Determination method for paleo-ground temperature characteristics of deep shale strata veins

Abstract

The invention provides a method for determining ancient ground temperature characteristics of a deep shale bed system vein body. The method comprises the following steps: acquiring a corresponding chart of mechanical bicrystal morphology geometric characteristics and deformation temperature of calcite; wherein the morphological geometric characteristics refer to width and density or strain and density; obtaining the morphological geometric characteristics of the mechanical bicrystal of the vein body calcite of the target deep shale bed series; and based on the morphological geometric characteristics of the calcite mechanical bicrystal of the target deep shale bed system vein body and the corresponding chart of the morphological geometric characteristics of the calcite mechanical bicrystal and the deformation temperature, determining the deformation temperature of the calcite mechanical bicrystal of the target deep shale bed system vein body, and taking the deformation temperature as the ancient ground temperature of the target deep shale bed system vein body. According to the method provided by the invention, the calcite mechanical bicrystal is used as a geological thermothermometer of the deep shale bed system, the paleo-ground temperature characteristics of the vein body of the deep shale bed system are determined, and a reliable method is provided for researching the fluid thermal history of the basin deep shale vein body.

Description

Technical Field

[0001] This invention belongs to the field of geological vein fluid activity research technology, specifically relating to a method for determining paleotemperature characteristics of deep shale veins. Background Technology

[0002] Currently, the paleotemperature and pressure characteristics of stratigraphic formations are mainly determined using the paleotemperature and pressure characteristics of calcite veins. The study of paleotemperature and pressure characteristics of calcite veins primarily relies on tracing information such as homogenization temperature, freezing point temperature, and salinity of mineral fluid inclusions. Specifically, vein inclusions capture and preserve information about the original fluid environment during the tectonic activity of the vein. By measuring the homogenization temperature, freezing point temperature, and salinity of these mineral fluid inclusions, the paleotemperature and pressure environment characteristics of the stratigraphic formation during the tectonic deformation period of the calcite vein can be effectively traced. However, in deep shale formations, due to objective factors such as narrow vein width and small inclusion development, it is difficult to obtain two-phase inclusions from veins that provide information for measuring homogenization temperature, freezing point temperature, and salinity, thus limiting the acquisition of paleotemperature and pressure characteristics of deep shale formations.

[0003] In summary, there is still a need to study technical solutions that can effectively determine the paleothermal characteristics of deep shale strata veins, so as to provide support for the study of the fluid thermal history of deep shale strata veins in the basin. Summary of the Invention

[0004] The purpose of this invention is to provide a method for effectively determining the paleothermal characteristics of deep shale strata veins, thereby facilitating the determination of these characteristics and providing support for the study of the fluid thermal history of deep shale strata veins in basins.

[0005] To achieve the above objectives, the present invention provides a method for determining the paleotemperature characteristics of deep shale strata veins, the method comprising:

[0006] A method for determining paleotemperature characteristics of deep shale veins, the method comprising:

[0007] Obtain a graph showing the morphological geometry of mechanical twinning of calcite and its corresponding deformation temperature; wherein, the morphological geometry refers to width and density or strain and density;

[0008] To obtain the morphological and geometric characteristics of mechanical twins of calcite in veins of the target deep shale strata;

[0009] Based on the morphological and geometric characteristics of calcite mechanical twins in the target deep shale strata vein and the corresponding chart of calcite mechanical twin morphological and geometric characteristics and deformation temperature, the deformation temperature of calcite mechanical twins in the target deep shale strata vein was determined and used as the paleogeothermal temperature of the target deep shale strata vein.

[0010] According to a preferred embodiment of the method for determining the paleothermal characteristics of deep shale strata veins provided by the present invention, obtaining a map showing the geometric characteristics of calcite mechanical twinning morphology and the corresponding deformation temperature includes:

[0011] Deformation temperature data and morphological geometry data of multiple calcite mechanical twins were obtained;

[0012] Based on the obtained deformation temperature data and morphological geometry data of calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperature of calcite mechanical twins are determined.

[0013] According to a preferred embodiment of the method for determining the paleotemperature characteristics of deep shale strata veins provided by the present invention, the determination of the corresponding chart of morphological and geometric characteristics and deformation temperature of calcite mechanical twins based on the obtained deformation temperature data and morphological and geometric characteristic data of each calcite mechanical twin includes:

[0014] Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the coordinate axes being the width and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of the width and density of calcite mechanical twins at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

[0015] More preferably, a lookup chart for the width and density of calcite mechanical twins at different deformation temperatures includes:

[0016] After projecting each calcite mechanical twin onto a coordinate system with the axes representing the width and density of the calcite mechanical twin, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each calcite mechanical twin, thereby determining the lookup chart for the width and density of the calcite mechanical twin at each deformation temperature.

[0017] More preferably, based on the deformation temperature data of mechanical twins of various calcite crystals, the division of different deformation temperature regions in the coordinate system includes:

[0018] Based on the deformation temperature data of mechanical twins in calcite from various sources, a trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is used as the boundary line for different deformation temperature regions to divide the region into different deformation temperature regions in the coordinate system.

[0019] More preferably, the boundary deformation temperature includes 170°C and 200°C.

[0020] According to a preferred embodiment of the method for determining the paleotemperature characteristics of deep shale strata veins provided by the present invention, the determination of the corresponding chart of morphological and geometric characteristics and deformation temperature of calcite mechanical twins based on the obtained deformation temperature data and morphological and geometric characteristic data of each calcite mechanical twin includes:

[0021] Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the coordinate axes being the strain and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of strain and density of calcite mechanical twin at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

[0022] More preferably, a lookup chart for strain versus density of calcite mechanical twins at different deformation temperatures is established, including:

[0023] After projecting the mechanical twins of each calcite crystal onto a coordinate system with the axes representing the strain and density of the mechanical twins, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each mechanical twin, thereby determining the lookup chart of strain and density of the mechanical twins at each deformation temperature.

[0024] More preferably, based on the deformation temperature data of mechanical twins of various calcite crystals, the division of different deformation temperature regions in the coordinate system includes:

[0025] Based on the deformation temperature data of mechanical twin crystals of calcite from various sources, a trend line of the relationship between strain and density of mechanical twin crystals of calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line of the relationship between strain and density of mechanical twin crystals of calcite below the boundary deformation temperature is used as the boundary line of different deformation temperature regions to divide different deformation temperature regions in the coordinate system.

[0026] Furthermore, the boundary deformation temperatures include 170℃ and 200℃.

[0027] In a preferred embodiment of the method for determining the paleotemperature characteristics of deep shale strata veins provided by the present invention, obtaining deformation temperature data and morphological geometric characteristic data of multiple calcite mechanical twins includes:

[0028] Multiple mechanical twinned calcite samples and mineral fluid inclusions in the veins containing each mechanical twinned calcite sample were obtained.

[0029] Using mechanical twinned calcite samples from each region, petrological thin sections of each mechanical twinned calcite were prepared; using the petrological thin sections of each mechanical twinned calcite, the morphological and geometric characteristics of each mechanical twinned calcite were determined.

[0030] The formation temperature of the mineral fluid inclusions in the veins containing each calcite mechanical twin sample was tested, and the obtained formation temperature data is the deformation temperature data of each calcite mechanical twin.

[0031] More preferably, the formation temperature test of the mineral fluid inclusions in the veins containing each calcite mechanical twin sample can be performed using, but is not limited to, existing mineral fluid inclusion formation temperature testing techniques. For example, the formation temperature of the mineral fluid inclusions can be determined by measuring the homogenization temperature, freezing point temperature, and salinity data of the mineral fluid inclusions.

[0032] In a preferred embodiment of the method for determining paleothermal characteristics of deep shale veins provided by the present invention, obtaining the morphological and geometric characteristics of calcite mechanical twins in the target deep shale vein includes:

[0033] Obtain mechanically twinned calcite samples from veins within the target deep shale strata;

[0034] Using mechanically twinned calcite samples from veins within the target deep shale strata, petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata were prepared. Using these petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata, the morphological and geometric characteristics of the mechanically twinned calcite samples from veins within the target deep shale strata were determined.

[0035] In a preferred embodiment of the method for determining paleothermal characteristics of deep shale strata veins provided by the present invention, the morphological and geometrical characteristics of calcite mechanical twins are determined using calcite mechanical twin petrographic thin sections in the following manner:

[0036] The morphological and geometric characteristics of calcite mechanical twins were observed and measured using an optical microscope, and statistical analysis was conducted to determine the morphological and geometric characteristics of calcite mechanical twins.

[0037] In a preferred embodiment of the method for determining paleothermal characteristics of deep shale strata veins provided by the present invention, the calcite mechanical twinned petrographic thin section is prepared by the following method:

[0038] After cleaning and drying the calcite mechanical twin crystal sample, it was cut into slices, and one side was polished and cleaned to obtain calcite mechanical twin crystal sample sheet.

[0039] Calcite mechanical twin crystal sample sheets were surface-cast with transparent epoxy resin to obtain calcite mechanical twin crystal sample sheets encapsulated in transparent epoxy resin.

[0040] The transparent epoxy resin in contact with the unpolished surface of the calcite mechanical twin crystal sample sheet that is wrapped in transparent epoxy resin is ground off. The unpolished surface is then polished until the thickness of the calcite mechanical twin crystal sample sheet is less than 1 mm. The transparent epoxy resin is then melted by heating, and the calcite mechanical twin crystal sample sheet is removed and washed to obtain the calcite mechanical twin crystal petrological thin section.

[0041] More preferably, the thickness of the calcite mechanical twin crystal sample sheet is 4-6 mm (preferably 5 mm);

[0042] More preferably, the polishing process includes coarse polishing, fine polishing and finishing polishing in sequence;

[0043] More preferably, the calcite mechanical twinned sample sheet is surface-cast using transparent epoxy resin, including:

[0044] After heating and melting transparent epoxy resin, it is poured into a mold with a thickness controlled at 3-5mm. Then it is dried and hardened. The polished surface of the calcite mechanical twin crystal sample sheet is placed on the cured transparent epoxy resin, and the heated and melted transparent epoxy resin is poured in again, so that the heated and melted transparent epoxy resin submerges the upper surface of the calcite mechanical twin crystal sample sheet by 3-5mm. The air bubbles are then removed by vacuuming. After curing, the calcite mechanical twin crystal sample sheet is obtained and is wrapped in transparent epoxy resin.

[0045] The technical solution provided by this invention uses calcite mechanical twins as a geothermal thermometer for deep shale formations. Based on the geometric characteristics of calcite mechanical twins in deep shale formations, the paleothermal characteristics of deep shale veins are determined, providing a reliable method for studying the fluid thermal history of deep shale veins in basins. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating a method for determining paleotemperature characteristics of deep shale strata veins according to a specific embodiment of the present invention.

[0047] Figure 2 This is a characteristic diagram of the temperature variation in the formation of mechanical twins in calcite in Embodiment 1 of the present invention.

[0048] Figure 3 This is a diagram illustrating the mechanical twinning process of calcite in Embodiment 1 of the present invention.

[0049] Figure 4 This is a diagram showing the corresponding width, density, and deformation temperature of mechanical twin crystals of calcite in Embodiment 1 of the present invention.

[0050] Figure 5 This is a diagram showing the mechanical bicrystalline strain, density, and deformation temperature of calcite in Embodiment 1 of the present invention.

[0051] Figure 6This is a homogenization temperature characteristic diagram of fluid inclusions in the vein of the deep shale strata A in Embodiment 1 of the present invention.

[0052] Figure 7 This is a homogenization temperature characteristic diagram of fluid inclusions in the B deep shale strata vein in Embodiment 1 of the present invention.

[0053] Figure 8 This is a characteristic diagram of the thermal history of the deep shale formation A in Embodiment 1 of the present invention, showing its burial depth and subsidence.

[0054] Figure 9 This is a diagram showing the thermal history characteristics of the deep shale formation B in Embodiment 1 of the present invention, representing the burial depth, subsidence, and thermal history. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0056] Calcite mechanical twins are products of slip deformation within calcite crystals caused by mechanical forces. It is a form of crystal plastic deformation. Calcite mechanical twins exhibit slip twinning or deformation twinning structures and can explain the direction and intensity of tectonic movements. The width, density, and strain of calcite mechanical twins are related to the deformation temperature environment. Calcite mechanical twins based on deep shale veins can determine the paleotemperature characteristics of deep shale veins.

[0057] In one specific embodiment, a method for determining the paleotemperature characteristics of deep shale strata veins is provided, such as... Figure 1 As shown, the method includes:

[0058] Step 101: Obtain the corresponding graph of the mechanical twin morphological geometry of calcite and deformation temperature; wherein, the morphological geometry refers to width and density or strain and density;

[0059] Step 102: Obtain the morphological and geometric characteristics of mechanical twins of calcite in the veins of the target deep shale strata;

[0060] Step 103: Based on the morphological and geometric characteristics of the calcite mechanical twins in the target deep shale strata vein and the corresponding chart of the morphological and geometric characteristics of the calcite mechanical twins and deformation temperature, determine the deformation temperature of the calcite mechanical twins in the target deep shale strata vein and use it as the paleogeothermal temperature of the target deep shale strata vein.

[0061] Furthermore, obtain the geometric characteristics of the mechanical twinning morphology of calcite and the corresponding deformation temperature, including:

[0062] Deformation temperature data and morphological geometry data of multiple calcite mechanical twins were obtained;

[0063] Based on the obtained deformation temperature data and morphological geometry data of calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperature of calcite mechanical twins are determined.

[0064] Furthermore, based on the obtained deformation temperature data and morphological geometry data of various calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperatures of calcite mechanical twins are determined as follows:

[0065] Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the coordinate axes being the width and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of the width and density of calcite mechanical twins at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

[0066] Furthermore, a lookup chart for the width and density of calcite mechanical twins at different deformation temperatures was established, including:

[0067] After projecting each calcite mechanical twin onto a coordinate system with the axes representing the width and density of the calcite mechanical twin, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each calcite mechanical twin, thereby determining the lookup chart for the width and density of the calcite mechanical twin at each deformation temperature.

[0068] Furthermore, based on the deformation temperature data of mechanical twins in various calcite samples, different deformation temperature regions are divided in the coordinate system, including:

[0069] Based on the deformation temperature data of mechanical twins in calcite from various sources, a trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is used as the boundary line for different deformation temperature regions to divide the region into different deformation temperature regions in the coordinate system.

[0070] Furthermore, the boundary deformation temperatures include 170℃ and 200℃.

[0071] Furthermore, based on the obtained deformation temperature data and morphological geometry data of various calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperatures of calcite mechanical twins are determined as follows:

[0072] Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the coordinate axes being the strain and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of strain and density of calcite mechanical twin at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

[0073] Furthermore, a lookup chart for strain versus density of calcite mechanical twins at different deformation temperatures was established, including:

[0074] After projecting the mechanical twins of each calcite crystal onto a coordinate system with the axes representing the strain and density of the mechanical twins, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each mechanical twin, thereby determining the lookup chart of strain and density of the mechanical twins at each deformation temperature.

[0075] Furthermore, based on the deformation temperature data of mechanical twins in various calcite samples, different deformation temperature regions are divided in the coordinate system, including:

[0076] Based on the deformation temperature data of mechanical twin crystals of calcite from various sources, a trend line of the relationship between strain and density of mechanical twin crystals of calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line of the relationship between strain and density of mechanical twin crystals of calcite below the boundary deformation temperature is used as the boundary line of different deformation temperature regions to divide different deformation temperature regions in the coordinate system.

[0077] Furthermore, the boundary deformation temperatures include 170℃ and 200℃.

[0078] Furthermore, the deformation temperature data and morphological geometry characteristic data of multiple calcite mechanical twins were obtained, including:

[0079] Multiple mechanical twinned calcite samples and mineral fluid inclusions in the veins containing each mechanical twinned calcite sample were obtained.

[0080] Using mechanical twinned calcite samples from each region, petrological thin sections of each mechanical twinned calcite were prepared; using the petrological thin sections of each mechanical twinned calcite, the morphological and geometric characteristics of each mechanical twinned calcite were determined.

[0081] The formation temperature of the mineral fluid inclusions in the veins containing each type of mechanical twin calcite sample was tested, and the obtained formation temperature data is the deformation temperature data of each type of mechanical twin calcite sample.

[0082] Furthermore, the formation temperature of mineral fluid inclusions in the veins containing mechanical twinned calcite samples can be tested using, but is not limited to, existing mineral fluid inclusion formation temperature testing techniques. For example, the formation temperature of mineral fluid inclusions can be determined by measuring the homogenization temperature, freezing point temperature, and salinity data of the inclusions.

[0083] Furthermore, the morphological and geometric characteristics of calcite mechanical twins in the veins of the target deep shale formation were obtained, including:

[0084] Obtain mechanically twinned calcite samples from veins within the target deep shale strata;

[0085] Using mechanically twinned calcite samples from veins within the target deep shale strata, petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata were prepared. Using these petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata, the morphological and geometric characteristics of the mechanically twinned calcite samples from veins within the target deep shale strata were determined.

[0086] Furthermore, using petrological thin sections of calcite mechanical twins, the morphological and geometric characteristics of calcite mechanical twins were determined in the following manner:

[0087] The morphological and geometric characteristics of calcite mechanical twins were observed and measured using an optical microscope, and statistical analysis was conducted to determine the morphological and geometric characteristics of calcite mechanical twins.

[0088] Furthermore, calcite mechanical twinning petrographic thin sections were prepared by the following method:

[0089] After cleaning and drying the calcite mechanical twin crystal sample, it was cut into slices, and one side was polished and cleaned to obtain calcite mechanical twin crystal sample sheet.

[0090] Calcite mechanical twin crystal sample sheets were surface-cast with transparent epoxy resin to obtain calcite mechanical twin crystal sample sheets encapsulated in transparent epoxy resin.

[0091] The transparent epoxy resin in contact with the unpolished surface of the calcite mechanical twin crystal sample sheet, which is wrapped in transparent epoxy resin, is ground off. The unpolished surface is then polished until the thickness of the calcite mechanical twin crystal sample sheet is less than 1 mm. The transparent epoxy resin is then melted by heating, and the calcite mechanical twin crystal sample sheet is removed and washed to obtain a calcite mechanical twin crystal petrological thin section.

[0092] Furthermore, the thickness of the calcite mechanical twin crystal sample sheet is 4-6 mm (preferably 5 mm);

[0093] Furthermore, the polishing process includes coarse polishing, fine polishing, and high-precision polishing in sequence;

[0094] Furthermore, the calcite mechanical twin crystal sample sheet was surface-cast using transparent epoxy resin, including:

[0095] After heating and melting transparent epoxy resin, it is poured into a mold with a thickness controlled at 3-5mm. Then it is dried and hardened. The polished surface of the calcite mechanical twin crystal sample sheet is placed on the cured transparent epoxy resin, and the heated and melted transparent epoxy resin is poured in again, so that the heated and melted transparent epoxy resin submerges the upper surface of the calcite mechanical twin crystal sample sheet by 3-5mm. The air bubbles are then removed by vacuuming. After curing, the calcite mechanical twin crystal sample sheet is obtained and is wrapped in transparent epoxy resin.

[0096] Example 1:

[0097] This embodiment provides a method for determining the paleotemperature characteristics of deep shale strata veins, the method comprising:

[0098] 1. Obtain corresponding graphs of calcite mechanical twin width, density, and deformation temperature; and corresponding graphs of calcite mechanical twin strain, density, and deformation temperature; specifically including:

[0099] 1.1 Obtain multiple calcite mechanical twin samples and mineral fluid inclusions in the veins containing each calcite mechanical twin sample; prepare petrological thin sections of each calcite mechanical twin sample using the samples; observe and measure the petrological thin sections of each calcite mechanical twin sample using an optical microscope, and statistically analyze the width, density, and strain of each calcite mechanical twin to determine the width, density, and strain data; test the formation temperature of the mineral fluid inclusions in the veins containing each calcite mechanical twin sample, and the obtained formation temperature data are the deformation temperature data of each calcite mechanical twin.

[0100] Among them, the formation temperature of mineral fluid inclusions in the veins containing mechanical twinned calcite samples was tested. The homogenization temperature, freezing point temperature and salinity data of the mineral fluid inclusions were measured, and the formation temperature of the mineral fluid inclusions was determined based on the homogenization temperature, freezing point temperature and salinity data of the mineral fluid inclusions.

[0101] The calcite mechanical twin petrographic thin section was prepared by the following method:

[0102] After cleaning and drying the calcite mechanical twin crystal sample, it was cut into 5mm thick sheets. One side was then coarsely polished, finely polished, and then finely polished before cleaning to obtain the calcite mechanical twin crystal sample sheet.

[0103] After heating and melting transparent epoxy resin, it is poured into a mold with a thickness of 3-5mm. Then it is dried and hardened. The polished surface of the calcite mechanical twin crystal sample sheet is placed on the cured transparent epoxy resin, and the heated and melted transparent epoxy resin is poured in again, so that the heated and melted transparent epoxy resin submerges the upper surface of the calcite mechanical twin crystal sample sheet by 3-5mm. The air bubbles are removed by vacuuming. After curing, the calcite mechanical twin crystal sample sheet is obtained by being wrapped in transparent epoxy resin.

[0104] The transparent epoxy resin in contact with the unpolished surface of the calcite mechanical twin crystal sample sheet, which is wrapped in transparent epoxy resin, is ground off. The unpolished surface is then polished until the thickness of the calcite mechanical twin crystal sample sheet is less than 1 mm. The transparent epoxy resin is then melted by heating, and the calcite mechanical twin crystal sample sheet is removed and washed to obtain a calcite mechanical twin crystal petrological thin section.

[0105] Calcite mechanical twinning includes four types: Type I lamellar twinning, Type II tabular twinning, Type III conical-arc twinning, and Type IV agglomerated-pattern twinning. A large number of Type I lamellar twins and a small number of Type II tabular twins are produced under low-temperature conditions with strain intensity of 0-5% and temperatures below 170-200℃. Figure 2 As shown, a large number of type II plate-like twins are generated under high temperature conditions of strain intensity of 0-6% and greater than 200-250℃; the environmental temperature at which the type III conical arcuate twins are formed is greater than 200℃; the formation of type IV agglomerated patch twins is controlled by dynamic recrystallization and accompanied by the migration of irregular calcite crystal faces, and the environmental temperature at which they are formed is greater than 250℃.

[0106] The macroscopic stress-strain curve of calcite mechanical twinning exhibits three stages: preloading (Ⅰ), pseudo-elastic stage (Ⅱ), and elastic deformation stage (Ⅲ). The elastic deformation stage consists of strain hardening and steady-state deformation. In the strain hardening stage, calcite undergoes initial dislocation deformation along its e-twin plane. Accompanied by an increase in stress-strain, twinning-related plastic deformation occurs, its density increases sharply, and the thickness of the mechanical twin plane increases. Therefore, the formation of calcite mechanical twinning generally involves three processes: twin dislocation formation, mechanical twinning thickening, and merging growth thickening, as shown in the attached figure. Figure 3 As shown.

[0107] 1.2 Based on the width and density data of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the axes representing the width and density of the calcite mechanical twin. According to the deformation temperature data of each calcite mechanical twin, a trend line relating the width and density of the calcite mechanical twin below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line relating the width and density of the calcite mechanical twin below the boundary deformation temperature is used as the boundary line for different deformation temperature regions. Different deformation temperature regions are divided in the coordinate system, thereby determining the query chart of the width and density of the calcite mechanical twin at each deformation temperature, i.e., the chart corresponding to the width, density and deformation temperature of the calcite mechanical twin.

[0108] The boundary deformation temperatures include 170℃ and 200℃.

[0109] The results are as follows Figure 4 As shown.

[0110] 1.3 Based on the strain and density data of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the axes of calcite mechanical twin strain and calcite mechanical twin density. According to the deformation temperature data of each calcite mechanical twin, a trend line of the relationship between calcite mechanical twin strain and density below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line of the relationship between calcite mechanical twin strain and density below the boundary deformation temperature is used as the boundary line of different deformation temperature regions to divide different deformation temperature regions in the coordinate system, thereby determining the query chart of calcite mechanical twin strain and density at each deformation temperature, namely the calcite mechanical twin strain, density and deformation temperature correspondence chart.

[0111] The boundary deformation temperatures include 170℃ and 200℃.

[0112] The results are as follows Figure 5 As shown.

[0113] The mechanical twinning morphology and geometry of calcite undergo significant changes in an environment of 170-200℃, such as... Figure 4As shown, the characteristics of calcite mechanical twinning change from Type I lamellar twinning to Type II tabular twinning. Below 170℃, elastic deformation of calcite mechanical twinning forms lamellar twinning structures (less than 1 μm wide); while above 200℃, with increasing strain and thermal activation of grain boundaries, numerous tabular twins form and merge, growing and thickening, with a twin density typically less than 40 twins / mm. Under similar strain conditions, twin width and twin density show a certain correlation, especially at temperatures below 170℃, exhibiting lamellar twinning characteristics (less than 1 mm and strain of 0-5%); at higher temperatures, mechanical twinning is predominantly tabular (1-5 μm), with a narrower density of 0-40 twins / mm and a strain intensity of 0-6%. Under certain temperature deformation conditions, calcite mechanical twinning often forms lamellar-tabular twinning structures, and the development density shows a typical negative correlation with temperature. Especially under relatively high temperature deformation conditions (above 200℃), calcite mechanical twinning is further affected by dynamic recrystallization of grains and pressure solution compaction, and they are significantly influenced by ambient temperature.

[0114] 2. Obtain mechanically twinned calcite samples from the veins of the target deep shale strata; prepare petrographic thin sections of the mechanically twinned calcite samples from the veins of the target deep shale strata using the samples; observe and measure the petrographic thin sections of the mechanically twinned calcite samples from the veins of the target deep shale strata using an optical microscope, and statistically analyze the width and density of the mechanically twinned calcite samples from the veins of the target deep shale strata to determine the width and density of the mechanically twinned calcite samples from the veins of the target deep shale strata.

[0115] The calcite mechanical twin petrographic thin section was prepared by the following method:

[0116] After cleaning and drying the calcite mechanical twin crystal sample, it was cut into 5mm thick sheets. One side was then coarsely polished, finely polished, and then finely polished before cleaning to obtain the calcite mechanical twin crystal sample sheet.

[0117] After heating and melting transparent epoxy resin, it is poured into a mold with a thickness of 3-5mm. Then it is dried and hardened. The polished surface of the calcite mechanical twin crystal sample sheet is placed on the cured transparent epoxy resin, and the heated and melted transparent epoxy resin is poured in again, so that the heated and melted transparent epoxy resin submerges the upper surface of the calcite mechanical twin crystal sample sheet by 3-5mm. The air bubbles are removed by vacuuming. After curing, the calcite mechanical twin crystal sample sheet is obtained by being wrapped in transparent epoxy resin.

[0118] The transparent epoxy resin in contact with the unpolished surface of the calcite mechanical twin crystal sample sheet, which is wrapped in transparent epoxy resin, is ground off. The unpolished surface is then polished until the thickness of the calcite mechanical twin crystal sample sheet is less than 1 mm. The transparent epoxy resin is then melted by heating, and the calcite mechanical twin crystal sample sheet is removed and washed to obtain a calcite mechanical twin crystal petrological thin section.

[0119] In this embodiment, the deep shale formation of Target A exhibits typical platy calcite mechanical twins, with a twin width of approximately 1-4 μm and a density of 30-50 twins / mm. The deep shale formation of Target B has larger calcite mechanical twins with lower density, with a twin width of approximately 3 μm and a density of 15-20 twins / mm.

[0120] 3. Based on the width and density of calcite mechanical twins in the vein of the target deep shale strata and the corresponding chart of calcite mechanical twin width, density and deformation temperature, determine the deformation temperature of calcite mechanical twins in the vein of the target deep shale strata and use it as the paleogeothermal temperature of the vein of the target deep shale strata.

[0121] The calcite mechanical twins in the deep shale formation of Target A have a width of 1-4 μm and a density of 30-50 twins / mm, indicating a paleotemperature of approximately 170℃ for the veins. The calcite mechanical twins in the deep shale formation of Target B have a width of approximately 3 μm and a density of 15-20 twins / mm, indicating a paleotemperature of approximately 200℃ for the veins. Target B exhibits a higher calcite mechanical twin formation temperature, i.e., a higher paleotemperature, compared to Target A.

[0122] To verify the paleogeothermal characteristics of the deep shale strata of Target A and Target B, fluid inclusions in these strata were measured and analyzed in the laboratory to obtain homogenization temperature information. Numerous fluid inclusions were found clustered along fractures in the deep shale strata veins of Target A, with common hydrocarbon inclusions and single-phase liquid inclusions present. Statistical analysis of the homogenization temperature data showed that the homogenization temperature of the fluid inclusions in the deep shale strata veins of Target A exhibited a bimodal distribution, with peak values ​​primarily around 120-140℃ and 160-180℃. (See attached figure). Figure 6 As shown, the homogenization temperature of inclusions in the deep shale veins of Target B exhibits three peak temperature ranges: 120-140℃, 160-180℃, and 200-220℃. Figure 7As shown, the homogenization temperature of inclusions, especially in the high-temperature range, is significantly increased, and the fluorescence characteristics of the veins reveal that hydrocarbon inclusions generally exhibit white fluorescence (indicating a high degree of thermal evolution), indicating that the formation of veins in the deep shale system of target B was carried out in a relatively high paleotemperature environment. Based on a one-dimensional basin simulation mathematical model, using the BaseinMod basin simulation software, when simulating the burial thermal history of typical wells in the deep shale systems of targets A and B, the data such as well stratigraphic layering and depth, sandstone, mudstone and limestone content, geothermal gradient and heat flow values ​​are mainly based on actual drilling data. The erosion calculation references the stratigraphic thickness of the region and the thermal history simulation data of apatite fission track. Combined with the corresponding fluid homogenization temperature of calcite inclusions, it is indicated that the mechanical twinning of calcite tectonic veins in the deep shale system of target A is mainly due to the formation of calcite veins and their twinning thickening and merging growth process caused by tectonic deformation in the Late Triassic and Late Jurassic. Figure 8 As shown. The mechanical twinning of the calcite veins in the deep shale strata of Target B is mainly due to the formation of calcite veins and the thickening and merging of twins caused by tectonic deformation in the Late Jurassic and Late Cretaceous periods, as shown in the figure. Figure 9 As shown, the calcite tectonic veins and twinning formations in the deep shale strata of Target B exhibit relatively late formation time and record high deformation temperatures. This demonstrates that paleotemperature of deep shale strata can be effectively determined based on the morphological geometry of calcite mechanical twinning.

[0123] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 within the scope of protection of the present invention.

Claims

1. A method for determining paleotemperature characteristics of deep shale strata veins, the method comprising: A method for determining paleotemperature characteristics of deep shale veins, the method comprising: Obtain a graph showing the morphological geometry of mechanical twinning of calcite and its corresponding deformation temperature; wherein, the morphological geometry refers to width and density or strain and density; To obtain the morphological and geometric characteristics of mechanical twins of calcite in veins of the target deep shale strata; Based on the morphological and geometric characteristics of calcite mechanical twins in the target deep shale strata vein and the corresponding chart of calcite mechanical twin morphological and geometric characteristics and deformation temperature, the deformation temperature of calcite mechanical twins in the target deep shale strata vein was determined and used as the paleogeothermal temperature of the target deep shale strata vein.

2. The determination method according to claim 1, wherein, Obtain the geometric characteristics of the mechanical twinning morphology of calcite and the corresponding deformation temperature, including: Deformation temperature data and morphological geometry data of multiple calcite mechanical twins were obtained; Based on the obtained deformation temperature data and morphological geometry data of calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperature of calcite mechanical twins are determined.

3. The determination method according to claim 2, wherein, Based on the obtained deformation temperature and morphological geometry data of various calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperatures of calcite mechanical twins are determined as follows: Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the axes being the width and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of the width and density of calcite mechanical twins at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

4. The determination method according to claim 3, wherein, A lookup chart for the width and density of mechanical twins in calcite at different deformation temperatures includes: After projecting the points of each calcite mechanical twin onto a coordinate system with the axes representing the width and density of the calcite mechanical twin, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each calcite mechanical twin, thereby determining the lookup chart for the width and density of the calcite mechanical twin at each deformation temperature.

5. The determination method according to claim 4, wherein, Based on the deformation temperature data of mechanical twinning of calcite from various sources, different deformation temperature regions are divided in the coordinate system, including: Based on the deformation temperature data of mechanical twins in calcite from various sources, a trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line relating the width and density of mechanical twins in calcite below the boundary deformation temperature is used as the boundary line for different deformation temperature regions to divide the region into different deformation temperature regions in the coordinate system.

6. The determining method according to claim 2, wherein, Based on the obtained deformation temperature and morphological geometry data of various calcite mechanical twins, the corresponding charts of morphological geometry characteristics and deformation temperatures of calcite mechanical twins are determined as follows: Based on the morphological and geometrical characteristics of each calcite mechanical twin, the points of each calcite mechanical twin are projected onto a coordinate system with the coordinate axes being the strain and density of the calcite mechanical twin. Combined with the deformation temperature data of each calcite mechanical twin, a lookup chart of strain and density of calcite mechanical twins at different deformation temperatures is established, which is the morphological and geometrical characteristics of the calcite mechanical twin and the corresponding deformation temperature chart.

7. The determining method according to claim 6, wherein, A strain-density lookup chart for mechanical twins of calcite at different deformation temperatures is established, including: After projecting the mechanical twins of each calcite crystal onto a coordinate system with the axes representing the strain and density of the mechanical twins, the coordinate system is divided into different deformation temperature regions based on the deformation temperature data of each calcite mechanical twin, thereby determining the lookup chart of strain and density of the calcite mechanical twins at each deformation temperature.

8. The determination method according to claim 7, wherein, Based on the deformation temperature data of mechanical twinning of calcite from various sources, different deformation temperature regions are divided in the coordinate system, including: Based on the deformation temperature data of mechanical twins in calcite from various sources, a trend line relating strain and density of mechanical twins in calcite below the boundary deformation temperature is fitted in the coordinate system. The fitted trend line relating strain and density of mechanical twins in calcite below the boundary deformation temperature is used as the boundary line for different deformation temperature regions to divide the region into different deformation temperature regions in the coordinate system.

9. The determining method according to claim 5 or 8, wherein, The boundary deformation temperatures include 170℃ and 200℃.

10. The determination method according to claim 2, wherein, Deformation temperature data and morphological geometry data of multiple calcite mechanical twins were obtained, including: Multiple mechanical twinned calcite samples and mineral fluid inclusions in the veins containing each mechanical twinned calcite sample were obtained. Using mechanical twinned calcite samples from each region, petrological thin sections of each mechanical twinned calcite were prepared; using the petrological thin sections of each mechanical twinned calcite, the morphological and geometric characteristics of each mechanical twinned calcite were determined. The formation temperature of the mineral fluid inclusions in the veins containing each type of mechanical twin calcite sample was tested, and the resulting formation temperature data is the deformation temperature data of each type of mechanical twin calcite sample.

11. The determination method according to claim 1, wherein, The morphological and geometric characteristics of calcite mechanical twins in the veins of the target deep shale formation include: Obtain mechanically twinned calcite samples from veins within the target deep shale strata; Using mechanically twinned calcite samples from veins within the target deep shale strata, petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata were prepared. Using these petrological thin sections of mechanically twinned calcite samples from veins within the target deep shale strata, the morphological and geometric characteristics of the mechanically twinned calcite samples from veins within the target deep shale strata were determined.

12. The determining method according to claim 10 or 11, wherein, The morphological and geometric characteristics of calcite mechanical twins were determined using petrological thin sections of calcite mechanical twins via the following method: The morphological and geometric characteristics of calcite mechanical twins were observed and measured using an optical microscope, and statistical analysis was conducted to determine the morphological and geometric characteristics of calcite mechanical twins. In a preferred embodiment of the method for determining paleothermal characteristics of deep shale strata veins provided by the present invention, the calcite mechanical twinned petrographic thin section is prepared by the following method: After cleaning and drying the calcite mechanical twin crystal sample, it was cut into slices, and one side was polished and cleaned to obtain calcite mechanical twin crystal sample sheet. Calcite mechanical twin crystal sample sheets were surface-cast with transparent epoxy resin to obtain calcite mechanical twin crystal sample sheets encapsulated in transparent epoxy resin. The transparent epoxy resin in contact with the unpolished surface of the calcite mechanical twin crystal sample sheet, which is wrapped in transparent epoxy resin, is ground off. The unpolished surface is then polished until the thickness of the calcite mechanical twin crystal sample sheet is less than 1 mm. The transparent epoxy resin is then melted by heating, and the calcite mechanical twin crystal sample sheet is removed and washed to obtain a calcite mechanical twin crystal petrological thin section.

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