A Method for Analyzing the Causes of Abnormal Pressure in High-Temperature and High-Pressure Buried Hills

Abstract

The present invention discloses a method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills, comprising the following steps: determining the Raman spectrum, fluid inclusion homogenization temperature, burial history and thermal history map of methane inclusions in the high-temperature and high-pressure buried hill reservoir to be analyzed; determining the paleopressure at the time of methane inclusion capture, obtaining the inclusion capture time, and calculating the paleopressure coefficient at the time of capture; establishing a two-dimensional profile numerical simulation model of the high-temperature and high-pressure buried hill reservoir, and correcting the model according to the logging pressure coefficient and the inclusion paleopressure coefficient to obtain a reliable numerical simulation model; restoring the pressure evolution history according to the numerical simulation model, tracking the pressure evolution characteristics of the hydrocarbon source rock, transport system and buried hill reservoir, and analyzing the causes of abnormal pressure in the buried hill in combination with parameters such as sedimentation rate, hydrocarbon generation rate and hydrocarbon generation amount, so as to effectively judge the causes of abnormal pressure in the high-temperature and high-pressure buried hill gas reservoir, with reliable results, and providing a reliable reference value for the exploration and development of this type of oil and gas reservoir.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas production, and in particular to a method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills. By analyzing and restoring the evolution characteristics of buried hill pressure, the causes of abnormal pressure in high-temperature and high-pressure buried hills are clarified, thereby better guiding the geological exploration and development and application of buried hill oil and gas. Background Art

[0002] Buried-hill oil and gas exploration has become a global hotspot and a key successor area for increasing reserves and production. As China National Offshore Oil Corporation (CNOOC) continues to advance into deepwater and deep-strata exploration, several granite high-temperature, high-pressure (HP), buried-hill oil and gas reservoirs have been discovered in Chinese waters, demonstrating the exploration potential of buried-hill reservoirs. Abnormally high pressure plays a significant role in the large-scale accumulation of buried-hill oil and gas. Therefore, clarifying the mechanism of abnormally high pressure in buried-hill reservoirs is of great theoretical and practical significance for reducing uncertainty in HP, HT, and buried-hill exploration and development, rationally evaluating reserve sizes, and formulating efficient development plans. Summary of the Invention

[0003] In response to the above problems, the present invention provides a method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills. This method has the advantages of high reliability and high evaluation accuracy, and can provide technical support for the exploration and development of buried hill gas reservoirs.

[0004] The technical solution of the present invention is:

[0005] A method for analyzing the cause of abnormal pressure in a high-temperature and high-pressure buried hill comprises the following steps:

[0006] S1. Prepare inclusion thin sections from high-temperature, high-pressure buried-hill reservoir samples from target wells. Identify gas-bearing / pure gas methane inclusions and their associated brine inclusions in the thin sections. Determine the Raman spectra of the methane inclusions, the homogenization temperature of the fluid inclusions, and the burial history and thermal history of the target wells.

[0007] S2. Determine the paleopressure at the time of capture of methane inclusions based on Raman spectroscopy;

[0008] S3. Determine the capture time of the inclusion based on the homogenization temperature of the fluid inclusion, the burial history of the target well, and the thermal history map;

[0009] S4. Calculate the paleo-pressure coefficient at the time of capture based on the capture time of the inclusions obtained in step S3 and the paleo-pressure at the time of capture of the methane inclusions obtained in step S2;

[0010] S5. Construct a two-dimensional cross-section numerical simulation model of the high-temperature and high-pressure buried-hill reservoir and restore the pressure evolution history of the area to be evaluated using basin simulation software;

[0011] S6. Calibrate the two-dimensional profile numerical simulation model according to the logging pressure coefficient and paleo-pressure coefficient of the buried hill reservoir in the target well to obtain a reliable numerical simulation model;

[0012] S7. Restore the pressure evolution history according to the calibrated two-dimensional profile numerical simulation model in step S6, track the pressure evolution characteristics of the source rock, transport system and the buried hill reservoir of the to-be-evaluated structure on the profile, and analyze and judge the causes of abnormal pressure in the buried hill.

[0013] For the said step S1, the preparation method of the inclusion thin section, the Raman spectrum of methane inclusions, the homogenization temperature of fluid inclusions, and the determination method of the burial history and thermal history map of the target well are as follows:

[0014] 1) Prepare the inclusion thin section: Prepare the core sample of the buried hill reservoir in the target well into an inclusion thin section with double-sided polishing and no cover slip, and observe the inclusion thin section under a microscope to identify methane inclusions and their associated brine inclusions;

[0015] 2) Determine the Raman spectrum of methane inclusions: Determine the Raman spectrum of methane inclusions in the high-temperature and high-pressure buried hill reservoir to be analyzed by performing laser Raman tests on gas-bearing / pure gas inclusions with regular shapes and well-preserved conditions;

[0016] 3) Determine the homogenization temperature of fluid inclusions: Select the brine inclusions symbiotic with methane inclusions for measurement to obtain the homogenization temperature of fluid inclusions in the high-temperature and high-pressure buried hill reservoir to be analyzed;

[0017] 4) Determine the burial history and thermal history map of the target well: Perform single-well basin simulation on the high-temperature and high-pressure buried hill target well through basin simulation software to restore the burial history and thermal history map of the to-be-evaluated area.

[0018] For the said step S2, the method for determining the pressure at the time of inclusion capture is as follows:

[0019] 1) Select the Raman spectrum test results of pure gas methane inclusions with regular shapes and well-preserved conditions in step S1;

[0020] 2) Determine the inclusion density using the displacement of the characteristic peak of Raman scattering of pure gas methane inclusions. The formula is as follows:

[0021] D = v1 - v0

[0022] ρ = -5.17331×10 -5 ×D 3 +5.53081×10 -4 ×D 2 -3.51387×10 -2 ×D

[0023] In the formula: ρ is the density of methane inclusions, g / cm 3 ; D is the displacement of the characteristic peak of methane Raman scattering, cm-1 ; v1 is the wavenumber of the methane Raman scattering characteristic peak after correction by the neon lamp, cm -1 ; v0 is the wavenumber of the Raman scattering characteristic peak of the methane standard gas when the pressure is close to 0, cm -1 ;

[0024] 3) Calculate the pressure at the time of inclusion capture.

[0025] In step S3, the method for determining the capture time of the inclusion is as follows:

[0026] Project the average homogenization temperature data of the pure gas methane inclusions and associated brine inclusions selected in step S2 onto the burial history and thermal history map of the target well in step S1 to obtain the capture time of the pure gas methane inclusions.

[0027] In step S4, the method for calculating the paleo-pressure coefficient at the time of inclusion capture is as follows:

[0028] 1) According to the inclusion capture time determined in step S3 and the burial history of the target well, obtain the paleo-burial depth at the time of capture;

[0029] 2) According to the paleo-pressure of the inclusion determined in step S2, combined with the paleo-burial depth, calculate the paleo-pressure coefficient at the time of inclusion capture. The formula is as follows:

[0030]

[0031] In the formula: C p - Paleo-pressure coefficient at the time of capture; P tra - Paleo-pressure at the time of capture, MPa; ρ 水 - Density of formation water, taking 1 g / cm 3 ; g - Acceleration due to gravity, taking 9.81 m / s 2 ; d tra - Paleo-burial depth, m.

[0032] In step S5, select a representative seismic profile of the target well. According to the reflection interfaces of each formation in the profile and the formation attribute parameters of the target well, select the corresponding terrestrial heat flow, sedimentary water interface temperature, and paleo-water depth data in the study area. Use the PetroMod software to establish a two-dimensional profile numerical simulation model, and restore the pressure evolution history of the area to be evaluated through the PetroMod 2D basin simulation module.

[0033] In step S6, according to the current mud logging pressure coefficient of the buried hill reservoir in the target well and the paleo-pressure coefficient of the inclusions in the buried hill reservoir in step S4, the two-dimensional profile numerical simulation model is corrected. According to the correction results, the formation property parameters of the target well in step S5, as well as the geothermal heat flow, sedimentary water interface temperature, and paleo-water depth data in the area to be evaluated, are adjusted until the simulated pressure at the methane inclusion sampling point in the buried hill reservoir is in good agreement with the mud logging pressure and the paleo-pressure, that is, the numerical simulation model is considered reliable.

[0034] In step S7, through the two-dimensional profile numerical simulation model corrected in step S6, the PetroMod2D software system is used to restore the pressure evolution history of this profile. Representative points in the two-dimensional profile model are selected to trace the pressure evolution characteristics of each point during the geological history period. Combining parameters such as the sedimentation rate, hydrocarbon generation rate, hydrocarbon generation amount, reservoir pressure, and caprock pressure in the study area, the genetic mechanism of the abnormal pressure in the buried hill is analyzed and judged.

[0035] Advantages of the present invention:

[0036] Aiming at the special gas reservoir type of high-temperature and high-pressure buried hill, through the paleo-pressure and capture time of inclusions, combined with the burial history to calculate the paleo-pressure coefficient of inclusions, and correcting the two-dimensional profile numerical simulation model according to the paleo-pressure coefficient and the current mud logging pressure coefficient, the reliability of the two-dimensional profile pressure evolution simulation results is effectively improved. Furthermore, the genetic mechanism of the abnormal pressure in the buried hill can be accurately analyzed and judged, which has important reference value for the analysis of the hydrocarbon accumulation process of this type of oil and gas reservoir. Brief description of the drawings

[0037] Figure 1 is a flow chart of a method for analyzing the origin of abnormal pressure in a high-temperature and high-pressure buried hill according to an embodiment of the present invention;

[0038] Figure 2 is a microscopic photograph of an inclusion thin section of the high-temperature and high-pressure buried hill reservoir of Well L1 according to an embodiment of the present invention;

[0039] Figure 3 is what is described in an embodiment of the present invention Figure 2 is the Raman spectrogram of the pure gas methane inclusion at the measuring point position in;

[0040] Figure 4 is what is described in an embodiment of the present invention Figure 2 is the uniform temperature distribution diagram of the brine inclusion associated with the pure gas methane inclusion in;

[0041] Figure 5 is the burial history and thermal history diagram of Well L1 according to an embodiment of the present invention

[0042] Figure 6 is the pressure simulation profile passing through Well L1 according to an embodiment of the present invention

[0043] Figure 7a It is the graph of the evolution characteristics of the pressure coefficient of the simulated points described in the embodiments of the present invention

[0044] Figure 7b It is the sedimentation rate graph of Well L1 described in the embodiments of the present invention

[0045] Figure 7c It is the graph of the cumulative hydrocarbon generation amount of the main hydrocarbon source rock (Point A) in each period described in the embodiments of the present invention. Detailed implementation manners

[0046] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0047] Embodiment:

[0048] As Figure 1 shown, a method for analyzing the origin of abnormal pressure in high-temperature and high-pressure buried hills includes the following steps:

[0049] S1. Select samples of the high-temperature and high-pressure buried hill reservoir in the target well to prepare inclusion thin sections, identify the gas-bearing / pure gas methane inclusions and their associated brine inclusions in the thin sections, and determine the Raman spectrum of the methane inclusions, the homogenization temperature of the fluid inclusions, the burial history and thermal history graph of the target well;

[0050] S2. Determine the paleo-pressure at the time of methane inclusion capture according to the Raman spectrum;

[0051] S3. Determine the capture time of the inclusions according to the homogenization temperature of the fluid inclusions, the burial history and thermal history graph of the target well;

[0052] S4. Calculate the paleo-pressure coefficient at the time of capture according to the inclusion capture time obtained in step S3 and the paleo-pressure at the time of methane inclusion capture obtained in step S2;

[0053] S5. Construct a two-dimensional profile numerical simulation model of the high-temperature and high-pressure buried hill reservoir, and restore the pressure evolution history of the area to be evaluated through basin simulation software;

[0054] S6. Correct the two-dimensional profile numerical simulation model according to the logging pressure coefficient and paleo-pressure coefficient of the buried hill reservoir in the target well to obtain a reliable numerical simulation model;

[0055] S7. Restore the pressure evolution history according to the corrected two-dimensional profile numerical simulation model in step S6, track the pressure evolution characteristics of the hydrocarbon source rock, transport system and the buried hill reservoir of the structure to be evaluated on the profile, and analyze and judge the origin of the abnormal pressure in the buried hill. Specific embodiment:

[0057] The present invention will be further described in detail below in conjunction with embodiments and specific implementation manners. It should be noted that the scope of application of the above embodiments of the present invention should not be understood to be limited to the following specific embodiments. Any technology implemented based on the content of the present invention belongs to the scope of the present invention.

[0058] Taking the drilling of the buried hill of L1 on the L structure in the Qiongdongnan Basin as an example, this embodiment makes a detailed introduction to the steps such as the restoration of the single-well burial history and thermal history diagram, the calculation of the paleopressure of the inclusions in the high-temperature and high-pressure buried hill reservoir, the establishment of the two-dimensional profile numerical simulation model, and the analysis of the causes of abnormal pressure in the buried hill reservoir.

[0059] The L structure is located on the west side of the Lingnan low uplift in the southern part of the Ledong-Lingshui sag in the Qiongdongnan Basin. The average geothermal gradient in the area is above 4.0 °C / 100m, and a high-pressure system is widely developed. The pressure coefficient of the buried hill reservoir is greater than 1.7, and the pressure coefficient of the overlying layer is within the range of 1.3 - 1.7. The L1 well on this structure drilled through the buried hill, and the logging revealed a gas layer thickness of more than 100 meters, belonging to a typical high-temperature and high-pressure buried hill gas reservoir.

[0060] (1) Preparation and observation of thin sections of inclusions in samples of the high-temperature and high-pressure buried hill reservoir of Well L1, determination of the Raman spectrum of methane inclusions, the homogeneous temperature of fluid inclusions, the burial history and thermal history diagram of Well L1;

[0061] 1) Preparation and observation of inclusions: Prepare the wall core samples of the buried hill reservoir of Well L1 into double-sided polished inclusion thin sections without coverslips with a thickness of 300 μm, and observe the petrographic characteristics of the inclusions under a ZEISS Axio Scope.A1 dual-channel microscope to find methane inclusions and the associated brine inclusions ([[ID=X]] Figure 2 )

[0062] 2) Laser Raman test: Select pure gas methane inclusions with regular shapes and well-preserved conditions for laser Raman tests. The measuring point positions are as Figure 2 shown. In this Raman spectrum test, a LABHR–VIS LabRAM HR800 research-grade microscopic laser Raman spectrometer is used. The test environment temperature is 25 °C, the light source is a Yag crystal frequency-doubled solid laser, and the wavelength is 532 nm. The Raman spectrum of this inclusion is collected as Figure 3 shown. The test results show that the position of the Raman spectrum peak at 2911.19 cm -1 is the characteristic peak of methane, and no other spectral peaks are seen, indicating that this inclusion is a pure gas methane inclusion;

[0063] 3) Homogeneous temperature test of fluid inclusions: To avoid the influence of inhomogeneous capture of inclusions on the test, select small-sized and regularly-shaped gas-liquid two-phase brine inclusions that coexist and are of the same period as the pure gas methane inclusions for determination ( Figure 2) For this measurement of the homogenization temperature of inclusions, an automatic hot and cold stage THMS600G produced by Linkam Company in the UK was used. The temperature measurement range is between -196 and 600 °C, and the precision error is about 0.1 °C. The test results show that the homogenization temperature range of pure gas methane inclusions associated with brine inclusions is between 139 and 153 °C, and the average homogenization temperature is 145.3 °C( Figure 4 )。

[0064] 4) Restoration of burial history and thermal history diagrams: Based on the stratigraphic layer data and lithologic logging data of Well L1, the heat flow value of the study area uses the public data published by Song Yang et al. in 2011. The temperature of the sedimentary water interface uses the public data of the global sea level temperature by Wygrała in 1989, and the paleo-water depth data uses the public data published by Kang Bo et al. in 2014. Through the PetroMod 1D basin simulation software, a single-well basin simulation of Well L1 was carried out to restore the burial history and thermal history diagrams of Structure L( Figure 5 )。

[0065] (2) Determine the paleo-pressure when methane inclusions were captured according to Raman spectroscopy;

[0066] The measuring point positions of pure gas methane inclusions are shown in detail in Figure 2 , and the test results of Raman spectroscopy diagrams are shown in detail in Figure 3 . Among them, the measured characteristic peak V1 of the Raman spectrum of methane inclusions is 2911.19 cm -1 , and the Raman scattering characteristic peak V0 of methane standard gas under a 25 °C test environment is 2917.45 cm -1 . Substituting the Raman scattering characteristic peak displacement into Equation 1-1 and Equation 1-2, the density ρ of this inclusion can be calculated as 0.2543 g / cm 3 . Through the inclusion density and average homogenization temperature, the capture pressure P of the inclusion is calculated according to the thermodynamic state equation of the supercritical state tra to be 82.14 MPa.

[0067] (3) Capture time of pure gas methane inclusions;

[0068] Project the average homogenization temperature of 145.3 °C of the gas-liquid two-phase brine inclusions that coexist and are synchronous with the pure gas methane inclusions onto the burial history diagram to obtain the capture time of the pure gas methane inclusions( Figure 5 ), that is, 0.8 Ma.

[0069] (4) Paleo-pressure coefficient when pure gas methane inclusions were captured;

[0070] According to the burial history and thermal history diagrams of Structure L, the paleo-burial depth d of this test point is obtained by restoring to 0.8 Ma through the PetroMod 1D basin simulation software traIt is 3990 m. Substitute the capture pressure and the paleo-burial depth into Equation 2 to obtain the paleo-pressure coefficient C p It is 2.06.

[0071] (5) Select a representative seismic profile passing through Structure L and including the main hydrocarbon-generating sag on its west side and the source-connected fault. The seismic reflection interfaces in the profile include a total of 8 reflection interfaces, namely T100, T70, T60, T50, T40, T30, T20, and T00. Among them, the strata between T100 and T70 are the main hydrocarbon source rocks, the strata between T70 and T60 are the secondary hydrocarbon source rocks, and Fault F1 is the source-connected fault connecting the hydrocarbon source rock and the buried hill reservoir of Structure L, which is an important conduction channel for the vertical migration of natural gas. According to the 8 seismic reflection interfaces in the profile, the stratigraphic layering data of Well L1, the sedimentation time of each stratum, and the lithology logging data, the lithology data above the T50 interface in the simulated profile adopt the lithology statistical data of Well L1. Since the hydrocarbon source rocks in the hydrocarbon-generating sag have a high shale content and are rich in organic matter, based on the shale content data of Well L1, the main hydrocarbon source rocks between T100 and T70 and the secondary hydrocarbon source rocks between T70 and T60 in the hydrocarbon-generating sag are set with a lithology of 95% mudstone and 5% siltstone. The geothermal heat flow value, the temperature of the sedimentary water interface, and the paleo-water depth data adopt the data simulated by Well L1 in Step 1. Based on the above conditions, use the PetroMod software system to establish a two-dimensional profile numerical simulation model, and restore the pressure evolution history of the to-be-evaluated area through the PetroMod 2D basin simulation module.

[0072] (6) Calibrate the two-dimensional profile numerical simulation model;

[0073] The logging pressure measurement of Well L1 shows that the current pressure coefficient of the buried hill reservoir is 1.78, and the paleo-pressure coefficient of the measurement point at 0.8 Ma calculated in Step 4 is 2.06. Calibrate the two-dimensional profile numerical simulation model established in Step 5 according to the logging pressure coefficient at 0 Ma and the paleo-pressure coefficient at 0.8 Ma, and adjust the shale content in the hydrocarbon-generating sag, as well as the geothermal heat flow value, the temperature of the sedimentary water interface, and the paleo-water depth data, until the simulated profile pressure is in good match with the calibration point data, and obtain a reliable numerical simulation model. Restore the pressure evolution history of this profile through the PetroMod 2D basin simulation module as Figure 6 shown.

[0074] (7) Analysis of the causes of abnormal pressure in the buried hill;

[0075] Select representative positions on the pressure evolution profile for pressure cause analysis. In this example, the main hydrocarbon source rock (Point A), the secondary hydrocarbon source rock (Point B), the main conduction channel (Point C), and the target structure (Point D) are selected for pressure evolution analysis. The selected simulation points are highly representative and cover the entire route of natural gas migration, starting from the hydrocarbon source rock in the hydrocarbon-generating sag, passing through the F1 source-connected fault, and finally reaching the buried hill trap of Structure L. The positions of each simulation point are shown in detailFigure 6 as shown

[0076] From the simulation results of each representative point, it can be seen that the pressure evolution in the study area is divided into three stages ( Figure 7a ): Stage ① is from burial to 10.5 Ma. This stage is a slow burial stage, and the pressure generally shows the characteristics of normal pressure - weak high pressure. The pressure of the source rock in the depression is relatively high, showing weak high pressure, with a pressure coefficient of 1.25 - 1.5. The pressure of the main conduction channel F1 fault is slightly lower than that in the depression, with a pressure coefficient of 1.2 - 1.3. The buried hill target structure is under normal pressure, with a pressure coefficient of 1.1 - 1.23; Stage ② is from 10.5 Ma to 2.0 Ma. This stage is a rapid pressure increase stage. The pressure of the source rock in the depression increases rapidly, with a pressure coefficient of 1.5 - 2.3. The pressure of the main conduction channel F1 fault increases accordingly, with a pressure coefficient of 1.3 - 2.0. The pressure of the buried hill target structure also increases correspondingly, with a pressure coefficient of 1.23 - 1.85; Stage ③ is from 2.0 Ma to the present. The pressure in the depression continues to increase slowly, with a pressure coefficient of 2.3 - 2.35. The pressure change of the main conduction channel fault is not significant, with a pressure coefficient of about 2.05. The pressure of the buried hill reservoir of L structure slowly releases and drops, with a pressure coefficient of 1.85 - 1.78.

[0077] Combined with the sedimentation rate in the study area ( Figure 7b ) and the hydrocarbon generation process of the source rock in the depression ( Figure 7c ), it is analyzed that the main cause of the abnormal high pressure in the high - temperature and high - pressure buried hill gas reservoir of L structure is the under - compaction pressure increase of the overlying mudstone during early burial and the subsequent pressure conduction of hydrocarbon fluids.

[0078] Specifically, Stage ① is the early stage of buried hill burial. Before 10.5 Ma, the buried hill was slowly buried, and the sedimentation rate in the study area continued to increase slowly ( Figure 7b ). During the process of rapid accumulation and compaction of sediments, the pore fluids in the formation were blocked and could not be discharged smoothly, resulting in the formation of weak high pressure. In this stage, the source rock in the depression matured slowly, but due to not entering the rapid hydrocarbon generation period, the hydrocarbon generation rate was small, K1 = 215.57 ( Figure 7c ), and the pressure in the depression increased slowly due to the hydrocarbon generation pressure increase of the source rock ( Figure 7a ); Stage ② is the rapid pressure increase stage of the buried hill. From 10.5 Ma to 2.0 Ma, the main source rock and secondary source rock in the depression entered the main hydrocarbon generation period, and the hydrocarbon generation rate was large, K2 = 498.34 ( Figure 7c ). Due to the large amount of hydrocarbons generated in the depression, the pressure increased rapidly, forming a large source - reservoir pressure difference between the depression and the buried hill reservoir of L structure, providing sufficient power for the injection of hydrocarbons. A large amount of hydrocarbon fluids generated in the depression were injected into the buried hill structure through the F1 fault, causing the pressure of the conduction system and the target structure to increase correspondingly. In this stage, the sedimentation rate in the study area increased rapidly and reached the maximum value of 568 m / Ma until 2.0 MaFigure 7b ), the pressure of the buried hill reservoir of the L structure also reaches the maximum. Stage ③ is the stage of balanced pressure release of the buried hill. Since 2.0 Ma, the depression has continued to generate hydrocarbons, but the hydrocarbon generation rate has slowed down, K3 = 367.78( Figure 7c ), resulting in a slow increase in the pressure of the depression. Hydrocarbons continue to release pressure through the conduction channels. Therefore, the pressure change in the fault is not significant during this stage. After 2.0 Ma, the sedimentation rate decreases( Figure 7b ), and the hydrocarbons flow and adjust in the buried hill reservoir, and the pressure of the buried hill is slowly and evenly released( Figure 7a ).

[0079] It can be seen from specific examples that the formation of abnormal pressure in high-temperature and high-pressure buried hills is closely related to hydrocarbon charging and reservoir formation. Therefore, the analysis of the causes of abnormal pressure is an important part of the analysis of the process of large-scale hydrocarbon reservoir formation, which can effectively reduce the exploration risk of high-temperature and high-pressure buried hill gas reservoirs. This method can accurately judge the causes of abnormal pressure in high-temperature and high-pressure buried hills, provide technical support for the fluid charging of high-pressure reservoirs, and has certain promotion and application value.

[0080] The above embodiments only represent the specific implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills, characterized in that: The steps include: S1. Prepare inclusion thin sections from high-temperature, high-pressure buried-hill reservoir samples from target wells. Identify gas-bearing / pure gas methane inclusions and their associated brine inclusions in the thin sections. Determine the Raman spectra of the methane inclusions, the homogenization temperature of the fluid inclusions, and the burial history and thermal history of the target wells. S2. Determine the paleopressure at the time of capture of methane inclusions based on Raman spectroscopy; S3. Determine the capture time of the inclusion based on the homogenization temperature of the fluid inclusion, the burial history of the target well, and the thermal history map; S4. Calculate the paleo-pressure coefficient at the time of capture based on the capture time of the inclusions obtained in step S3 and the paleo-pressure at the time of capture of the methane inclusions obtained in step S2; S5. Construct a two-dimensional cross-section numerical simulation model of the high-temperature and high-pressure buried-hill reservoir and restore the pressure evolution history of the area to be evaluated using basin simulation software; S6. Correct the two-dimensional profile numerical simulation model based on the well logging pressure coefficient and paleopressure coefficient of the target well buried hill reservoir to obtain a reliable numerical simulation model; S7, restoring the pressure evolution history based on the two-dimensional profile numerical simulation model corrected in step S6, tracking the pressure evolution characteristics of the source rock, the transport system, and the buried hill reservoir of the structure to be evaluated on the profile, and analyzing and determining the cause of the abnormal pressure in the buried hill; In step S2, the method for determining the pressure during capture of methane inclusions is as follows: 1) Selecting the Raman spectrum test results of the pure methane inclusions with regular shapes and good preservation in step S1; 2) The inclusion density is determined using the shift of the Raman scattering characteristic peak of pure methane inclusions. The formula is as follows: D=v1-v0 p=-5.17331×10 -5 ×D 3 +5.53081×10 -4 ×D 2 -3.51387×10 -2 ×D Where: ρ is the density of methane inclusions; D is the displacement of the characteristic peak of methane Raman scattering; v1 is the wave number of the characteristic peak of methane Raman scattering after neon lamp correction; v0 is the wave number of the characteristic peak of methane Raman scattering when the pressure is close to 0; 3) Calculate the pressure when the inclusion is captured.

2. The method for analyzing the cause of abnormal pressure in a high-temperature and high-pressure buried hill according to claim 1, characterized in that: In step S1, the method for preparing inclusion thin sections, determining the Raman spectrum of methane inclusions, the homogenization temperature of fluid inclusions, the burial history of the target well, and the thermal history map is as follows: 1) Preparation of inclusion thin sections: Double-sided polished, uncovered inclusion thin sections were prepared from the target well buried hill reservoir core sample. The inclusion thin sections were observed under a microscope to identify methane inclusions and their associated brine inclusions. 2) Determine the Raman spectrum of methane inclusions: Laser Raman testing is performed on regularly shaped, well-preserved gas-bearing / pure gas inclusions to determine the Raman spectrum of the methane inclusions in the high-temperature, high-pressure buried-hill reservoir to be analyzed; 3) Determine the homogenization temperature of fluid inclusions: Select brine inclusions coexisting with methane inclusions for measurement to obtain the homogenization temperature of the fluid inclusions in the high-temperature and high-pressure buried-hill reservoir to be analyzed; 4) Determine the burial history and thermal history map of the target well: Use basin simulation software to perform single-well basin simulation on the high-temperature and high-pressure buried-hill target well to restore the burial history and thermal history map of the area to be evaluated.

3. A method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills according to claim 1 or 2, characterized in that: In step S3, the method for determining the capture time of the inclusions is as follows: the average uniform temperature data of the pure gas methane inclusions and the associated brine inclusions selected in step S2 are projected onto the burial history and thermal history map of the target well in step S1 to obtain the capture time of the pure gas methane inclusions.

4. The method for analyzing the cause of abnormal pressure in a high-temperature and high-pressure buried hill according to claim 1, characterized in that: Step S4, the paleo-pressure coefficient calculation method when the methane inclusion is captured is as follows: 1) Obtaining the ancient burial depth at the time of capture based on the inclusion capture time determined in step S3 and the target well burial history map; 2) Based on the inclusion paleopressure determined in step S2 and the paleoburial depth, calculate the paleopressure coefficient at the time of inclusion capture using the following formula: ， Where: C p is the paleopressure coefficient at the time of capture; P tra Paleopressure at capture; ρ 水 The density of formation water is 1g / cm 3 ;g acceleration due to gravity, take 9.81m / s 2 ;d tra Ancient burial depth.

5. The method for analyzing the cause of abnormal pressure in a high-temperature and high-pressure buried hill according to claim 1, characterized in that: Step S5: Select a representative seismic profile of the target well. Based on the reflection interfaces of each stratum in the profile and the stratigraphic attribute parameters of the target well, select the geothermal heat flow, sediment-water interface temperature, and paleowater depth data corresponding to the study area. Use PetroMod software to establish a two-dimensional profile numerical simulation model, and use the PetroMod 2D basin simulation module to restore the pressure evolution history of the area to be evaluated.

6. A method for analyzing the causes of abnormal pressure in high-temperature and high-pressure buried hills according to claim 1 or 5, characterized in that: In step S6, the two-dimensional profile numerical simulation model is corrected based on the current logging pressure coefficient of the buried-hill reservoir of the target well and the paleopressure coefficient of the buried-hill reservoir inclusions in step S4. The formation attribute parameters of the target well in step S5, as well as the geothermal flow, sedimentary-water interface temperature, and paleowater depth data of the evaluation area are adjusted based on the correction results until the simulated pressure at the sampling point of the methane inclusions in the buried-hill reservoir is well matched with the logging pressure and the paleopressure, and the numerical simulation model is considered reliable.

7. The method for analyzing the cause of abnormal pressure in a high-temperature and high-pressure buried hill according to claim 1, characterized in that: Step S7: Using the two-dimensional profile numerical simulation model corrected in step S6, the PetroMod 2D software system is used to restore the pressure evolution history of the profile. Representative points in the two-dimensional profile model are selected to track the pressure evolution characteristics of each point during the geological history period. Combined with the sedimentation rate, hydrocarbon generation rate, hydrocarbon generation amount, reservoir pressure, and cap rock pressure of the study area, the cause of the abnormal pressure in the buried hill is analyzed and determined.

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