Carbon dioxide monitoring method and device

Abstract

This invention discloses a carbon dioxide monitoring method, comprising: setting up a temperature sensor, a strain gauge pressure sensor, and a Ca... 2+ Concentration sensor and tracer concentration sensor; injecting tracer into injection well to monitor CO2 movement and leakage; when formation temperature rises above threshold A and formation pressure changes above threshold B, Ca... 2+ When the concentration exceeds threshold C and the tracer concentration falls below threshold D, if at least three conditions are met, or only two conditions are met, and at least one condition exceeds the corresponding threshold by 20-30%, then the formation parameters and tracer characteristic data are input into a pre-trained machine learning model to calculate the amount of additive to be added and injected into the injection well. This invention further claims protection for the aforementioned carbon dioxide monitoring device. This invention can intelligently evaluate and maintain the performance of the tracer during CO2 monitoring, accurately monitoring the movement trajectory and leakage of CO2.

Description

Technical Field

[0001] The present invention relates to the field of carbon dioxide monitoring, and more specifically, to a method and device for carbon dioxide monitoring. Background Art

[0002] In today's society, with the acceleration of industrialization, carbon dioxide emissions and monitoring have become an important research direction in the field of environmental science and engineering. As one of the main greenhouse gases, changes in carbon dioxide concentration in the atmosphere have a profound impact on the global climate and ecological environment. Therefore, accurate monitoring of carbon dioxide concentration changes in different environmental media is crucial for assessing climate change trends, formulating emission reduction strategies, and ensuring environmental sustainability.

[0003] Among the many sources of carbon dioxide emissions, industrial activities are a key area, such as power plants, cement plants, steel mills, etc. These industrial facilities will release a large amount of carbon dioxide into the atmosphere during the production process. In order to effectively monitor and manage these emissions, advanced monitoring technologies and equipment are needed. Traditional carbon dioxide monitoring methods include chemical absorption, infrared absorption, etc., but these methods often face some limitations in practical applications. For example, the chemical absorption method may require a complex sample pretreatment process and consume a large amount of reagents; the infrared absorption method has high requirements for instrument calibration and may affect measurement accuracy in the presence of interfering gases.

[0004] For example, in the invention patent with publication number CN118330136A, it discloses an online monitoring device for carbon dioxide emission concentration, which achieves the monitoring purpose through the coordinated work of the reaction system, the stirring device and the carbon dioxide monitoring device. The liquid inlet pipe, the reaction tank and the lower discharge pipe in the reaction system constitute the basic reaction and liquid transmission channel. The liquid inlet pipe is used to input reaction liquids such as lime water, and is connected to the lime water generation tank to ensure the supply of the reaction liquid; the reaction tank is used as a reaction place, and a flue gas inlet and a flue gas outlet are arranged on the top, and a stirring device is arranged inside. The stirring device is a hollow structure, driven by a motor, and the flue gas holes arranged on it can make the flue gas fully contact with the reaction liquid, thereby improving the reaction efficiency. This device solves the problems of incomplete reaction, inaccurate measurement and large floor space in traditional monitoring devices to a certain extent. However, it mainly focuses on the monitoring of carbon dioxide concentration of fixed pollution sources (such as factory chimney emissions), and mainly focuses on the monitoring of the reaction process of flue gas and lime water. The monitoring of carbon dioxide in complex geological environments (such as formations) and the compatibility problems of tracers and formation fluids that may occur during the monitoring process are not involved.

[0005] In geological environments, the behavior of carbon dioxide is more complex. There are various physical and chemical processes in the formation, such as changes in temperature and pressure, and differences in the chemical composition of formation water, all of which affect the storage, migration and transformation of carbon dioxide. For example, an increase in formation temperature may change the phase of carbon dioxide, causing it to transform from a liquid or gaseous state to a supercritical state, thereby affecting its mobility and distribution in the formation; changes in formation pressure will also drive the migration of carbon dioxide, causing it to diffuse or aggregate in porous media. At the same time, components such as calcium ions in formation water may react chemically with carbon dioxide to form carbonate precipitation, which not only affects the permeability of the formation, but may also change the chemical properties of the formation water.

[0006] In order to gain a deeper understanding of the dynamic changes of carbon dioxide in the geological environment, tracer technology is widely used. By injecting tracers into the formation and monitoring their concentration changes at different locations, the movement trajectory of carbon dioxide and possible leakage can be tracked. However, the complexity of the formation environment poses a challenge to the performance of tracers. Changes in formation temperature, pressure, and chemical composition may lead to degradation of tracers and chemical reactions with formation fluids, thereby affecting the monitoring effect of tracers. For example, high temperature may accelerate the decomposition of tracer molecules, causing them to lose their tracing ability; ions in formation water may react with tracers to change their chemical structure and properties, resulting in the inability of tracers to accurately reflect the true situation of carbon dioxide.

[0007] In addition, in geological environments, accurately determining the migration direction and distribution range of carbon dioxide is crucial for assessing its impact on groundwater, soil and other ecological and environmental elements. Traditional monitoring methods are difficult to obtain comprehensive and real-time dynamic information on carbon dioxide in formations, and lack effective means to deal with the compatibility issues between tracers and formation fluids. Therefore, a more comprehensive and accurate carbon dioxide monitoring method and device is needed that can monitor key formation parameters in real time, timely assess the compatibility of tracers and formation fluids, and take corresponding measures to adjust them, so as to achieve accurate monitoring and effective management of the behavior of carbon dioxide in geological environments. Summary of the invention

[0008] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0009] Another object of the present invention is to provide a carbon dioxide monitoring method, which can intelligently evaluate and maintain the performance of the tracer during the carbon dioxide monitoring process and accurately monitor the movement trajectory and leakage of carbon dioxide.

[0010] In order to achieve these purposes and other advantages according to the present invention, a carbon dioxide monitoring method is provided, comprising:

[0011] S1. Temperature sensors are installed in the formations near the injection wells at different depths in the reservoir to monitor the formation temperature with an accuracy of not less than ±0.5°C;

[0012] S2. Install a strain gauge pressure sensor at the connection point between the injection wellbore and the formation to monitor the formation pressure, with a measurement range of 0~100MPa and an accuracy of not less than ±1MPa;

[0013] S3. Install a calcium ion concentration sensor on the downhole tubing of the injection well to monitor the calcium ion concentration of the formation water with an accuracy of not less than ±10ppm;

[0014] S4. Install multiple tracer concentration sensors in the produced fluid pipeline of the production well, with a detection limit of 1 ppb and an accuracy of no less than ±5 ppb;

[0015] S5. Inject the tracer into the injection well to monitor the movement trajectory and leakage of carbon dioxide;

[0016] S6. Using a temperature sensor to monitor the formation temperature in real time, using a strain gauge pressure sensor to monitor the formation pressure change in real time, using a calcium ion concentration sensor to monitor the calcium ion concentration of the formation water in real time, and using a tracer concentration sensor to track the concentration of the tracer in the produced fluid in real time;

[0017] S7, when the conditions: the formation temperature rises above threshold A, the formation pressure change exceeds threshold B, the calcium ion concentration exceeds threshold C, and the tracer concentration is lower than threshold D, when at least three of the conditions are met, or only two of the conditions are met, and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, go to step S8, otherwise go to step S9;

[0018] S8, inputting the formation parameters and tracer characteristic data into the pre-trained machine learning model, the model calculates the amount of additives required in the tracer to maintain compatibility with the formation fluid and injects it into the injection well, and then goes to step S9;

[0019] S9. Continue to monitor the movement and leakage of carbon dioxide.

[0020] Preferably, the additives in S8 include 10 to 20 parts of a buffer, 30 to 60 parts of a chelating agent and 20 to 40 parts of an anti-foaming agent in parts by weight, wherein the buffer includes a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax, and the mass ratio of disodium hydrogen phosphate to potassium dihydrogen phosphate in the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system is 7.54:1; the mass ratio of the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system to borax is 3:1; the chelating agent includes EDTA disodium salt; the anti-foaming agent includes polydimethylsiloxane and polyether-modified silicone oil, and the mass ratio of the polyether-modified silicone oil to the polydimethylsiloxane is 3:2.

[0021] Preferably, the carbon dioxide monitoring method further comprises the following steps:

[0022] A1. When any tracer concentration sensor M detects that the tracer concentration is lower than a threshold value D, the position information of the tracer concentration sensor is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor;

[0023] A2, comparing the tracer concentration detected by the tracer concentration sensor M with the tracer concentration sensor X and the tracer concentration sensor Y, and at the same time comparing the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y with a set threshold value E;

[0024] A3. If only one of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y is greater than the tracer concentration detected by the tracer concentration sensor M, but the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are both greater than the threshold value E, an injection well is opened near the tracer concentration sensor M, and the injection well is opened with a downward inclination of 30°;

[0025] Among them, E is less than D.

[0026] Preferably, the carbon dioxide monitoring method further comprises the following steps:

[0027] B1. When any tracer concentration sensor N detects that the tracer concentration is lower than a threshold value E, the position information of the tracer concentration sensor is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor N;

[0028] B2. comparing the tracer concentration detected by the tracer concentration sensor N with the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y, and comparing the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y with the threshold value E;

[0029] B3. If both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are less than the tracer concentration detected by the tracer concentration sensor N, an injection well is opened at a position between the tracer concentration sensor N and the tracer concentration sensor X and at a position between the tracer concentration sensor N and the tracer concentration sensor Y, respectively. The two injection wells are arranged opposite to each other and are both inclined downward by 30°. The two injection wells are axially spaced 80-100° from each other, and the radial spacing is: 80-90% of the maximum height difference between the tracer concentration sensor N and the tracer concentration sensor X, and between the tracer concentration sensor N and the tracer concentration sensor Y;

[0030] Among them, E is less than D.

[0031] Preferably, the carbon dioxide monitoring method further comprises the following steps:

[0032] C1. When any tracer concentration sensor L detects that the tracer concentration is lower than a threshold value E, the position information of the tracer concentration sensor L is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor L;

[0033] C2. comparing the tracer concentration detected by the tracer concentration sensor L with the tracer concentration sensors X and Y, and comparing the tracer concentrations detected by the tracer concentration sensors X and Y with a threshold value E;

[0034] C3. If both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are greater than the tracer concentration detected by the tracer concentration sensor L, and both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are greater than the threshold value E, then continue monitoring;

[0035] Among them, E is less than D.

[0036] Preferably, the injection rate of the additive in the carbon dioxide monitoring method S8 is:

[0037] When at least three of the conditions are met, the injection rate of the additive is 35-50 mL / min;

[0038] When only two conditions are met, and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, the injection rate of the additive is 20-30 mL / min.

[0039] Preferably, the formation parameters in the pre-trained machine learning model in S8 include formation temperature, formation pressure, and calcium ion concentration of formation water, and the tracer characteristic data include degradation rate of the tracer in the formation and complexation constant between the tracer and calcium ions.

[0040] The present invention further claims protection for a carbon dioxide monitoring device based on the carbon dioxide monitoring method, comprising:

[0041] Temperature sensors are installed in formations near injection wells at different depths in the oil reservoir, the accuracy of the temperature sensors is not less than ±0.5°C, and are used to monitor formation temperature in real time;

[0042] The strain gauge pressure sensor is installed at the connection point between the injection wellbore and the formation. Its measurement range is 0~100MPa, and its accuracy is not less than ±1MPa. It is used to monitor the formation pressure changes in real time.

[0043] The calcium ion concentration sensor is installed on the downhole tubing of the injection well, with an accuracy of no less than ±10ppm, and is used to monitor the calcium ion concentration of formation water in real time;

[0044] The tracer concentration sensor is installed in the produced fluid pipeline of the production well, with a detection limit of 1ppb and an accuracy of no less than ±5ppb, and is used to track the concentration of the tracer in the produced fluid in real time;

[0045] A tracer injection unit, used to inject tracers into injection wells to monitor the movement trajectory and leakage of carbon dioxide;

[0046] A control unit, which is electrically connected to the temperature sensor, the strain gauge pressure sensor, the calcium ion concentration sensor, the tracer concentration sensor and the tracer injection unit, and is configured to: receive and judge the monitoring data from each sensor, and when the formation temperature rises above a threshold value A, the formation pressure change exceeds a threshold value B, the calcium ion concentration exceeds a threshold value C, and the tracer concentration is lower than a threshold value D, when at least three of the conditions are met, or only two of the conditions are met, and at least one of the conditions exceeds the corresponding threshold value by more than 20-30%, the control unit starts the additive calculation process; otherwise, the control unit instructs to continue monitoring the movement trajectory and leakage of carbon dioxide;

[0047] When the additive calculation process is initiated, the formation parameters and tracer property data are input into a pre-trained machine learning model, which calculates the amount of additive required to maintain compatibility of the tracer with the formation fluid.

[0048] The present invention has at least the following beneficial effects:

[0049] The carbon dioxide monitoring method provided by the present invention uses a temperature sensor to monitor the formation temperature in real time, a strain gauge pressure sensor to monitor the formation pressure change in real time, a calcium ion concentration sensor to monitor the calcium ion concentration of formation water in real time, and a tracer concentration sensor to track the concentration of the tracer in the produced fluid in real time. When it is monitored that the formation temperature rises above a threshold value A, the formation pressure change exceeds a threshold value B, the calcium ion concentration exceeds a threshold value C, and the tracer concentration is lower than a threshold value D, according to the set conditions (at least three conditions are met, or only two conditions are met and at least one of the conditions exceeds the corresponding threshold value by more than 20-30%), The formation parameters and tracer characteristic data are input into the pre-trained machine learning model. The model can accurately calculate the amount of additives required to maintain the compatibility of the tracer with the formation fluid based on formation parameters such as formation temperature, formation pressure, calcium ion concentration of formation water, and tracer characteristic data such as tracer degradation rate in the formation and complexation constant between the tracer and calcium ions. The model can intelligently evaluate and maintain tracer performance, effectively solving the problem of the impact of formation environment changes on tracer performance, ensuring that the tracer can still accurately reflect the situation of carbon dioxide under complex formation conditions, and improving the accuracy and reliability of monitoring.

[0050] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a flow chart of the carbon dioxide monitoring method described in one technical solution of the present invention. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can implement the invention with reference to the description.

[0053] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0054] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0055] Example 1

[0056] Installation of temperature sensors: Install temperature sensors in the formations near injection wells at different depths in the reservoir to monitor formation temperature changes in real time. Ensure that the temperature sensors are firmly installed and that the measuring end of the temperature sensors is in full contact with the formation to accurately obtain formation temperature data. The temperature sensors are high-precision models with an accuracy of no less than ±0.5°C, and can monitor small changes in formation temperature in real time.

[0057] Installation of strain gauge pressure sensor: Install strain gauge pressure sensor at the connection point between injection wellbore and formation to monitor formation pressure changes in real time. Before installation, clean and pre-treat the connection part of injection wellbore to ensure that the sensor installation surface is flat. During installation, use professional installation tools to accurately install and seal the strain gauge sensor to prevent pressure leakage from affecting measurement accuracy. The measurement range of this pressure sensor is 0~100MPa, and the accuracy is not less than ±1MPa;

[0058] Installation of calcium ion concentration sensor: Select a suitable location on the downhole tubing of the injection well to install the calcium ion concentration sensor to monitor the changes in calcium ion concentration in formation water in real time. The appropriate installation location should take into account the flow characteristics of formation water to ensure that the calcium ion concentration of formation water can be accurately measured. After the sensor is installed, it needs to be calibrated and tested to ensure that its accuracy is not less than ±10ppm;

[0059] Installation of tracer concentration sensor: On the produced fluid pipeline of the production well, multiple tracer concentration sensors are evenly distributed according to the pipeline length and monitoring requirements to track the concentration of the tracer in the produced fluid in real time. The tracer concentration sensor is installed on the side or top of the pipeline to ensure that the produced fluid can fully contact the detection part of the tracer concentration sensor. The detection limit of the tracer concentration sensor is 1ppb, and the accuracy is not less than ±5ppb;

[0060] Tracer injection: Inject the tracer into the injection well to monitor the movement trajectory and leakage of carbon dioxide. According to the monitoring purpose and formation characteristics, select the appropriate tracer. Common tracers include chemical substances (such as fluorescein) or radioactive isotopes. Before injecting the tracer, perform purity detection and concentration calibration on the tracer to ensure that its quality and concentration meet the monitoring requirements;

[0061] Condition judgment for additive injection: setting the time interval (5-15 minutes) for real-time data collection and recording of the temperature sensor, the strain gauge pressure sensor, the calcium ion concentration sensor and the tracer concentration sensor.

[0062] According to the geological characteristics of the reservoir, the CO2 injection scheme, the tracer characteristics and other factors, the formation temperature rise threshold A, the formation pressure change threshold B, the formation water calcium ion concentration threshold C, the tracer concentration threshold D and the tracer concentration threshold E (E <D)。

[0063] According to the data recorded by the temperature sensor, the strain gauge pressure sensor, the calcium ion concentration sensor and the tracer concentration sensor, it is determined whether the following conditions are met: the formation temperature rise exceeds threshold value A, the formation pressure change exceeds threshold value B, the calcium ion concentration exceeds threshold value C and the tracer concentration is lower than threshold value D. When at least three of the conditions are met, or only two of the conditions are met and at least one of the conditions exceeds the corresponding threshold value by more than 20-30%, the formation parameters and tracer characteristic data are input into the pre-trained machine learning model to calculate the amount of additives required in the tracer to maintain the compatibility of the tracer with the formation fluid, and the additives are injected based on the calculated amount. If the above conditions are not met, the movement trajectory and leakage of carbon dioxide continue to be monitored.

[0064] Calculation of additive injection amount: The formation parameters collected by each sensor and the tracer characteristic data obtained by laboratory analysis are input into the pre-trained machine learning model to predict the amount of additive required to maintain the compatibility of the tracer with the formation fluid. The formation parameters include formation temperature, formation pressure, and calcium ion concentration of formation water; the tracer characteristic data include the degradation rate of the tracer in the formation and the complexation constant between the tracer and calcium ions.

[0065] The pre-trained machine learning model is constructed based on a neural network algorithm. It is trained by a large amount of historical data and experimental data, and can accurately predict the amount of additives required to maintain the compatibility of tracers and formation fluids. Specifically: the pre-trained machine learning model is constructed using a multi-layer perceptron (MLP) algorithm, which consists of an input layer, several hidden layers, and an output layer. The input layer receives data such as formation temperature, formation pressure, calcium ion concentration of formation water, degradation rate of tracers in formations, and complex constants between tracers and calcium ions; the hidden layer uses a linear activation function (ReLU function) to perform feature transformation and complex mapping on the input data, and the learning rate of the hidden layer is set to 0.01; the output layer outputs the amount of additives required, and adds necessary noise to simulate the real situation. During the training process, the mean square error is used as the loss function, the stochastic gradient descent (SGD) is used as the optimizer, and matplotlib is used to draw the training loss curve to facilitate the observation of the decline in loss during the training process.

[0066] Long-term monitoring and optimization: During the CO2 monitoring process, the monitoring system is continuously operated to continuously collect data such as formation temperature, pressure, calcium ion concentration, and tracer concentration. Over time, a large amount of monitoring data is accumulated. These data will be used to further analyze the long-term behavior of CO2 in the formation and the performance changes of the tracer. The pre-trained machine learning model is optimized and adjusted regularly using the newly accumulated monitoring data. For example, every month or quarter, the model is retrained based on the latest data to improve the model's prediction accuracy for changes in the formation environment and changes in tracer performance. At the same time, based on actual monitoring results and experience, the thresholds of formation temperature, pressure, calcium ion concentration, and the composition and proportion of additives are adjusted in a timely manner to continuously optimize the entire monitoring and control process to ensure the effectiveness and reliability of CO2 monitoring.

[0067] Example 2

[0068] The present invention also provides an optimized composition of additives adapted to the carbon dioxide monitoring method: the additives include 10-20 parts of a buffer, 30-60 parts of a chelating agent, and 20-40 parts of an anti-foaming agent in parts by weight, wherein the buffer includes a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (mass ratio of 3:1), the mass ratio of disodium hydrogen phosphate and potassium dihydrogen phosphate in the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system is 7.54:1, the chelating agent is EDTA disodium salt, and the anti-foaming agent includes polydimethylsiloxane and polyether modified silicone oil (mass ratio of 3:2). In a complex formation environment, changes in formation temperature and pressure and fluctuations in the chemical composition of formation water may cause the chemical properties of the tracer to be unstable. Among them, the buffer can effectively resist changes in the pH value in the formation environment, maintain a relatively stable pH range, thereby slowing down the degradation rate of the tracer, extending its effective monitoring time, and ensuring accurate tracking of the movement trajectory and leakage of carbon dioxide over a long period of time; the chelating agent uses EDTA disodium salt, and the content is 30-60 parts. Metal ions such as calcium ions in formation water may react with tracers to make them inactive or change their chemical properties, affecting the accuracy of monitoring. Disodium EDTA has a strong complexing ability and can preferentially bind to metal ions such as calcium ions in formation water to prevent them from complexing with tracers, thereby maintaining the original performance of the tracer, ensuring that its interaction with carbon dioxide is not disturbed, and improving the reliability of monitoring results; the anti-foaming agent contains 20~40 parts, which are composed of polydimethylsiloxane and polyether modified silicone oil in a mass ratio of 3:2. During the injection and migration of carbon dioxide, foam may be generated due to physical stirring or chemical reactions. The presence of foam will interfere with the accurate measurement of tracer concentration by the tracer concentration sensor, resulting in increased monitoring data errors. The anti-foaming agent can quickly reduce the surface tension of the foam, break the foam, prevent the foam from accumulating in the produced fluid pipeline, ensure that the tracer concentration sensor can accurately detect the tracer concentration, and provide reliable data support for carbon dioxide monitoring.

[0069] In Example 2, the buffer, chelating agent and antifoaming agent are combined in a specific ratio, and the components work together. The buffer stabilizes the pH environment and provides suitable chemical conditions for the chelating agent and antifoaming agent to work; the chelating agent removes metal ions that may affect the tracer, and also helps to reduce other side reactions caused by metal ions (such as precipitation formation, etc.), which is indirectly beneficial to the defoaming effect of the antifoaming agent; the antifoaming agent ensures the physical stability of the monitoring system, which is beneficial for the buffer and chelating agent to be evenly distributed and function in the solution. This synergistic effect comprehensively improves the overall performance of the additive, maintains the compatibility of the tracer with the formation fluid to the greatest extent, and improves the accuracy and effectiveness of carbon dioxide monitoring.

[0070] Example 3

[0071] The present invention further optimizes the adjustment of the injection well according to the tracer concentration: when any tracer concentration sensor detects that the tracer concentration is lower than a threshold value D, the position information of the sensor is immediately located, and two tracer concentration sensors X and Y adjacent to the sensor are determined. The tracer concentration detected by the tracer concentration sensor is compared with the tracer concentration detected by sensors X and Y, and the tracer concentration detected by sensors X and Y is compared with the threshold value E;

[0072] If only one of the tracer concentrations detected by sensors X and Y is greater than the tracer concentration detected by the tracer concentration sensor, but the tracer concentrations detected by sensors X and Y are both greater than threshold E, an injection well is opened near the sensor. The injection well is opened with a downward inclination of 30° to optimize the injection direction effect of carbon dioxide.

[0073] When any tracer concentration sensor detects that the tracer concentration is lower than the threshold value E, the position information of the sensor is immediately located, and the two tracer concentration sensors X and Y adjacent to the sensor are determined. The tracer concentration detected by the tracer concentration sensor is compared with the tracer concentration detected by sensors X and Y, and the tracer concentration detected by sensors X and Y is compared with the threshold value E;

[0074] If both of the tracer concentrations detected by sensors X and Y are less than the tracer concentration detected by the tracer concentration sensor, an injection well is opened at a position between the tracer concentration sensor and sensor X and at a position between the tracer concentration sensor and sensor Y. The two injection wells are arranged opposite to each other and are both inclined downward by 30°, and are axially spaced 80-100° (preferably 90°) from each other, and the radial spacing is 80-90% (preferably 85%) of the maximum height difference between the tracer concentration sensor and sensor X, and between sensor N and sensor Y.

[0075] When any tracer concentration sensor detects that the tracer concentration is lower than the threshold value E, the position information of the sensor is immediately located, and the two tracer concentration sensors X and Y adjacent to the sensor are determined. The tracer concentration detected by the tracer concentration sensor is compared with the tracer concentration detected by sensors X and Y, and the tracer concentration detected by sensors X and Y is compared with the threshold value E;

[0076] If both of the tracer concentrations detected by sensors X and Y are greater than the tracer concentration detected by the tracer concentration sensor, and both of the tracer concentrations detected by sensors X and Y are greater than threshold E, monitoring continues without temporarily adjusting the injection well.

[0077] Among them, E<D.

[0078] Example 3: Based on the actual seepage characteristics of the formation, the injection layout of the tracer is optimized in three-dimensional space to maximize the lateral sweep range of the tracer in the formation and improve the effectiveness of carbon dioxide monitoring.

[0079] Example 4

[0080] The present invention further optimizes the injection efficiency of the additive according to the monitoring conditions:

[0081] When at least three conditions are met, injecting the additive into the injection well at a rate of 35-50 mL / min (preferably 43 mL / min);

[0082] When only two conditions are met and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, inject at a rate of 20-30 mL / min (preferably 26 mL / min).

[0083] During the injection process, the injection pressure and flow rate are closely monitored to ensure that the additives are accurately injected into the formation.

[0084] In Example 4, when at least three conditions are met, a higher injection rate of 35-50 mL / min is used, which can inject a sufficient amount of additives into the formation in a short time, and quickly respond to the impact of complex formation environmental changes on the tracer. For example, when the formation temperature rises sharply, the pressure changes greatly, and the tracer concentration decreases significantly, the high injection rate can quickly replenish the additives, enhance the ability to maintain the chemical stability of the tracer, effectively slow down the degradation rate of the tracer, ensure that the tracer can continuously and accurately monitor the movement trajectory and leakage of carbon dioxide, and improve the timeliness and reliability of monitoring. When only two conditions are met and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, the injection rate of 20-30 mL / min can not only replenish the additives to a certain extent to maintain the performance of the tracer, but also avoid the problems such as formation pressure fluctuations caused by too fast injection rate. This moderate injection rate can reduce unnecessary interference to the formation while ensuring the effective work of the tracer, so that the additives can continue to play a role for a long time, which helps to maintain the stability of the entire monitoring process, extend the effective monitoring period of the tracer, reduce the overall use of additives, improve resource utilization efficiency, and also help to reduce costs. By flexibly adjusting the additive injection rate according to different conditions, the entire monitoring system can better adapt to changes in the formation at different stages and under different working conditions.

[0085] Comparative Example 1

[0086] Instead of using the multi-parameter comprehensive judgment of this application, the traditional monitoring method with a fixed threshold of tracer concentration is adopted: the tracer is directly injected into the injection well to monitor the movement trajectory and leakage of carbon dioxide. A single tracer concentration threshold M is set, M<D, and when the tracer concentration is lower than the threshold M, the tracer is considered to be completely ineffective.

[0087] Comparative Example 2

[0088] The monitoring method provided by the present invention is adopted, and the additive composition adopted is: the additive comprises 30-60 parts of a chelating agent and 20-40 parts of an anti-foaming agent in parts by weight, wherein the chelating agent is EDTA disodium salt, and the anti-foaming agent comprises polydimethylsiloxane and polyether modified silicone oil (in a mass ratio of 3:2).

[0089] Comparative Example 3

[0090] The monitoring method provided by the present invention is adopted, and the additive composition adopted is: the additive comprises 10-20 parts of a buffer and 20-40 parts of an anti-foaming agent in parts by weight, wherein the buffer comprises a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (with a mass ratio of 3:1), the mass ratio of disodium hydrogen phosphate and potassium dihydrogen phosphate in the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system is 7.54:1, and the anti-foaming agent comprises polydimethylsiloxane and polyether modified silicone oil (with a mass ratio of 3:2).

[0091] Comparative Example 4

[0092] The monitoring method provided by the present invention is adopted, and the additive composition adopted is: the additive comprises 10-20 parts of a buffer and 30-60 parts of a chelating agent in parts by weight, wherein the buffer comprises a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (mass ratio is 3:1), the mass ratio of disodium hydrogen phosphate and potassium dihydrogen phosphate in the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system is 7.54:1, and the chelating agent is EDTA disodium salt.

[0093] Comparative Example 5

[0094] The monitoring method provided by the present invention is adopted, but does not include the step of optimizing the injection well adjustment according to the tracer concentration.

[0095] Experimental setup

[0096] In the small oil reservoir test area, multiple groups of similar injection wells and production wells were selected. The initial average formation temperature in the test area was 35°C, the average formation pressure was 20Mpa, and the average calcium ion concentration of the formation water was 40ppm. The monitoring period of multiple groups of injection wells and production wells was three months.

[0097] In the first group of wells, the monitoring method of Example 1 of the present invention is adopted, that is, a temperature sensor, a strain gauge pressure sensor, a calcium ion concentration sensor and a tracer concentration sensor are installed, and the formation temperature rise threshold A is set to 4°C, the formation pressure change threshold B is set to 8MPa, the formation water calcium ion concentration threshold C is set to 90ppm, and the tracer concentration threshold D is set to 8ppb. When it is monitored that the formation temperature rise exceeds the threshold A, the formation pressure change exceeds the threshold B, the calcium ion concentration exceeds the threshold C, and the tracer concentration is lower than the threshold D, the additive provided in Example 2 is injected into the injection well according to the satisfaction of at least three conditions or the satisfaction of two specific conditions. The injection rate of the additive is as follows: when at least three of the conditions are satisfied, the injection rate of the additive is 45mL / min; when only two conditions are satisfied and at least one of the conditions exceeds the corresponding threshold by more than 25%, the injection rate of the additive is 25mL / min. The additives include 15 parts of a buffer, 45 parts of a chelating agent and 30 parts of an anti-foaming agent in parts by weight, wherein the buffer includes a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (mass ratio of 3:1), the chelating agent is EDTA disodium salt, and the anti-foaming agent includes polydimethylsiloxane and polyether modified silicone oil (mass ratio of 3:2); the tracer concentration threshold E is set to 4 ppb, and when any tracer concentration meets the conditions of Example 3, the injection well adjustment is optimized according to the scheme provided in Example 3 based on the tracer concentration.

[0098] In the second group of wells, the monitoring method provided in Comparative Example 1 was adopted, that is, only the tracer concentration sensor was used for monitoring, and other parameters such as formation temperature, pressure and calcium ion concentration were not considered. The tracer concentration threshold M was set to 7 ppb. When the tracer concentration was lower than the threshold M, the tracer was directly injected.

[0099] In the third group of wells, the monitoring method provided by the present invention was adopted, but the additive composition adopted was: the additive included 45 parts of chelating agent and 30 parts of anti-foaming agent by weight, wherein the chelating agent was disodium EDTA, and the anti-foaming agent included polydimethylsiloxane and polyether modified silicone oil (mass ratio was 3:2).

[0100] In the fourth group of wells, the monitoring method provided by the present invention is adopted, but the additive composition adopted is: the additive includes 15 parts of buffer and 30 parts of anti-foaming agent in parts by weight, wherein the buffer includes disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (mass ratio is 3:1), and the anti-foaming agent includes polydimethylsiloxane and polyether modified silicone oil (mass ratio is 3:2).

[0101] In the fifth group of wells, the monitoring method provided by the present invention was adopted, but the additive composition adopted was: the additive included 15 parts of buffer and 45 parts of chelating agent by weight, wherein the buffer included disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax (mass ratio of 3:1), and the chelating agent was disodium EDTA salt.

[0102] In the sixth group of wells, the monitoring method provided by the present invention is used, but does not include the step of optimizing the injection well adjustment according to the tracer concentration.

[0103] One month later:

[0104] In the first group of well test areas, the formation temperature gradually increased by an average of 2.5°C, which did not exceed threshold A; the formation pressure increased by 4MPa, which did not exceed threshold B; the formation water calcium ion concentration increased to 48ppm, which did not exceed threshold C; the tracer concentration decreased to 14ppb, which was higher than threshold D. The monitoring system continued to monitor normally, and the additive calculation process was not started.

[0105] The second group of well test areas: the tracer concentration dropped to 13 ppb and no further tracer injection was performed.

[0106] The third group of well test area: the tracer concentration dropped to 13ppb, which did not reach the set threshold, and continued to be monitored. However, due to the lack of consideration of other factors, changes in the formation environment have begun to affect the performance of the tracer, and the increase in temperature has accelerated the degradation of the tracer.

[0107] The fourth group of well test area: The tracer concentration dropped to 14ppb, which did not reach the set threshold and continued to be monitored.

[0108] The fifth group of well test area: The tracer concentration dropped to 13ppb, which did not reach the set threshold and continued to be monitored.

[0109] The sixth group of well test areas: The changes in formation temperature, pressure and calcium ion concentration were similar to those of the first group. The tracer concentration dropped to 14 ppb, and the tracer concentration dropped faster in some areas, reaching 11 ppb.

[0110] Two months later:

[0111] The first group of well test area: the formation temperature rises to 42°C, the formation pressure rises to 28MPa, the formation water calcium ion concentration reaches 55ppm, and the tracer concentration drops to 9~11ppb. At this time, at least three conditions are met (the formation temperature is close to threshold A, the formation pressure exceeds threshold B, and the tracer concentration is lower than threshold D). The control unit starts the additive calculation process, calculates and injects the appropriate amount of additives, and optimizes the injection well layout at the corresponding position based on the tracer concentration sensor data comparison. Under the action of the additive, the tracer concentration stabilizes between 8~10ppb, the formation temperature rise rate slows down, and the formation pressure changes tend to be stable.

[0112] Well test area of ​​the second group: The tracer concentration dropped to 7 ppb, close to the set threshold. Although no action was taken at this time, the formation temperature rose to 41°C (not monitored and considered), causing further degradation of the tracer.

[0113] In the third group of well test areas, the formation temperature reached 45°C, the formation pressure was 30MPa, the formation water calcium ion concentration was 75ppm, and the tracer concentration dropped to 6ppb. This was because of the lack of buffers to resist the changes in pH in the formation environment. The degradation of the tracer was accelerated. In the second month, the tracer concentration was lower than the threshold value D, making it difficult to accurately monitor the movement trajectory of carbon dioxide, which affected the accuracy of the carbon dioxide monitoring effect evaluation and the test was stopped.

[0114] The fourth group of well test area: the tracer concentration dropped to 9ppb, the formation temperature was 45°C, the formation pressure was 29MPa, and the formation water calcium ion concentration was 78ppm. Due to the lack of chelating agent, the complexation between calcium ions and tracers intensified, the tracer performance decreased significantly, and the concentration approached the threshold D.

[0115] The fifth group of well test area: the tracer concentration dropped to 11ppb, the formation temperature was 44°C, the formation pressure was 29MPa, and the formation water calcium ion concentration was 72ppm. As the carbon dioxide injection volume increased, the foam problem gradually became prominent, affecting the uniform distribution of the tracer in the produced fluid, resulting in large fluctuations in the tracer concentration sensor measurement value, and the test was stopped.

[0116] The sixth group of well test area: the formation temperature is 47°C, the formation pressure is 30MPa, and the formation water calcium ion concentration is 75ppm. Due to the unreasonable layout of the injection wells, the tracer concentration fluctuates greatly, ranging from 4 to 6ppb.

[0117] After March:

[0118] The first group of well test areas: the formation temperature reached 43°C, the formation pressure was 30MPa, the formation water calcium ion concentration was 62ppm, and the tracer concentration was stable at around 9ppb. Through continuous monitoring and timely adjustment of additive injection and injection well layout, the risk of carbon dioxide leakage was effectively controlled.

[0119] The second group of well test area: the tracer concentration dropped below 5ppb, and the tracer was re-injected. However, due to the continuous deterioration of the formation environment, the newly injected tracer quickly became ineffective, and it was impossible to accurately monitor the dynamics of carbon dioxide, posing a risk of leakage.

[0120] The third group of well test area: the test has been stopped.

[0121] The fourth group of well test area: the tracer concentration quickly fell below the threshold value D, and the test was stopped.

[0122] The fifth group of well test area: the test has been stopped.

[0123] The sixth group of well test area: the formation temperature is 47°C, the formation pressure is 31MPa, the formation water calcium ion concentration is 78ppm, and the tracer concentration drops below 4ppb. It is impossible to accurately monitor the dynamics of carbon dioxide, and there is a high risk of carbon dioxide leakage.

[0124] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the carbon dioxide monitoring method and apparatus of the present invention will be obvious to those skilled in the art.

[0125] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A carbon dioxide monitoring method, characterized in that: include: S1. Temperature sensors are installed in the formations near the injection wells at different depths in the reservoir to monitor the formation temperature with an accuracy of not less than ±0.5°C; S2. Install a strain gauge pressure sensor at the connection point between the injection wellbore and the formation to monitor the formation pressure, with a measurement range of 0~100MPa and an accuracy of not less than ±1MPa; S3. A calcium ion concentration sensor is installed on the downhole tubing of the injection well to monitor the calcium ion concentration of the formation water with an accuracy of not less than ±10ppm; S4. Install multiple tracer concentration sensors in the produced fluid pipeline of the production well, with a detection limit of 1 ppb and an accuracy of no less than ±5 ppb; S5. Inject the tracer into the injection well to monitor the movement trajectory and leakage of carbon dioxide; S6. Using a temperature sensor to monitor the formation temperature in real time, using a strain gauge pressure sensor to monitor the formation pressure change in real time, using a calcium ion concentration sensor to monitor the calcium ion concentration of the formation water in real time, and using a tracer concentration sensor to track the concentration of the tracer in the produced fluid in real time; S7, when the conditions: the formation temperature rises above threshold A, the formation pressure change exceeds threshold B, the calcium ion concentration exceeds threshold C, and the tracer concentration is lower than threshold D, when at least three of the conditions are met, or only two of the conditions are met, and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, go to step S8, otherwise go to step S9; S8, inputting the formation parameters and tracer characteristic data into the pre-trained machine learning model, the model calculates the amount of additives required in the tracer to maintain compatibility with the formation fluid and injects it into the injection well, and then goes to step S9; S9. Continue to monitor the movement and leakage of carbon dioxide.

2. The carbon dioxide monitoring method according to claim 1, characterized in that: The additives in S8 include 10-20 parts of a buffer, 30-60 parts of a chelating agent and 20-40 parts of an anti-foaming agent in parts by weight, wherein the buffer includes a disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system and borax, the mass ratio of disodium hydrogen phosphate and potassium dihydrogen phosphate in the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system is 7.54:1, and the mass ratio of the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer system to borax is 3:1; the chelating agent includes EDTA disodium salt; the anti-foaming agent includes polydimethylsiloxane and polyether modified silicone oil, and the mass ratio of the polyether modified silicone oil to the polydimethylsiloxane is 3:

2.

3. The carbon dioxide monitoring method according to claim 1 or 2, characterized in that: The following steps are also included: A1. When any tracer concentration sensor M detects that the tracer concentration is lower than a threshold value D, the position information of the tracer concentration sensor is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor; A2, comparing the tracer concentration detected by the tracer concentration sensor M with the tracer concentration sensor X and the tracer concentration sensor Y, and at the same time comparing the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y with a set threshold value E; A3. If only one of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y is greater than the tracer concentration detected by the tracer concentration sensor M, but the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are both greater than the threshold value E, an injection well is opened near the tracer concentration sensor M, and the injection well is opened with a downward inclination of 30°; Among them, E is less than D.

4. The carbon dioxide monitoring method according to claim 1 or 2, characterized in that: The following steps are also included: B1. When any tracer concentration sensor N detects that the tracer concentration is lower than a threshold value E, the position information of the tracer concentration sensor is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor N; B2. comparing the tracer concentration detected by the tracer concentration sensor N with the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y, and comparing the tracer concentration detected by the tracer concentration sensor X and the tracer concentration sensor Y with the threshold value E; B3. If both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are less than the tracer concentration detected by the tracer concentration sensor N, an injection well is opened at a position between the tracer concentration sensor N and the tracer concentration sensor X and at a position between the tracer concentration sensor N and the tracer concentration sensor Y, respectively. The two injection wells are arranged opposite to each other and are both inclined downward by 30°. The two injection wells are axially spaced 80-100° from each other, and the radial spacing between the two injection wells is: 80-90% of the maximum height difference between the tracer concentration sensor N and the tracer concentration sensor X, and between the tracer concentration sensor N and the tracer concentration sensor Y; Among them, E is less than D.

5. The carbon dioxide monitoring method according to claim 1 or 2, characterized in that: The following steps are also included: C1. When any tracer concentration sensor L detects that the tracer concentration is lower than a threshold value E, the position information of the tracer concentration sensor L is located to determine two tracer concentration sensors X and Y adjacent to the tracer concentration sensor L; C2. comparing the tracer concentration detected by the tracer concentration sensor L with the tracer concentration sensors X and Y, and comparing the tracer concentrations detected by the tracer concentration sensors X and Y with a threshold value E; C3. If both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are greater than the tracer concentration detected by the tracer concentration sensor L, and both of the tracer concentrations detected by the tracer concentration sensor X and the tracer concentration sensor Y are greater than the threshold value E, then continue monitoring; Among them, E is less than D.

6. The carbon dioxide monitoring method according to claim 2, characterized in that: The injection rate of the additive in S8 is: When at least three of the conditions are met, the injection rate of the additive is 35-50 mL / min; When only two conditions are met, and at least one of the conditions exceeds the corresponding threshold by more than 20-30%, the injection rate of the additive is 20-30 mL / min.

7. The carbon dioxide monitoring method according to claim 6, characterized in that: The formation parameters in the pre-trained machine learning model in S8 include formation temperature, formation pressure, and calcium ion concentration of formation water, and the tracer characteristic data include the degradation rate of the tracer in the formation and the complexation constant between the tracer and calcium ions.

8. A carbon dioxide monitoring device, characterized in that: include: Temperature sensors are installed in formations near injection wells at different depths in the oil reservoir, the accuracy of the temperature sensors is not less than ±0.5°C, and are used to monitor formation temperature in real time; The strain gauge pressure sensor is installed at the connection point between the injection wellbore and the formation. Its measurement range is 0~100MPa, and its accuracy is not less than ±1MPa. It is used to monitor the formation pressure changes in real time. The calcium ion concentration sensor is installed on the downhole tubing of the injection well, with an accuracy of no less than ±10ppm, and is used to monitor the calcium ion concentration of formation water in real time; The tracer concentration sensor is installed in the produced fluid pipeline of the production well, with a detection limit of 1ppb and an accuracy of no less than ±5ppb, and is used to track the concentration of the tracer in the produced fluid in real time; A tracer injection unit, used to inject tracers into injection wells to monitor the movement trajectory and leakage of carbon dioxide; A control unit, which is electrically connected to the temperature sensor, the strain gauge pressure sensor, the calcium ion concentration sensor, the tracer concentration sensor and the tracer injection unit, and is configured to: receive and judge the monitoring data from each sensor, and when the formation temperature rises above a threshold value A, the formation pressure change exceeds a threshold value B, the calcium ion concentration exceeds a threshold value C, and the tracer concentration is lower than a threshold value D, when at least three of the conditions are met, or only two of the conditions are met, and at least one of the conditions exceeds the corresponding threshold value by more than 20-30%, the control unit starts the additive calculation process; otherwise, the control unit instructs to continue monitoring the movement trajectory and leakage of carbon dioxide; When the additive calculation process is initiated, the formation parameters and tracer property data are input into a pre-trained machine learning model, which calculates the amount of additive required to maintain compatibility of the tracer with the formation fluid.

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