Method for quantifying carbon dioxide leakage in wellbore based on multipath monitoring closed inversion

Abstract

This invention discloses a method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion. The method acquires monitoring data from the wellbore section, shallow formation, and surface atmosphere. For the wellbore section monitoring data, the total leakage through the wellbore section cross-section is calculated. For the shallow formation monitoring data, the free-state interception and dissolved-state interception are calculated, and their sum is the total shallow formation interception. For the surface atmosphere monitoring data, the soil diffusion and atmospheric diffusion are calculated, and their sum is the total surface atmosphere diffusion. A mass conservation closed-loop equation is constructed, and the closure residual is judged and optimized according to the standard uncertainty weights of the monitoring sub-items, outputting the final leakage flux after closed-loop inversion optimization. This invention constructs a multi-path leakage closure verification framework constrained by mass conservation. By mutually verifying the inversion values ​​inside the wellbore with the sum of shallow formation interception and surface diffusion, the reliability and accuracy of the leakage quantification results are improved.

Description

Technical Field

[0001] This invention relates to the field of risk assessment of carbon dioxide geological storage wellbore leakage, and in particular to a method for quantifying wellbore carbon dioxide leakage based on multipath monitoring closed-loop inversion. Background Technology

[0002] In recent years, the massive consumption of fossil fuels has led to a significant increase in greenhouse gas emissions, especially carbon dioxide, resulting in a substantial increase in the global greenhouse effect. Currently, carbon dioxide capture, storage, and utilization (CCUS) technology is a key technology for reducing carbon emissions and addressing global warming. Wellbores are the main channels for injecting carbon dioxide into reservoirs and are crucial for long-term storage. However, during carbon dioxide storage, its high partial pressure and corrosiveness threaten the integrity of the wellbore, leading to leakage risks. If carbon dioxide leaks to the surface, it not only affects emission reduction targets but also threatens human health (asphyxiation from high concentrations) and the ecological environment (soil acidification, vegetation death). However, existing wellbore leakage monitoring technologies have the following problems: (1) Existing single leakage monitoring methods have high uncertainty, and the leakage results calculated by different methods often contradict each other, making them unsuitable for accurate risk assessment and decision-making.

[0003] (2) The distribution ratio of the leaking fluid along the "wellbore-formation-atmosphere" path is difficult to quantify, resulting in insufficient accuracy in the leakage assessment and increasing the uncertainty in the design of the plugging scheme. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring and closed-loop inversion. This method solves the problems of inaccurate leakage detection by single monitoring technologies and the difficulty in quantifying the distribution ratio of leaking fluid in the "wellbore-formation-atmosphere" leakage path. The method is simple and easy to use, providing technical support for quantifying leakage risks in carbon dioxide geological storage wellbores.

[0005] The technical solution adopted in this invention is: A method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring and closed-loop inversion includes the following steps: S1. Acquire monitoring data of the well section, shallow formation, and surface atmosphere respectively, and perform time synchronization and spatial registration preprocessing on the three types of monitoring data; S2. Based on the monitoring data of the well section, the depth of the leak point is located by spatial cross-matching of temperature anomalies and acoustic anomalies, and the total leakage through the cross section of the well section is calculated based on the coupled inversion model of well flow and heat transfer. ; S3. Based on the shallow strata monitoring data, calculate the amount of free state interception in the shallow strata in a free state. and the amount of dissolved substances already dissolved in groundwater The sum of the two is defined as the total interception of shallow strata. ; S4. Calculate the soil diffusion and dissipation amount based on the aforementioned surface atmospheric monitoring data. and atmospheric diffusion and dissipation The sum of the two is defined as the total atmospheric emissions. ; S5. Constructing a closed equation for the conservation of matter. ,in The closed-loop residuals are used as the basis for judgment and optimization based on the standard uncertainty weights of each monitoring sub-item, and the final leakage flux after closed-loop inversion optimization is output. .

[0006] In the above scheme, in step S1, the well section monitoring data includes: temperature and acoustic signals of the entire well section collected by distributed optical fiber sensors deployed in the well annulus, and pressure time series data collected by wellhead pressure sensors.

[0007] In the above scheme, step S2 specifically includes the following steps: S2.1. The isolated forest algorithm is used to extract abnormal features from the preprocessed temperature and sound data to identify the local cooling segment caused by the Joule-Thomson effect and the accompanying high-frequency flow noise source when carbon dioxide leaks. S2.2. Spatial cross-matching of the temperature anomaly depth and the acoustic noise location depth to pinpoint the specific depth of the leak point in the well section; S2.3. Using the temperature and pressure attenuation characteristics at the locked depth as input, the pre-built wellbore two-phase flow and heat transfer coupled inversion model is invoked to calculate the equivalent leakage coefficient of the leakage channel. This allows for the inversion of the total leakage flux through the cross-section of the wellbore section. :

[0008]

[0009] In the formula, The instantaneous carbon dioxide leakage rate in the wellbore is expressed in kg / s. S² represents the equivalent leakage coefficient of the leakage path. The temperature change is expressed in K. The specific heat capacity of carbon dioxide is J / (kg·K); The density of the fluid inside the well is kg / m³. The length of the temperature drop region is in meters (m). The change over time, expressed in seconds, represents the observed temperature change. The time elapsed; The total duration of the leak is in seconds. The total leakage from the wellbore is expressed in kg.

[0010] In the above scheme, in step S1, the shallow formation monitoring data includes: underground resistivity distribution data obtained by a time-shifted high-density electrical resistivity electrode array deployed around the target well, and groundwater dissolved inorganic carbon concentration and stable carbon isotope ratio obtained by a shallow monitoring well network.

[0011] In the above scheme, in step S3, the amount of free state interception The method for obtaining the data is as follows: input the resistivity distribution data into the rock physics model to convert it into carbon dioxide saturation distribution, and then perform volume integration on the spatial range of the high saturation anomaly to calculate the amount of free carbon dioxide intercepted. The amount of dissolved interception The method for obtaining the data is as follows: the dissolved inorganic carbon increment is calculated back based on the water sample from shallow monitoring wells.

[0012] In the above scheme, the amount of free state interception The calculation method is as follows:

[0013] In the formula, This serves as an index for the survey lines of a high-density electrical resistivity tomography (EDT) profile. i =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, j =1, 2, ... n ; m and n Both represent any positive integer; For the first i Survey Line No. j Carbon dioxide density per grid, kg / m³; For the first i Survey Line No. j The carbon dioxide saturation of each grid cell is dimensionless. For the first i Survey Line No. j Porosity of each grid, dimensionless; For the first i Survey Line No. j The horizontal projected area of ​​each grid, m 2 ; For the first i Survey Line No. j The thickness of each grid cell, in meters; Dissolved interception The calculation method is as follows:

[0014] In the formula, The inorganic carbon concentration, in mol / m³, is the concentration of water in the monitoring well after the leak. The background inorganic carbon concentration before leakage is expressed in mol / m³. For the volume of the affected aquifer, m 3 ; and , respectively, represent the molar masses of carbon dioxide and inorganic carbon, in kg / mol.

[0015] In the above scheme, in step S1, the surface atmospheric monitoring data includes soil carbon dioxide flux obtained from the soil accumulation chamber, and atmospheric carbon dioxide concentration and wind speed data obtained from infrared imaging.

[0016] In the above scheme, in step S4, the soil diffusion and dissipation amount The carbon dioxide flux data measured by the soil accumulation chamber was obtained by spatial area integration. atmospheric dispersion The carbon dioxide concentration field and wind speed field were measured by infrared imaging and calculated based on the plume cross-section flux method.

[0017] In the above scheme, the soil diffusion and dissipation amount The calculation method is as follows:

[0018]

[0019]

[0020] In the formula, Carbon dioxide flux per unit area of ​​soil, kg·m - ²·s - ¹; To accumulate the effective volume of the chamber, m 3 ; To accumulate the floor area, m 2 ; The rate of change of carbon dioxide mass concentration in the cavity over time, in kg. m 3 s 1 ; The instantaneous carbon dioxide leakage rate in the surface soil of this area is expressed in kg / s. For the cumulative chamber method profile survey line index, =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, =1, 2, ... n ; For the first Survey Line No. Measured carbon dioxide flux per grid cell, kg·m³ - ²·s - ¹; The background flux value of the soil in this area is kg·m. - ²·s - ¹; For the first Survey Line No. The representative area of ​​each grid, m 2 ; atmospheric dispersion The calculation method is as follows:

[0021]

[0022] In the formula, The instantaneous atmospheric escape rate of carbon dioxide is expressed in kg / s. This is the index of survey lines for the plume profile. =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, =1, 2, ... n ; For the first Line 1 Carbon dioxide mass concentration within the grid, kg / m³ 3 ; The carbon dioxide mass concentration at the upwind background point, in kg / m³ 3 , used to subtract atmospheric background; For the first Line 1 Wind speed within the grid, m / s; For the first Line 1 The area of ​​the plume interface within the column grid, in m / s.

[0023] In the above scheme, step S5 involves setting the standard relative uncertainty weights for each monitoring sub-item and performing the following judgments and optimizations: like If the monitoring data at each section is deemed relatively accurate, the final leakage flux output value is calculated using a weighted average of absolute uncertainty.

[0024] In the formula, The final leakage amount is expressed in kg. The absolute uncertainty of the wellbore section inversion, in kg, originates from distributed fiber optic temperature measurement error, pressure sensor measurement error, and inversion model error. The absolute uncertainty of the shallow strata solution, in kg, originates from errors in high-density electrical resistivity inversion, rock physics model conversion, and hydrochemical analysis. The absolute uncertainty in the solution of the surface atmosphere, in kg, originates from the calculation error of the soil accumulation chamber flux and the error of the atmospheric dispersion model; the uncertainty propagation is calculated using the error propagation law or the Monte Carlo simulation method. like Then, a closed-loop inversion optimization based on weighted least squares is carried out—using the reciprocal of the uncertainty of each monitoring sub-item as the weight, within the feasible region formed by their respective uncertainty boundaries, the most probable values ​​of the leakage flux that minimize the sum of squared closed residuals are sought. This ensures that the recalculated closure residual converges to ≤20%, and outputs the final leakage flux after closure inversion optimization. ,Right now: .

[0025] The beneficial effects of this invention are: This invention constructs a closed-loop verification framework for multi-path leakage based on the constraint of material conservation. By cross-verifying the inversion values ​​inside the wellbore with the sum of shallow formation interception and surface dissipation, it effectively suppresses the transmission and accumulation of single-path monitoring errors and significantly improves the reliability and accuracy of leakage quantification results.

[0026] This invention achieves quantitative characterization of the distribution ratio of leaking fluid along the "wellbore-formation-atmosphere" cross-media by multi-path collaborative calculation of the wellbore interior, shallow strata and surface atmosphere, breaking through the technical bottleneck that a single monitoring method cannot clarify the distribution ratio of leaking fluid in each medium. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the wellbore carbon dioxide leakage quantification method based on multi-path monitoring closed-loop inversion of the present invention; Figure 2 It is to achieve Figure 1 A schematic diagram of the system structure used in the method; Figure 3 This is a distributed optical fiber monitoring layout diagram in an embodiment of the present invention; Figure 4 This is a schematic diagram of time-shifted high-density resistivity resistivity in an embodiment of the present invention, wherein (a) is a schematic diagram of the arrangement of the time-shifted high-density resistivity resistivity system; and (b) is a resistivity profile obtained by time-shifted high-density resistivity resistivity inversion. Figure 5 This is a schematic diagram of soil carbon dioxide flux accumulation chamber monitoring in an embodiment of the present invention, wherein (a) is a schematic diagram of the accumulation chamber method layout; and (b) is a spatial distribution map of soil CO2 flux monitoring results in the study area.

[0029] In the diagram: 1. Carbon dioxide injection string; 2. Casing string; 3. Distributed fiber optic sensor; 4. Cement sheath; 5. Formation; 6. Check valve; 7. Wellhead flow meter; 8. Fiber optic demodulator; 9. Accumulation chamber; 10. Flux accumulation chamber method data acquisition and control unit; 11. Electrode; 12. High-density electrical resistivity tomography data acquisition and control unit; 13. Infrared imaging monitoring station; 14. Shallow groundwater; 15. Shallow monitoring well; 16. Gas-liquid separator. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] In this invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0033] Furthermore, it should be noted that the features of the various embodiments of the present invention can be combined or integrated in whole or in part, and as those skilled in the art will understand, they can interact and operate in different ways. Each embodiment can be implemented independently of each other or in association with one another.

[0034] like Figure 1 As shown, this invention proposes a method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion, comprising the following steps: S1. Synchronous acquisition and preprocessing of multi-path leakage monitoring data.

[0035] S1.1 Acquire monitoring data for the wellbore section, shallow formation, and surface atmosphere, respectively, including: Wellbore section monitoring data: Temperature and acoustic signals of the entire well section are collected by distributed fiber optic sensors (integrating a distributed temperature sensing module DTS and a distributed acoustic sensing module DAS) deployed in the wellbore annulus, as well as pressure time series data collected by the wellhead pressure sensor. Shallow formation monitoring data: underground resistivity distribution data obtained from time-shifted high-density electrical resistivity electrode arrays deployed around the target wells, and groundwater chemical parameters (dissolved inorganic carbon concentration, stable carbon isotope ratio, and tracer concentration) obtained from the shallow monitoring well network. Surface atmospheric monitoring data: soil carbon dioxide flux obtained from the soil accumulation chamber, and atmospheric carbon dioxide concentration and wind speed data obtained from infrared imaging.

[0036] S1.2. Perform time benchmark unification, spatial coordinate registration, and instrument drift correction on all collected data to form a standardized multi-section monitoring dataset.

[0037] S2, direct inversion of leakage source strength from monitoring data inside the wellbore.

[0038] S2.1. Use machine learning algorithms (such as the isolated forest algorithm) to extract abnormal features from the preprocessed temperature and sound wave data, and identify the local cooling segment caused by the Joule-Thomson effect and the accompanying high-frequency flow noise source when carbon dioxide leaks.

[0039] S2.2. Spatial cross-matching of the temperature anomaly depth and the acoustic noise location depth is performed to pinpoint the specific depth of the leak point in the well section (the overlapping depth is determined as the leak point depth).

[0040] S2.3. Using the temperature and pressure attenuation characteristics at the locked depth as input, the pre-built wellbore two-phase flow and heat transfer coupled inversion model is invoked to calculate the equivalent leakage coefficient of the leakage channel. This allows for the inversion of the total leakage rate through the cross-section of the wellbore section. .

[0041]

[0042]

[0043] In the formula, The instantaneous carbon dioxide leakage rate in the wellbore is expressed in kg / s. S² represents the equivalent leakage coefficient of the leakage path. The temperature change is expressed in K. The specific heat capacity of carbon dioxide is J / (kg·K); The density of the fluid inside the well is kg / m³. The length of the temperature drop region is in meters (m). The change over time, expressed in seconds, represents the observed temperature change. The time elapsed; The total duration of the leak is in seconds. The total leakage from the wellbore is expressed in kg.

[0044] S3. Joint calculation of leakage retention in shallow formations.

[0045] S3.1 Based on the resistivity anomaly obtained by time-shifted high-density electrical resistivity tomography (EDS), and combined with a rock physics model, the resistivity variation is converted into the carbon dioxide saturation distribution in shallow formations. The amount of free state interception in formation pores is calculated by integration. .

[0046]

[0047] In the formula, Index of survey lines for high-density electrical resistivity tomography (OTT) i =1, 2, ... m ); Indexing of depth or horizontal segments along the survey line ( j =1, 2, ... n ); For the first i Survey Line No. j Carbon dioxide density per grid, kg / m³; For the first i Survey Line No. j The carbon dioxide saturation of each grid cell is dimensionless. For the first i Survey Line No. j Porosity of each grid, dimensionless; For the first i Survey Line No. j The horizontal projected area of ​​each grid, m 2 ; For the first iSurvey Line No. j The thickness of each grid, in meters.

[0048] S3.2. Based on the dissolved inorganic carbon increment obtained from the analysis of shallow monitoring well water samples, calculate the amount of dissolved carbon intercepted in groundwater. .

[0049]

[0050] In the formula, The inorganic carbon concentration, in mol / m³, is the concentration of water in the monitoring well after the leak. The background inorganic carbon concentration before leakage is expressed in mol / m³. For the volume of the affected aquifer, m 3 ; and , respectively, represent the molar masses of carbon dioxide and inorganic carbon, in kg / mol.

[0051] S3.3, Define the total interception of shallow strata. This represents the portion of the leakage flux that has escaped from the wellbore but has not yet entered the atmosphere.

[0052] S4. Joint calculation of surface atmospheric emissions.

[0053] S4.1. The soil diffusion and emission amount is obtained by spatial area integration of the carbon dioxide flux data measured by the soil accumulation chamber. .

[0054]

[0055]

[0056]

[0057] In the formula, Carbon dioxide flux per unit area of ​​soil, kg·m - ²·s - ¹; To accumulate the effective volume of the chamber, m 3 ; To accumulate the floor area, m 2 ; The rate of change of carbon dioxide mass concentration in the cavity over time, in kg. m 3 s 1 ; The instantaneous carbon dioxide leakage rate in the surface soil of this area is expressed in kg / s. Index of survey lines for cumulative chamber method profiles ( =1, 2, ... m ); Indexing of depth or horizontal segments along the survey line ( =1, 2, ... n ); For the first Survey Line No. Measured carbon dioxide flux per grid cell, kg·m³ - ²·s - ¹; The background flux value of the soil in this area is kg·m. - ²·s - ¹; For the first Survey Line No. The representative area of ​​each grid, m 2 ; S4.2 Atmospheric carbon dioxide concentration field and wind speed field measured by infrared imaging; atmospheric dispersion and emission calculated based on plume cross-section flux method. .

[0058]

[0059]

[0060] In the formula, The instantaneous atmospheric escape rate of carbon dioxide is expressed in kg / s. Index of survey lines for plume profiles ( =1, 2, ... m ); Indexing of depth or horizontal segments along the survey line ( =1, 2, ... n ); For the first Line 1 Carbon dioxide mass concentration within the grid, kg / m³ 3 ; upwind background carbon dioxide mass concentration, kg / m³ 3 , used to subtract atmospheric background; For the first Line 1 Wind speed within the grid, m / s; For the first Line 1 The area of ​​the plume interface within the column grid, in m / s.

[0061] S4.3, Define the total atmospheric emissions from the Earth's surface. This represents the portion of the leakage flux that has entered the surface environment.

[0062] S5. Material conservation closed-loop comparison and verification of multi-path leakage.

[0063] S5.1 Constructing a closed equation for the conservation of matter:

[0064] in, This represents the total leakage amount; This represents the total interception volume in shallow strata. This refers to the total amount of energy released from the Earth's surface atmosphere. This refers to the closure residual (i.e., the amount of leakage or cumulative error that the monitoring system failed to capture).

[0065] S5.2 Set the standard relative uncertainty weights for each monitoring sub-item (predetermined by the instrument calibration accuracy and the standard deviation of the inversion model), and perform the following judgments and optimizations: like If the monitoring data at each section is deemed relatively accurate, the final leakage flux output value is calculated using a weighted average of absolute uncertainty.

[0066] In the formula, The final leakage amount is expressed in kg. The absolute uncertainty of the wellbore section inversion, in kg, originates from distributed fiber optic temperature measurement error, pressure sensor measurement error, and inversion model error. The absolute uncertainty of the shallow strata solution, in kg, originates from errors in high-density electrical resistivity inversion, rock physics model conversion, and hydrochemical analysis. The absolute uncertainty in the solution of the surface atmosphere, in kg, originates from the calculation error of the soil accumulation chamber flux and the error of the atmospheric dispersion model; the uncertainty propagation is calculated using the error propagation law or the Monte Carlo simulation method. like Then, a closed-loop inversion optimization based on weighted least squares is carried out—using the reciprocal of the uncertainty of each monitoring sub-item as the weight, within the feasible region formed by their respective uncertainty boundaries, the most probable values ​​of the leakage flux that minimize the sum of squared closed residuals are sought. This ensures that the recalculated closure residual converges to ≤20%, and outputs the final leakage flux after closure inversion optimization. ,Right now:

[0067] Figure 2 A schematic diagram of the system used to implement the wellbore carbon dioxide leakage quantification method based on multi-path monitoring and closed-loop inversion of this invention is provided. The system includes: Carbon dioxide injection string 1 is a channel for transporting carbon dioxide from the surface to the deep target formation. Casing string 2 is composed of multiple casings connected in sequence by threaded joints, forming a permanent pressure-bearing pipe string inside the wellbore, isolating different formation fluids, preventing carbon dioxide from rising along the wellbore, and providing a physical carrier for optical fibers / electrodes. Distributed fiber optic sensors 3 are deployed close to the casing string 2 or cement sheath 4 to collect temperature (DTS) and acoustic (DAS) signals in real time throughout the wellbore, which are used to monitor leakage, casing deformation and injection profile. The cement sheath 4, which fills the annulus between the casing string 2 and the formation 5, is a critical sealing barrier. If microfractures occur, carbon dioxide can escape along this channel. Formation 5 mainly consists of reservoirs and caprocks; One-way valve 6 is installed on carbon dioxide injection string 1 to prevent high-pressure carbon dioxide in the wellbore from flowing back to the surface after injection stops, thus ensuring safe well shut-in. The wellhead flow meter 7 accurately measures the instantaneous flow rate and cumulative total amount of carbon dioxide injected into the surface, serving as the first data checkpoint for mass conservation accounting. The fiber optic demodulator 8 is connected to the distributed fiber optic 3 signal and is used to emit laser pulses and analyze the Brillouin / Raman / Rayleigh scattering signals returned by the fiber optic cable, converting the optical signal into engineering data such as temperature and strain. Accumulation chamber 9 is an airtight cavity that combines volume (V) and soil cover area (S). The flux accumulation chamber method data acquisition and processing unit 10 opens and closes the accumulation chamber 9 at regular intervals, and collects a variety of key data simultaneously. Based on the preset flux calculation model, it performs real-time calculations to directly obtain the CO2 flux at each monitoring point and the instantaneous leakage rate of the entire area. Electrode 11 is deployed in shallow layers or between wells to supply current to the formation and measure the potential difference to obtain formation resistivity information; The high-density electrical resistivity data acquisition and control unit 12 is specifically designed to control the excitation and measurement timing of the electrode array, run the imaging algorithm, and generate underground resistivity profile maps. Infrared imaging monitoring station 13 utilizes the absorption characteristics of carbon dioxide in specific infrared bands to remotely scan and image the atmosphere around the well site and identify leaked gas clouds. Shallow groundwater 14: pH value and conductivity of the water body vary with the amount of carbon dioxide leakage; Shallow monitoring well 15 penetrates the shallow groundwater layer and is used for real-time sampling or sensor deployment to monitor water level and water quality changes, and to capture tracer signals; The gas-liquid separator 16, located in a shallow monitoring well or surface vent, separates the extracted groundwater from the potentially escaping free gas, facilitating the separate detection of the gas phase (carbon dioxide concentration) and the liquid phase (inorganic carbon concentration).

[0068] Among them, the distributed fiber optic sensor 3 and the pressure sensor (not shown) installed at the wellhead together form the well section monitoring module; the electrode array 11 and the shallow monitoring well network 15 together form the shallow formation monitoring module; and the accumulation chamber 9 and the infrared imaging monitoring station 13 together form the surface atmosphere monitoring module.

[0069] The following example uses the parameters of a typical carbon dioxide injection well (well depth 2000m, injection pressure 15 MPa, formation temperature 70℃). Assume the leak point is located at a well depth of 1200m, the leakage rate is 0.005 kg / s, the leakage lasts for 10 days, and the total leakage is 4320 kg. Figure 3 This is the monitoring layout diagram of the distributed fiber optic sensor 3 in this embodiment (DTS and DAS are integrated in the same optical cable, which can simultaneously acquire two physical signals: temperature and acoustic waves. The optical fiber is laid on the outer wall of the casing string 2 and the inner side of the cement sheath 4, which can monitor the key cementing process and also achieve permanent monitoring), obtained through the inversion model in step S2. =4450kg. Figure 4 This is a schematic diagram of the time-shifted high-density electrical resistivity tomography (EDT) in this embodiment, obtained through step S3. =1200kg. Figure 5 This is a schematic diagram of soil carbon dioxide flux monitoring in this embodiment, obtained through step S4. =3020kg. Closed residual =230kg, with a relative error of approximately 5.2%, indicating that the monitoring data from each path are consistent and the final leakage amount is... The uncertainty of the three factors is calculated using a weighted average. In step S2, the relative uncertainty is taken as 7%, with errors originating from temperature measurement accuracy errors, inversion model simplification errors, and fluid property parameter value errors. The absolute uncertainty... In step S3, the relative uncertainty is set at 12%, and the errors originate from the rock physics model error in resistivity to saturation conversion, the error in aquifer porosity and volume estimation, and the error of multiple solutions in electrical inversion. The absolute uncertainty is... In step S5, the relative uncertainty is set at 8%, with errors originating from spatial interpolation errors in the soil accumulation chamber flux and simplification errors in the atmospheric dispersion model. The absolute uncertainty is... .

[0070] Substitute the monitoring results and absolute uncertainty from steps S2-S4 above into the following formula for calculation. The result was 4323 kg, which effectively improved the accuracy of the leakage calculation.

[0071]

[0072] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0073] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0074] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion, characterized in that, Includes the following steps: S1. Acquire monitoring data of the well section, shallow formation, and surface atmosphere respectively, and perform time synchronization and spatial registration preprocessing on the three types of monitoring data; S2. Based on the monitoring data of the well section, the depth of the leak point is located by spatial cross-matching of temperature anomalies and acoustic anomalies, and the total leakage through the cross section of the well section is calculated based on the coupled inversion model of well flow and heat transfer. ; S3. Based on the shallow strata monitoring data, calculate the amount of free state interception in the shallow strata in a free state. and the amount of dissolved substances already dissolved in groundwater The sum of the two is defined as the total interception of shallow strata. ; S4. Calculate the soil diffusion and dissipation amount based on the aforementioned surface atmospheric monitoring data. and atmospheric diffusion and dissipation The sum of the two is defined as the total atmospheric emissions. ; S5. Constructing a closed equation for the conservation of matter. ,in The closed-loop residual is used as the basis for judgment and optimization based on the standard uncertainty weights of each monitoring sub-item, and the final leakage flux after closed-loop inversion optimization is output. .

2. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 1, characterized in that, In step S1, the well section monitoring data includes: temperature and acoustic signals of the entire well section collected by distributed optical fiber sensors deployed in the well annulus, and pressure time series data collected by wellhead pressure sensors.

3. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 2, characterized in that, Step S2 specifically includes the following steps: S2.

1. The isolated forest algorithm is used to extract abnormal features from the preprocessed temperature and sound data to identify the local cooling segment caused by the Joule-Thomson effect and the accompanying high-frequency flow noise source when carbon dioxide leaks. S2.

2. Spatial cross-matching of the temperature anomaly depth and the acoustic noise location depth to pinpoint the specific depth of the leak point in the well section; S2.

3. Using the temperature and pressure attenuation characteristics at the locked depth as input, the pre-built wellbore two-phase flow and heat transfer coupled inversion model is invoked to calculate the equivalent leakage coefficient of the leakage channel. This allows for the inversion of the total leakage flux through the cross-section of the wellbore section. : In the formula, The instantaneous carbon dioxide leakage rate in the wellbore is expressed in kg / s. S² represents the equivalent leakage coefficient of the leakage path. The temperature change is expressed in K. The specific heat capacity of carbon dioxide is J / (kg·K); The density of the fluid inside the well is kg / m³. The length of the temperature drop region is in meters (m). The change over time, expressed in seconds, represents the observed temperature change. The time elapsed; The total duration of the leak is in seconds. The total leakage from the wellbore is expressed in kg.

4. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 1, characterized in that, In step S1, the shallow formation monitoring data includes: underground resistivity distribution data obtained by a time-shifted high-density electrical resistivity electrode array deployed around the target well, and groundwater dissolved inorganic carbon concentration and stable carbon isotope ratio obtained by a shallow monitoring well network.

5. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 4, characterized in that, In step S3, the amount of free state interception The method for obtaining the data is as follows: input the resistivity distribution data into the rock physics model to convert it into carbon dioxide saturation distribution, and then perform volume integration on the spatial range of the high saturation anomaly to calculate the amount of free carbon dioxide intercepted. The amount of dissolved interception The method for obtaining the data is as follows: the dissolved inorganic carbon increment is calculated back based on the water sample from shallow monitoring wells.

6. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 5, characterized in that, Free state interception The calculation method is as follows: In the formula, This serves as an index for the survey lines of a high-density electrical resistivity tomography (EDT) profile. i =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, j =1, 2, ... n ; m and n Both represent any positive integer; For the first i Survey Line No. j Carbon dioxide density per grid, kg / m³; For the first i Survey Line No. j The carbon dioxide saturation of each grid cell is dimensionless. For the first i Survey Line No. j Porosity of each grid, dimensionless; For the first i Survey Line No. j The horizontal projected area of ​​each grid, m 2 ; For the first i Survey Line No. j The thickness of each grid cell, in meters; Dissolved interception The calculation method is as follows: In the formula, The inorganic carbon concentration, in mol / m³, is the concentration of water in the monitoring well after the leak. The background inorganic carbon concentration before leakage is expressed in mol / m³. For the volume of the affected aquifer, m 3 ; and , respectively, represent the molar masses of carbon dioxide and inorganic carbon, in kg / mol.

7. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 1, characterized in that, In step S1, the surface atmospheric monitoring data includes soil carbon dioxide flux obtained from the soil accumulation chamber and atmospheric carbon dioxide concentration and wind speed data obtained from infrared imaging.

8. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 7, characterized in that, In step S4, the amount of soil diffusion and dissipation... The carbon dioxide flux data measured by the soil accumulation chamber was obtained by spatial area integration. atmospheric dispersion The carbon dioxide concentration field and wind speed field were measured by infrared imaging and calculated based on the plume cross-section flux method.

9. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 8, characterized in that, The soil diffusion and escaping amount The calculation method is as follows: In the formula, Carbon dioxide flux per unit area of ​​soil, kg·m - ²·s - ¹; To accumulate the effective volume of the chamber, m 3 ; To accumulate the floor area, m 2 ; The rate of change of carbon dioxide mass concentration in the cavity over time, in kg. m 3 s 1 ; The instantaneous carbon dioxide leakage rate in the surface soil of this area is expressed in kg / s. For the cumulative chamber method profile survey line index, =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, =1, 2, ... n ; For the first Survey Line No. Measured carbon dioxide flux per grid cell, kg·m³ - ²·s - ¹; The background flux value of the soil in this area is kg·m. - ²·s - ¹; For the first Survey Line No. The representative area of ​​each grid, m 2 ; atmospheric dispersion The calculation method is as follows: In the formula, The instantaneous atmospheric escape rate of carbon dioxide is expressed in kg / s. This is the index of survey lines for the plume profile. =1, 2, ... m ; For depth or horizontal segment indexing along the survey line, =1, 2, ... n ; For the first Line number Carbon dioxide mass concentration within the grid, kg / m³ 3 ; The carbon dioxide mass concentration at the upwind background point, in kg / m³ 3 , used to subtract atmospheric background; For the first Line number Wind speed within the grid, m / s; For the first Line number The area of ​​the plume interface within the column grid, in m / s.

10. The method for quantifying wellbore carbon dioxide leakage based on multi-path monitoring closed-loop inversion according to claim 1, characterized in that, In step S5, the standard relative uncertainty weights for each monitoring sub-item are set, and the following judgments and optimizations are performed: like If the monitoring data at each section is deemed relatively accurate, the final leakage flux output value is calculated using a weighted average of absolute uncertainty. In the formula, The final leakage amount is expressed in kg. The absolute uncertainty of the wellbore section inversion, in kg, originates from distributed fiber optic temperature measurement error, pressure sensor measurement error, and inversion model error. The absolute uncertainty of the shallow strata solution, in kg, originates from errors in high-density electrical resistivity inversion, rock physics model conversion, and hydrochemical analysis. The absolute uncertainty in the solution of the surface atmosphere, in kg, originates from the calculation error of the soil accumulation chamber flux and the error of the atmospheric dispersion model; the uncertainty propagation is calculated using the error propagation law or the Monte Carlo simulation method. like Then, a closed-loop inversion optimization based on weighted least squares is carried out—using the reciprocal of the uncertainty of each monitoring sub-item as the weight, within the feasible region formed by their respective uncertainty boundaries, the most probable values ​​of the leakage flux that minimize the sum of squared closed residuals are sought. This ensures that the recalculated closure residual converges to ≤20%, and outputs the final leakage flux after closure inversion optimization. ,Right now: 。

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