A carbon dioxide energy storage well soaking time dynamic optimization method based on pressure analysis

Abstract

This application relates to the field of data processing technology and proposes a dynamic optimization method for the stagnation time of carbon dioxide energy storage wells based on pressure analysis. The method includes: collecting pressure data at the inlet end of the experimental well during CO2 injection and constructing a pressure data sequence for each collection cycle; dividing the well into a first stage, adjusting the carbon dioxide injection rate at collection times after the first stage, and updating the first stage; identifying the start time of stagnation based on the updated first stage; collecting the wellhead casing pressure of the experimental well, establishing a wellhead casing pressure sequence for each collection cycle, determining the collection cycle to be confirmed and the wellhead casing pressure sub-sequence to be confirmed, and determining the end time of stagnation by combining the changing trends of all wellhead casing pressure sequences before the wellhead casing pressure sub-sequence to be confirmed. This application aims to improve the accuracy of the optimal stagnation time.

Description

Technical Field

[0001] This application relates to the field of data processing technology, specifically to a dynamic optimization method for carbon dioxide energy storage well shut-in time based on pressure analysis. Background Technology

[0002] Carbon dioxide energy storage involves using electricity to compress CO2 into a high-pressure state during off-peak hours and injecting it into underground pore or fracture spaces such as depleted oil and gas reservoirs, salt caverns, and deep aquifers for storage. During peak hours, the high-pressure CO2 is released to drive turbines and generate electricity, achieving energy recycling. After injection, the CO2 does not immediately enter a storage or release state; injection must be paused and the wellhead sealed for a period of time—this settling process is called well simmering. The core purpose of the well simmering stage is to allow the injected CO2 to fully interact with the underground formation and pore fluids to reach a stable state. Excessive simmering time wastes storage cycles and reduces utilization efficiency, while insufficient simmering time prevents the injected CO2 from reaching a stable state, affecting subsequent energy storage efficiency and formation safety. Formation pressure is a key indicator reflecting the interaction between underground CO2 and the formation; using pressure to determine the simmering time is crucial for the technology's successful implementation.

[0003] The optimal well-sealing time can be determined based on numerical simulation and empirical formulas. However, there are actual differences in different well-sealing processes. These two methods cannot adjust the final optimal well-sealing time according to the actual pressure changes during the well-sealing stage, which affects the accuracy of the well-sealing time value. Summary of the Invention

[0004] This application provides a dynamic optimization method for the stagnation time of carbon dioxide energy storage wells based on pressure analysis, in order to solve the problem that the optimal stagnation time cannot be adjusted according to actual pressure changes, resulting in insufficient accuracy in the stagnation time value. The specific technical solution adopted is as follows:

[0005] One embodiment of this application provides a method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis. The method includes the following steps:

[0006] Pressure data at the inlet of the experimental well were collected at different times during different collection cycles during CO2 injection, and pressure data sequences for each collection cycle were constructed.

[0007] Based on the differences between adjacent pressure data in the pressure data sequences of different acquisition cycles, the first stage is divided. Based on the changing trends of all pressure data contained in the pressure data sequence of the acquisition cycle, the carbon dioxide injection rate at the acquisition time in the acquisition cycle after the first stage is adjusted and the first stage is updated. Based on the positive and negative signs of the first-order difference sequence of the pressure data sequence in the acquisition cycle after the updated first stage, the start time of well shut-in is identified.

[0008] The well is sealed starting from the beginning of the sealing process. Wellhead casing pressure is collected at different times during different collection cycles to establish a wellhead casing pressure sequence for each collection cycle. Based on this sequence, a predicted wellhead casing pressure sequence is obtained. The collection cycle to be confirmed is determined based on the similarity between the current and predicted wellhead casing pressure sequences. The sequence to be confirmed is identified based on the similarity between adjacent wellhead casing pressure sub-sequences derived from the wellhead casing pressure sequence of the to-be-confirmed collection cycle, as well as the curve fitting results of sequences composed of different wellhead casing pressure sequences. Finally, the end time of the sealing process is determined by combining the changing trends of all wellhead casing pressure sequences preceding the to-be-confirmed sequence.

[0009] Furthermore, the specific method for dividing the first stage is as follows:

[0010] When the first-order difference sequence of the pressure data sequence in the acquisition period contains both positive and negative numbers, the acquisition period is recorded as the stage transition acquisition period.

[0011] The time period between the start of CO2 injection and the last acquisition time of the first phase acquisition cycle is denoted as the first phase.

[0012] Furthermore, the specific method for adjusting the carbon dioxide injection rate at each acquisition time during the acquisition cycle following the first stage is as follows:

[0013] Any acquisition cycle after the first stage is designated as the target acquisition cycle. Linear fitting is performed on all pressure data contained within the pressure data sequence of the target acquisition cycle to obtain the fitting slope. The normalized value of the absolute value of the fitting slope is calculated and summed with the number 1. The product of this sum and the carbon dioxide injection rate at the last acquisition moment of the target acquisition cycle is designated as the first product of the target acquisition cycle. 75% of the preset carbon dioxide injection rate is designated as the second product of the target acquisition cycle. The minimum value between the first and second products of the target acquisition cycle is designated as the adjusted carbon dioxide injection rate of the target acquisition cycle. The carbon dioxide injection rate at the next adjacent acquisition moment after the target acquisition cycle is set as the adjusted carbon dioxide injection rate of the target acquisition cycle.

[0014] Furthermore, the specific steps included in updating the first stage are as follows:

[0015] When the carbon dioxide injection rate at the time of acquisition differs from the preset carbon dioxide injection rate, the standard slope is calculated.

[0016] When the fitting slope corresponding to the target acquisition period is greater than the standard slope, the time period from the start of CO2 injection to the last acquisition moment of the target acquisition period will be used as the first stage of the update.

[0017] Furthermore, the specific calculation method for the standard slope is as follows:

[0018] The average of the fitted slopes that are less than 0 among all the fitted slopes corresponding to all acquisition cycles from the first stage to the target acquisition cycle is recorded as the standard slope.

[0019] Furthermore, the method for determining the start time of the well simmering is as follows:

[0020] Any acquisition period after the updated first stage is designated as the acquisition period to be processed. When the first-order difference sequence of the pressure data sequence of the acquisition period to be processed contains both positive and negative numbers, the acquisition period to be processed is designated as the conversion period. The acquisition time corresponding to the first pressure data of the two pressure data corresponding to the first negative number in the first-order difference sequence of the pressure data sequence of the first conversion period after the updated first stage is designated as the well start time.

[0021] Furthermore, the specific method for determining the collection period to be confirmed is as follows:

[0022] When the correlation coefficient between the wellhead casing pressure sequence of the acquisition period and the wellhead casing pressure prediction sequence of the next adjacent acquisition period is less than the preset similarity threshold, the acquisition period is recorded as an acquisition period to be confirmed.

[0023] Furthermore, the specific identification method for the wellhead casing pressure sequence to be confirmed is as follows:

[0024] The wellhead casing pressure sequence of the collection period to be confirmed is divided into a first preset number of wellhead casing pressure sub-sequences. Anomaly detection is performed on the correlation coefficient of two adjacent wellhead casing pressure sequences to obtain the number of anomaly points.

[0025] When the number of outliers is not zero, select the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last outlier and all subsequent wellhead casing pressure sequences, and determine the wellhead casing pressure sequence to be confirmed based on the selected wellhead casing pressure sequence.

[0026] Furthermore, the specific method for determining the wellhead casing pressure sequence to be confirmed based on the selected wellhead casing pressure sequence includes:

[0027] Curve fitting is performed on the selected wellhead casing pressure sequence and the sequence composed of all subsequent wellhead casing pressure sequences to obtain the goodness of fit of the fitted curve. When the goodness of fit is greater than or equal to the preset inflection point judgment threshold, the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last anomaly point is determined as the wellhead casing pressure sequence to be confirmed.

[0028] Furthermore, the method for obtaining the end time of the well simmering is as follows:

[0029] Curve fitting is performed on the sequence consisting of all wellhead casing pressure sequences from the first wellhead casing pressure sequence after the start of well sumption to the wellhead casing pressure sequence to be confirmed, and the inflection point confirmation curve is obtained. The acquisition time corresponding to the first zero derivative value in the derivative of the inflection point confirmation curve within the acquisition time period corresponding to the wellhead casing pressure sequence to be confirmed is recorded as the end time of well sumption.

[0030] The beneficial effects of this application are:

[0031] To identify the start of well shut-in, this application divides the CO2 injection process into three stages. The first stage is defined by the characteristic that carbon dioxide enters the rock pores, causing the inlet pressure to gradually decrease and stabilize. Since the carbon dioxide dissolution efficiency decreases in the second stage, the injection pressure also decreases. To avoid an imbalance between the injection pressure and dissolution efficiency at the second-stage injection rate, the carbon dioxide injection rate is adjusted for each acquisition cycle after the first stage, and the first stage is updated to obtain a more accurate result. The accurate start time of well shut-in is then identified based on the changing trend of the pressure data sequence after the first stage. This is done to avoid the risk of abrupt changes in flow path or seepage during carbon dioxide diffusion in rocks with high porosity. Instability causes sudden local fluctuations in wellhead casing pressure, affecting the identification of inflection points. Based on the similarity between the wellhead casing pressure sequence and the predicted wellhead casing pressure sequence, the inflection point is identified within the unconfirmed acquisition period. Furthermore, the unconfirmed wellhead casing pressure sub-sequences within the wellhead casing pressure sub-sequences divided from the wellhead casing pressure sequence are identified. The time period corresponding to the unconfirmed wellhead casing pressure sub-sequence is a smaller time period within which the determined inflection point is located. Finally, based on the fact that when the wellhead casing pressure-time curve shows an inflection point, the diffusion mechanism of carbon dioxide changes from being mixed with multiple flow mechanisms to becoming dominant, and combined with the changing trends of all wellhead casing pressure sequences before the unconfirmed wellhead casing pressure sub-sequence, the end time of well shut-in is determined. This solves the problem of insufficient accuracy in determining the well shut-in time due to the inability to adjust the optimal well shut-in time value according to actual pressure changes, thus improving the accuracy of the determined well shut-in time. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1This is a schematic diagram of a method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis, provided as an embodiment of this application. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Please see Figure 1 The diagram illustrates a flowchart of a dynamic optimization method for carbon dioxide energy storage well shut-in time based on pressure analysis, according to an embodiment of this application. The method includes the following steps:

[0036] Step S001: Collect pressure data at the inlet end of the experimental well at different collection times during different collection cycles during CO2 injection, and construct a pressure data sequence for each collection cycle.

[0037] The test well selected in this embodiment is a horizontal well in a tight oil reservoir located in the Fuyu oil layer, and the horizontal section of the test well is 827 meters long.

[0038] CO2 was injected into the test well, and pressure data at the inlet end was collected at equal time intervals from the moment the CO2 injection began.

[0039] In this embodiment, the time interval for the pressure data at the inlet is set to 10 seconds, and one collection cycle is 2 minutes. In actual applications, as other implementation methods, implementers can decide the values ​​of the time interval and collection cycle according to the actual situation. This application does not impose any special restrictions.

[0040] The pressure data from all acquisition moments within the same acquisition cycle are arranged sequentially to obtain the pressure data sequence for that acquisition cycle.

[0041] In this embodiment, a moving average filtering algorithm is used to denoise the pressure data sequence. The use of a moving average filtering algorithm for denoising is a well-known technique and will not be described further. As other implementation methods, while achieving the goal of data denoising, implementers may employ other methods in the prior art, such as median filtering, for data denoising; this application does not impose any special limitations.

[0042] At this point, the pressure data sequence for each acquisition cycle has been obtained.

[0043] Step S002: Based on the differences between adjacent pressure data in the pressure data sequence of different acquisition cycles, divide the first stage. Based on the changing trend of all pressure data contained in the pressure data sequence of the acquisition cycle, adjust the carbon dioxide injection rate at the acquisition time in the acquisition cycle after the first stage, and update the first stage. Based on the positive and negative signs of the first-order difference sequence of the pressure data sequence in the acquisition cycle after the updated first stage, identify the start time of well shut-in.

[0044] After CO2 is injected into the test well, the crude oil near the well gradually becomes saturated. The pressure data at the inlet gradually increases and then the first peak appears. As CO2 is continuously injected, the dissolution efficiency of carbon dioxide gradually decreases, and the free carbon dioxide begins to dominate. The seepage resistance at the bottom layer increases. When it reaches a certain level, the pressure data at the inlet gradually increases again and then tends to stabilize, with a second peak appearing. The moment corresponding to the second peak is the moment when well shut-off begins.

[0045] The CO2 injection process is divided into three stages: the first stage, the second stage, and the third stage. In the first stage, the CO2 is injected at the full rate of the preset injection rate. In the second stage, the CO2 injection rate is adjusted. In the third stage, the CO2 injection is stopped.

[0046] Starting from the first acquisition cycle, each acquisition cycle is analyzed sequentially. The first-order difference sequence of the pressure data sequence of the acquisition cycle is calculated. When the first-order difference sequence contains both positive and negative numbers, the acquisition cycle is recorded as the stage transition acquisition cycle.

[0047] The same method can be used to determine whether the collection period of all collected pressure data is a phase transition collection period.

[0048] Based on the order of data collection, the first phase of the data collection cycle is identified, and the time period between the start of CO2 injection and the last data collection moment of the first phase of the data collection cycle is recorded as the first phase.

[0049] It is understandable that the first-order difference sequence of the pressure data sequence during the first phase of the conversion acquisition cycle contains both positive and negative numbers, indicating that the first peak occurred during the first phase of the conversion acquisition cycle. In the first phase, carbon dioxide enters the rock pores, and the pressure data at the inlet gradually decreases and reaches stability.

[0050] In the second stage, the carbon dioxide dissolution efficiency begins to decrease, and the carbon dioxide injection pressure also decreases. The two restrict each other. In order to avoid an imbalance between the carbon dioxide injection pressure and the carbon dioxide dissolution efficiency at the second-stage injection rate, it is necessary to accurately determine the time to stop injecting CO2.

[0051] Any acquisition period after the first stage is designated as the target acquisition period. A linear regression algorithm is used to linearly fit all pressure data contained in the pressure data sequence of the target acquisition period to obtain the fitting slope. The normalized value of the absolute value of the fitting slope is calculated and summed with the number 1. The product of this sum and the carbon dioxide injection rate at the last acquisition moment of the target acquisition period is designated as the first product of the target acquisition period. 75% of the preset carbon dioxide injection rate is designated as the second product of the target acquisition period. The minimum value between the first product and the second product of the target acquisition period is designated as the adjusted carbon dioxide injection rate of the target acquisition period. The carbon dioxide injection rate at the next adjacent acquisition moment after the target acquisition period is set as the adjusted carbon dioxide injection rate of the target acquisition period.

[0052] In this embodiment, the preset carbon dioxide injection rate is set to 120-150 t / d. In this embodiment, the sigmoid function is used to calculate the normalized value, and the least squares method is used for linear fitting. The sigmoid function and linear fitting are well-known techniques and will not be elaborated further here. As other implementation methods, the implementer can use other methods from the prior art, such as the tanh function, to calculate the normalized value.

[0053] Understandably, when the fitting slope is less than 0, the carbon dioxide injection rate at this time will cause an imbalance between the carbon dioxide injection pressure and the carbon dioxide dissolution efficiency, resulting in a decrease in the carbon dioxide injection pressure and potentially prolonging the optimal well-clogging time. Therefore, the carbon dioxide injection rate at the acquisition time is corrected. When the fitting slope is equal to 0, reducing the carbon dioxide injection rate to 75% of the original value will not cause an imbalance between the carbon dioxide injection pressure and the carbon dioxide dissolution efficiency.

[0054] When the carbon dioxide injection rate at the acquisition time differs from the preset carbon dioxide injection rate, the average of the fitted slopes less than 0 among all acquisition cycles from the first stage to the target acquisition cycle is recorded as the standard slope. When the fitted slope corresponding to the target acquisition cycle is greater than the standard slope, the time period from the start of CO2 injection to the last acquisition time of the target acquisition cycle is recorded as the first stage, thus updating the division of the first stage.

[0055] After updating the division of the first stage, any acquisition period after the updated first stage is designated as the acquisition period to be processed. When the first-order difference sequence of the pressure data sequence in the acquisition period to be processed contains both positive and negative numbers, the acquisition period to be processed is designated as the conversion period. For the first conversion period after the updated first stage, the acquisition time corresponding to the first pressure data among the two pressure data corresponding to the first negative number in the first-order difference sequence of the pressure data sequence in the conversion period is designated as the well-closing start time.

[0056] Understandably, the time period from the last acquisition moment of the updated first stage to the start of the well suffocation is the second stage, and the time period from the start of the well suffocation to the end of the well suffocation in the test well is the third stage. The standard slope represents the degree of pressure decrease generated by CO2 injection in the second stage. When the fitted slope corresponding to the target acquisition period is greater than the standard slope, the division of the first stage is updated. However, when the fitted slope corresponding to the target acquisition period is less than or equal to the standard slope, the pressure generated by CO2 injection and the CO2 dissolution efficiency are out of balance in the second stage. Therefore, the CO2 injection rate is not adjusted at this time.

[0057] At this point, the start time of well sealing is obtained.

[0058] Step S003: Start well shunting from the beginning of the shunting process, collect wellhead casing pressure at different collection times during different collection cycles of the test well, establish a wellhead casing pressure sequence for the collection cycle, obtain a wellhead casing pressure prediction sequence based on the wellhead casing pressure sequence, determine the collection cycle to be confirmed based on the similarity between the wellhead casing pressure sequence and the wellhead casing pressure prediction sequence, identify the wellhead casing pressure sequence to be confirmed based on the similarity between two adjacent wellhead casing pressure sub-sequences divided from the wellhead casing pressure sequence of the collection cycle to be confirmed, and the curve fitting results of the sequence composed of different wellhead casing pressure sub-sequences, and determine the well shunting end time by combining the changing trends of all wellhead casing pressure sequences before the wellhead casing pressure sequence to be confirmed.

[0059] The well was sealed from the start of the sealing process, and the wellhead casing pressure was collected at different collection times.

[0060] Wellhead casing pressure refers to the static pressure within the casing annular space after the well is shut in. In this embodiment, the wellhead casing pressure collection time interval is set to 10 minutes, and one collection cycle is one day. In actual application, as other implementation methods, implementers can decide the value of the time interval and collection duration according to the actual situation. This application does not impose any special restrictions.

[0061] All wellhead casing pressures collected in the same acquisition cycle are arranged sequentially to obtain the wellhead casing pressure sequence for the same acquisition cycle.

[0062] During the well-sealing process, carbon dioxide ionization ends, and the pressure decay shifts from a mixing mechanism to a diffusion mechanism. This is the optimal moment to stop well-sealing. Determining the optimal well-sealing time based on this moment ensures that carbon dioxide reacts fully with crude oil while maintaining sufficient reservoir pressure.

[0063] When performing carbon dioxide energy storage well shut-in, the permeability and viscosity of the rocks in different test wells are different, which will lead to different carbon dioxide dissolution efficiencies. Therefore, the optimal shut-in time will vary for different test wells, and the appropriate shut-in time needs to be dynamically adjusted according to the wellhead casing pressure.

[0064] When the inflection point of the wellhead casing pressure-time curve has not yet appeared, carbon dioxide gradually diffuses, and multiple flow mechanisms are involved, resulting in a decaying trend in the wellhead casing pressure-time curve. When the inflection point of the wellhead casing pressure-time curve appears, the flow mechanism undergoes a fundamental change, and the diffusion mechanism of carbon dioxide becomes dominant.

[0065] Before the inflection point appears in the wellhead casing pressure-time curve, the diffusion of carbon dioxide in rocks with high porosity may cause sudden local fluctuations in wellhead casing pressure due to abrupt changes in the flow path or instability in percolation, affecting the identification of the inflection point. To avoid this influence, a predicted wellhead casing pressure sequence for the next adjacent acquisition cycle is obtained based on the wellhead casing pressure sequence of the acquisition cycle.

[0066] Specifically, in this embodiment, the ARMA autoregressive moving average model is used to predict the wellhead casing pressure sequence during the acquisition period to obtain the wellhead casing pressure prediction sequence. The use of the ARMA autoregressive moving average model to obtain the prediction sequence is a well-known technique and will not be described in detail here.

[0067] The wellhead casing pressure sequences of 500 adjacent acquisition cycles during the normal well stagnation process in history were extracted by those skilled in the art. The first quartile of the Pearson correlation coefficient of all adjacent acquisition cycles' wellhead casing pressure sequences was used as the similarity threshold.

[0068] The wellhead casing pressure sequences of 500 acquisition cycles with inflection points during the normal well stagnation process of the experimental well were extracted by those skilled in the art. For each acquisition cycle with an inflection point, the wellhead casing pressure sequence of the acquisition cycle with an inflection point was divided into a first preset number of wellhead casing pressure sub-sequences. The sequence formed by all wellhead casing pressure sequences after the wellhead casing pressure sequence with an inflection point was recorded as the standard sequence. Curve fitting was performed on the standard sequence to obtain the goodness of fit. The mean of the goodness of fit of all standard sequences corresponding to the 500 acquisition cycles with inflection points was recorded as the inflection point judgment threshold.

[0069] In this embodiment, the least squares method is used for curve fitting; calculating the Pearson correlation coefficient, calculating the first quartile, and using the least squares method for curve fitting are well-known techniques and will not be described in detail here.

[0070] The Pearson correlation coefficient between the wellhead casing pressure sequence of the acquisition period and the predicted wellhead casing pressure sequence of the next adjacent acquisition period is denoted as the adjacent period similarity of the acquisition period. When the adjacent period similarity of the acquisition period is less than the similarity threshold, it is determined that there may be an inflection point in the acquisition period, and the acquisition period is denoted as the acquisition period to be confirmed.

[0071] The wellhead casing pressure sequence of the acquisition period to be confirmed is divided into a first preset number of wellhead casing pressure sub-sequences. The Pearson correlation coefficient between two adjacent wellhead casing pressure sequences is calculated. The LOF anomaly detection algorithm is used to detect anomalies in the Pearson correlation coefficients of all adjacent wellhead casing pressure sequences to obtain the number of anomalies. When the number of anomalies is 0, there is no inflection point in the acquisition period to be confirmed. The acquisition period to be confirmed is determined to have a possible inflection point due to the influence of high porosity rocks on carbon dioxide diffusion, which affects the wellhead casing pressure sequence of the acquisition period to be confirmed. Local fluctuations occur in the column; when the number of outliers is not zero, the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last outlier is selected, and curve fitting is performed on the sequence composed of the selected wellhead casing pressure sequence and all subsequent wellhead casing pressure sequences to obtain the goodness of fit of the fitted curve. When the goodness of fit is greater than or equal to the inflection point judgment threshold, the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last outlier is determined to be the wellhead casing pressure sequence to be confirmed, and there is an inflection point in the wellhead casing pressure sequence to be confirmed.

[0072] In this embodiment, the first preset quantity is set to 24; the use of the LOF anomaly detection algorithm for anomaly detection is a well-known technique and will not be described in detail here.

[0073] The sequence consisting of all wellhead casing pressure sequences from the first wellhead casing pressure sequence after the start of well sealing to the wellhead casing pressure sequence to be confirmed is denoted as the inflection point confirmation sequence. The inflection point confirmation sequence is curve-fitted using a cubic polynomial function to obtain the inflection point confirmation curve. The acquisition time corresponding to the first zero derivative value in the derivative of the inflection point confirmation curve within the acquisition time period corresponding to the wellhead casing pressure sequence to be confirmed is denoted as the well sealing end time. The well sealing end time is the optimal time to stop well sealing.

[0074] It is understandable that the time interval between the start and end of the well suffocation is the optimal time for carbon dioxide energy storage well suffocation, dynamically determined based on the pressure data at the inlet end of the test well and the casing pressure at the wellhead.

[0075] This achieves dynamic optimization of the carbon dioxide energy storage well shut-in time.

[0076] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis, characterized in that, The method includes the following steps: Pressure data at the inlet of the experimental well were collected at different times during different collection cycles during CO2 injection, and pressure data sequences for each collection cycle were constructed. Based on the differences between adjacent pressure data in the pressure data sequences of different acquisition cycles, the first stage is divided. Based on the changing trends of all pressure data contained in the pressure data sequence of the acquisition cycle, the carbon dioxide injection rate at the acquisition time in the acquisition cycle after the first stage is adjusted and the first stage is updated. Based on the positive and negative signs of the first-order difference sequence of the pressure data sequence in the acquisition cycle after the updated first stage, the start time of well shut-in is identified. The well is sealed starting from the beginning of the sealing process. Wellhead casing pressure is collected at different times during different collection cycles to establish a wellhead casing pressure sequence for each collection cycle. Based on this sequence, a predicted wellhead casing pressure sequence is obtained. The collection cycle to be confirmed is determined based on the similarity between the current and predicted wellhead casing pressure sequences. The sequence to be confirmed is identified based on the similarity between adjacent wellhead casing pressure sub-sequences derived from the wellhead casing pressure sequence of the to-be-confirmed collection cycle, as well as the curve fitting results of sequences composed of different wellhead casing pressure sequences. Finally, the end time of the sealing process is determined by combining the changing trends of all wellhead casing pressure sequences preceding the to-be-confirmed sequence.

2. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 1, characterized in that, The specific method for dividing the first stage is as follows: When the first-order difference sequence of the pressure data sequence in the acquisition period contains both positive and negative numbers, the acquisition period is recorded as the stage transition acquisition period. The time period between the start of CO2 injection and the last acquisition time of the first phase acquisition cycle is denoted as the first phase.

3. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 1, characterized in that, The specific methods for adjusting the carbon dioxide injection rate at each acquisition time during the acquisition cycle following the first stage are as follows: Any acquisition cycle after the first stage is designated as the target acquisition cycle. Linear fitting is performed on all pressure data contained in the pressure data sequence of the target acquisition cycle to obtain the fitting slope. The normalized value of the absolute value of the fitting slope is calculated and the sum of the number 1. The product of the sum and the carbon dioxide injection rate at the last acquisition moment of the target acquisition cycle is designated as the first product of the target acquisition cycle. 75% of the preset carbon dioxide injection rate is recorded as the second product of the target acquisition period; the minimum value between the first and second products of the target acquisition period is recorded as the adjusted carbon dioxide injection rate of the target acquisition period; and the carbon dioxide injection rate at the next adjacent acquisition time after the target acquisition period is set as the adjusted carbon dioxide injection rate of the target acquisition period.

4. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 3, characterized in that, The specific steps involved in updating the first stage are as follows: When the carbon dioxide injection rate at the time of acquisition differs from the preset carbon dioxide injection rate, the standard slope is calculated. When the fitting slope corresponding to the target acquisition period is greater than the standard slope, the time period from the start of CO2 injection to the last acquisition moment of the target acquisition period will be used as the first stage of the update.

5. The method for dynamic optimization of carbon dioxide energy storage well shut-in time based on pressure analysis according to claim 4, characterized in that, The specific method for calculating the standard slope is as follows: The average of the fitted slopes that are less than 0 among all the fitted slopes corresponding to all acquisition cycles from the first stage to the target acquisition cycle is recorded as the standard slope.

6. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 1, characterized in that, The method for determining the start time of well sealing is as follows: Any acquisition period after the updated first stage is designated as the acquisition period to be processed. When the first-order difference sequence of the pressure data sequence of the acquisition period to be processed contains both positive and negative numbers, the acquisition period to be processed is designated as the conversion period. The acquisition time corresponding to the first pressure data of the two pressure data corresponding to the first negative number in the first-order difference sequence of the pressure data sequence of the first conversion period after the updated first stage is designated as the well start time.

7. The method for dynamic optimization of carbon dioxide energy storage well shut-in time based on pressure analysis according to claim 1, characterized in that, The specific method for determining the collection period to be confirmed is as follows: When the correlation coefficient between the wellhead casing pressure sequence of the acquisition period and the wellhead casing pressure prediction sequence of the next adjacent acquisition period is less than the preset similarity threshold, the acquisition period is recorded as an acquisition period to be confirmed.

8. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 1, characterized in that, The specific identification method for the wellhead casing pressure sequence to be confirmed is as follows: The wellhead casing pressure sequence of the collection period to be confirmed is divided into a first preset number of wellhead casing pressure sub-sequences. Anomaly detection is performed on the correlation coefficient of two adjacent wellhead casing pressure sequences to obtain the number of anomaly points. When the number of outliers is not zero, select the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last outlier and all subsequent wellhead casing pressure sequences, and determine the wellhead casing pressure sequence to be confirmed based on the selected wellhead casing pressure sequence.

9. The method for dynamically optimizing the simmering time of carbon dioxide energy storage wells based on pressure analysis according to claim 8, characterized in that, The specific method for determining the wellhead casing pressure sequence to be confirmed based on the selected wellhead casing pressure sequence includes: Curve fitting is performed on the selected wellhead casing pressure sequence and the sequence composed of all subsequent wellhead casing pressure sequences to obtain the goodness of fit of the fitted curve. When the goodness of fit is greater than or equal to the preset inflection point judgment threshold, the next wellhead casing pressure sequence in the adjacent wellhead casing pressure sequence corresponding to the last anomaly point is determined as the wellhead casing pressure sequence to be confirmed.

10. The method for dynamic optimization of carbon dioxide energy storage well shut-in time based on pressure analysis according to claim 1, characterized in that, The method for obtaining the end time of well sealing is as follows: Curve fitting is performed on the sequence consisting of all wellhead casing pressure sequences from the first wellhead casing pressure sequence after the start of well sumption to the wellhead casing pressure sequence to be confirmed, and the inflection point confirmation curve is obtained. The acquisition time corresponding to the first zero derivative value in the derivative of the inflection point confirmation curve within the acquisition time period corresponding to the wellhead casing pressure sequence to be confirmed is recorded as the end time of well sumption.

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