A method for obtaining thermal history of deep ancient strata in sedimentary basins

Abstract

The present invention provides a method for obtaining the thermal history of ancient strata in deep sedimentary basins. The method includes: obtaining vitrinite reflectance data of mudstones in various layers of a work area to determine the highest paleo-geothermal gradient in the work area; obtaining fission track and (U-Th) / He test data of clastic rock strata samples in shallow Mesozoic and Cenozoic layers of the work area to simulate the thermal history of the clastic rock strata in the work area, and determining the burial history of the work area in combination with the highest paleo-geothermal gradient; obtaining fission track and (U-Th) / He test data of clastic rock strata samples in deep Paleozoic layers of the work area to determine the temperature evolution path of the deep clastic rock strata in the work area; obtaining cluster isotope test data and in-situ U-Pb dating data of carbonate rock strata samples in deep Paleozoic layers of the work area to determine the temperature evolution path of the deep carbonate rock strata in the work area; determining the paleo-geothermal gradient evolution of the work area based on the temperature evolution path of the deep clastic rock and carbonate rock strata in the work area in combination with the burial history of the work area, and restoring the paleo-heat flow evolution of the work area in combination with thermal conductivity data.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum geological exploration, and in particular relates to a method for obtaining the thermal history of deep ancient strata in a sedimentary basin. Background Art

[0002] Basin thermal history is a key factor constraining oil and gas accumulation and the maturation and evolution of source rocks. It plays a crucial role in the evaluation of deep and ultra-deep oil and gas accumulation in basins and in the study of continental dynamics. Currently, methods for reconstructing basin thermal history primarily fall into two categories: paleothermal scales and geodynamic methods. Because paleothermal scales can validate simulation results using measured paleothermal data, they are considered highly accurate and feasible. Commonly used paleothermal scales include vitrinite reflectance and low-temperature thermochronology. As the most reliable indicator of organic matter maturity, vitrinite reflectance (Ro) is the most commonly used paleothermal scale in basin paleothermal studies. The Easy%Ro model is currently used to reconstruct basin thermal history. Low-temperature thermochronology paleothermal scales primarily include fission track and (U-Th) / He. The most commonly used fission track paleothermometers are apatite fission track and zircon fission track. The annealing temperature for apatite fission track is 110-125°C, and for zircon fission track is 210-240°C. The minerals used for (U-Th) / He thermal dating are primarily apatite and zircon. The He partial retention zone in apatite is generally between 40-75°C, and the (U-Th) / He closure temperature of zircon is between 140-200°C. The combined use of multiple parameters, such as apatite (U-Th) / He and fission track data, and zircon (U-Th) / He and fission track data, can reveal thermal evolution within the 40-240°C temperature range. However, due to the lack of vitrinite and heavy minerals such as zircon and apatite in deep, ancient carbonate formations, traditional paleothermometers (Ro and low-temperature thermochronology) cannot accurately reveal the thermal history of deep, ancient formations.

[0003] In recent years, cluster isotopes have shown great potential in restoring the thermal history of carbonate formations. As the formation temperature changes, the cluster isotope values (Δ 47 ) will change accordingly. Currently, models have been established to explain the evolution of calcite and dolomite cluster isotopes with formation temperature, and these models have been successfully applied to the reconstruction of the thermal history of carbonate formations. The development of laser in situ U-Pb dating of carbonate rocks has provided new insights into the thermal history of carbonate rocks. Combining U-Pb isotope dating of calcite or dolomite cements with cluster isotope thermometry can be used to reconstruct the thermal history of deep carbonate rocks that have undergone multi-cycle tectonic transformation.

[0004] At present, the detailed restoration of the thermal history of deep and ancient strata in sedimentary basins remains a key difficulty in industry research. Summary of the Invention

[0005] The object of the present invention is to provide a technical solution capable of accurately restoring the thermal history of deep and ancient strata in sedimentary basins.

[0006] To achieve the above object, the present invention provides a method for obtaining the thermal history of deep ancient strata in a sedimentary basin, the method comprising:

[0007] Obtain thermal conductivity data of different lithologies at each layer in the work area (including Mesozoic and Cenozoic strata, Mesozoic strata refer to Neogene Q, Paleogene E, Jurassic J, Triassic T strata, Paleozoic strata refer to Permian P, Carboniferous C, Silurian S, Ordovician O, Cambrian ∈, Sinian Z strata);

[0008] Obtain vitrinite reflectance data of mud shale at each layer in the work area to determine the highest paleo-geothermal gradient in the work area;

[0009] Obtain fission track and (U-Th) / He test data from shallow Mesozoic and Cenozoic clastic rock samples in the work area to simulate the thermal history of the clastic rock formations in the work area. Combined with the highest paleo-geothermal gradient in the work area, the amount of stratum denudation in the work area is determined, thereby determining the burial history of the work area.

[0010] Obtain fission track and (U-Th) / He test data of clastic rock samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formations in the work area;

[0011] Obtain cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area;

[0012] Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, combined with the burial history of the work area, the paleo-geothermal gradient evolution of the work area is determined;

[0013] Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow evolution of the work area is restored.

[0014] According to a preferred embodiment of the above method, obtaining the thermal conductivity data of different lithologies at various layers in the work area includes:

[0015] Thermal conductivity tests were performed on different lithologic samples at various layers in the work area, and the thermal conductivity values of different lithologic samples at various layers in the work area were obtained as thermal conductivity data of different lithologic samples at various layers in the work area.

[0016] According to a preferred embodiment of the above method, obtaining vitrinite reflectance data of mudstone at each layer in the work area to determine the highest paleo-geothermal gradient in the work area includes:

[0017] The vitrinite reflectance of the mud shale samples in each layer of the work area is tested, and the vitrinite reflectance of the mud shale samples in each layer of the work area is obtained as the vitrinite reflectance data of the mud shale in each layer of the work area;

[0018] The highest paleo-geothermal gradient in the work area was restored using the vitrinite reflectance data of mudstone in each layer of the work area.

[0019] According to a preferred embodiment of the above method, fission track and (U-Th) / He test data of clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area are obtained to simulate the thermal history of the shallow clastic rock formations in the work area, and the amount of stratum erosion in the work area is determined in combination with the highest paleo-geothermal gradient in the work area, thereby determining the burial history of the work area, including:

[0020] Heavy mineral separation was performed on clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area;

[0021] The thermal history of shallow clastic rock formations in the work area is simulated using fission track and (U-Th) / He test data of clastic rock formation samples from the shallow Mesozoic and Cenozoic layers in the work area.

[0022] Based on the thermal history simulation results of the shallow clastic rock formations in the work area and the highest paleo-geothermal gradient in the work area, the amount of stratum denudation in the work area was determined;

[0023] Determine the burial history of the work area based on the amount of stratum denudation in the work area;

[0024] Furthermore, the amount of stratum denudation is determined using the following formula:

[0025] h=ΔT / G

[0026] Where h is the amount of erosion, in meters; △T is the temperature difference caused by the uplift process, in degrees Celsius; and G is the geothermal gradient, in degrees Celsius / km.

[0027] According to a preferred embodiment of the above method, obtaining fission track and (U-Th) / He test data of clastic rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formation in the work area includes:

[0028] Heavy mineral separation was performed on clastic rock samples from deep Paleozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from deep Paleozoic layers in the work area;

[0029] By using the fission track and (U-Th) / He test data of clastic rock strata samples from the deep Paleozoic layers in the work area, the temperature evolution path of the clastic rock strata samples from each layer in the deep work area is restored, thereby determining the temperature evolution path of the clastic rock strata in the deep work area.

[0030] According to a preferred embodiment of the above method, obtaining cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area includes:

[0031] Cluster isotope testing and in-situ U-Pb dating of carbonate rock formation samples from deep Paleozoic layers in the work area were carried out. The cluster isotope testing results and in-situ U-Pb dating results of carbonate rock formations were used as cluster isotope testing data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area.

[0032] By using cluster isotope test data of carbonate rock formation samples from the deep Paleozoic layers in the work area and in situ U-Pb dating data of carbonate rock formation samples, the temperature evolution path of carbonate rock formation samples from various layers in the deep work area is restored, thereby determining the temperature evolution path of carbonate rock formations in the deep work area.

[0033] According to a preferred embodiment of the above method, based on the temperature evolution path of the deep clastic rock formation and the temperature evolution path of the deep carbonate rock formation in the work area, combined with the burial history of the work area, determining the paleo-geothermal gradient evolution of the work area includes:

[0034] Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, the temperatures of samples at different depths during the target period were determined. The burial depths of these samples were determined in combination with the burial history of the work area. The geothermal gradients at each target period were determined using the following formula, thereby determining the paleo-geothermal gradient evolution of the work area:

[0035] G=(T1-T2) / (Z1-Z2)

[0036] Where G is the paleo-geothermal gradient, unit is ℃ / km; T pis the paleo-temperature of sample a in a certain period, in °C; T2 is the paleo-temperature of sample b in the same period as sample a, in °C; Z1 is the burial depth of sample a in a certain period, in km; Z2 is the burial depth of sample b in the same period as sample a, in km.

[0037] According to a preferred embodiment of the above method, based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies at various layers in the work area, restoring the paleo-heat flow evolution of the work area includes:

[0038] Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow of each layer in the work area is determined using the following formula, thereby determining the paleo-heat flow evolution of the work area:

[0039] q=-K·G

[0040] Where q is the paleo heat flow, unit is mW / m 2 ; K is thermal conductivity, unit is W / (m·K); G is paleo-geothermal gradient, unit is ℃ / km.

[0041] The technical solution provided by the present invention is based on the reconstruction of the temperature evolution of ancient carbonate rock systems using cluster isotopes and in situ U-Pb dating of carbonate rocks, combined with various paleotemperature scales such as fission track and (U-Th) / He, to accurately restore the thermal history of deep ancient strata in sedimentary basins. Specifically, the technical solution provided by the present invention is aimed at deep ancient strata in sedimentary basins, through cluster isotopes and in situ U-Pb dating of carbonate rocks, low-temperature thermochronology paleotemperature scale, and precise stratification, combined with paleo-geothermal gradient determination, paleo-heat flow determination, and low-temperature thermochronology simulation, to finely restore the temperature history of sedimentary basins, and then reconstruct the thermal history of deep ancient strata in sedimentary basins in combination with sedimentary burial history, thereby effectively realizing the fine restoration of the thermal history of deep and ancient strata in sedimentary basins. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a graph showing the thermal conductivity data of different lithologies in each layer in Example 1.

[0043] Figure 2 This is the paleo-geothermal gradient map of Well YF1 in Example 1.

[0044] Figure 3 These are the thermal history simulation results of the shallow clastic rock formation in Well YF1 in Example 1 and the burial history map of the work area.

[0045] Figure 4 This is a temperature evolution path diagram of the deep clastic rock formation in Well YF1 in Example 1.

[0046] Figure 5 This is a temperature evolution path diagram of the deep carbonate formation in Well YF1 in Example 1.

[0047] Figure 6 This is the evolution history diagram of the paleo-geothermal gradient and paleo-heat flow of Well YF1 in Example 1. DETAILED DESCRIPTION

[0048] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0049] An embodiment of the present invention provides a method for obtaining the thermal history of deep ancient strata in a sedimentary basin, the method comprising:

[0050] Step 101: Acquire thermal conductivity data of different lithologies at various layers in the work area (including Mesozoic and Cenozoic strata, Mesozoic strata refer to Neogene Q, Paleogene E, Jurassic J, and Triassic T strata, and Paleozoic strata refer to Permian P, Carboniferous C, Silurian S, Ordovician O, Cambrian ∈, and Sinian Z strata);

[0051] Step 102: Obtain vitrinite reflectance data of mudstone at each layer in the work area to determine the highest paleo-geothermal gradient in the work area;

[0052] Step 103: Obtain fission track and (U-Th) / He test data of clastic rock formation samples from shallow Mesozoic and Cenozoic layers in the work area to simulate the thermal history of the clastic rock formation in the work area, and determine the amount of stratum denudation in the work area in combination with the highest paleo-geothermal gradient in the work area, thereby determining the burial history of the work area;

[0053] Step 104: Obtain fission track and (U-Th) / He test data of clastic rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formation in the work area;

[0054] Step 105: Obtain cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area;

[0055] Step 106, based on the temperature evolution path of the deep clastic rock formation and the temperature evolution path of the deep carbonate rock formation in the work area, combined with the burial history of the work area, determine the paleo-geothermal gradient evolution of the work area;

[0056] Step 107 : Restore the ancient heat flow evolution of the work area based on the ancient geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area.

[0057] In the above step 101, the thermal conductivity data of different lithologies at each layer is obtained.

[0058] In one embodiment, obtaining thermal conductivity data of different lithologies at various layers in a work area includes:

[0059] Thermal conductivity tests were performed on different lithologic samples at various layers in the work area, and the thermal conductivity values of different lithologic samples at various layers in the work area were obtained as thermal conductivity data of different lithologic samples at various layers in the work area.

[0060] In the above step 102, the highest paleo-geothermal gradient of the work area is determined.

[0061] In one embodiment, obtaining vitrinite reflectance data of mudstone at each layer in the work area to determine the highest paleo-geothermal gradient in the work area includes:

[0062] The vitrinite reflectance of the mud shale samples in each layer of the work area is tested, and the vitrinite reflectance of the mud shale samples in each layer of the work area is obtained as the vitrinite reflectance data of the mud shale in each layer of the work area;

[0063] The highest paleo-geothermal gradient of the work area was restored using the vitrinite reflectance data of the mudstone in each layer of the work area.

[0064] Furthermore, the highest paleo-geothermal gradient of the work area was restored using the vitrinite reflectance data of the mudstone in each layer of the work area in the following way:

[0065] Thermodel software was used to restore the highest paleo-geothermal gradient in the work area based on the EasyRo% method and the vitrinite reflectance data of shale in each layer of the work area.

[0066] In the above step 103, the burial history of the work area is determined.

[0067] In one embodiment, fission track and (U-Th) / He test data of clastic rock samples from shallow Mesozoic and Cenozoic layers in the work area are obtained to simulate the thermal history of the shallow clastic rock formations in the work area. The amount of stratum denudation in the work area is determined in combination with the highest paleo-geothermal gradient in the work area, thereby determining the burial history of the work area, including:

[0068] Heavy mineral separation was performed on clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area;

[0069] The thermal history of shallow clastic rock formations in the work area is simulated using fission track and (U-Th) / He test data of clastic rock formation samples from the shallow Mesozoic and Cenozoic layers in the work area.

[0070] Based on the thermal history simulation results of the shallow clastic rock formations in the work area and the highest paleo-geothermal gradient in the work area, the amount of stratum denudation in the work area was determined;

[0071] Determine the burial history of the work area based on the amount of stratum denudation in the work area;

[0072] Furthermore, during the thermal history simulation of the shallow clastic rock formations in the work area, HeFTy software was used to randomly simulate multiple preset thermal history paths based on the Monte Carlo method. The preset thermal history paths were fitted based on the fission track and (U-Th) / He test data of the clastic rock formation samples in the shallow Mesozoic and Cenozoic layers of the work area, and the preset thermal history path with the highest fitting degree was selected as the thermal history of the shallow clastic rock formations in the work area. Among them, the fan model was used for the apatite fission track, the parallel curve model was used for the zircon fission track, the Flower (2009) model was used for the apatite (U-Th) / He, and the Guenthner (2013) model was used for the zircon (U-Th) / He.

[0073] Among them, based on the amount of stratum denudation in the work area, the burial history of the work area is determined using the following methods:

[0074] Based on the amount of stratum denudation in the work area, the basin simulation software BasinMod 1D was used to reconstruct the burial history of the work area according to the drilling layer data;

[0075] Furthermore, the amount of stratum denudation is determined using the following formula:

[0076] h=ΔT / G

[0077] Where h is the amount of erosion, in meters; △T is the temperature difference caused by the uplift process, in degrees Celsius; and G is the geothermal gradient, in degrees Celsius / km.

[0078] In the above step 104, the temperature evolution path of the deep clastic rock formation in the work area is determined.

[0079] In one embodiment, obtaining fission track and (U-Th) / He test data of clastic rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formation in the work area includes:

[0080] Heavy mineral separation was performed on clastic rock samples from deep Paleozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from deep Paleozoic layers in the work area;

[0081] By using the fission track and (U-Th) / He test data of clastic rock samples from deep Paleozoic layers in the work area, the temperature evolution path of clastic rock samples from each layer in the work area is restored, thereby determining the temperature evolution path of the deep clastic rock formation in the work area;

[0082] Furthermore, in the process of determining the temperature evolution path of deep clastic rock formations, HeFTy software was used to randomly simulate multiple preset thermal history paths based on the Monte Carlo method. The preset thermal history paths were fitted according to the fission track of clastic rock formation samples and (U-Th) / He test data of the deep Paleozoic strata in the work area, and the preset thermal history paths with the highest fitting degree were selected as the thermal history of the deep clastic rock formations in the work area, that is, the temperature evolution path of the deep clastic rock formations in the work area; among them, the fan model was used for the apatite fission track, the parallel curve model was used for the zircon fission track, the Flower (2009) model was used for the apatite (U-Th) / He, and the Guenthner (2013) model was used for the zircon (U-Th) / He.

[0083] In the above step 105, the temperature evolution path of the deep carbonate rock formation in the work area is determined.

[0084] In one embodiment, obtaining cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area includes:

[0085] Cluster isotope testing and in-situ U-Pb dating of carbonate rock formation samples from deep Paleozoic layers in the work area were carried out. The cluster isotope testing results and in-situ U-Pb dating results of carbonate rock formations were used as cluster isotope testing data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area.

[0086] Using cluster isotope test data and in-situ U-Pb dating data of carbonate rock samples from deep Paleozoic layers in the work area, the temperature evolution path of carbonate rock samples from each layer in the work area is restored, thereby determining the temperature evolution path of carbonate rock formations in the deep work area;

[0087] Furthermore, in the process of restoring the temperature evolution path of the carbonate rock formation samples, the initial diagenetic temperature of the carbonate rock formation samples is determined according to the burial history of the work area as the starting temperature condition for the simulation, the current temperature of the formation is determined according to the steady-state temperature measurement data and the oil test temperature data as the ending temperature condition for the simulation, the sedimentary age of the carbonate rock formation samples is determined according to the in situ U-Pb dating data of the carbonate rock formation as the initial age condition for the simulation, and the temperature evolution path of the carbonate rock formation samples is restored in combination with the exchange / diffusion model; in the simulation process, different temperature-time (Tt) evolution paths are preset according to the burial history of the work area, and the exchange / diffusion model is used to simulate the cluster isotope temperature (TΔ47) evolution path of the carbonate rock formation samples. When the simulated value is consistent with the measured value, it indicates that the preset temperature-time (Tt) evolution path is reasonable and can accurately reflect the thermal history information experienced by the sample. The temperature-time (Tt) evolution path at this time is the temperature evolution path of the carbonate rock formation.

[0088] In the above step 106, the paleo-geothermal gradient evolution of the work area is determined.

[0089] In one embodiment, based on the temperature evolution path of the deep clastic rock formation and the temperature evolution path of the deep carbonate rock formation in the work area, combined with the burial history of the work area, the paleo-geothermal gradient evolution of the work area is determined, including:

[0090] Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, the temperatures of samples at different depths during the target period were determined. The burial depths of these samples were determined in combination with the burial history of the work area. The geothermal gradients at each target period were determined using the following formula, thereby determining the paleo-geothermal gradient evolution of the work area:

[0091] G=(T1-T2) / (Z1-Z2)

[0092] Where G is the paleo-geothermal gradient, unit is ℃ / km; T p is the paleo-temperature of sample a in a certain period, in °C; T2 is the paleo-temperature of sample b in the same period as sample a, in °C; Z1 is the burial depth of sample a in a certain period, in km; Z2 is the burial depth of sample b in the same period as sample a, in km.

[0093] In the above step 107, the paleoheat flow evolution of the work area is determined.

[0094] In one embodiment, based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies at various layers in the work area, restoring the paleo-heat flow evolution of the work area includes:

[0095] Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow of each layer in the work area is determined using the following formula, thereby determining the paleo-heat flow evolution of the work area:

[0096] q=-K·G

[0097] Where q is the paleo heat flow, unit is mW / m 2 ; K is thermal conductivity, unit is W / (m·K); G is paleo-geothermal gradient, unit is ℃ / km.

[0098] Example 1:

[0099] This embodiment provides a method for obtaining the thermal history of ancient deep strata in a sedimentary basin. The method is used to obtain the thermal history of the YF1 well area in a certain basin. The method includes:

[0100] (1) Collect samples of various lithologies from various layers at different depths in the YF1 well, from old to new.

[0101] (2) Thermal conductivity tests were performed on different lithologic samples at each layer of the YF1 well. The thermal conductivity values of different lithologic samples at each layer of the YF1 well were obtained as the thermal conductivity data of different lithologic samples at each layer of the YF1 well. The results are as follows: Figure 1 shown.

[0102] Samples of different lithologies in different layers of Well YF1 were collected and measured using a TCS thermal conductivity meter to obtain the thermal conductivity values of different layers and lithologies, and a thermal conductivity histogram of Well YF1 was drawn.

[0103] (3) Performing vitrinite reflectance tests on mud shale samples from each layer of Well YF1, and obtaining the vitrinite reflectance of mud shale samples from each layer of Well YF1 as the vitrinite reflectance data of mud shale from each layer of Well YF1;

[0104] Using Thermodel software and the EasyRo% method, the highest paleo-geothermal gradient of Well YF1 was restored based on the vitrinite reflectance data of the shale in each layer of Well YF1. The results are as follows: Figure 2 shown.

[0105] (4) Heavy mineral sorting was performed on the clastic rock formation samples from the shallow Mesozoic and Cenozoic layers of the YF1 well (Jurassic in this example) to obtain zircon and apatite particles, and the obtained zircon and apatite particles were subjected to fission track and (U-Th) / He tests. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data of the clastic rock formation samples from the shallow Mesozoic and Cenozoic layers of the YF1 well.

[0106] The thermal history of the shallow clastic formations in the YF1 well was simulated using the fission track and (U-Th) / He test data of the shallow Mesozoic and Cenozoic clastic formation samples. Specifically, HeFTy software was used to randomly simulate multiple preset thermal history paths based on the Monte Carlo method. The preset thermal history paths were fitted based on the fission track and (U-Th) / He test data of the shallow Mesozoic and Cenozoic clastic formation samples in the YF1 well. The preset thermal history path with the highest fitting degree was selected as the thermal history of the shallow clastic formations in the YF1 well. Among them, the fan model was used for apatite fission track, the parallel curve model was used for zircon fission track, the Flower (2009) model was used for apatite (U-Th) / He, and the Guenthner (2013) model was used for zircon (U-Th) / He.

[0107] Based on the thermal history simulation results of the shallow clastic rock formation in Well YF1 and the highest paleo-geothermal gradient of Well YF1, the amount of formation erosion in Well YF1 was determined using the following formula:

[0108] h=ΔT / G

[0109] Where h is the amount of erosion, in meters; △T is the temperature difference caused by the uplift process, in degrees Celsius; and G is the geothermal gradient, in degrees Celsius / km.

[0110] Based on the stratum denudation of Well YF1, the basin simulation software BasinMod 1D was used to reconstruct the burial history of the work area according to the drilling layer data. The results are as follows: Figure 3 shown.

[0111] Using fission track and (U-Th) / He test data from the shallow, young clastic formations in the YF1 well, we simulated the thermal history of the shallow clastic formations in the work area. The simulation results show a good fit between the various paleothermal scales, indicating a high degree of reliability in the thermal history path. The thermal history simulation results indicate that the shallow clastic formations in the YF1 well experienced a maximum paleotemperature of approximately 160°C. Combined with the maximum paleotemperature gradient calculated using vitrinite reflectance recovery, we indicate that large-scale uplift and erosion began at approximately 90 Ma in the YFI well, with a denudation thickness of approximately 4.5 km.

[0112] (5) Heavy mineral sorting was performed on the clastic rock formation samples from the deep Paleozoic layer of the YFI well (Cambrian in this example) to obtain zircon and apatite particles, and the obtained zircon and apatite particles were subjected to fission track and (U-Th) / He tests. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data of the clastic rock formation samples from the deep Paleozoic layer of the YFI well.

[0113] The fission track and (U-Th) / He test data of clastic rock formation samples from the deep Paleozoic layer of the YFI well were used to restore the temperature evolution path of the clastic rock formation samples from each layer in the YFI well, thereby determining the temperature evolution path of the deep clastic rock formation in the YFI well. Specifically, HeFTy software was used to randomly simulate multiple preset thermal history paths based on the Monte Carlo method. The preset thermal history paths were fitted according to the fission track and (U-Th) / He test data of clastic rock formation samples from the deep Paleozoic layer of the YF1 well. The preset thermal history path with the highest fitting degree was selected as the thermal history of the deep clastic rock formation in the YF1 well, that is, the temperature evolution path of the deep clastic rock formation in the YF1 well. Among them, the fan model was used for the apatite fission track, the parallel curve model was used for the zircon fission track, the Flower (2009) model was used for the apatite (U-Th) / He, and the Guenthner (2013) model was used for the zircon (U-Th) / He. The results are shown in Figure 2. Figure 4 shown.

[0114] Using fission track and (U-Th) / He test data from deep Paleozoic clastic layers in the YFI well, the temperature evolution paths of clastic layers from various layers in the YFI well were reconstructed. The results show that the paleothermal scales fit well, indicating a high degree of reliability in the thermal history paths. The results indicate that the maximum paleotemperature experienced by the deep clastic layers in the YF1 well was around 280°C. Around 260 Ma, the temperature of the deep clastic layers rapidly increased to approximately 200°C due to the influence of the Emeishan mantle plume. Around 250 Ma, the formation temperature rapidly decreased to approximately 120°C. Subsequently, due to deep burial, the formation temperature reached a maximum paleotemperature of 280°C around 90 Ma. Later, due to large-scale uplift and erosion during the Yanshan-Himalayan movement, the formation temperature gradually decreased to the present-day temperature.

[0115] (6) Cluster isotope testing and in-situ U-Pb dating of carbonate rock formation samples from the deep Paleozoic layer of the YFI well were carried out, and the obtained cluster isotope testing results and in-situ U-Pb dating results of carbonate rock formations were used as cluster isotope testing data and in-situ U-Pb dating data of carbonate rock formations in the deep Paleozoic layer of the YFI well; cluster isotope testing data and in-situ U-Pb dating data of carbonate rock formations in the deep Paleozoic layer of the YFI well were used to restore the temperature evolution path of carbonate rock formation samples in each layer of the YFI well, thereby realizing the determination of the temperature evolution path of carbonate rock formations in the deep YFI well; wherein, in the process of restoring the temperature evolution path of carbonate rock formation samples, the initial diagenetic temperature of carbonate rock formation samples was determined as the initial diagenetic temperature according to the burial history. The starting temperature condition during the simulation is to determine the current temperature of the formation based on the steady-state temperature measurement data and the oil test temperature data as the termination temperature condition during the simulation. The sedimentary age of the carbonate formation sample is determined based on the in-situ U-Pb dating data of the carbonate formation as the initial age condition during the simulation. The temperature evolution path of the carbonate formation sample is restored in combination with the corresponding solid-state rearrangement model. During the simulation process, different temperature-time (Tt) evolution paths are preset according to the burial history of the YFI well, and the exchange / diffusion model is used to simulate the cluster isotope temperature (TΔ47) evolution path of the carbonate formation sample. When the simulated value is consistent with the measured value, it shows that the preset temperature-time (Tt) evolution path is reasonable and can accurately reflect the thermal history information experienced by the sample. The temperature-time (Tt) evolution path at this time is the temperature evolution path of the carbonate formation. The results are as follows. Figure 5 shown.

[0116] After thin-section observation, cathodoluminescence, and XRD analysis of deep carbonate formation samples from Well YF1, cluster isotope analysis was performed on matrix powder samples that exhibited no or weak cathodoluminescence, a calcite or dolomite content exceeding 90%, and were unaffected by later diagenetic alteration and recrystallization. Simultaneously, in situ U-Pb dating of the carbonate formations was performed on these matrix samples undergoing cluster isotope analysis to determine their depositional age. Numerical analysis of carbon and oxygen isotopes derived from cluster isotope analysis indicates that the samples were unaffected by recrystallization. The main reason for their cluster isotope temperatures exceeding the diagenetic temperature is solid-state rearrangement caused by deep burial heating. Therefore, a solid-state rearrangement model can be used to reconstruct the sample's temperature history. The initial diagenetic temperature of the sample was determined according to the burial history, which was used as the starting temperature condition for the simulation. The present temperature of the formation was determined according to the steady-state temperature measurement data and the oil test temperature data, which was used as the termination temperature condition for the simulation. The sedimentary age of the sample was determined by in situ U-Pb dating of the carbonate rock formation, which was used as the initial age condition for the simulation. Under the constraints of the above three conditions, the temperature evolution process of the sample was simulated using the solid-state rearrangement model. The simulated cluster isotope temperature was consistent with the measured cluster isotope temperature, indicating that the obtained temperature evolution path is reasonable. The results of cluster isotope simulation show that the deep carbonate rock formation sample has undergone three heating and cooling processes since its deposition. The three heating processes correspond to the post-deposition-early Silurian heating process, the Early Permian-Middle Permian heating process and the Late Permian-Late Cretaceous heating process. The three cooling processes correspond to the Early Silurian-Early Permian, Middle Permian-Late Permian and Late Cretaceous-present. The formation temperature was around 160°C during the Middle Permian period. The warming was mainly affected by the Permian Emeishan mantle plume. The formation temperature then reached its highest level of about 260°C in the Late Cretaceous.

[0117] (7) Based on the temperature evolution path of the deep clastic rock formation in the YFI well and the temperature evolution path of the deep carbonate rock formation in the YFI well, the temperature of samples at different depths in the target period was determined respectively. The burial depths of these samples were determined respectively in combination with the burial history of the YFI well. The geothermal gradient of each target period was determined using the following formula, thereby realizing the determination of the paleo-geothermal gradient evolution of the YFI well:

[0118] G=(T1-T2) / (Z1-Z2)

[0119] Where G is the paleo-geothermal gradient, unit is ℃ / km; T p is the paleo-temperature of sample a in a certain period, in °C; T2 is the paleo-temperature of sample b in the same period as sample a, in °C; Z1 is the burial depth of sample a in a certain period, in km; Z2 is the burial depth of sample b in the same period as sample a, in km.

[0120] The results are as follows Figure 6 shown.

[0121] (8) Based on the paleo-geothermal gradient evolution of Well YF1 and the thermal conductivity data of different lithologies in each layer of Well YF1, the paleo-heat flow of each layer of Well YF1 was determined using the following formula, thereby determining the paleo-heat flow evolution of Well YF1:

[0122] q=-K·G

[0123] Where q is the paleo heat flow, unit is mW / m 2 ; K is thermal conductivity, unit is W / (m·K); G is paleo-geothermal gradient, unit is ℃ / km.

[0124] The results are as follows Figure 6 shown.

[0125] The results of paleo-geothermal gradient and paleo-heat flow calculations show that the paleo-heat flow evolution of Well YF1 can be divided into three stages: the stable heat flow stage before the Permian, the high heat flow stage during the Permian, and the heat flow decline stage after the Permian. Before the Permian, the heat flow of Well YF1 remained basically unchanged, stabilizing at 55 mW / m 2 The corresponding paleo-geothermal gradient is also relatively stable at 15°C / km. During the Permian period, due to the influence of the Emeishan mantle plume, the heat flow value of the YF1 well increased rapidly, with the highest paleo-heat flow at 90mW / m 2 Around 1900, the corresponding geothermal gradient also reached its highest point, about 35℃ / km; afterwards, due to the weakening of the Emeishan mantle plume activity, the heat flow value began to gradually decrease and stabilized near the current earth's heat flow value, which is 62℃ / km. The corresponding geothermal gradient also gradually decreased and stabilized at around 20℃ / km.

[0126] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining the thermal history of deep ancient strata in a sedimentary basin, the method comprising: Obtain thermal conductivity data of different lithologies at each layer in the work area; Obtain vitrinite reflectance data of mud shale at each layer in the work area to determine the highest paleo-geothermal gradient in the work area; Obtain fission track and (U-Th) / He test data from shallow Mesozoic and Cenozoic clastic rock samples in the work area to simulate the thermal history of the clastic rock formations in the work area. Combined with the highest paleo-geothermal gradient in the work area, the amount of stratum denudation in the work area is determined, thereby determining the burial history of the work area. Obtain fission track and (U-Th) / He test data of clastic rock samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formations in the work area; Obtain cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area; Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, combined with the burial history of the work area, the paleo-geothermal gradient evolution of the work area is determined; Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow evolution of the work area is restored.

2. The method according to claim 1, wherein Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, combined with the burial history of the work area, the paleo-geothermal gradient evolution of the work area is determined to include: Based on the temperature evolution paths of the deep clastic rock formations and the deep carbonate rock formations in the work area, the temperatures of samples at different depths during the target period were determined. The burial depths of these samples were determined in combination with the burial history of the work area. The geothermal gradients at each target period were determined using the following formula, thereby determining the paleo-geothermal gradient evolution of the work area: G=(T1-T2) / (Z1-Z2) Where G is the paleo-geothermal gradient, in units of °C / km; T1 is the paleo-geothermal of sample a at a certain period, in units of °C; T2 is the paleo-geothermal of sample b at the same period as sample a, in units of °C; Z1 is the burial depth of sample a at a certain period, in units of km; Z2 is the burial depth of sample b at the same period as sample a, in units of km.

3. The method according to claim 1, wherein Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow evolution of the work area was restored, including: Based on the paleo-geothermal gradient evolution of the work area and the thermal conductivity data of different lithologies in each layer of the work area, the paleo-heat flow of each layer in the work area is determined using the following formula, thereby determining the paleo-heat flow evolution of the work area: q=-K·G Where q is the paleo heat flow, unit is mW / m 2 ; K is thermal conductivity, unit is W / (m·K); G is paleo-geothermal gradient, unit is ℃ / km.

4. The method according to claim 1, wherein Obtaining thermal conductivity data of different lithologies at each layer in the work area includes: Thermal conductivity tests were performed on different lithologic samples at various layers in the work area, and the thermal conductivity values of different lithologic samples at various layers in the work area were obtained as thermal conductivity data of different lithologic samples at various layers in the work area.

5. The method according to claim 1, wherein The maximum paleo-geothermal gradient of the work area is determined by taking the vitrinite reflectance data of the mud shale at each layer in the work area, including: The vitrinite reflectance of the mud shale samples in each layer of the work area is tested, and the vitrinite reflectance of the mud shale samples in each layer of the work area is obtained as the vitrinite reflectance data of the mud shale in each layer of the work area; The highest paleo-geothermal gradient in the work area was restored using the vitrinite reflectance data of mudstone in each layer of the work area.

6. The method according to claim 1, wherein The fission track and (U-Th) / He test data of clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area were obtained to simulate the thermal history of the shallow clastic rock formations in the work area. The amount of stratum denudation in the work area was determined in combination with the highest paleo-geothermal gradient in the work area, thereby determining the burial history of the work area, including: Heavy mineral separation was performed on clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from the shallow Mesozoic and Cenozoic layers in the work area; The thermal history of shallow clastic rock formations in the work area is simulated using fission track and (U-Th) / He test data of clastic rock formation samples from the shallow Mesozoic and Cenozoic layers in the work area. Based on the thermal history simulation results of the shallow clastic rock formations in the work area and the highest paleo-geothermal gradient in the work area, the amount of stratum denudation in the work area was determined; Based on the amount of stratum erosion in the work area, the burial history of the work area was determined.

7. The method according to claim 6, wherein: The amount of stratum erosion is determined using the following formula: h=ΔT / G Where h is the amount of erosion, in meters; △T is the temperature difference caused by the uplift process, in degrees Celsius; and G is the geothermal gradient, in degrees Celsius / km.

8. The method according to claim 1, wherein Obtaining fission track and (U-Th) / He test data of clastic rock samples from deep Paleozoic layers in the work area to determine the temperature evolution path of the deep clastic rock formation in the work area includes: Heavy mineral separation was performed on clastic rock samples from deep Paleozoic layers in the work area to obtain zircon and apatite particles, and fission track and (U-Th) / He tests were performed on the obtained zircon and apatite particles. The obtained fission track and (U-Th) / He test results were used as the fission track and (U-Th) / He test data for the clastic rock samples from deep Paleozoic layers in the work area; By using the fission track and (U-Th) / He test data of clastic rock strata samples from the deep Paleozoic layers in the work area, the temperature evolution path of the clastic rock strata samples from each layer in the deep work area is restored, thereby determining the temperature evolution path of the clastic rock strata in the deep work area.

9. The method according to claim 1, wherein: Obtaining cluster isotope test data and in-situ U-Pb dating data of carbonate rock formation samples from the deep Paleozoic layers in the work area to determine the temperature evolution path of the deep carbonate rock formation in the work area includes: Cluster isotope testing and in-situ U-Pb dating of carbonate rock formation samples from deep Paleozoic layers in the work area were carried out. The cluster isotope testing results and in-situ U-Pb dating results of carbonate rock formations were used as cluster isotope testing data and in-situ U-Pb dating data of carbonate rock formation samples from deep Paleozoic layers in the work area. By using cluster isotope test data of carbonate rock formation samples from the deep Paleozoic layers in the work area and in situ U-Pb dating data of carbonate rock formation samples, the temperature evolution path of carbonate rock formation samples from various layers in the deep work area is restored, thereby determining the temperature evolution path of carbonate rock formations in the deep work area.

10. The method according to claim 1, wherein In the process of restoring the temperature evolution path of carbonate rock formation samples, the initial diagenetic temperature of the carbonate rock formation samples is determined according to the burial history of the work area as the starting temperature condition for the simulation. The current temperature of the formation is determined according to the steady-state temperature measurement data and the oil test temperature data as the ending temperature condition for the simulation. The sedimentary age of the carbonate rock formation samples is determined by the in-situ U-Pb dating data of the carbonate rock formation as the initial age condition for the simulation. The temperature evolution path of the carbonate rock formation samples is restored in combination with the exchange / diffusion model.

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