Method for determining absolute age of oil and gas accumulation

Abstract

According to the method for determining the absolute age of oil and gas accumulation, the absolute age of oil and gas accumulation or the time limit range of oil and gas accumulation can be accurately determined by measuring the isotope absolute age of diagenetic minerals having a direct period relationship with hydrocarbon inclusions and reservoir asphalt, the test accuracy is high, and the stability is good.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum and natural gas geological exploration and evaluation, and relates to a method for determining the absolute age of oil and gas accumulation. Background Art

[0002] The goal of geological evaluation in oil and gas exploration is to accurately understand the formation and distribution patterns of oil and gas reservoirs. The period and history of oil and gas accumulation are key issues and research challenges, and this falls within the scope of oil and gas reservoir chronology. Traditional geological analysis methods combine the tectonic evolution of a basin with its hydrocarbon generation and expulsion history to roughly infer the formation time of oil and gas reservoirs. These methods include trap formation time, source rock primary hydrocarbon expulsion period, saturation pressure, oil-gas-water contact tracing, and reservoir geochemistry. With the introduction of isotope dating techniques such as fluid inclusion analysis and authigenic illite K-Ar dating and crude oil / asphalt Re-Os dating, oil and gas reservoir chronology has undergone a significant shift from traditional qualitative research to semi-quantitative or quantitative studies. However, these commonly used chronological methods all have obvious defects: (1) Traditional geological analysis methods can only qualitatively determine the time limit of oil and gas accumulation, which is affected by complex geological conditions and has great uncertainty and multiple solutions; (2) The crude oil / asphalt Re-Os dating method is only applicable to oil reservoirs of a single source or a single period, and gives the time of crude oil cracking (or the time of oil and gas reservoir destruction), not the time of oil and gas reservoir formation. In addition, this method has strict requirements on samples. It is difficult to enrich and purify Re-Os isotopes in crude oil / asphalt, and it is easily affected by the external environment. The detection success rate is low and it is difficult to promote and apply; (3) The fluid inclusion method is the most commonly used method to determine the time of accumulation, but there are the following problems in determining the time of accumulation of complex oil and gas reservoirs: ① The homogenization temperature of the brine inclusions associated with the hydrocarbon inclusions is measured to represent the temperature when the hydrocarbons were injected, and the relative time of oil and gas accumulation is determined by combining the burial history and thermal history. Due to the many uncertainties in the restoration of burial history and thermal history, the accumulation time determined by the homogenization temperature of the inclusions also has great uncertainty. Moreover, this method requires the presence of observable hydrocarbon inclusions and associated brine inclusions in the host minerals. Since samples that meet these conditions are generally difficult to find, the application of this technology is greatly limited. ② The factors such as the easy formation of heterogeneous capture inclusions in deep reservoirs and the easy reequilibrium of fluid inclusions in carbonate minerals increase the difficulty of selecting and identifying fluid inclusions and rationally interpreting temperature measurement results. ③ For areas where superimposed basins have experienced multiple uplift processes, the relative dating of inclusions is multifaceted. (4) Although K-Ar and Ar-Ar isotope dating of authigenic illite can explain the earliest time of oil and gas filling, it is only applicable to clastic oil and gas reservoirs (generally older than E), requires the development of authigenic illite in the reservoir, and can only determine the earliest time of oil and gas filling. The accuracy of dating is affected by the separation and purification of authigenic illite minerals, and the testing cycle is too long.

[0003] In summary, while there are many methods for determining the age of oil and gas accumulation, they all have their own shortcomings and limitations, and cannot provide an absolute age for oil and gas accumulation. A reliable, low-cost, and easily scalable method is urgently needed to determine the absolute age of oil and gas accumulation. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a method for determining the absolute age of oil and gas accumulation. This method can be used to determine the absolute age of oil and gas accumulation or to limit the time limit of oil and gas accumulation with high accuracy and good stability.

[0005] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for determining the absolute age of oil and gas accumulation, the method comprising:

[0007] (1) Perform petrographic analysis on rock samples to determine the formation sequence of hydrocarbon inclusions, reservoir asphalt, and host minerals;

[0008] (2) laser ablation of carbonate diagenetic minerals in the rock sample that have a clear relationship with the hydrocarbon inclusions and reservoir asphalt;

[0009] (3) Set the erosion point and measure the peeling sample 204 Pb, 206 Pb, 207 Pb, 208 Pb, 232 Th and 238 U conducts the test;

[0010] (4) According to the standard substance 207 Pb / 206 Pb and 238 U / 206 The test results of Pb and its corresponding fractionation coefficient for unknown samples 207 Pb / 206 Pb and 238 U / 206 Pb was fractionated and corrected;

[0011] (5) After the fractionation correction 207 Pb / 206 Pb and 238 U / 206 Pb data are used to construct the U-Pb dating TW diagram and calculate the age data of the carbonate diagenetic minerals to be tested;

[0012] (6) Determine the absolute age and time range of oil and gas accumulation based on the sequence of formation of hydrocarbon inclusions, reservoir asphalt, and host minerals, combined with the age data of carbonate diagenetic minerals.

[0013] As a preferred technical solution of the present invention, the order of formation of the hydrocarbon inclusions, reservoir asphalt and host minerals in step (1) is determined according to the type, shape, color, gas-liquid ratio, occurrence and combination characteristics of the hydrocarbon inclusions.

[0014] As a preferred technical solution of the present invention, the host mineral in step (1) is a carbonate diagenetic mineral.

[0015] As a preferred technical solution of the present invention, the carbonate diagenetic mineral includes calcite, dolomite or ulexite.

[0016] As a preferred technical solution of the present invention, in step (2), the carbonate diagenetic mineral is positioned in the laser ablation software before the laser ablation.

[0017] As a preferred technical solution of the present invention, step (2) is to use an inductively coupled plasma mass spectrometer to perform laser ablation on the sample. 204 Pb, 206 Pb, 207 Pb, 208 Pb, 232 Th and 238 The U ion signal intensity is recorded, and the spot size is selected according to the signal intensity.

[0018] As a preferred technical solution of the present invention, the number of the ablation points is 20 to 50.

[0019] As a preferred technical solution of the present invention, step (3) adopts a grid method for screening, and the erosion points are set by simultaneously performing screening and point arrangement.

[0020] As a preferred technical solution of the present invention, in the test process of step (4), the calibration standard substance, the age calibration standard substance and the quality control standard substance are tested after every 5 to 10 samples are tested.

[0021] As a preferred technical solution of the present invention, step (5) uses Isoplot software to construct a U-Pb dating TW diagram.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] (1) The present invention provides a method for determining the absolute age of oil and gas accumulation. The method avoids the intermediate process of estimating the accumulation time using temperature, burial history, thermal history, etc. required by the fluid inclusion homogenization temperature method, as well as the human factors and unreliable factors in inclusion temperature measurement and inclusion selection, and the dating results are more direct and reliable.

[0024] (2) The present invention provides a method for determining the absolute age of oil and gas accumulation. The method adopts a grid screening and screening-while-distributing method, which improves the efficiency of point selection and the success rate of testing, and overcomes the shortcomings of the prior art such as long testing cycle and low success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a diagram showing the U-Pb dating results of the calcite dating standard sample WC-1 according to an embodiment of the present invention;

[0026] Figure 2 This is a comparison of the signals before and after Pb background removal and the ASH-15D dating results provided by the embodiment of the present invention;

[0027] Figure 3 This is a comprehensive diagram of the litho-reservoir-forming events of the Sinian Dengying Formation in the central Sichuan region provided by an embodiment of the present invention;

[0028] Figure 4 This is a U-Pb dating result diagram of calcite associated with the first phase asphalt in the Deng 4 reservoir of Well 39 in Moxi, Sichuan, provided by an embodiment of the present invention;

[0029] Figure 5 This is a U-Pb dating result diagram of calcite associated with the second phase asphalt in the Deng 4 reservoir of Well Moxi 103 in central Sichuan, provided by an embodiment of the present invention;

[0030] Figure 6 This is a U-Pb dating result diagram of asphalt calcite veins filled in the Qixia Formation reservoir of Moxi 109 Well in central Sichuan, provided by an embodiment of the present invention.

[0031] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0032] The technical solution of this application is further explained below through specific implementation methods.

[0033] A specific embodiment of the present invention provides a method for determining the absolute age of oil and gas accumulation, the method comprising:

[0034] (1) Perform petrographic analysis on rock samples to determine the formation sequence of hydrocarbon inclusions, reservoir asphalt, and host minerals;

[0035] (2) laser ablation of carbonate diagenetic minerals in the rock sample that have a clear relationship with the hydrocarbon inclusions and reservoir asphalt;

[0036] (3) Set the erosion point and measure the peeling sample 204 Pb, 206 Pb, 207 Pb, 208 Pb, 232 Th, 238 U conducts the test;

[0037] (4) According to the standard substance 207 Pb / 206 Pb and 238 U / 206 The test results of Pb and its corresponding fractionation coefficient for unknown samples 207 Pb / 206 Pb and 238 U / 206 Pb was fractionated and corrected;

[0038] (5) After the fractionation correction 207 Pb / 206 Pb and 238 U / 206 Pb data are used to construct the U-Pb dating TW diagram and calculate the age data of the carbonate diagenetic minerals to be tested;

[0039] (6) Determine the absolute age and time range of oil and gas accumulation based on the sequence of formation of hydrocarbon inclusions, reservoir asphalt, and host minerals, combined with the age data of the carbonate diagenetic minerals.

[0040] In the present invention, hydrocarbon inclusions and reservoir asphalt are direct fluid records of oil and gas charging and accumulation. By measuring the absolute isotopic age of carbonate diagenetic minerals or other minerals that have a direct period relationship with hydrocarbon inclusions and reservoir asphalt, the absolute age or time limit of oil and gas accumulation can be accurately determined.

[0041] In one embodiment of the present invention, the rock sample is made into inclusion slices with a thickness of 0.06 mm to 0.08 mm.

[0042] In a specific embodiment of the present invention, the method of determining the sequence of formation of hydrocarbon inclusions, reservoir asphalt and host minerals by observing the type, shape, color, gas-liquid ratio, occurrence and inclusion combination characteristics of hydrocarbon inclusions in the host mineral through petrographic observation is a commonly used method in the field and is not specifically limited here.

[0043] In one embodiment of the present invention, a rock slice is placed in a laser ablation sample cell, the focus is fine-tuned to make the image clear, and the carbonate diagenetic minerals to be tested that have a clear relationship with hydrocarbon inclusions and reservoir asphalt are found and located in the laser ablation software system.

[0044] In one embodiment of the present invention, the aerosol produced by the ablation is carried into a double-focusing sector magnetic field ICP-MS plasma mass spectrometer using a carrier gas and recorded using the Tune tuning mode. 206 Pb, 207 Pb, 238 U ion signal intensity and 207 Pb / 206 Pb and 238 U / 206 Pb ratio.

[0045] In a specific embodiment of the present invention, the appropriate spot size is 60 μm to 200 μm, and the ion signal intensity is ensured to be significantly stronger than the background signal and the peak shape conforms to the normal distribution.

[0046] In a specific embodiment of the present invention, except for the light spot, the other parameters of the laser ablation can be adjusted according to the properties of the rock sample, etc., and no specific selection is made here.

[0047] In one embodiment of the present invention, the screening principle of the grid method is 238 U / 206 Pb ratio greater than 2, 207 Pb / 206 The Pb ratio is less than 0.6.

[0048] In a specific embodiment of the present invention, points are densely distributed next to points that meet the conditions, and then the next grid point screening is performed until all erosion points are optimized and set.

[0049] In a specific embodiment of the present invention, the specific steps of grid screening and screening-while-distributing are conventional steps in the art and are not specifically limited here.

[0050] In one embodiment of the present invention, after testing 10 unknown sample points, the calibration standard material, the age calibration standard material, and the quality control standard material are tested.

[0051] In one embodiment of the present invention, two calibration standard materials NIST614 (used for 207 Pb / 206 Pb correction), 3 age calibration standard materials WC-1 (for 238 U / 206 Pb correction) and two quality control standard substances.

[0052] In one embodiment of the present invention, fractionation correction of unknown samples using the fractionation coefficient of a standard substance is a conventional method in the art, and the specific steps are not further limited herein.

[0053] In a specific embodiment of the present invention, based on the sequential relationship between the formation of hydrocarbon inclusions, reservoir asphalt and host carbonate minerals, combined with the determined U-Pb age of carbonate minerals, the specific methods for determining the absolute time or absolute time limit of oil and gas accumulation can be divided into the following situations: 1. If primary hydrocarbon inclusions or asphalt inclusions are developed in groups or isolated distributions, or distributed along the edges of crystal growth rings in carbonate minerals, the age of carbonate minerals can be regarded as the absolute time of oil and gas accumulation; 2. If primary hydrocarbon inclusions do not develop in carbonate minerals, but only develop in the carbonate minerals; 1. If secondary hydrocarbon inclusions are present in a beaded pattern in microcracks within crystals or in microcracks that cut through mineral crystals, the age of carbonate mineral formation must be earlier than that of oil and gas accumulation, which can define the earliest time of oil and gas accumulation. 2. If reservoir asphalt is distributed in the contact zone or gap between two phases of carbonate minerals with different petrographic characteristics, the ages of these two phases of carbonate minerals can define the time range of oil and gas accumulation. 3. If it is judged from petrographic evidence that reservoir asphalt formed earlier or later than carbonate minerals, the age of the carbonate mineral can be used as the latest or earliest time of oil and gas accumulation.

[0054] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0055] Example

[0056] This embodiment provides a method for determining the absolute age of oil and gas accumulation, the method comprising:

[0057] (1) obtaining a representative rock sample of a reservoir section of an oil and gas reservoir; wherein the representative rock sample characteristics include a rock sample having pores and / or holes and cracks filled with carbonate cements, and a rock sample having pores and / or holes filled with crude oil and / or asphalt;

[0058] (2) Prepare inclusion thin sections from representative rock samples with a thickness of 0.06 mm to 0.08 mm;

[0059] (3) Use polarizing and fluorescence microscopes to conduct petrographic observations on inclusion thin sections, and identify carbonate diagenetic minerals containing hydrocarbon inclusions in the thin sections, or carbonate diagenetic minerals associated with reservoir asphalt (the hydrocarbon inclusions include liquid hydrocarbon inclusions, gas-liquid two-phase hydrocarbon inclusions, gaseous hydrocarbon inclusions, oil-gas-water three-phase inclusions, asphalt inclusions, gas-oil-asphalt inclusions, and other fluid inclusions containing hydrocarbons); observe in detail the type, shape, color, gas-liquid ratio, occurrence, and inclusion combination characteristics of the hydrocarbon inclusions in the host minerals to determine the formation sequence of the hydrocarbon inclusions and the host minerals. If the carbonate minerals have multiple sequences or growth rings, it is necessary to combine cathodoluminescence photography to clarify the diagenetic sequence relationship of the multi-stage carbonate cements.

[0060] (4) Place the observed rock slice into the laser ablation sample chamber and purge the sample chamber with helium until it is filled with helium. Fine-tune the focus to make the image clear. Find and locate the carbonate diagenetic minerals that have a clear relationship with hydrocarbon inclusions or reservoir asphalt in the laser ablation software system.

[0061] (5) The instrument parameters of the double-focusing sector magnetic field ICP-MS were tuned using NIST 614 glass standard material, with a laser beam spot diameter of 90 μm and a laser energy density of 2.0 J / cm 2 , the erosion frequency is 10HZ, and the parameters such as the He, N2, Ar gas flow rate and the position of the cone are adjusted to make 206 Pb and 238 U signal is the strongest, while ensuring the oxide yield (ThO + / Th + ) is less than 1.0%, Th + / U + The signal ratio is between 0.8 and 1.0.

[0062] (6) Laser is used to perform point ablation on the mineral to be tested, and the aerosol produced by the ablation is carried into the double-focusing sector magnetic field ICP-MS plasma mass spectrometer using carrier gas, and the Tune tuning mode is used to record the 206 Pb, 207 Pb, 238 U ion signal intensity and 207 Pb / 206 Pb and 238 U / 206 Pb ratio, select the appropriate spot size (60μm~200μm) according to the signal intensity to ensure that the ion signal intensity is significantly stronger than the background and the peak shape conforms to the normal distribution.

[0063] (7) Use the grid method to screen and set 20 to 30 erosion points on the mineral to be tested: First, roughly divide the grid area according to the shape characteristics of the sample to be tested. When dividing the grid area, it is necessary to combine the morphology, growth bands and sequence relationship of the diagenetic minerals to ensure that all measurement points are located in the minerals formed in a single period and cannot span multiple periods. The principle of erosion point screening is 238 U / 206 Pb ratio greater than 2, 207 Pb / 206 If the Pb ratio is less than 0.5, densely distribute points next to the points that meet the conditions, and then proceed to the next grid point screening until 20 to 50 erosion points are selected and set. If the entire sample is scanned and no enough points that meet the screening conditions are found, the next grid point is selected. 207 Pb / 206 The points are placed near the test points where the Pb ratio is relatively low and the U signal strength is relatively high. In this case, it is recommended to set 30-50 erosion points.

[0064] (8) The acquisition procedure is as follows: blank for 5 seconds before instrument analysis, pre-stripping for 5 to 10 times, the pre-stripping spot should be larger than the test spot, the stripping time is 20 seconds, and blank for 10 seconds after instrument analysis. After each test of ten unknown samples, repeat the test of two calibration standard materials NIST614 (for 207 Pb / 206 Pb correction), 3 age calibration standard materials WC-1 (for 238 U / 206 Pb correction) and two quality control standard substances.

[0065] (9) In order to save standard samples, unknown samples with different U and Pb contents can be tested in the same sequence. Different spot sizes and ablation frequencies can be set for standard samples and unknown samples. It is only necessary to ensure that the depth / width ratio of the ablation pit is consistent.

[0066] (10) After the test is completed and the element signal is obtained, the data is imported into the Iolite software for data processing. First, the signal is subjected to instrument blank subtraction and instrument drift correction, and the calculated 207 Pb / 206 Pb, 238 U / 206 Pb ratio. Then, according to the standard substance 207 Pb / 206 Pb 238 U / 206 The measured value of Pb and its standard value are used to obtain the corresponding fractionation coefficient. 207 Pb / 206 Pb, 238 U / 206The Pb ratio was corrected and the TW diagram of the sample was checked and adjusted in real time using the VisualAge module to obtain the best fitting effect.

[0067] (11) Export the data to Excel for error expansion and age correction. The first step is to use the Isoplot plug-in to draw the TW diagram of WC-1, fix the upper intersection point to 0.85, calculate the age at the lower intersection point as the uncorrected age, and calculate the correction factor = WC-1 uncorrected age / WC-1 recommended age. The second step is to calculate the unknown sample 238 U / 206 The Pb ratio is multiplied by the correction factor ( Figure 1 ) and expand the error. The third step is to use the Isoplot plug-in to perform TW plotting on the unknown sample and calculate the lower intersection age and initial Pb isotope composition of the carbonate mineral to be tested.

[0068] In order to improve the detection limit of the instrument and be able to measure samples with lower Pb content, it is necessary to reduce the Pb background of the experimental analysis. To this end, the present invention explores how to reduce the Pb background. In addition to the normal cleaning of the cone, laser sample chamber, and homogenizer, the pipeline is replaced from a conventional Tygon hose to a Tygon hose with an FEP lining tube, and the entire gas pipeline from the laser gas outlet to the mass spectrometer is shortened. Instead of using a narrow pipeline with a shut-off valve, the residual Pb in the pipeline is effectively avoided, which can reduce the Pb content in the sample. 207 The Pb background was reduced from the original 200-300 cps to below 10-20 cps. Figure 2 As shown in the figure, by reducing the Pb background, the age of the ASH-15D standard with ultra-low Pb content can be accurately measured, and the accuracy and error are greatly improved compared with those before background removal.

[0069] The method provided in this example was used to restore the complex diagenetic-reservoir-forming process of the Sinian System in the central Sichuan region on an absolute time scale, and the absolute time of the key reservoir-forming period was precisely defined ( Figure 3 ), among which the formation time of the first phase of paleo-oil reservoir was the late Caledonian period, the destruction time of the first phase of paleo-oil reservoir was the early Hercynian period, the formation time of the second phase of paleo-oil reservoir was the late Indosinian period, the period of large-scale cracking and gas generation of crude oil was the early Yanshanian period, and the uplift stage since the Late Cretaceous was the adjustment and formation period of paleo-gas reservoir.

[0070] Figure 4 The calcite veins are network-like bodies filled in asphalt after the first phase of the ancient oil reservoir in the pores of the Deng 4 member of the Moxi Well 39 in the Moxi area of ​​central Sichuan was destroyed. The absolute age of the calcite is 301.3±4.5Ma, indicating that the destruction of the first phase of the ancient oil reservoir occurred in the early Hercynian period.

[0071] Figure 5The U-Pb dating results of calcite associated with the second phase asphalt in the Deng 4 reservoir of Well Moxi 103 in Moxi area in central Sichuan are as follows: Figure 3 As shown, the absolute age of calcite is 213.3±2.8Ma, revealing the crude oil filling process in the late Indosinian period.

[0072] Figure 6 These are the U-Pb dating results of asphalt calcite veins in the Qixia Formation reservoir of Well 109 in Moxi area, central Sichuan. The absolute age of the calcite is 213±13Ma, revealing the crude oil charging process in the late Indosinian period. The accumulation time of the Qixia Formation is consistent with that of the Dengying Formation, reflecting the simultaneous oil and gas accumulation process in multiple systems under the control of strike-slip faults in the late Indosinian period.

[0073] The data in the above examples were all obtained on an NWR 193HE excimer laser in series with an Element XR ICP-MS.

[0074] The applicant declares that the present invention is not limited to the above-described detailed structural features through the above-described embodiments, and does not necessarily rely on the above-described detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0075] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0077] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for determining the absolute age of oil and gas accumulation, characterized in that: The method comprises: (1) Perform petrographic analysis on rock samples to determine the formation sequence of hydrocarbon inclusions, reservoir asphalt, and host minerals; (2) laser ablation of carbonate diagenetic minerals in the rock sample that have a clear relationship with the hydrocarbon inclusions and reservoir asphalt; (3) Set the erosion point and measure the peeling sample 204 Pb, 206 Pb, 207 Pb, 208 Pb, 232 Th and 238 U conducts the test; (4) According to the standard substance 207 Pb / 206 Pb and 238 U / 206 The test results of Pb and its corresponding fractionation coefficient for unknown samples 207 Pb / 206 Pb and 238 U / 206 Pb was fractionated and corrected; (5) After the fractionation correction 207 Pb / 206 Pb and 238 U / 206 Pb data are used to construct the U-Pb dating TW diagram and calculate the age data of the carbonate diagenetic minerals to be tested; (6) Determine the absolute age and time range of oil and gas accumulation based on the sequence of formation of hydrocarbon inclusions, reservoir asphalt, and host minerals, combined with the age data of the carbonate diagenetic minerals.

2. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: The order of formation of the hydrocarbon inclusions, reservoir asphalt and host minerals in step (1) is determined according to the type, shape, color, gas-liquid ratio, occurrence and combination characteristics of the hydrocarbon inclusions.

3. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: The host mineral in step (1) is a carbonate diagenetic mineral.

4. The method for determining the absolute age of oil and gas accumulation according to claim 3, characterized in that: The carbonate diagenetic minerals include calcite, dolomite or ulexite.

5. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: Step (2) before the laser ablation, the carbonate diagenetic mineral is positioned in the laser ablation software.

6. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: Step (2) The laser-ablated sample is analyzed using an inductively coupled plasma mass spectrometer. 204 Pb, 206 Pb, 207 Pb, 208 Pb, 232 Th, 238 The U ion signal intensity is recorded, and the spot size is selected according to the signal intensity.

7. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: The number of the ablation points is 20 to 50.

8. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: Step (3) adopts the grid method for screening, and the erosion points are set by simultaneously performing screening and point arrangement.

9. The method for determining the absolute age of oil and gas accumulation according to claim 8, characterized in that: During the test process of step (4), the calibration standard substance, age calibration standard substance and quality control standard substance are tested after every 5 to 10 samples are tested.

10. The method for determining the absolute age of oil and gas accumulation according to claim 1, characterized in that: Step (5) Use Isoplot software to construct the U-Pb dating TW diagram.

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