A wellbore breach leakage monitoring system and method for carbon dioxide geological sequestration

Abstract

The present application relates to the technical field of environmental monitoring, in particular to a wellbore damage leakage monitoring system and method for carbon dioxide geological storage, the system comprising: a wellbore, a probe, a fiber-optic temperature sensor and a fiber-optic strain sensor, the probe comprising an open circular ring, the upper end face of the circular ring having a groove, and the fiber-optic sensor being embedded in the groove; a plurality of annular probes being fitted on the wellbore at intervals. The present application can arrange resistivity probes around the wellbore in 360 degrees, and the resistivity monitors detailed information of the formation around the wellbore, and the distributed fiber-optic sensor provides a spatial resolution of meters or even centimeters, so that carbon dioxide leakage or migration in any direction can be captured in all directions, and the detection sensitivity and reliability of the system are improved, and the advantage of continuous real-time monitoring of the fiber-optic sensor is used as a trigger mechanism to dynamically adjust the resistivity scanning frequency, so as to realize timely detection and response to wellbore damage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pollution prevention and environmental monitoring, and particularly relates to a system and method for monitoring wellbore damage leakage in a carbon dioxide geological storage model experiment. BACKGROUND

[0002] With the intensification of global climate change, mitigating greenhouse gas emissions has become an international focus. Carbon dioxide geological storage (CO2Geological Sequestration, CGS) is a potential carbon emission reduction technology that has attracted attention from academia and industry. It reduces the concentration of CO2 in the atmosphere by injecting CO2 into deep geological structures for storage, thereby mitigating the greenhouse effect. However, in CGS projects, the wellbore connects the surface with the underground storage layer, and it is subjected to high pressure and high flow rate CO2 impact, facing durability challenges. If the wellbore is damaged or fails, it will not only lead to CO2 leakage, affecting the storage effect, but also may cause environmental risks such as groundwater pollution and earthquakes. Therefore, the safety of the wellbore needs to be comprehensively evaluated and continuously monitored.

[0003] The current monitoring technology usually deploys a high-precision sensor network around the wellbore to obtain the stress state, temperature field distribution, and formation pressure changes of the wellbore to achieve monitoring. However, this method needs to stop the injection operation and cannot achieve monitoring during CO2 injection. Moreover, if pressure and temperature sensors are used for monitoring, the spatial resolution is limited, and the detection range is small. Some geophysical methods can provide large-scale underground information, but it is difficult to accurately locate small-scale wellbore leakage. Geochemical monitoring can detect CO2 leakage by analyzing the CO2 concentration and isotope composition in groundwater or soil gas, but this method often lags behind the actual leakage event, leading to a delayed response, which is not conducive to early warning.

[0004] The invention patent with application number 202311464662.X proposes a CO2 leakage monitoring system and method for underground storage area to monitor CO2 leakage in the storage area. The CO2 storage area and its surrounding clay layer form the monitored area together. The CO2 storage area is connected to the CO2 injection device through the injection well. Resistivity probes are arranged in the clay layer to obtain resistivity data. Fiber optic temperature and pressure sensors are arranged in layers in the CO2 storage area. The obtained resistivity data is processed to obtain a CO2 underground plume map by combining actual geological data, and the specific location of the underground CO2 leakage is determined to monitor the CO2 leakage. The disadvantages of this method are as follows:

[0005] 1. Although the above system and method are based on fiber optic sensors and resistivity monitoring technology, their purpose is to monitor the area surrounding the carbon dioxide storage zone. They monitor the movement of carbon dioxide over a relatively large area, but cannot accurately monitor whether the well body itself has been damaged or leaking.

[0006] 2. The above method cannot be applied to wellbore damage and leakage monitoring for the following reasons:

[0007] 2.1 Due to the presence of blind spots in the resistivity probe, if the resistivity probe method described in the invention is used to monitor the integrity of the wellbore, the probe needs to be laid out around the wellbore. This greatly increases the risk of carbon dioxide leakage and the difficulty of data acquisition and processing, as well as the monitoring cost. The resistivity probe and fiber optic sensor are placed in clay and sand layers respectively. The spatial difference makes it difficult for the two systems to achieve precise time synchronization, thus making it difficult to capture instantaneous changes or establish accurate time correlations between different parameters. Furthermore, the geological conditions at different locations vary, increasing the difficulty of data interpretation. For example, one system may detect an anomaly first, while the other system may need more time to confirm it, potentially delaying emergency response time.

[0008] 2.2 Resistivity monitoring is typically performed periodically, rather than continuously in real time. This means there is a "monitoring vacuum" between scans. Because each complete resistivity scan takes a certain amount of time (which can range from tens of minutes to several days), rapidly changing processes cannot be captured. This discontinuous monitoring mode means that important events that may occur between scans (such as CO2 leaks or wellbore damage) may be missed. Summary of the Invention

[0009] To address the problem that existing technologies cannot achieve real-time monitoring of wellbore damage and leakage during carbon dioxide injection, the present invention aims to provide a wellbore damage and leakage monitoring system for carbon dioxide geological storage, comprising: a wellbore with an injection port at the bottom, a probe for detecting resistivity, an optical fiber temperature sensor, and an optical fiber strain sensor, characterized in that: the probe includes an open ring with a groove on the upper end face of the ring, and the optical fiber sensor is embedded in the groove; a plurality of annular probes are spaced apart on the wellbore.

[0010] Furthermore, the injection port on the wellbore is wrapped with n layers of filter screens, with the holes on adjacent layers of filter screens alternating, and the diameter of the holes in each layer is... The following constraints must be met: The number of holes P in each filter screen satisfies: The filter screen closest to the backfill is the first layer of filter screen.

[0011] Furthermore, the number of probes is related to the wellbore depth, and the number satisfies the following relationship: , wherein D is the total depth of the wellbore; S is the electrode probe spacing; and R is the desired vertical resolution.

[0012] The application further provides a wellbore damage leakage monitoring method for carbon dioxide geological storage, characterized by comprising:

[0013] S1, determining a monitoring area and dividing a plurality of annular sub-areas vertically along the wellbore;

[0014] S2, sleeving an annular probe embedded with a fiber-optic temperature sensor and a fiber-optic strain sensor at each annular sub-area along the wellbore;

[0015] S3, state detection

[0016] S31, establishing a fiber-optic sensor trigger reference, including a first-level trigger and a second-level trigger;

[0017] S31, conventional monitoring, the annular probe monitoring resistivity, the fiber-optic temperature sensor monitoring temperature, and the fiber-optic strain sensor monitoring strain force, if the abnormal monitoring is a first-level trigger, then step S3111 is entered, if the abnormal monitoring is a second-level trigger, then step S3121 is entered;

[0018] S3111, completing resistivity monitoring in a period;

[0019] S3112, increasing the resistivity monitoring frequency and shortening the resistivity monitoring period; entering step S32;

[0020] S3121, canceling resistivity monitoring in a period;

[0021] S3122, increasing the resistivity monitoring frequency and shortening the resistivity monitoring period; entering step S32;

[0022] S32, wellbore damage evaluation.

[0023] Further, the step S32 comprises:

[0024] S3211, obtaining resistivity in a conventional monitoring stage, substituting temperature data and strain data in an abnormal monitoring stage into the resistivity in the same period to calculate resistivity in the abnormal monitoring stage:

[0025] ;

[0026] wherein, is a lithology coefficient; is initial porosity; is current temperature; is reference temperature; is strain; is porosity-strain coefficient; is a cementation exponent; is a saturation exponent; is a water saturation; is a formation water resistivity;

[0027] S3212, obtaining a judgment variable , is a ratio of the resistivity in the abnormal monitoring stage and the resistivity in the normal monitoring stage, if is equal to a preset threshold , no damage leakage occurs in the wellbore; if is greater than the preset threshold , but less than 1.4 , slight damage leakage occurs in the wellbore, and a leakage warning is issued; if is greater than 1.4 , damage leakage occurs in the wellbore, and a major leakage alarm is issued.

[0028] Further, in the step S31, the first trigger condition is: or , and the second trigger condition is: or , wherein is a temperature difference of the optical fiber temperature sensor in the normal working state and the abnormal state; is a strain difference of the optical fiber strain sensor in the normal working state and the abnormal state; is a reference value of the optical fiber temperature sensor and the optical fiber strain sensor in the normal working state.

[0029] Further, in the step S3112, the resistivity monitoring frequency is increased, the optical fiber monitoring frequency is increased to 10 Hz, and the monitoring period is shortened to 2-3 minutes; in the step S3122, the resistivity monitoring period is shortened to 1-2 minutes, and the optical fiber sensor monitoring frequency is increased to 20 Hz.

[0030] Compared with the prior art, the application has the following advantages and positive effects:

[0031] 1. High spatial resolution and continuity monitoring: The resistivity probe can be arranged around the wellbore in 360 degrees, and the resistivity monitoring can provide detailed information about the formation around the wellbore. Distributed optical fiber sensors can be arranged along the entire wellbore, providing meter-level or even centimeter-level spatial resolution. This layout can provide more comprehensive monitoring coverage, capturing carbon dioxide leakage or migration in any direction, greatly improving the detection sensitivity and reliability of the system. The resistivity measurement and temperature and strain data collected by the optical fiber sensor are highly coincident in space, which makes the correlation analysis between the data more accurate. For example, CO2 leakage may cause changes in resistivity and temperature anomalies at the same time, and the simultaneous changes in the two data can more reliably indicate the occurrence of leakage. The multi-parameter monitoring capability greatly improves the accuracy and reliability of anomaly detection.

[0032] 2. The present application uses the advantage of continuous real-time monitoring of optical fiber sensors as a trigger mechanism to dynamically adjust the resistivity scanning frequency to achieve timely detection and response to wellbore damage. The dynamic adjustment method, on the one hand, through rapid response to abnormal changes, can discover potential problems earlier, provide basis for preventive maintenance, and help to take preventive measures in time to improve the safety of the entire CO2 injection system; on the other hand, in abnormal conditions, increase the sampling frequency to obtain more detailed data, which can capture more details and help to more accurately analyze the problem; in addition, in normal state, keep low frequency, save energy and data storage space, through intelligent adjustment of monitoring frequency, reduce energy consumption and maintenance cost under normal circumstances; in addition, it can avoid long-term high frequency work, reduce equipment wear and tear, and prolong the service life.

[0033] 3. Early warning capability and reliability of long-term monitoring: Because multiple parameters can be monitored in real time and continuously, this combined technology can capture early and subtle changes, thereby achieving early warning of potential problems. Both optical fiber sensors and resistivity electrodes have good durability and are suitable for long-term embedding, meeting the needs of long-term monitoring of the CGS project. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, and the advantages thereof, a brief introduction will be given below to the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0035] Figure 1 The cross-sectional view of the wellbore monitoring system of the embodiment of the present application is shown in the figure.

[0036] Figure 2 The sensor layout of the embodiment of the present application is shown in the figure.

[0037] Figure 3 This is a schematic diagram of the wellbore damage and leakage monitoring method according to an embodiment of the present invention;

[0038] Figure 4 This is a flowchart illustrating the specific implementation of fiber-optic triggered resistivity monitoring in an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram of the resistivity of the well shaft without damage and leakage according to an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of resistivity variation due to well barrel damage and leakage in an embodiment of the present invention;

[0041] In the above figures, 1. Resistivity ring probe; 2. Fiber optic temperature sensor; 3. Fiber optic strain sensor; 4. Resistivity transmission line; 5. Fiber optic cable; 6. Power supply and acquisition controller; 7. Fiber optic demodulator; 8. Computer and client; 9. Wellbore; 10. Gas injection port. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, provides a detailed description of the specific implementation, structure, features, and effects of a method proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] The specific solutions provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0045] Example 1: This invention proposes a wellbore damage and leakage monitoring system for carbon dioxide geological storage, such as... Figure 1 As shown, the system includes resistivity ring probes 1, fiber optic temperature sensors 2 and fiber optic strain sensors 3 placed at the same depth as the resistivity ring probes, and transmits monitoring data to a power supply and acquisition controller 6 and a fiber optic demodulator 7 via resistivity transmission lines 4 and optical fibers 5. The computer and client receive resistivity data and fiber optic temperature and strain data, determine trigger thresholds, and decide whether to initiate abnormal monitoring. If abnormal monitoring occurs, after one cycle, data coupling processing and risk assessment determine whether the wellbore has suffered damage or leakage, and compare the results with risk thresholds to determine whether to issue an alarm.

[0046] The CPU of the computer and the client 8 receives control instructions to manage the operation of individual unit modules. The power supply and acquisition control instrument 6 is connected to the resistivity loop probe, and through the program instructions output by the CPU, the working state of each electrode on the probe is managed to complete a collection. The data is sent through the resistivity transmission line 4, and the resistivity value is calculated in real time. The change of the optical signal in the optical fiber temperature and strain sensor is transmitted to the optical fiber demodulator 7 through the optical fiber, and the wavelength to temperature and strain conversion is completed by identifying and calculating the spectrum. Further, the point data is transmitted to the computer and the client 8, and the automatic data processing program is pre-programmed to automatically complete the calculation and storage.

[0047] In addition, an alarm device connected to the computer 8 can be provided, and the client software can be installed on multiple computers connected to the Internet. After obtaining permission, the monitoring device can be operated to set the collection parameters, send control instructions, transmit monitoring data, etc., and can also accept leakage alarm information.

[0048] The resistivity loop probe 1 uses a copper ring as the electrode material and is installed outside the experimental wellbore in the form of two half-circle buckles. One side is reserved for the resistivity transmission line 4 welding interface, and the other side is pre-designed with a recess to place the optical fiber sensor. The optical fiber 5 is wound around the outside of the ring and goes up along the wellbore to be connected to the above-mentioned control device. The gap between the pipes and the inside is filled and fixed with epoxy resin. The number of each resistivity loop probe is related to the depth of the wellbore, and the number satisfies the following relationship: , where D is the total depth of the wellbore, S is the electrode probe spacing, and R is the required vertical resolution. In this example, the wellbore diameter is 100 mm, the loop probe inner diameter is about 105 mm, the thickness is about 5 mm, and the width is 20 mm.

[0049] The loop resistivity probe proposed in this embodiment is easy to operate, and the sleeve ring design can arrange the resistivity probe around the wellbore in 360 degrees. This layout can provide more comprehensive monitoring coverage and capture carbon dioxide leakage or migration in any direction, greatly improving the detection sensitivity and reliability of the system. The resistivity measurement and temperature and strain data collected by the optical fiber sensor are highly coincident in space, which makes the correlation analysis between the data more accurate.

[0050] In this embodiment, the injection wellbore 9 is made of gypsum, and the top of the injection wellbore is provided with a shrinkage hole joint. The carbon dioxide injection device is connected to the injection wellbore through the shrinkage hole joint. The bottom is discretely provided with a gas injection hole, and the outside of the pipe body is wrapped with n layers of gauze to prevent sand particles in the carbon dioxide storage area from entering the wellbore and blocking the gas injection hole 10. The holes on the adjacent two layers of filter screens are alternately distributed, and the diameter of each layer of holes satisfies the following constraint condition: The number P of holes of each layer of filter screens satisfies: The filter screen closest to the backfill is the first layer of filter screen.

[0051] Example 2: This example proposes a method for monitoring wellbore damage and leakage in a carbon dioxide geological storage model experiment. It can monitor the wellbore status in real time during the carbon dioxide injection process and when injection is stopped, especially wellbore rupture and carbon dioxide leakage. The method includes the following steps:

[0052] (1) Determine the monitoring area

[0053] According to the size of the experimental model box ( The influence range of the injection well was determined. A monitoring area was established with the well 9 as the center and a cylindrical area with a diameter of 0.1m and a depth of 0.8m. The entire annular area was divided into 10 vertically arranged annular sub-areas of equal size, each with a height of 0.08m.

[0054] (2) Deploy resistivity ring probes and distributed fiber optic sensors

[0055] Ten resistivity annular probes 1 are set at the midpoint of the 10 sub-regions divided on the wellbore, and ten fiber optic temperature sensors 2 and ten fiber optic strain sensors 3 are placed in the grooves reserved in the collar to ensure good contact between the sensors and the formation. The resistivity transmission line 4 and the optical fiber 5 are pulled upward along the wellbore to the sealed formation.

[0056] (3) Combine resistivity monitoring and fiber optic sensor technologies

[0057] a. Determination of trial operation and routine monitoring parameters

[0058] Connect the power supply and resistivity acquisition device, and conduct a trial run to check the working status of all electrodes. Test different electrode combinations to ensure the system can cover the entire target area. During resistivity measurement, each resistivity ring probe 1 is powered sequentially, and all electrodes of adjacent resistivity probes simultaneously perform potential measurements. The fiber optic sensor performs optical time domain reflectance (OTDR) measurement to check fiber integrity and signal attenuation. A 2-hour continuous measurement test is conducted to ensure system stability.

[0059] The fiber optic sensor automatically converts the monitored optical signal changes into formation temperature and strain data using a fiber optic demodulator, improving the signal-to-noise ratio and saving significant data processing time. The calculation method is as follows:

[0060] ;

[0061] ;

[0062] in: This is due to temperature-induced Bragg wavelength shift. thermal expansion coefficient of the optical fiber; thermo-optic coefficient of the optical fiber; temperature change; Bragg wavelength shift caused by pressure; effective strain-optic coefficient of the optical fiber; mechanical strain (caused by pressure).

[0063] According to the statistical analysis results during the trial operation, the normal temperature range (27.3-27.5°C) and strain range (0.1-0.5%) of each monitoring point were determined, the normal resistivity value range of each region and depth was determined (see the attached figure), and the reasonable scanning period of resistivity in the example under normal circumstances was determined to be (5-10) minutes. The natural variation amplitude of resistivity was analyzed, and the background value could provide data filtering basis for subsequent experimental results. In this example, the sampling frequency of the optical fiber sensor was set to 5 times per second, and the data was collected all day long without interruption. The temperature monitoring resolution was 0.05°C, and the monitoring range was -20°C to 80°C; the strain accuracy could reach 1 (micro-strain), and the monitoring range was usually .

[0064] b. Abnormal monitoring trigger mechanism and abnormal state monitoring

[0065] The trigger mechanism of resistivity monitoring was established by using the optical fiber sensor to dynamically adjust the resistivity scanning frequency. First, the trigger threshold needs to be determined. Before CO2 injection, i.e. during the trial operation, the long-term background temperature and strain data collected by the optical fiber sensor were used to establish a high-precision reference model. And set the trigger mechanism:

[0066] Primary trigger mechanism (early warning level): or The optical fiber sensor detects changes in temperature and pressure, shortens the resistivity scanning period (period of 2-3 minutes), and increases the monitoring frequency of the optical fiber sensor to 10Hz. Real-time data saving, transmission to the data processing module, and automatic preliminary evaluation according to the data analysis method in the following text.

[0067] Secondary trigger mechanism (alert level): or The fiber optic sensor detected significant temperature changes and strain anomalies. If any resistivity scans from the previous cycle were incomplete, they were immediately cancelled, and a new cycle was started to acquire new resistivity data, ensuring that abnormal data at the moment of wellbore failure was not collected. The new resistivity scan cycle was set to (1-2) minutes, and the monitoring frequency of the fiber optic sensor was increased to 20Hz. Data was collected and transmitted to the data processing module. Combining temperature and strain data with a preset data processing algorithm, the wellbore condition was assessed to determine if leakage had occurred, and injection suspension and emergency maintenance were considered. A computer and client 8 were used to connect the fiber optic monitoring system and the resistivity monitoring system. An automatic threshold judgment program and a resistivity trigger program were developed, allowing the computer and client to automatically control the monitoring process, reducing manual operation and improving the anti-interference capability and accuracy of the monitoring system.

[0068] Specifically, the mean values ​​of formation temperature and strain are calculated. and standard deviation The trigger threshold is set to At 27.5℃ and 0.45%, normal periodic monitoring was conducted. During the monitoring process, the current optical signal was recorded and automatically calculated into the ambient temperature and strain values ​​by the fiber optic demodulator, and compared with the reference values. Compare them.

[0069] refer to Figure 4 Reference data of the initial state is obtained through fiber optic sensors to determine the temperature under normal operating conditions. ) and strain ( (benchmark value) Regular monitoring is performed, during which the current optical signal is recorded and automatically calculated into the ambient temperature and strain values ​​using a fiber optic demodulator, and compared with a reference value. Compare the results. When the temperature difference... or strain difference Exceeding 70% of the benchmark value (i.e. or If a Level 1 response is triggered, otherwise, routine monitoring continues. Upon Level 1 triggering, the computer and the client's built-in operating program control the resistivity transilluminator to continue and complete the current cycle of resistivity monitoring, confirming the current status. After completing the current cycle of resistivity monitoring, the resistivity monitoring frequency is increased and the fiber optic monitoring frequency is raised to 10Hz, shortening the monitoring cycle to 2-3 minutes. Data is collected according to the adjusted cycle, and abnormal resistivity values ​​are identified and judged, initiating the wellbore damage and leakage assessment process. If the temperature difference... or strain difference Exceeding the benchmark value ( or ), triggering a secondary response. Upon secondary triggering, regardless of whether there is an ongoing resistivity monitoring, immediately cancel and start a new round of scanning to prevent missing important data monitoring of the wellbore leakage moment after completing the current unimportant period, causing delay in early warning, and shorten the resistivity monitoring period to 1-2 minutes during the new round of scanning, and adjust the fiber sensor monitoring frequency to 20Hz.

[0070] This embodiment fully utilizes the real-time point measurement of the fiber sensor and the regional accuracy of the resistivity monitoring, and proposes a dynamically adjusted coupling monitoring method, which has the following advantages: 1. Timely discovery of problems: through rapid response to abnormal changes, potential problems can be discovered earlier, providing basis for preventive maintenance, helping to take preventive measures in time and improving the safety of the entire CO2 injection system. 2. Improve data quality: increase sampling frequency in abnormal conditions to obtain more detailed data, which can capture more details and help to more accurately analyze the problem causes. 3. Reduce operating costs: maintain a lower frequency in normal conditions to save energy and data storage space, and reduce energy consumption and maintenance costs under normal conditions through intelligent adjustment of monitoring frequency. 4. Prolong equipment life: avoid long-term high-frequency work to reduce equipment wear and tear and prolong service life.

[0071] (4) Wellbore damage and leakage evaluation

[0072] In the conventional monitoring stage, the resistivity around the wellbore can be calculated without the participation of fiber monitoring data, which can be calculated using the Archie equation widely used in the field of geophysics, and the calculated value is the conventional stage resistivity value:

[0073] ;

[0074] Where, is the resistivity value of the formation; is the lithology coefficient, which is determined through core analysis and laboratory testing, and is generally about 0.62 for sandstone and about 0.1-0.4 for clay; is the porosity; is the cementation exponent, which is determined by experiment, and is generally about 2 for sandstone and about 1.5-1.9 for clay; is the water saturation; is the saturation exponent (usually about 2); is the formation water resistivity.

[0075] This example is adapted to the physical model experiment of geological storage, and the Archie equation is modified. The fiber temperature and strain data in the abnormal monitoring stage are substituted into the equation, and the wellbore resistivity value in the abnormal monitoring stage can be calculated by coupling with the resistivity data in the same period :

[0076] ;

[0077] wherein, is the initial porosity; is the current temperature (in °C); is the reference temperature (usually 25 °C); is the strain; is the porosity-strain coefficient, usually determined experimentally, and can be between 3-5 for sandstone and higher for clay.

[0078] The ratio I of the abnormal monitoring stage resistivity to the value of the conventional monitoring stage can determine the wellbore damage and the leakage direction of CO2;

[0079] From I = 1.1 (1.1 is an empirical value or determined by experiment), it is considered that the wellbore does not leak, and the change of the resistivity value is caused by the normal diffusion motion of carbon dioxide in the formation, and if I > 1.1 at the subsequent time, the diffusion concentration gradually increases;

[0080] When there is an area of I > 1.5, it is considered that the wellbore has damaged leakage, and a major leakage alarm is directly issued.

[0081] The present application provides a kind of high efficiency, accurate, timely carbon dioxide injection wellbore monitoring method, by optical fiber trigger mechanism and data fusion, can realize the real-time monitoring and positioning of wellbore leakage and rupture, system has real-time data processing and alarm function, ensure that the problem is found in the first time and issues an alarm, provide strong guarantee for the safe operation of carbon dioxide geological storage, reduce environmental and engineering risk.

[0082] It should be noted that: the above-mentioned embodiment of the present application is only for description, and does not represent the advantages and disadvantages of the embodiment. The process depicted in the drawing does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0083] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

Claims

1. A method for monitoring a wellbore breach leakage for carbon dioxide geologic sequestration, comprising a wellbore breach leakage monitoring system, the system comprising: The well shaft with gas injection holes in the lower part, probe for detecting resistivity, optical fiber temperature sensor and optical fiber strain sensor, characterized in that: the probe comprises an open circular ring, the upper end face of the circular ring has a groove, and the optical fiber temperature sensor and the optical fiber strain sensor are embedded in the groove; a plurality of annular probes are sleeved on the well shaft at intervals; the method comprises: S1, determining the area to be monitored, and evenly dividing a plurality of annular sub-areas along the vertical direction of the well shaft; S2, sleeving the annular probe embedded with the optical fiber temperature sensor and the optical fiber strain sensor at each annular sub-area along the well shaft; S3, state detection S31, establishing a fiber sensor trigger reference, including a primary trigger and a secondary trigger; S31, conventional monitoring, the annular probe monitors the resistivity, the optical fiber temperature sensor monitors the temperature, and the optical fiber strain sensor monitors the strain force, if the abnormal monitoring is a primary trigger, then step S3111 is converted, if the abnormal monitoring is a secondary trigger, then step S3121 is converted; S3111, completing the resistivity monitoring in the period; S3112, increasing the resistivity monitoring frequency and shortening the resistivity monitoring period; entering step S32; S3121, canceling the resistivity monitoring in the period; S3122, increasing the resistivity monitoring frequency and shortening the resistivity monitoring period; entering step S32; S32, well shaft damage evaluation; S3211, obtaining the resistivity in the conventional monitoring stage, substituting the temperature data and the strain data in the abnormal monitoring stage, and coupling the resistivity in the same period to calculate the resistivity in the abnormal monitoring stage: ； wherein, is a lithology factor; is an initial porosity; is a current temperature; is a reference temperature; is a strain; is a porosity-strain factor; is a cementation exponent; is a saturation exponent; is a water saturation; is a formation water resistivity; S3212, obtain a judgment variable , is the ratio of the abnormal monitoring stage resistivity and the conventional monitoring stage resistivity, if is equal to a preset threshold value , the wellbore does not have a breakage leakage; if is greater than a preset threshold value , but less than 1.4 , the wellbore has a slight breakage leakage, and a leakage warning is issued; if is greater than 1.4 , the wellbore has a breakage leakage, and a major leakage alarm is issued.

2. The monitoring method of claim 1, wherein, The primary trigger condition in step S31 is: or The secondary trigger condition is: or wherein is the temperature difference of the optical fiber temperature sensor under normal working state and abnormal state; is the strain difference of the optical fiber strain sensor under normal working state and abnormal state; is the reference value of the optical fiber temperature sensor and the optical fiber strain sensor under normal working state.

3. The monitoring method of claim 1, wherein, In the step S3112, the resistivity monitoring frequency and the optical fiber monitoring frequency are increased to 10 Hz, and the monitoring period is shortened to 2-3 minutes; in the step S3122, the resistivity monitoring period is shortened to 1-2 minutes, and the optical fiber sensor monitoring frequency is increased to 20 Hz.

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