Supercritical carbon dioxide fluid component anomaly detection method and system and medium

Abstract

The invention provides a supercritical carbon dioxide fluid component anomaly detection method and system and a medium. The method comprises the following steps: measuring the actual sound velocity of a fluid containing impurity SCO2; the theoretical sound velocity of pure SCO2 is calculated according to a sound velocity-temperature pressure model of pure SCO2 by measuring the temperature and pressure of actual fluid; and calculating the relative deviation between the actual sound velocity of the SCO2 fluid and the theoretical sound velocity of pure SCO2 under the working condition, and if the relative deviation exceeds a set threshold value, judging that the fluid components are abnormal. In view of a linear relationship between the sound velocity of the mixture and the volume fraction of impurities in the mixture, an impurity content calculation algorithm is constructed on the basis of a linear superposition principle, and the algorithm is built in a detection system, so that the impurity content is accurately measured and calculated. For the characteristic that the underground temperature and pressure change range is large, the method breaks through the limitation of the temperature, the pressure and the fluid state, and precise calculation of the theoretical sound velocity of SCO2 and judgment of the impurity content are achieved.

Description

Technical Field

[0001] This invention relates to the field of fluid detection technology, specifically providing a method, system, and medium for detecting abnormal composition of supercritical carbon dioxide fluid. Background Technology

[0002] In high-temperature, high-pressure downhole oil displacement processes, the use of supercritical carbon dioxide (SCO2) as the displacement medium may introduce other gases (such as nitrogen (N2), oxygen (O2), methane (CH4), hydrogen sulfide (H2S), and oxygen (O2)) as impurities, significantly affecting the fluid's acoustic velocity characteristics. However, existing acoustic velocity-based fluid composition anomaly detection technologies primarily target pure gases and fail to effectively handle mixed gases containing impurities, leading to insufficient accuracy in measurements. Furthermore, these technologies are typically validated under standard experimental conditions, lacking adaptability to extreme high-temperature, high-pressure environments, thus limiting their application. Insufficient research on the characteristics of supercritical fluids and their impurities in existing methods limits technology transfer. The acoustic velocity of SCO2 varies complexly under different impurity concentrations, and existing technologies lack effective mathematical models and algorithms, resulting in difficulties in data interpretation. Finally, traditional detection methods have long response times, failing to meet the real-time monitoring requirements of dynamically changing environments. Therefore, to improve the detection accuracy and reliability of downhole high-temperature, high-pressure supercritical carbon dioxide fluids containing impurities, it is urgent to develop more targeted and adaptable detection technologies to achieve effective monitoring of the SCO2 fluid state and composition. Summary of the Invention

[0003] To achieve the above objectives, in a first aspect, the present invention provides a method for detecting abnormal composition in supercritical carbon dioxide fluid, comprising the following steps: under the condition that the fluid composition is determined to be abnormal, and given that a known impurity is present under the current operating conditions, the downstream propagation time T is obtained through a high-precision time measurement module. AB Backflow propagation time T BA Calculate the actual sound velocity of the fluid containing SCO2 impurities. C : ; The theoretical sound velocity of pure SCO2 was calculated by measuring the temperature and pressure under actual fluid conditions and based on the sound velocity-temperature-pressure model of pure SCO2. ; The relative deviation between the actual sound velocity of the impurity-containing fluid and the theoretical sound velocity of pure SCO2 under the same operating condition is obtained. If the relative deviation exceeds a set threshold, it is determined that the fluid composition is abnormal.

[0004] In one technical solution of the above-mentioned method for detecting abnormal composition of supercritical carbon dioxide fluid, a through-beam inclined-flow ultrasonic flow meter is used to transmit and receive ultrasonic signals according to the downhole environment. The ultrasonic flow meter includes two ultrasonic transducers arranged opposite to each other, which are used to transmit and receive ultrasonic signals respectively.

[0005] In one technical solution of the above-mentioned method for detecting abnormal composition of supercritical carbon dioxide fluid, the relative deviation The calculation formula is: ; Where C is the actual sound velocity of the fluid containing impurities, C0 is the theoretical sound velocity of pure impurities under the temperature and pressure conditions, and δ is the preset threshold.

[0006] In one technical solution of the above-mentioned method for detecting anomalies in supercritical carbon dioxide fluid composition, the sound velocity-temperature-pressure model of pure SCO2 is trained and constructed based on the sound velocity database of supercritical pure SCO2; the sound velocity database contains sound velocity sample data of different temperature and pressure combinations under supercritical conditions, and the model directly outputs the sound velocity of pure SCO2 with only temperature and pressure as input parameters.

[0007] In one technical solution of the above-mentioned method for detecting abnormal composition of supercritical carbon dioxide fluid, the method further includes: for fluids with abnormal composition, calculating the impurity volume content using a linear superposition method based on the linear correlation between the impurity volume content and the sound velocity of the mixture; if the relative deviation does not exceed a set threshold, the fluid is a pure fluid.

[0008] In one technical solution of the above-mentioned method for detecting abnormal composition of supercritical carbon dioxide fluid, the impurity volume content is linearly correlated with the sound velocity of the mixture as follows: ; in, Let be the actual sound velocity of the mixture at a predetermined pressure P and temperature T. Let be the speed of sound of pure carbon dioxide at P and T. Pure impurities x Speed ​​of sound at P and T x Where T is the volumetric impurity content, P is the temperature, and P is the pressure. During online detection, the sound velocity of the mixture is measured in real time. The speed of sound of pure carbon dioxide is obtained using the sound speed-temperature-pressure model, given temperature T and pressure P. Speed ​​of sound with pure impurities The volumetric impurity content was then calculated by utilizing the linear correlation between the volumetric impurity content and the sound velocity of the mixture. .

[0009] Secondly, the present invention provides a supercritical carbon dioxide fluid composition anomaly detection system, comprising: an actual sound velocity measurement module, used to measure the actual sound velocity of the fluid containing impurities under operating conditions; The theoretical sound velocity acquisition module is used to calculate the theoretical sound velocity of pure SCO2 based on the sound velocity-temperature-pressure model of pure SCO2 by measuring the temperature and pressure under actual fluid conditions. The calculation module is used to obtain the relative deviation between the actual sound velocity of the impurity-containing fluid and the theoretical sound velocity of pure SCO2 under the operating condition. If the relative deviation exceeds a set threshold, it is determined that there is an abnormality in the fluid composition.

[0010] Thirdly, the present invention provides a computer-readable storage medium storing a plurality of program codes adapted to be loaded and run by a processor to perform the supercritical carbon dioxide fluid composition anomaly detection method.

[0011] The beneficial effects of this invention are as follows: This invention monitors supercritical CO2 under high temperature and high pressure, and the composition and phase of the fluid are different; the monitoring device of this invention is placed in a high temperature and high pressure environment downhole, and the monitoring device, sensor and measuring circuit are designed to withstand high temperature and high pressure.

[0012] By employing high-precision temperature and pressure measurement technology and a dynamic sound velocity correction model, the theoretical sound velocity C0 of SCO2 can be calculated, adapting to the high temperature and high pressure characteristics of SCO2 and ensuring accurate sound velocity measurement even under drastic temperature and pressure changes, thereby achieving higher detection accuracy.

[0013] High-precision time-of-flight measurement chips are used to measure the high-precision ultrasonic flight time, and the actual sound velocity C under high temperature and high pressure conditions is calculated with high precision, thereby improving the reliability and accuracy of the data.

[0014] This invention utilizes remote sound velocity comparison technology to achieve online, automated fluid state monitoring, eliminating the need for frequent calibration and reducing equipment maintenance costs. Simultaneously, the highly stable communication and anti-interference measures incorporated into the design ensure the system's long-term stability under complex operating conditions.

[0015] This invention constructs a sound velocity model containing SCO2 impurities and compares the measured actual sound velocity with the theoretical sound velocity in real time. This enables sensitive detection of fluctuations in the composition of SCO2 fluid, making this invention more advantageous in monitoring changes in trace impurities in supercritical CO2. Attached Figure Description

[0016] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein: Figure 1 This is a schematic flowchart of a method for detecting abnormal composition of supercritical carbon dioxide fluid according to an embodiment of the present invention; Figure 2 This is a pressure measurement circuit diagram according to an embodiment of the present invention; Figure 3 This is a flowchart of a pressure measurement process according to an embodiment of the present invention; Figure 4 This is a schematic diagram of MS1030 according to an embodiment of the present invention; Figure 5 This is a flowchart of the sound velocity measurement calculation according to an embodiment of the present invention; Figure 6 This is a flowchart of a temperature measurement process according to an embodiment of the present invention; Figure 7 This is a three-dimensional data graph of sound velocity-temperature-pressure according to an embodiment of the present invention; Figure 8 This is a schematic flowchart of a method for detecting abnormal composition of supercritical carbon dioxide fluid according to an embodiment of the present invention.

[0017] Figure 9 This is a schematic diagram illustrating the linear change in sound velocity with varying impurity volume content for different types of impurities according to an embodiment of the present invention. Detailed Implementation

[0018] Some embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] Example 1 Under given temperature and pressure conditions, the sound velocity of a mixture composed of supercritical carbon dioxide and a single impurity gas changes approximately linearly with the volumetric impurity content. In other words, when the temperature, pressure, and impurity type are fixed, the sound velocity of the mixture is a monotonic function of the impurity volumetric content, used to characterize changes in the impurity concentration. The following example illustrates this under the condition that the fluid composition is determined to be abnormal, and that the current operating conditions contain a known impurity.

[0020] like Figure 1-9 As shown, the present invention provides a method for detecting abnormal composition of supercritical carbon dioxide fluid, comprising the following steps: Step S1: By measuring the temperature and pressure under actual fluid conditions, the theoretical sound velocity of pure SCO2 is calculated based on the sound velocity-temperature-pressure model of pure SCO2. .

[0021] In this embodiment, as Figure 2-3As shown, in order to obtain the actual sound velocity, a high-precision high-temperature strain gauge absolute pressure sensor (0.1%FS) from KELLER was used, and the pressure P was measured through a model conditioning circuit and an A / D conversion channel.

[0022] The theoretical velocity of pure CO2 was calculated by measuring the temperature T and pressure P of the actual fluid and using a temperature-pressure model. C0 = f(P, T).

[0023] Step S2: Obtain the downstream propagation time T using a high-precision time measurement module. AB Backflow propagation time T BA Calculate the actual sound velocity of the fluid containing SCO2 impurities. C : .

[0024] In this embodiment, a through-beam oblique-inflow ultrasonic flow meter is used according to the downhole environment. This flow meter employs two ultrasonic transducers, which function as a transmitter and a receiver respectively, and are installed on both sides of the pipe to transmit and receive ultrasonic signals. Ultrasonic transmission in a liquid is affected by the flow velocity. The propagation speed of ultrasound is faster with the current than against the current. The ultrasonic transmission time T between the two transducers is measured. AB Reversal time T BA Then, the actual sound speed of the fluid can be obtained through calculation.

[0025] The speed of sound downstream is The speed of sound against the current is Calculate the propagation time with and against the current: (1) (2) In the formula: ρ is the fluid velocity, m / s; c is the ultrasonic wave propagation speed, m / s; D is the inner diameter of the pipe, m; L is the length of the sound channel, m.

[0026] The measured fluid velocity can then be determined. The velocity of sound in a fluid, c, and T BA and T AB Both are related. The relationship between the speed of sound and the propagation time with and against the current can be obtained by transforming formulas (1) and (2): (3).

[0027] The propagation time T of ultrasonic waves in the fluid downstream was measured using a high-precision time measurement module. AB and the time of backflow propagation T BA The actual fluid sound velocity is calculated using equation (3). .

[0028] like Figure 4 As shown, the hardware circuit uses the MS1030 high-precision time measurement module to perform high-precision measurement of downstream and upstream propagation time, with a measurement accuracy of 15 PS. Figure 5 The diagram shows the flowchart for calculating the speed of sound.

[0029] Furthermore, a high-precision PT1000 resistance temperature detector (RTD) is used to measure the fluid temperature, converting the fluid temperature T into resistance R. t The MS1030 utilizes a built-in high-precision resistance measurement circuit to achieve the reference resistance R0 and the resistance R through capacitor charging and discharging. t Measurement, such as Figure 6 As shown, the temperature was calculated: ; R0—Resistance at 0℃, 1000 ohms, A=3.90802×10 -3 1 / ℃, B=5.80195×10 -7 1 / ℃, C=-4.27350×10 -12 1 / ℃4.

[0030] The velocity of sound in pure SCO2 is only affected by temperature and pressure. The theoretical velocity of sound is obtained by establishing a sound velocity-temperature-pressure model through measurements of the actual fluid's temperature (T) and pressure (P). Sound velocity data for SCO2 at 9-40 MPa and 40-150 °C were obtained from the NIST database; the three-dimensional data is shown in the figure below. Figure 7 As shown, a sound speed-temperature-pressure model is established:

[0031] in, , , , , , , .

[0032] This data is then embedded into the software, and the theoretical velocity of pure SCO2 is calculated based on the measured temperature and pressure.

[0033] Step S3: Obtain the relative deviation between the actual sound velocity of the SCO2 fluid containing impurities and the theoretical sound velocity of pure SCO2 under the operating condition. If the relative deviation exceeds a set threshold, it is determined that there is an abnormality in the fluid composition. Based on the linear correlation between the volume content of impurities and the sound velocity of the mixture, the volume content of impurities is calculated using the linear superposition method. If the relative deviation does not exceed the set threshold, the fluid is a pure fluid.

[0034] In this embodiment, the theoretical sound velocity of pure SCO2 under the temperature and pressure conditions is compared with the actual fluid sound velocity C. Since impurities of different concentrations (such as nitrogen) significantly alter the sound velocity of SCO2, the relative deviation between the actual and theoretical sound velocities is: : .

[0035] when When the value exceeds the threshold δ, it is determined to be an abnormality of fluid impurities. This method detects fluid anomalies by changing the velocity of sound, solving the problem of real-time monitoring of SCO2 fluid composition in complex downhole environments. It has the advantages of being fast, accurate, and highly adaptable, providing a reliable technical means for real-time detection of fluid composition under high temperature and high pressure conditions.

[0036] In one embodiment, in a mixed system consisting of supercritical carbon dioxide and a single impurity gas, under predetermined temperature T and pressure P conditions, such as Figure 9 As shown, the sound velocity c in the mixture has an approximately linear functional relationship with the impurity volume content x.

[0037] Specifically, this relationship can be described in the following form: ; in, The speed of sound for pure carbon dioxide. For the speed of sound in a mixture, The velocity of sound is the velocity of pure impurities.

[0038] Therefore, the formula for calculating the volumetric impurity content x is: ; By obtaining the sound velocities of pure CO2 and pure impurities using the sound velocity-temperature-pressure model, the volumetric impurity content can be obtained.

[0039] Compared with traditional theoretical sound velocity calculation methods, this method breaks through the limitations of temperature, pressure and fluid state, and can achieve accurate calculation of SCO2 theoretical sound velocity, as well as determine the impurity content.

[0040] This section enables precise measurement of high pressure and, in conjunction with the sound velocity-temperature-pressure model, allows for theoretical sound velocity calculation. Given the large and varied downhole pressure, this method is more suitable for SCO2 fluid compared to traditional sound velocity calculation methods.

[0041] Example 2 This invention discloses a supercritical carbon dioxide fluid composition anomaly detection system, comprising: The actual sound velocity measurement module is used to measure the actual sound velocity of fluid containing SCO2 impurities under operating conditions. The theoretical sound velocity acquisition module is used to calculate the theoretical sound velocity of pure SCO2 based on the sound velocity-temperature-pressure model of pure SCO2 by measuring the temperature and pressure under actual fluid conditions. The calculation module is used to obtain the relative deviation between the actual sound velocity of the SCO2 fluid containing impurities and the theoretical sound velocity of pure SCO2 under the same operating condition. If the relative deviation exceeds a set threshold, it is determined that there is an abnormality in the fluid composition.

[0042] Furthermore, it should be understood that since the various modules are only provided to illustrate the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the processor's software, hardware, or a combination of software and hardware. Therefore, the number of modules shown in the figures is merely illustrative.

[0043] Example 3 The present invention also provides a computer-readable storage medium. In one embodiment of the computer-readable storage medium according to the present invention, the computer-readable storage medium can be configured to store a program for performing the supercritical carbon dioxide fluid composition anomaly detection method of the above-described method embodiments. This program can be loaded and run by a processor to implement the above-described supercritical carbon dioxide fluid composition anomaly detection method. For ease of explanation, only the parts related to the embodiments of the present invention are shown; for specific technical details not disclosed, please refer to the method section of the embodiments of the present invention. The computer-readable storage medium can be a storage device comprising various electronic devices. Optionally, in the embodiments of the present invention, the computer-readable storage medium is a non-transitory computer-readable storage medium.

[0044] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the original technical features, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for detecting abnormal composition in supercritical carbon dioxide fluid, characterized in that, Includes the following steps: Given that the fluid composition is determined to be abnormal, and that a known impurity is present in the current operating conditions, the downstream propagation time T is obtained using a high-precision time measurement module. AB Backflow propagation time T BA Calculate the actual sound velocity of the fluid containing SCO2 impurities. C : ； The theoretical sound velocity of pure SCO2 was calculated by measuring the temperature T and pressure P under actual fluid conditions, based on the sound velocity-temperature-pressure model of pure SCO2. ; The relative deviation between the actual sound velocity of the impurity-containing fluid and the theoretical sound velocity of pure SCO2 under the same operating condition is obtained. If the relative deviation exceeds a set threshold, it is determined that the fluid composition is abnormal.

2. The method according to claim 1, characterized in that, Based on the downhole environment, a through-beam oblique-inflow ultrasonic flow meter is used to transmit and receive ultrasonic signals. The ultrasonic flow meter includes two ultrasonic transducers arranged opposite each other, which are used to transmit and receive ultrasonic signals respectively.

3. The method for detecting abnormal composition of supercritical carbon dioxide fluid according to claim 1, characterized in that, The relative deviation The calculation formula is: ； Where C is the actual sound velocity of the fluid containing impurities, C0 is the theoretical sound velocity of pure impurities under the temperature and pressure conditions, and δ is the preset threshold.

4. The method according to claim 1, characterized in that, The sound velocity-temperature-pressure model of pure SCO2 is constructed based on the sound velocity database of supercritical pure SCO2. The sound velocity database contains sample data of sound velocities under different temperature and pressure combinations in the supercritical state. The sound velocity-temperature-pressure model takes only temperature and pressure as input parameters and directly outputs the sound velocity of pure SCO2.

5. The method according to claim 1, characterized in that, The method further includes: for fluids with abnormal composition, calculating the impurity volume content using a linear superposition method based on the linear correlation between the impurity volume content and the sound velocity of the mixture; If the relative deviation does not exceed the set threshold, the fluid is a pure fluid.

6. The method according to claim 5, characterized in that, The volumetric impurity content is linearly correlated with the sound velocity of the mixture as follows: ； in, Let be the actual sound velocity of the mixture at a predetermined pressure P and temperature T. Let be the speed of sound of pure carbon dioxide at P and T. Pure impurities x Speed ​​of sound at P and T x This represents the volumetric impurity content. During online detection, the sound velocity of the mixture is measured in real time. The speed of sound of pure carbon dioxide is obtained using the sound speed-temperature-pressure model, given temperature T and pressure P. Speed ​​of sound with pure impurities And by utilizing the linear correlation between the volumetric impurity content and the sound velocity of the mixture, the volumetric impurity content x can be calculated in reverse: 。 7. A supercritical carbon dioxide fluid composition anomaly detection system, characterized in that, include: The actual sound velocity measurement module is used to measure the actual sound velocity of fluids containing impurities under operating conditions. The theoretical sound velocity acquisition module is used to calculate the theoretical sound velocity of pure SCO2 based on the sound velocity-temperature-pressure model of pure SCO2 by measuring the temperature and pressure under actual fluid conditions. The calculation module is used to obtain the relative deviation between the actual sound velocity of the impurity-containing fluid and the theoretical sound velocity of pure SCO2 under the operating condition. If the relative deviation exceeds a set threshold, it is determined that there is an abnormality in the fluid composition.

8. A computer-readable storage medium storing a plurality of program codes, characterized in that, The program code is adapted to be loaded and run by a processor to perform the supercritical carbon dioxide fluid composition anomaly detection method of any one of claims 1 to 6.

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