs to be determined by using the vitrinite reflectance (Ro) of the mudstone in the adjacent reservoir and the EasyRo model; or by using the cluster isotopes of micritic limestone or dolomite to determine the maximum burial temperature (see ZL202411492554.8 for details). S4: Cluster isotope temperature (T-) of carbonate samples based on maximum burial temperature. 47 The solid-state relocation effect was assessed, and a kinetic model of solid-state relocation was used to quantitatively recover the effect of solid-state relocation on T- 47 The impact ultimately resulted in obtaining the T- before the solid-state reset. 47-R Specifically, there are three situations: S41: When the maximum burial temperature is lower than the solid-state reset threshold temperature of calcite or dolomite (100℃ for calcite, 150℃ for dolomite), the T-Δ value of the sample is... 47 Unaffected by solid-state reset, T-Δ 47 Cluster isotope temperature (T-Δ) affected only by recrystallization 47-R ); S42: When the maximum burial temperature is higher than the solid-state relocation threshold temperature but lower than the complete relocation threshold temperature (175-100℃ for calcite, 250℃ for dolomite), the sample has undergone partial solid-state relocation. The temperature rise (t) caused by solid-state relocation needs to be determined using a solid-state relocation model (Stolper and Eiler, 2015; Lloyd et al., 2018), and then T-Δ... 47 Subtracting this increase, we can obtain the cluster isotope temperature (T-Δ) affected only by recrystallization. 47-R ); S43: When the maximum burial temperature exceeds the threshold temperature for complete reset, the sample undergoes complete solid-state reset, T-Δ 47 Since the temperature has reached equilibrium with the formation burial temperature, it is impossible to determine the increase in cluster isotope temperature using a solid-state reset model, nor is it possible to obtain cluster isotope temperatures (T-ΔT) affected only by recrystallization. 47-R ); S5: Based on T- before solid-state reset 47-R To assess whether recrystallization has occurred in the sample, the following two steps are involved: S51: Utilizing the sample's δ 18 O and T- 47-R Data, combined with oxygen isotope thermometers, were used to calculate the oxygen isotope (δ¹⁸O) of the mineral equilibrium fluid. 18 Of); S52: Compilation δ 18 O, T- 47-R and δ 18 Of's illustration, along with T- 47-R Increase, mineral δ 18 O continues to decrease, but δ 18 The Of value remains essentially unchanged, indicating that the sample has undergone significant recrystallization. S6: Based on the confirmation of the above recrystallization process, using the maximum T-Δ 47-R The initial temperature of oil and gas injection can then be obtained.

[0030] S7: Based on the oil and gas charging temperature determined above, and combined with the burial temperature evolution history of the reservoir, the time when the reservoir temperature reaches the oil and gas charging temperature is the time of initial oil and gas charging.

[0031] In a preferred embodiment, in order to ensure that the sample is relatively pure dolomite, a dolomite sample with a dolomite content of more than 95% is selected in step S1; otherwise, the kinetic parameters in subsequent steps cannot be determined and the experiment cannot continue.

[0032] In a preferred embodiment, selecting samples of different particle sizes is to determine the degree of recrystallization and ensure that all particle sizes are counted. Therefore, for each selected sample, the particle size of 30-50 crystals is specifically measured to obtain the average particle size of the sample.

[0033] Example A method for determining the initial charging time of oil and gas using carbonate cluster isotope temperature includes the following steps: Step 1: Collect dolomite samples from the oil and gas reservoir section of the study area for petrological analysis: 1. Carbonate rock samples were collected from a gas field in a basin. The samples were crushed to below 100 mesh. X-ray diffraction analysis (XRD) was performed on the powder samples, and the dolomite content was found to be above 95%. 2. Grind the above samples into thin sections and conduct petrological observations on the thin sections using a polarizing microscope. Select samples that are mainly composed of matrix particles or grains and have no significant late cementing. 3. For the selected samples, measure the particle size of 30-50 grains in each sample and calculate the average particle size of the sample.

[0034] Step 2: Perform oxygen isotope (δ¹²) analysis on the above samples. 18 O) and cluster isotopes (Δ) 47 The analysis specifically includes the following 6 steps: 1. Extract qualified sample powders with different average particle sizes with dichloromethane (DCM) for 24 hours to remove any residual soluble organic matter in the samples to avoid contamination of cluster isotope testing. 2. Based on the sample obtained by the above treatment, the powder was reacted with 3.0% H2O2 in a Teflon tube for 2 hours. During the reaction, ultrasonic vibration was applied. Then the upper suspension was poured off. This process was repeated several times until no more bubbles were generated to remove any possible residual organic matter and clay minerals. The sample was then dried at a low temperature (less than 40°C) for 24 hours. 3. Weigh approximately 10 mg of the dried sample and react it with 103% phosphoric acid at 90°C to produce CO2. After a series of purifications, the purified CO2 was tested using a ThermoMAT253 isotope mass spectrometer to obtain the relative abundance of CO2 molecules with mass numbers of 44-47. Each sample was measured three times to ensure that the sample error was within 0.02 per thousand. 4. Following the method provided by Huntington et al. (2009), the δ0.05 of the dolomite sample was calculated. 18 O and the original Δ 47 Value. This example yields the δ value of dolomite. 18 O ranged from -3.919 to -7.758‰, and the specific results are shown in Table 1.

[0035] Table 1. δ¹⁸O values ​​of dolomite samples from a certain area of ​​a basin. 18 O、Δ 47 (CDES90) and T-Δ 47 (°C) data

[0036] Table 1 (continued) δ¹⁸O values ​​of dolomite samples from a certain area of ​​a basin 18 O、Δ 47 (CDES90) and T-Δ 47 (°C) data

[0037] 5. Then, using solid carbonate standards (ETH1~ETH4) and internal laboratory standards, the original Δ of the sample was determined. 47 Values ​​converted to an absolute reference frame (Δ) 47 (CDES 90℃), after conversion, the Δ of the sample in the study area was obtained. 47 The values ​​range from 0.400 to 0.489‰, and the specific results are shown in Table 1.

[0038] 6. Δ based on an absolute reference system 47 The cluster isotope temperature (T-) of the sample was calculated using the temperature calibration equation established by Bonifacie et al. (2017). 47 The T- of the sample was calculated. 47 The values ​​range from 67.94 to 117.76℃.

[0039]

[0040] Step 3: Determine the maximum burial temperature of the reservoir in the study area: The reservoir in the study area underwent late uplift, and the current formation temperature cannot represent the maximum burial temperature. Shale samples from the same strata as the target formation were collected, thin sections were prepared, and microscopic observation and vitrinite reflectance testing were performed. Specifically, the vitrinite reflectance (Ro) of the mudstone in the adjacent reservoir and the EasyRo model were used to determine that the maximum burial temperature of the reservoir in the study area was 200℃.

[0041] Step 4: Based on the maximum burial temperature, determine the cluster isotope temperature (T-) of the carbonate sample. 47 The solid-state relocation effect was assessed, and a kinetic model of solid-state relocation was used to quantitatively recover the effect of solid-state relocation on T- 47 The impact ultimately resulted in obtaining the T- before the solid-state reset. 47-R : 1. The maximum burial temperature of the reservoir in the study area is 200℃, which is higher than the solid-state reset threshold temperature but lower than the complete reset threshold temperature of 250℃, indicating that the sample underwent partial solid-state reset. 2. The apparent equilibrium temperature of the dolomite in the current study area is close to 120℃ (e.g., Figure 2 As shown in the figure, using the solid-state resetting model (Lloyd et al., 2018), it is concluded that if dolomite reaches recrystallization equilibrium at 100℃, the equilibrium temperature after solid-state resetting is between 120 and 130℃. Given that the apparent equilibrium temperature of current dolomite samples is close to 120℃, this is consistent with the result that dolomite reaches recrystallization equilibrium at 90℃ before undergoing solid-state resetting. Figure 3 The temperature rise caused by the solid-state reset was determined to be 30±5℃ (1σ), and then T-Δ was calculated. 47 Subtracting this increase, we can obtain the cluster isotope temperature (T-Δ) affected only by recrystallization. 47-R ).

[0042] Step 5: Based on the T- before solid-state reset 47-R To assess whether recrystallization has occurred in the sample, the following two steps are included: 1. Utilizing the sample's δ 18 O and T- 47-R Data, combined with an oxygen isotope thermometer for dolomite (Horita, 2014), were used to calculate the oxygen isotopes (δ¹⁸O) of the fluid in equilibrium with the mineral. 18 Of);

[0043] Where T is the temperature at which dolomite forms, in K; α dolomite-fluid The oxygen isotope fractionation coefficient between dolomite and the fluid is given.

[0044] 2. Compilation and drawing 18 O, T- 47-R and δ 18 The chart of Of, based on the chart analysis, if with T- 47-R Increase, mineral δ 18 O continuously decreases, and δ 18 If the 'O' value remains essentially unchanged, it can be determined that the sample has undergone significant recrystallization.

[0045] Step Six: Based on the confirmation of the above recrystallization process, utilize the maximum T-Δ 47-R The oil and gas injection temperature can be obtained at 93℃ (e.g.) Figure 4(As shown). The homogenization temperature data of the fluid inclusions are 93.20-93.5℃, with an average temperature of 93.6℃ (refer to the following reference: Wang Cunwu. Overpressure Development, Evolution and Genetic Mechanism of Carbonate Strata in Northeast Sichuan [D]. China University of Geosciences, 2008.), which is basically consistent with the data obtained in this experiment.

[0046] Step 7: Based on the determined hydrocarbon charging temperature and the evolution history of the reservoir's burial temperature, the time when the reservoir temperature reaches the hydrocarbon charging temperature, i.e., the initial hydrocarbon charging time, is 187 Ma in the Early Jurassic period (e.g., 187 Ma). Figure 5 (As shown).

[0047] The above describes a method for determining oil and gas charging time using cluster isotopes of dolomite samples. A similar method is used to determine oil and gas charging time using calcite and cluster isotopes, but there are differences in the solid-state resetting model and oxygen isotope thermometer.

Claims

1. A method for determining the initial charging time of oil and gas using carbonate cluster isotopes, comprising the following steps: S1. Collect carbonate rock samples from the oil and gas reservoir section for petrological analysis; S2. Perform oxygen isotope δ¹⁴ analysis on the carbonate rock sample. 18 O and carbonate cluster isotopes Δ 47 Test analysis was conducted, and the cluster isotope temperature T-Δ of the carbonate rock sample was calculated based on the test analysis results. 47 ; S3. Test to determine the maximum burial temperature of the oil and gas reservoir where the carbonate rock sample is located; S4. Based on the maximum burial temperature, the T- of the carbonate rock sample... 47 The solid-state relocation effect was assessed, and a kinetic model of solid-state relocation was used to quantitatively recover the effect of solid-state relocation on the T-values ​​of the carbonate rock sample. 47 The influence of the solid-state resetting of the carbonate rock sample was used to obtain the cluster isotope temperature T- of the sample. 47-R ; S5. Based on the cluster isotope temperature T- of the carbonate rock sample before solid-state resetting. 47-R To assess whether the carbonate rock sample has undergone recrystallization; S6. Based on the confirmation of recrystallization in the carbonate rock samples, utilize the maximum T- of the recrystallized samples. 47-R The initial oil and gas injection temperature of the carbonate rock sample was determined. S7. Based on the initial oil and gas charging temperature and combined with the burial temperature evolution history of the oil and gas reservoir where the carbonate rock sample is located, the time when the temperature of the oil and gas reservoir reaches the initial oil and gas charging temperature is the initial oil and gas charging time of the oil and gas reservoir where the carbonate rock sample is located.

2. The method according to claim 1, characterized in that, The carbonate rock sample mentioned in step S1 is selected from limestone or dolomite; The steps for collecting and analyzing carbonate rock samples from the oil and gas reservoir are as follows: S11, X-ray diffraction analysis is performed on the powder sample of the carbonate rock to obtain its mineral composition, and samples are selected. S12. Grind the selected samples into thin castings, and then use a polarizing microscope to observe the petrological aspects of the thin castings to select qualified samples. S13. Using the microscopic image of the rock thin section of the qualified sample, determine the grain size of calcite or dolomite crystals in the rock, calculate the average value, and obtain the average grain size of the entire carbonate rock sample.

3. The method according to claim 2, characterized in that, In step S11, the selection criteria for the sample are: a relative content of dolomite or calcite greater than 95%; In step S12, the selection criteria for qualified samples are: samples that are mainly composed of matrix particles or grains and have no significant late cementing.

4. The method according to claim 2 or 3, characterized in that, In step S5, the steps for assessing whether the carbonate rock sample has undergone recrystallization are as follows: S51. Utilizing the oxygen isotope δ of the sample 18 O and T- before solid-state resetting of the carbonate rock sample 47-R Data, combined with oxygen isotope thermometer readings, were used to calculate the oxygen isotope δ¹⁴ of the fluid in equilibrium with the mineral. 18 Of; S52. Plot the oxygen isotope δ of the sample. 18 O, T- of the carbonate rock sample before solid-state resetting 47-R and the oxygen isotope δ of the mineral equilibrium fluid 18 Of's plate, with the carbonate rock sample before solid-state resetting T- 47-R Increase, mineral oxygen isotope δ 18 O continuously decreases, but the oxygen isotope δ of the mineral equilibrium fluid remains constant. 18 If the 'O' value remains essentially unchanged, then the sample has undergone significant recrystallization.

5. The method according to claim 4, characterized in that, Calculate the oxygen isotope δ of the mineral equilibrium fluid according to Equation I or Equation II below. 18 Of: In Equation I, T is the temperature at which dolomite forms, in K; α dolomite-fluid The oxygen isotope fractionation coefficient between dolomite and the fluid; In Equation II, T is the temperature at which calcite forms, in K; α calcite-fluid The oxygen isotope fractionation coefficient between calcite and the fluid is given.

6. The method according to claim 5, characterized in that, In step S2, the carbonate rock sample is subjected to oxygen isotope δ¹⁸O analysis. 18 O and carbonate cluster isotopes Δ 47 The test analysis was conducted as follows: S21. Remove residual soluble organic matter from the qualified sample; S22. Based on the sample obtained in step S21, the powder is reacted with H2O2 to remove residual organic matter and clay minerals, and then dried. S23. Take the dried sample and react it with phosphoric acid to produce CO2. Use an isotope mass spectrometer to test the purified CO2 and obtain the relative abundance of CO2 molecules with a mass number of 44-47. S24. Calculate the oxygen isotope δ of the sample based on the relative abundance of the CO2 molecules. 18 O and the original Δ 47 value.

7. The method according to claim 6, characterized in that, In step S2, the cluster isotope temperature T-Δ of the carbonate rock sample is calculated according to the following operation. 47 : S25. Using solid carbonate standards ETH1~ETH4 and laboratory carbonate rock sample standards, the original Δ of the sample was determined. 47 Value converted to Δ in absolute reference system 47 value; S26. Δ based on the aforementioned absolute reference system 47 The value was used to calculate the cluster isotope temperature T of the sample. 47 .

8. The method according to claim 7, characterized in that, In step S2, the cluster isotope temperature T-Δ of the carbonate rock sample is calculated according to the following formula III. 47 : In Formula III, 47 This represents the Δ of the absolute reference system of the sample at CDES90℃. 47 Value, T-Δ 47 This indicates the cluster isotope temperature of the sample.

9. The method according to any one of claims 1-8, characterized in that, In step S3, the test is performed as follows: S31. If the oil and gas reservoir only undergoes a continuous burial process, then the current burial temperature is the maximum burial temperature, wherein the current burial temperature is obtained based on the geothermal gradient determined by the burial depth and the temperature test of the well. S32. If the oil and gas reservoir undergoes late-stage uplift and the current formation temperature cannot represent the maximum burial temperature, the maximum burial temperature can be determined using the vitrinite reflectance Ro and EasyRo model of the mudstone in the adjacent reservoir; or the maximum burial temperature can be determined using the cluster isotopes of micritic limestone or dolomite.

10. The method according to claim 1, characterized in that, In step S4, the T-situ density of the carbonate rock sample before solid-state resetting is obtained. 47-R Process according to any of the following methods S41~S43: S41. When the maximum burial temperature is lower than the solid-state reset threshold temperature of calcite or dolomite, the T-Δ of the sample... 47 Without being affected by solid-state resetting, the cluster isotope temperature T-Δ of the carbonate rock sample is... 47 The temperature of cluster isotopes affected only by recrystallization; S42. When the maximum burial temperature is higher than the solid-state reset threshold temperature of calcite or dolomite but lower than the complete reset threshold temperature, the sample has undergone partial solid-state reset. A solid-state reset model is needed to determine the temperature rise t caused by the solid-state reset, and then the cluster isotope temperature T-Δ of the carbonate rock sample is calculated. 47 Subtracting this increase, we obtain the cluster isotope temperature affected only by recrystallization; S43, when the maximum burial temperature is higher than the threshold temperature for complete reset of calcite or dolomite, the sample undergoes complete solid-state reset, and the cluster isotope temperature T-Δ of the carbonate rock sample is obtained. 47 When the temperature reaches equilibrium with the burial temperature of the formation, and the increase in cluster isotope temperature cannot be determined using the solid-state reset model, nor can the cluster isotope temperature affected only by recrystallization be obtained, the experiment is terminated.

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