In-situ micro-area dolomitization quantitative evaluation method for carbonate rock

Abstract

The application discloses a kind of in-situ micro area carbonate rock dolomitization quantitative evaluation method, it is related to geological exploration technical field, comprising the following steps: sample thin section is successively collected along target section stratum longitudinal direction, and the micro area of dolomite, dolomitization calcite and the replacement interface of both contact is demarcated on sample thin section surface, carbon and oxygen isotope point measurement is carried out to micro area, the paleosalinity discriminant index of micro area and the homogenization temperature of corresponding fluid inclusion are calculated, the two-dimensional quantitative surface scanning of multiple elements is carried out to micro area respectively, and the interface coupling dissolution-precipitation replacement intensity index corresponding to micro area is calculated, macroscopic dolomitization hydrothermal reconstruction comprehensive index is obtained, and the dolomitization degree of target section stratum is graded evaluation output;The application directly converts microcosmic reaction mechanism into macroscopic reservoir evaluation index, can accurately predict the high-quality secondary pore development area controlled by deep fault and hydrothermal activity, provides reliable quantitative basis for deep-ultra deep carbonate rock oil and gas exploration selection.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, specifically a quantitative evaluation method for in-situ micro-area de-dolomitization of carbonate rocks. Background Technology

[0002] Carbonate rocks occupy an important position in global oil and gas reserves. As exploration continues to advance into deeper and ultra-deeper layers, the modification of reservoir porosity by diagenesis in deep burial environments is receiving increasing attention. De-dolomitization (calcite replacing dolomite) is an important manifestation of deep fluid-rock interaction. Intense hydrothermal de-dolomitization can usually form economically valuable de-dolomitized solution pore and microfracture networks, which are key indicators for finding deep "sweet spot" reservoirs.

[0003] Currently, traditional methods for evaluating the de-dolomitization and diagenetic evolution of carbonate rocks mainly include: 1. Conventional rock thin section and scanning electron microscopy observation: These are qualitative descriptions, making it difficult to accurately quantify the degree of degradation and obtain chemical information about fluid properties; 2. Whole-rock carbon and oxygen isotope and trace element testing: This is currently the most commonly used geochemical method. However, because traditional testing often uses macroscopic crushing sampling (millimeters to centimeters), the data obtained are actually a "mixed signal" of dolomite and de-dolomitized calcite, completely masking the microscopic chemical gradient at the true metasomatic interface; 3. Limitations of traditional diagenetic theories: Previous evaluations have mostly been based on thermodynamic equilibrium dissolution-precipitation models. However, de-dolomitization under deep-buried, high-pressure environments is largely controlled by a non-equilibrium interfacial coupled dissolution-precipitation (ICDP) mechanism, with the reaction typically confined to nano- to micro-scale fluid films. Current technologies lack quantitative characterization methods and computational models for this microscopic kinetic mechanism.

[0004] Therefore, there is an urgent need for a method that can overcome the bottleneck of conventional macroscopic testing resolution and quantitatively assess the intensity of dolomite removal and reservoir stimulation potential through in-situ micro-region geochemical information. Summary of the Invention

[0005] In view of this, the present invention proposes an in-situ micro-area quantitative evaluation method for de-dolomitization of carbonate rocks. This method captures the microscopic geochemical fingerprint of the fluid-mineral interface and combines it with the ICDP dynamic model to achieve accurate quantitative evaluation of the intensity of de-dolomitization. It is particularly suitable for the quantitative evaluation and prediction of high-quality hydrothermal modified carbonate reservoirs in deep and ultra-deep burial environments.

[0006] This invention discloses a quantitative evaluation method for de-dolomitization of carbonate rocks in situ within a micro-area, comprising the following steps: Step S1: Continuously sample and prepare thin sections of samples along the longitudinal direction of the target section strata, screen thin sections of samples that contain both dolomite and de-dolomitized calcite, and delineate a number of corresponding micro-regions on the surface of the thin sections, including dolomite, de-dolomitized calcite and the replacement interface between the two. Step S2: For all micro-regions of the selected sample sections, carbon and oxygen isotope measurements are performed on the de-dolomitized calcite replacement areas using the in-situ targeted sampling method. The paleosalinity discrimination index of the micro-region is further calculated, and the homogenization temperature of the fluid inclusions corresponding to the micro-region is determined. Step S3: Perform multi-element two-dimensional quantitative surface scanning on all micro-regions of the selected sample slices to extract the two-dimensional absolute concentration distribution data of metal elements on both sides of the boundary layer in the displacement interface, and generate the element two-dimensional absolute concentration distribution matrix. Step S4: Based on the two-dimensional absolute concentration distribution matrix of elements, calculate the interfacial coupling dissolution-precipitation replacement strength index corresponding to all microregions of the screened sample slices; Step S5: Calculate the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation based on the interfacial coupling dissolution-precipitation replacement intensity index corresponding to the micro-area of ​​all sample thin sections in the target section, and evaluate the degree of de-dolomitization of the target section strata based on the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation.

[0007] The technical advantages of this invention are as follows: 1. This invention uses in-situ isotope point measurement combined with LA-ICP-TOF-MS two-dimensional surface scanning technology to improve the accuracy of geochemical analysis to the micrometer level or even the submicrometer level, accurately capture reaction boundary layer information with a width ≤1μm, and completely eliminate the data ambiguity caused by traditional whole rock testing.

[0008] 2. This invention integrates the characteristic elements (such as high Sr content) brought by deep hydrothermal fluids with fluid fingerprints such as light rare earth enrichment and europium (Eu) positive anomaly, and constructs the ICDP metasomatic intensity index formula, realizing the numerical characterization of non-equilibrium diagenesis process.

[0009] 3. This invention directly transforms the microscopic reaction mechanism into macroscopic reservoir evaluation indicators, which can accurately predict high-quality de-dolomitized porosity development zones controlled by deep faults and hydrothermal activity, providing a reliable quantitative basis for the selection of exploration areas for deep-ultra-deep carbonate rocks. Detailed Implementation

[0010] The present invention will be further described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0011] A quantitative evaluation method for in-situ micro-area de-dolomitization of carbonate rocks includes the following steps: Step S1: Continuously sample and prepare thin sections of samples along the longitudinal direction of the target section strata, screen thin sections of samples that contain both dolomite and de-dolomitized calcite, and delineate a number of corresponding micro-regions on the surface of the thin sections, including dolomite, de-dolomitized calcite and the replacement interface between the two. The method for preparing sample slices through continuous sampling in step S1 is as follows: Step S11: Based on the macroscopic characteristics of the core samples and the response characteristics of the logging curves of the target reservoir section, divide the strata of the target section into multiple diagenetic facies units with similar stratigraphic properties along the longitudinal direction.

[0012] Step S12: Based on the properties of the diagenetic facies units, collect multiple sets of thin sections along the longitudinal direction of the strata at specific distances; The sample sheet thickness is 30 mm. ~50 The area of ​​the micro-region is .

[0013] The method for collecting sample sections is as follows: 1) For diagenetic facies units containing both dolomite and de-dolomitized calcite, high-density sampling should be carried out with at least two sets of samples per meter of stratigraphic interval. 2) For diagenetic facies units that do not simultaneously contain dolomite and de-dolomitized calcite, sparse sampling shall be carried out with an interval of not less than 10m between adjacent samples.

[0014] Step S2: For all micro-regions of the selected sample sections, carbon and oxygen isotope measurements are performed on the de-dolomitized calcite replacement areas using the in-situ targeted sampling method. The paleosalinity discrimination index of the micro-region is further calculated, and the homogenization temperature of the fluid inclusions corresponding to the micro-region is determined. The method for calculating the paleosalinity discriminant index is as follows: In the formula, Z represents the paleosalinity discriminant index of the microregion; This indicates the de-dolomitized calcite metasomatic zone in the micro-region. Mean; This indicates the de-dolomitized calcite metasomatic zone in the micro-region. Mean.

[0015] The in-situ targeted sampling method involves using a laser microprobe system to target sampling points in the de-dolomitized calcite replacement zone within the micro-region and calculating the average carbon and oxygen isotope values ​​of the de-dolomitized calcite replacement zone.

[0016] Step S3: Perform multi-element two-dimensional quantitative surface scanning on all micro-regions of the selected sample slices to extract the two-dimensional absolute concentration distribution data of metal elements on both sides of the boundary layer in the displacement interface, and generate the element two-dimensional absolute concentration distribution matrix. Multi-element two-dimensional quantitative surface scanning can be performed using laser ablation inductively coupled plasma time-of-flight mass spectrometry (ICP-MS). The surface scan measures the metal elements Ca, Mg, Sr, Fe, Mn, and rare earth elements. The boundary layer is along the normal direction of the metasomatic reaction front, and the Mg concentration is within... In regions where the concentration drops by more than 50% within a given span and the corresponding Ca concentration increases by more than 30%, the boundary layer width is 0.5. ~1.0 between.

[0017] Step S4: Based on the two-dimensional absolute concentration distribution matrix of elements, calculate the interfacial coupling dissolution-precipitation replacement strength index corresponding to all microregions of the screened sample slices; The interfacial coupling dissolution-precipitation replacement strength index is calculated using the following formula: In the formula, Indicates the interfacial coupling dissolution-precipitation replacement strength index; This represents the median absolute concentration of Sr in the calcite region within the two-dimensional absolute concentration distribution matrix of the element; This represents the median absolute concentration of Sr in the dolomite region within the two-dimensional absolute concentration distribution matrix of the elements; This represents the ratio of the median La and Yb concentrations in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, divided by the standard values ​​of North American shale. This represents the ratio of the median La and Yb concentrations in the dolomite region within the two-dimensional absolute concentration distribution matrix of elements, divided by the standard values ​​of North American shale. This indicates the europium anomaly index in the calcite region; The calculation method for the europium anomaly index is shown in the following formula: In the formula, This represents the relative ratio of the median absolute concentration of europium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. This represents the relative ratio of the median absolute concentration of samarium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. This represents the relative ratio of the median absolute concentration of gadolinium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. The method for dividing the dolomite and calcite regions within the two-dimensional absolute concentration distribution matrix of elements is as follows: The mass percentage concentration of Mg in the matrix is ​​set as the discrimination threshold. The calcite connected region and the dolomite connected region are automatically identified and divided in the two-dimensional absolute concentration distribution matrix of the elements. Specifically, based on the difference in the theoretical stoichiometry of magnesium (Mg) in pure calcite and pure dolomite, the mass percentage concentration of magnesium (Mg) in the matrix is ​​set as a fixed discrimination threshold, and the range of the fixed discrimination threshold is as follows: ; Then, data processing software is used to automatically retrieve each pixel in the two-dimensional absolute concentration distribution matrix. The set of pixels with a magnesium (Mg) element mass percentage concentration greater than or equal to the fixed discrimination threshold is automatically identified and divided into dolomite connected regions, and the set of pixels with a magnesium (Mg) element mass percentage concentration less than the fixed discrimination threshold is automatically identified and divided into calcite connected regions. When the rare earth element detected in the micro-region is below the instrument detection limit: the concentration of the element below the detection limit is set to 1 / 2 times the instrument detection limit for calculation.

[0018] Step S5: Calculate the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation based on the interfacial coupling dissolution-precipitation replacement intensity index corresponding to the micro-area of ​​all sample thin sections in the target section, and evaluate the degree of de-dolomitization of the target section strata based on the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation.

[0019] The calculation method for the comprehensive index of macroscopic de-dolomite hydrothermal modification is as follows: In the formula, This represents the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation of the target strata; This represents the spatial weighting coefficient of the i-th sample section within the target stratum; This represents the interfacial coupling dissolution-precipitation replacement strength index corresponding to the micro-region in the i-th sample slice; Wherein, the spatial weighting coefficient of the i-th sample section within the target stratum. The calculation method is as follows: In the formula, This represents the thickness of the continuous diagenetic facies zone represented by the i-th sample section in the vertical direction; H Indicates the total thickness of the strata in the target section; The thickness of the continuous diagenetic facies zone represented by the sample thin section in the vertical direction ( The thickness (or uniform thickness) of the sample section refers to the overall thickness or uniform thickness of the diagenetic facies unit of the same type developed in the longitudinal strata. The specific rules for determining it are as follows: 1) If only one representative thin section was collected within a certain diagenetic facies unit, then the thickness of the continuous strata of the diagenetic facies represented by that thin section is... It is directly equal to the total longitudinal thickness of the diagenetic facies unit; 2) If multiple sets of thin sections are collected within a heterogeneous diagenetic facies unit based on the strength of heterogeneity (the number of thin sections is m, and...) The thickness of the continuous strata in the diagenetic zone is then... The facies zone distribution method is used to determine the thickness: the total longitudinal thickness of the diagenetic facies zone unit is divided by the number of sample sections m, which is taken as the average thickness of the continuous strata represented by each individual sample section in the unit, and the sum of the thicknesses of the continuous strata represented by all individual sample sections in the unit is equal to the total longitudinal thickness of the diagenetic facies zone unit.

[0020] In calculation At the same time, the interfacial coupling dissolution-precipitation replacement intensity index of the micro-regions corresponding to the sample thin sections containing both dolomite and de-dolomitized calcite is calculated according to step S4. For sample thin sections that do not simultaneously contain dolomite and de-dolomitized calcite, the interfacial coupling dissolution-precipitation replacement strength index corresponding to the micro-regions is directly assigned a value of 0.

[0021] The specific method for classifying and evaluating the degree of dolomitization of the target section strata based on the comprehensive index of macroscopic dolomitization hydrothermal stimulation is as follows: Step S51: Within the target strata, the sum of the thicknesses of the continuous diagenetic facies zones represented by the thin sections of samples containing all micro-regions that satisfy the high-temperature hydrothermal fluid stimulation background is recorded as the total effective hydrothermal stimulation thickness. ; Step S52: Calculate the total effective thickness of the hydrothermal modification. Total thickness of the target section H The percentage is denoted as the proportion of hydrothermal modification thickness. ; The method for determining whether a microregion meets the background of high-temperature hydrothermal fluid modification is as follows: when the microregion meets the paleosalinity discriminant index... , Remove dolomite-calcite replacement area mean And the temperature of the fluid inclusion homogeneity When the temperature is between 155℃ and 170℃, the micro-region is considered to meet the background of high-temperature hydrothermal fluid modification. Step S53: Based on the thickness ratio of the hydrothermal modification The result is a determination of whether to conduct a graded evaluation of the degree of de-dolomiteification. When satisfied At that time, The index-based hierarchical evaluation, and the specific output results are as follows: 3) When When the Sr concentration in the calcite area of ​​the surface scan is greater than 300 ppm, the strata in the target section are classified as strongly de-dolomitized hydrothermal metasomatic grade. 4) When When the Sr concentration in the calcite area of ​​the surface scan is less than 300 ppm, the strata in the target section are classified as moderately de-dolomitized and locally replaced. 3) When At that time, the strata of the target section were classified as moderately de-dolomitized and locally replaced. 4) When At that time, the strata of the target section were classified as unaltered stable class; When satisfied If the target segment is determined to be unaffected by effective tectonic hydrothermal fluid flow, no action will be taken. The index-based grading evaluation directly outputs the overall evaluation of the target segment as an undefined stability level.

[0022] Example: This embodiment uses a carbonate core sample from an ultra-deep Ordovician fault-controlled diagenetic environment in the Tarim Basin of northwestern my country as an example to verify the effectiveness of this method: Step S1: Total formation thickness of the target reservoir section First, using conventional logging curves (GR, resistivity) combined with imaging logging (FMI) and macroscopic observation of core samples, and other well-known conventional techniques in the field, based on the heterogeneity of lithology and diagenetic alteration, this 50m stratum was vertically divided into two types of diagenetic facies units with similar stratigraphic properties: 1. Phase A (Strongly de-dolomite hydrothermal refractory section): Longitudinal cumulative continuous thickness Because this section belongs to a heterogeneous transition zone with crack development, continuous sampling at a high density of 2 samples / m was conducted, and a total of valid samples were collected. These eight samples, after microscopic morphology screening, all exhibited interfaces between dolomite and de-dolomitized calcite. Based on the light and dark boundaries of the cathodoluminescence images, the area locked on the thin section surface was [area missing]. Spatial positioning of the core micro-region; 2. Phase B (dense, unmodified, stable dolomite protolith): longitudinal cumulative continuous thickness Because this section consists of a thick, homogeneous, and dense rock layer, a sparse, fixed-point sampling rule was adopted (one sample every 11.5m), and a total of control samples were collected. All four samples were screened and found to be pure dolomite rock, without any de-dolomitized calcite.

[0023] This embodiment is in A total of 12 samples were collected from the stratigraphic section.

[0024] Step S2: Using a laser microprobe system and the in-situ micro-area targeted sampling method, in-situ carbon and oxygen isotope single-point measurements are performed on the dolomite matrix area and the de-dolomitized calcite replacement area within the core micro-area of ​​the A-phase sample.

[0025] The specific isotope values ​​and results measured in each target region are as follows: 1) Three measuring points were deployed within the original dolomite matrix area far from the metasomatic front to obtain in-situ measurements. Value is The mean is ; Value is The mean is It presents a typical background of normal seawater formation; 2) Three measuring points were deployed within the de-dolomitized calcite zone generated by the alteration reaction to obtain its in-situ... Value is The single-point mean is ; Value is The mean is It exhibits a strong negative bias in carbon and oxygen isotopes due to high-temperature hydrothermal modification. 3) Two measuring points are precisely deployed on each side of the fluid boundary layer adjacent to the metasomatic reaction front. Their isotopic values ​​are between the dolomite matrix region and the de-dolomitized calcite region, showing a continuous transitional chemical gradient.

[0026] Data from the de-dolostified calcite metasomatic zone were extracted and calculated, yielding a mean paleosalinity discriminant index Z=119.3 for each point within the micro-region. Simultaneously, the homogenization temperature of fluid inclusions spatially overlapping with isotopic sites within this micro-region was measured. for According to Z<120 and By using the criteria of being in the high-temperature range of 155℃ to 170℃ and combining the drastically negative isotopic response of de-dolomitized calcite compared to the dolomite matrix, the background parameter matrix of the core micro-region underwent deep high-temperature hydrothermal fluid modification was successfully constructed.

[0027] Step S3: Use the LA-ICP-TOF-MS system to perform multi-element two-dimensional quantitative surface scanning on the eight core micro-regions located. Set the laser beam diameter to... Scan rate Synchronous data acquisition The rare earth element data is processed using a 100% quality normalization algorithm to eliminate matrix effects, generating a high-resolution two-dimensional absolute concentration distribution matrix and grayscale images of characteristic elements.

[0028] Step S4: In the two-dimensional absolute concentration distribution matrix, the software automatically identifies the fluid boundary layer (approximately 0.8 μm wide) along the normal direction of the replacement reaction front, where the Mg concentration drops sharply by 55% within a 1 μm span and the Ca concentration increases sharply by 55%. The median values ​​of each element in the calcite formation region and dolomite residue region defined in the data matrix are extracted and calculated: Sr... cal =345ppm, Sr dol =78ppm; PAAS-standardized light / heavy rare earth ratio (La / Yb)N_cal=4.2, (La / Yb)N dol =1.1; using the formula The europium anomaly index Eu in the calcite region was calculated. cal =1.35, substituting into the formula for the interfacial coupling dissolution-precipitation replacement intensity index, the interfacial coupling dissolution-precipitation (ICDP) replacement intensity index of the eight modified sample microregions in phase zone A is obtained. In order: , , , , , , , (The arithmetic mean of the test results of the above 8 independent core micro-regions is 12.50).

[0029] Step S5: In this embodiment, a total of K=12 samples were selectively collected within the 50m target layer. Following the test in step S2, the micro-regions of the 8 samples within phase band A fully satisfied Z<120. and The criteria for determining whether a micro-region is in the high-temperature range are qualified micro-regions that meet the requirements of a high-temperature hydrothermal fluid modification background; however, the four pure dolomite sample micro-regions in phase zone B do not meet the requirements of a hydrothermal modification background due to their distance from the fracture zone in terms of isotope and temperature characteristics.

[0030] The specific pre-filtering and weighted calculation process is as follows: (1) Pre-filter verification: The cumulative development thickness of phase zone A in the high-temperature hydrothermal background is satisfied. Total stratigraphic thickness of the target section The calculated percentage of hydrothermal modification thickness was obtained. .because It is necessary to conduct a graded evaluation of the degree of de-dolomiteification.

[0031] (2) Graded evaluation output: 4 single samples of phase zone B that do not meet the hydrothermal background, their According to the rules, the value was directly and forcibly assigned to 0. The parameters of all 12 samples were substituted into the spatial phase weighted model for homogeneous accumulation calculation. The specific process is as follows: 1. Calculate the spatial weighting coefficients for each sample. : Eight thin sections were collected at equal intervals from facies zone A, which is 4 m thick. After averaging, the stratigraphic zone thickness corresponding to each thin section should be... Spatial weighting coefficients corresponding to a single sample slice for ; Four thin sections were collected at equal intervals from a homogeneous facies zone B with a thickness of 46 m. ​​After averaging, the stratigraphic zone thickness corresponding to each thin section should be... Spatial weighting coefficients corresponding to a single sample slice for ; 2. Calculate the comprehensive index of macroscopic de-dolomite hydrothermal venting modification. : The four unmodified protofacies samples did not possess a two-phase reaction interface. Set directly to 0; based on the practical measurement results of step S4, each of the 8 qualified modified sample micro-regions within phase band A is independent. They are respectively: , , , , , , , (Its arithmetic mean is 12.50). The above individual parameters are multiplied by their corresponding spatial weight coefficients, substituted into the weighted formula, and summed to obtain the final macroscopic comprehensive index for the de-dolomite hydrothermal modification. Because the high-temperature hydrothermal fluid modification background is first satisfied (Z=119.3<120), =162℃>155℃); further combined with quantitative indicators, based on the graded output results, the overall accurate evaluation output of this 50m target reservoir section is a medium-level de-dolomite-removed local replacement grade.

[0032] As can be seen, the model successfully utilizes two-dimensional surface scan data of micro-mass spectrometry, while objectively subtracting the "dilution effect" of up to 92% of the homogeneous and dense protolith in the formation on the overall reservoir stimulation potential. Finally, by combining macro-geological profiles and fault zone distribution characteristics, a multi-scale comprehensive output and reservoir classification prediction model of the degree of de-dolomitization controlled by strike-slip faults is constructed.

[0033] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.

Claims

1. A quantitative evaluation method for dedollitization of carbonate rocks in situ within a micro-area, characterized in that, Includes the following steps: Step S1: Continuously sample and prepare thin sections of samples along the longitudinal direction of the target section strata, screen thin sections of samples that contain both dolomite and de-dolomitized calcite, and delineate a number of corresponding micro-regions on the surface of the thin sections, including dolomite, de-dolomitized calcite and the replacement interface between the two. Step S2: For all micro-regions of the selected sample sections, carbon and oxygen isotope measurements are performed on the de-dolomitized calcite replacement areas using the in-situ targeted sampling method. The paleosalinity discrimination index of the micro-region is further calculated, and the homogenization temperature of the fluid inclusions corresponding to the micro-region is determined. Step S3: Perform multi-element two-dimensional quantitative surface scanning on all micro-regions of the selected sample slices to extract the two-dimensional absolute concentration distribution data of metal elements on both sides of the boundary layer in the displacement interface, and generate the element two-dimensional absolute concentration distribution matrix. Step S4: Based on the two-dimensional absolute concentration distribution matrix of elements, calculate the interfacial coupling dissolution-precipitation replacement strength index corresponding to all microregions of the screened sample slices; Step S5: Calculate the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation based on the interfacial coupling dissolution-precipitation replacement intensity index corresponding to the micro-area of ​​all sample thin sections in the target section, and evaluate the degree of de-dolomitization of the target section strata based on the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation.

2. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The method for preparing sample slices through continuous sampling in step S1 is as follows: Step S11: Based on the macroscopic characteristics of the core samples and the response characteristics of the logging curves of the target reservoir section, divide the strata of the target section into multiple diagenetic facies units with similar stratigraphic properties along the vertical direction; Step S12: Based on the properties of the diagenetic facies units, collect multiple sets of thin sections along the longitudinal direction of the strata at specific distances; The sample sheet thickness is 30 mm. ~50 The area of ​​the micro-region is .

3. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 2, characterized in that: The method for collecting the sample slices in step S12 is as follows: 1) For diagenetic facies units containing both dolomite and de-dolomitized calcite, high-density sampling should be carried out with at least two sets of samples per meter of stratigraphic interval. 2) For diagenetic facies units that do not simultaneously contain dolomite and de-dolomitized calcite, sparse sampling shall be carried out with an interval of not less than 10m between adjacent samples.

4. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The method for calculating the paleosalinity discriminant index in step S2 is as follows: In the formula, Z represents the paleosalinity discriminant index of the microregion; This indicates the de-dolomitized calcite metasomatic zone in the micro-region. Mean; This indicates the de-dolomitized calcite metasomatic zone in the micro-region. Mean.

5. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The in-situ targeted sampling method specifically involves using a laser microprobe system to target and deploy sampling points in the de-dolomitized calcite replacement zone within the micro-region, and calculating the average carbon and oxygen isotope values ​​of the de-dolomitized calcite replacement zone.

6. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The test method for multi-element two-dimensional quantitative surface scanning in step S3 is to perform two-dimensional scanning using laser ablation inductively coupled plasma time-of-flight mass spectrometry. Among them, the metal elements measured by surface scanning are Ca, Mg, Sr, Fe, Mn and rare earth elements.

7. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The boundary layer mentioned in step S3 is: along the normal direction of the metasomatic reaction front, the Mg concentration is at... Intersecting abrupt change regions where the concentration drops by more than 50% within a given range and the corresponding Ca concentration increases by more than 30%.

8. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 6, characterized in that: The interfacial coupling dissolution-precipitation replacement strength index mentioned in step S4 is calculated using the following formula: In the formula, Indicates the interfacial coupling dissolution-precipitation replacement strength index; This represents the median absolute concentration of Sr in the calcite region within the two-dimensional absolute concentration distribution matrix of the element; This represents the median absolute concentration of Sr in the dolomite region within the two-dimensional absolute concentration distribution matrix of the elements; This represents the ratio of the median La and Yb concentrations in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, divided by the standard values ​​of North American shale. This represents the ratio of the median La and Yb concentrations in the dolomite region within the two-dimensional absolute concentration distribution matrix of elements, divided by the standard values ​​of North American shale. This indicates the europium anomaly index in the calcite region; The calculation method for the europium anomaly index is shown in the following formula: In the formula, This represents the relative ratio of the median absolute concentration of europium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. This represents the relative ratio of the median absolute concentration of samarium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. This represents the relative ratio of the median absolute concentration of gadolinium in the calcite region within the two-dimensional absolute concentration distribution matrix of elements, after standardization with North American shale standard values. The method for dividing the dolomite and calcite regions within the two-dimensional absolute concentration distribution matrix of elements is as follows: The mass percentage concentration of Mg in the matrix is ​​set as the discrimination threshold. The calcite connected region and the dolomite connected region are automatically identified and divided in the two-dimensional absolute concentration distribution matrix of the elements. When the rare earth element detected in the micro-region is below the instrument detection limit: the concentration of the element below the detection limit is set to 1 / 2 times the instrument detection limit for calculation.

9. The method for quantitative evaluation of de-dolomitization of carbonate rocks in situ according to claim 1, characterized in that: The calculation method for the comprehensive index of macroscopic de-dolomite hydrothermal modification mentioned in step S5 is as follows: In the formula, This represents the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation of the target strata; This represents the spatial weighting coefficient of the i-th sample section within the target stratum; This represents the interfacial coupling dissolution-precipitation replacement strength index corresponding to the micro-region in the i-th sample slice; Wherein, the spatial weighting coefficient of the i-th sample section within the target stratum. The calculation method is as follows: In the formula, This represents the thickness of the continuous diagenetic facies zone represented by the i-th sample section in the vertical direction; H Indicates the total thickness of the strata in the target section; In calculation At the same time, the interfacial coupling dissolution-precipitation replacement intensity index of the micro-regions corresponding to the sample thin sections containing both dolomite and de-dolomitized calcite is calculated according to step S4. For sample thin sections that do not simultaneously contain dolomite and de-dolomitized calcite, the interfacial coupling dissolution-precipitation replacement strength index corresponding to the micro-regions is directly assigned a value of 0.

10. A quantitative evaluation method for de-dolomitization of carbonate rocks in situ according to claim 9, characterized in that: The specific method for classifying and evaluating the degree of dolomitization of the target section strata based on the comprehensive index of macroscopic de-dolomitization hydrothermal stimulation, as described in step S5, is as follows: Step S51: Within the target strata, the sum of the thicknesses of the continuous diagenetic facies zones represented by the sample thin sections of all micro-regions that satisfy the high-temperature hydrothermal fluid stimulation background is recorded as the total effective hydrothermal stimulation thickness. ; Step S52: Calculate the total effective thickness of the hydrothermal modification. Total thickness of the target section H The percentage is denoted as the proportion of hydrothermal modification thickness. ; The method for determining whether a microregion meets the background of high-temperature hydrothermal fluid modification is as follows: when the microregion meets the paleosalinity discriminant index... , Remove dolomite-calcite replacement area mean And the temperature of the fluid inclusion homogeneity When the temperature is between 155℃ and 170℃, the micro-region is considered to meet the background of high-temperature hydrothermal fluid modification. Step S53: Based on the thickness ratio of the hydrothermal modification The result is a determination of whether to conduct a graded evaluation of the degree of de-dolomiteification. When satisfied At that time, The index-based hierarchical evaluation, and the specific output results are as follows: 1) When When the Sr concentration in the calcite area of ​​the surface scan is greater than 300 ppm, the strata in the target section are classified as strongly de-dolomitized hydrothermal metasomatic class. 2) When When the Sr concentration in the calcite area of ​​the surface scan is less than 300 ppm, the strata in the target section are classified as moderately de-dolomitized and locally replaced. 3) When At that time, the strata of the target section were classified as moderately de-dolomitized and locally replaced. 4) When At that time, the strata of the target section were classified as unaltered stable class; When satisfied If the target segment is determined to be unaffected by effective tectonic hydrothermal fluid flow, no action will be taken. The index-based grading evaluation directly outputs the overall evaluation of the target segment as an undefined stability level.

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