System and method for rapid analysis of c1-c8 gas samples by gas chromatography-mass spectrometry

Abstract

The application relates to the technical field of petroleum logging gas analysis, in particular to a system and method for rapidly analyzing C1-C8 gas samples by gas chromatography-mass spectrometry. First, a system for rapidly analyzing C1-C8 gas samples by gas chromatography-mass spectrometry is disclosed, a first valve is connected with a sample inlet pipe, the first valve, a first quantitative ring, a second quantitative ring and a second valve are connected, and a sampling gas path is formed; the first quantitative ring, the first valve, a low-carbon pre-column, a low-carbon separation column and a chromatographic detection module are connected, and a low-carbon detection gas path is formed; the second quantitative ring, the second valve, a high-carbon pre-column and a gas resistance are connected, and a high-carbon separation gas path is formed; the second valve, the high-carbon pre-column and a mass spectrometric detection module are connected, and a high-carbon detection gas path is formed; and the high-carbon separation gas path is switched to form the high-carbon detection gas path through the second valve. Secondly, a method for rapidly analyzing C1-C8 gas samples by gas chromatography-mass spectrometry by using the system is disclosed. The analysis period of the C1-C8 gas samples can be shortened to 45 seconds or less, and the system has the effects of short analysis time, good separation effect, accurate component identification and accurate quantification.

Description

Technical Field

[0001] This application relates to the technical field of gas analysis in oil well logging, and in particular to a system and method for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS). Background Technology

[0002] In oil drilling sites, to promptly detect oil and gas shows, degassing devices are typically used to separate hydrocarbons carrying formation oil and gas information from the drilling fluid. These hydrocarbons are then analyzed using analytical instruments—a process known as online logging monitoring. Previously, online chromatographs used in the oil logging industry only separated and quantified methane, ethane, propane, n-butane, isobutane, n-pentane, and isopentane (C1-C5) gases. As exploration and development have progressed, understanding the spatial distribution of remaining reservoirs and the degree of water washing and flooding has become increasingly challenging. To precisely interpret oil, gas, and water layers, accurately identify oil-water and gas-water interfaces, and quickly assess the degree of water washing and flooding in reservoirs, oil exploration sites require the identification and analysis of more components, including methane and octane (C1-C8). This has led to the development of online logging analysis systems for high-carbon components, which utilize chromatographic analysis for widespread application.

[0003] Currently, the online chromatographs commonly used in the oil logging industry for analyzing C1-C8 components typically have an analysis cycle of over 120 seconds. To address this drawback of long analysis time, Chinese Patent Publication No. CN 110887900 A discloses a multi-component dual-flow analysis device and method for logging chromatographs. By modifying the gas path flow of the chromatograph and rapidly separating hydrocarbon components, it simultaneously detects C1-C5 and C6-C8 components in two separate paths, reducing the multi-component analysis cycle time to 60 seconds.

[0004] In response to the aforementioned technologies, more reliable and efficient methods can be sought to further shorten the analysis time of C1-C8 multi-component gas samples, achieving the goal of rapid analysis and better meeting the needs of rapid drilling and thin-layer oil and gas identification. Summary of the Invention

[0005] To address the issue of long analysis times in current mass spectrometry analysis of C1-C8 components, the primary objective of this application is to provide a system for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry. Through gas path design, this system can simultaneously analyze C6-C8 components using mass spectrometry while performing chromatographic analysis of C1-C5 components, reducing the overall detection cycle to less than 45 seconds and achieving accurate quantification of C1-C8 gas samples.

[0006] The second objective of this application is to provide a rapid gas chromatography-mass spectrometry (GC-MS) method for analyzing C1-C8 gas samples, which is simple to operate, accurate in quantification, and rapid in detection.

[0007] To achieve the first objective of this application, this application provides a system for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS), employing the following technical solution:

[0008] A system for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS), characterized in that the system comprises a first valve, a first quantitative loop, a low-carbon pre-column, a low-carbon separation column, a chromatographic detection module, a second valve, a second quantitative loop, a high-carbon pre-column, a gas resistance system, and a mass spectrometry detection module.

[0009] The first valve is connected to the sample inlet tube, and the first valve, the first metering loop, the second metering loop, and the second valve are connected to form a sampling gas path;

[0010] The first quantitative loop, the first valve, the low-carbon pre-column, the low-carbon separation column, and the chromatographic detection module are connected to form a low-carbon detection gas path;

[0011] The second metering ring, the second valve, the high-carbon pre-column, and the gas resistance connection form a high-carbon separation gas path;

[0012] The second valve, the high-carbon pre-column, and the mass spectrometry detection module are connected through the high-carbon detection gas path;

[0013] The high-carbon separation gas path is formed by switching the second valve to form the high-carbon detection gas path.

[0014] This application, through the above-mentioned gas path setup, separates and detects C1-C5 low-carbon components by gas chromatography and C6-C8 high-carbon components by gas mass spectrometry. The two parts are tested simultaneously, which can shorten the detection cycle of C1-C8 gas samples to less than 60 seconds. At the same time, the gas mass spectrometer has high sensitivity, and the quantitative detection results of C6-C8 high-carbon components are more accurate.

[0015] The implementation can include any or all of the following features.

[0016] Furthermore, it also includes a backflush air path, in which the low-carbon pre-column and the first valve are connected to form the backflush air path; the low-carbon detection air path is formed by switching the first valve to form the backflush air path.

[0017] The backflush gas path is used to remove some samples containing high-carbon components that are temporarily retained in the low-carbon pre-column, in order to eliminate the possibility of interference from high-carbon components in the chromatographic detection module of the low-carbon detection gas path.

[0018] Furthermore, when the first valve and the second valve are in the first state, the system forms the sampling gas path;

[0019] When the first valve is in the first state, the system forms the backflush air path; when the first valve is switched to the second state, the system forms the low-carbon detection air path.

[0020] When the second valve is in the first state, the system forms the high-carbon detection gas path; when the second valve is switched to the second state, the system forms the high-carbon separation gas path.

[0021] Furthermore, the first valve has ports 1 to 10, and the second valve has ports 1 to 10;

[0022] When the first valve and the second valve are in the first state, port 1 of the first valve is connected to the sample inlet tube, and the sample passes through port 2 of the first valve, the first metering loop, port 9 of the first valve, port 10 of the first valve, port 1 of the second valve, port 2 of the second valve, the second metering loop, port 9 of the second valve, and port 10 of the second valve in sequence before being connected to the sample outlet tube to form the sampling gas path.

[0023] When the first valve is in the first state, port 8 of the first valve is connected to the second carrier gas, and the second carrier gas passes through port 7 of the first valve, the low-carbon pre-column, port 3 of the first valve, and port 4 of the first valve in sequence before being discharged, forming the backflush gas path.

[0024] When the second valve is in the first state, port 7 of the second valve is connected to the fourth carrier gas. The fourth carrier gas passes sequentially through port 8 of the second valve, the high-carbon pre-column, port 5 of the second valve, port 6 of the second valve, and the mass spectrometry detection module to form the high-carbon detection gas path.

[0025] Furthermore, when the first valve is in the second state, port 8 of the first valve is connected to the second carrier gas, and the second carrier gas sequentially passes through port 9 of the first valve, the first metering ring, port 2 of the first valve, port 3 of the first valve, the low-carbon pre-column, port 7 of the first valve, port 6 of the first valve, the low-carbon separation column, and the chromatographic detection module to form the low-carbon detection gas path.

[0026] When the second valve is in the second state, port 3 of the second valve is connected to the third carrier gas. The third carrier gas passes sequentially through port 2 of the second valve, the second metering ring, port 9 of the second valve, port 8 of the second valve, the high-carbon pre-column, port 5 of the second valve, port 4 of the second valve, and the gas resistance to form the high-carbon separation gas path.

[0027] Furthermore, when the first valve is in the first state, port 5 of the first valve is connected to the first carrier gas, and after port 6 of the first valve is connected to port 5, it is sequentially connected to the low-carbon separation column and the chromatographic detection module.

[0028] Furthermore, when the first valve and the second valve are in the second state: the sample inlet pipe is connected to port 1 of the first valve, and port 1 of the first valve is connected in sequence to port 10 of the first valve, port 1 of the second valve, and port 10 of the second valve before being connected to the sample outlet pipe;

[0029] When the first valve is in the second state, the first carrier gas is discharged after passing through port 5 and port 4 of the first valve in sequence.

[0030] When the second valve is in the second state, the fourth carrier gas passes through port 7 and port 6 of the second valve in sequence and then enters the chromatographic detection module.

[0031] Further, the first carrier gas, the second carrier gas, the third carrier gas, and the fourth carrier gas are each connected to a flow controller, wherein the flow controller pressure of the first carrier gas is set to 58 psi, the flow controller pressure of the second carrier gas is set to 42 psi, the flow controller pressure of the third carrier gas is set to 18 psi, and the flow controller pressure of the fourth carrier gas is set to 8 psi.

[0032] The elution times of components C1-C5 in the chromatographic section are adjusted by controlling the pressure of the flow controllers for the first and second carrier gases. The elution times of components C6-C8 are determined by adjusting the pressure of the flow controllers for the third and fourth carrier gases. This approach aims to obtain accurate quantitative results while minimizing the analysis time in both the chromatographic and mass spectrometric sections.

[0033] Furthermore, the high-carbon pre-column is a dimethylpolysiloxane chromatographic column with a stationary phase ratio of 78% to 86%.

[0034] This high-carbon pre-column with a stationary phase ratio is used to reduce the resolution of C6-C8 components, resulting in continuous, incompletely separated mass spectrometry peaks. The retention time is determined by the highest point of each peak, and then a complete ion peak is extracted at that retention time based on the characteristic ions of the target component. This allows for the extraction of individual ion mass spectra from the continuous, incompletely separated C6-C8 peaks using the characteristic ions of each component. Quantitative detection in the mass spectrometry portion is achieved by obtaining the peak area from the ion spectra. Simultaneously, the reduced resolution of C6-C8 components shortens the separation time, thus reducing the analysis time for the mass spectrometry portion. The high-carbon pre-column with a stationary phase ratio of 78%–86% achieves a resolution of 75%–84% for C6-C8 components, meeting the condition of continuous, incompletely separated mass spectrometry peaks, and allowing for a peak elution time of less than 45 seconds. Since the analysis time for low-carbon components is typically less than 30 seconds, accurate analysis of C1-C8 components can be completed in less than 45 seconds.

[0035] To achieve the second objective of this application, this application provides a method for rapid analysis of C1-C8 gas samples using the above-mentioned system via gas chromatography-mass spectrometry, employing the following technical solution:

[0036] A method for rapid analysis of C1-C8 gas samples using the above-described system gas chromatography-mass spectrometry, characterized in that the first valve and the second valve are switched to a first state, the sampling gas path is connected, and the sample is filled into the first quantitative loop and the second quantitative loop;

[0037] Switch the first valve and the second valve to the second state:

[0038] The low-carbon detection gas path is connected, and the second carrier gas is input into the low-carbon detection gas path. The second carrier gas carries the sample in the first quantitative loop through the low-carbon pre-column and the low-carbon separation column, and separates the C1-C5 low-carbon components, which are then detected by the chromatographic detection module.

[0039] The high-carbon separation gas path is connected, and a third carrier gas is input into the high-carbon separation gas path. The third carrier gas carries the sample in the second quantitative loop through the high-carbon pre-column and the gas resistance. The C1-C5 low-carbon components in the sample are first discharged through the gas resistance, while the C6-C8 high-carbon components are temporarily retained in the high-carbon pre-column.

[0040] After the C1-C5 low-carbon components of the chromatographic detection module are injected, the first valve is switched to the first state, the low-carbon detection gas path is cut off, the low-carbon pre-column is connected to the second carrier gas, and the second carrier gas backflushs out the sample remaining in the low-carbon pre-column.

[0041] After the high carbon separation is completed, the second valve is switched to the first state, the high carbon separation gas path is cut off, the high carbon pre-column is connected to the fourth carrier gas, and the fourth carrier gas carries the C6-C8 high carbon components temporarily retained in the high carbon pre-column into the mass spectrometry detection module for detection;

[0042] The low-carbon pre-column and the low-carbon separation column completely separate the C1-C5 low-carbon components, while the high-carbon pre-column partially separates the C6-C8 high-carbon components with a separation degree of 75% to 86%.

[0043] Furthermore, the sampling gas path is opened for 6s to 10s; the second valve is in the second state for 10s to 12s; when the first valve and the second valve switch between the first state and the second state, the first valve and the second valve switch states synchronously.

[0044] During the sampling process, if the sampling time is too short, it will cause an imbalance in the pressure within the loop; if the time is too long, it will cause the gas sample to be lost.

[0045] The duration of the second valve's second state is crucial for the separation of low-carbon components by the high-carbon pre-column and the temporary retention of high-carbon components. Too short a time will result in incomplete evacuation of C1-C5 components, while too long a time will reduce the injection volume in the subsequent mass spectrometry detection module, leading to a lower response and increased testing time. Experimental observations revealed that in this system, the second valve is switched off after 10-12 seconds in the second state. This precisely controls the switching point between the C5 and C6 peak elutions, allowing most of the C1-C5 low-carbon components to be evacuated from the gas path beforehand. This reduces the amount of low-carbon components entering the mass spectrometry ion source, prevents the relatively large C5 peak from covering the C6-C8 peaks, and also helps reduce peak tailing in the C6-C8 range. This approach effectively shortens testing time and improves detection accuracy.

[0046] Furthermore, the ion source energy of the mass spectrometry detection module is 30 eV.

[0047] Reducing the electron bombardment energy prevents the molecules from breaking down completely, further reducing the generation of low-mass fragments. This makes it easier to achieve a consistent decay rate for C6-C8 molecules after separation at the front end, facilitating correction during subsequent data processing.

[0048] Furthermore, when the mass spectrometry detection module quantifies the C6-C8 high-carbon components, C5 is used as an internal standard. Based on the C5 chromatographic signal value Xc5 measured by the chromatographic detection module and the C5 mass spectrometry signal value Yc5 measured by the mass spectrometry detection module, the internal standard coefficient I = Xc5 / Yc5 is obtained. The signal obtained by the mass spectrometry detection module is corrected using the internal standard coefficient I according to the formula Ya = Ysi*I, where Ysi is the signal value measured by the mass spectrometry detection module and Ya is the corrected signal value.

[0049] Due to instrument instability and signal attenuation over long periods, mass spectrometry measurements may deviate from their intended value, while chromatography measurements have smaller errors. The higher measurement stability of the chromatograph allows the C5 value obtained from chromatography to be considered a reference value. By comparing the C5 values ​​of the two instruments, the response changes in the mass spectrometry C5 value caused by instrument conditions can be corrected, resulting in more accurate and reliable final detection data for the mass spectrometry portion of this application.

[0050] In summary, this application provides a system and method for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS), which has the following beneficial effects:

[0051] The analysis cycle is short. Compared with the current 120s C1-C8 component analysis cycle, the analysis cycle of this application is significantly improved, and the analysis cycle of a single C1-C8 component can be shortened to 45s, which is conducive to obtaining oil and gas information more quickly during drilling.

[0052] The separation effect is good and the component identification is accurate. The C1-C5 components are clearly separated and identified according to the peak order of retention time. The C6-C8 components are identified by retention time combined with the unique ion extraction capability of mass spectrometry, which prevents insufficient molecular fragmentation, reduces low-mass fragments, and effectively separates low-carbon and high-carbon components. It can effectively eliminate interfering substances and ensure that the ionization effect of C6-C8 components is the same.

[0053] Accurate quantification. Combining the advantages of chromatography and mass spectrometry, the internal standard method is used to correct the mass spectrometry measurement values ​​by referring to the chromatographic values. This eliminates the need for an additional internal standard gas, reducing measurement errors caused by mass spectrometry attenuation and making the measurement results more accurate and reliable. Attached Figure Description

[0054] Figure 1 This is a pneumatic circuit diagram with the first and second valves in their first state.

[0055] Figure 2 This is a pneumatic circuit diagram showing the first and second valves in their second state.

[0056] Figure 3 This is a graph showing the changes in the opening time of the shut-off valve.

[0057] Figure 4 This is a graph showing the changes in the opening time data of the first and second valves in step S2.

[0058] Figure 5 It is the attenuation rate of C6-C8 components before the separation of C1-C5 components.

[0059] Figure 6 It is the decay rate of C6-C8 components after the separation of C1-C5 components.

[0060] Figure 7 This is a comparison of the C5 signals at the mass spectrometry and chromatographic ends.

[0061] Figure 8 This is a comparison chart of the C6 signal before and after mass spectrometry signal correction.

[0062] Explanation of reference numerals in the attached figures:

[0063] 1. Low-carbon component analysis unit;

[0064] 10. First valve; 100. Port 10; 101. Port 1; 102. Port 2; 103. Port 3; 104. Port 4; 105. Port 5; 106. Port 6; 107. Port 7; 108. Port 8; 109. Port 9;

[0065] 11. First quantitative loop;

[0066] 12. Low-carbon pre-column;

[0067] 13. Low-carbon separation column;

[0068] 14. Chromatography detection module;

[0069] 15. Sample inlet tube; 150. Shut-off valve;

[0070] 16. First carrier gas;

[0071] 17. Second carrier gas;

[0072] 2. High-carbon component analysis unit;

[0073] 20. Second valve; 200. Port 10; 201. Port 1; 202. Port 2; 203. Port 3; 204. Port 4; 205. Port 5; 206. Port 6; 207. Port 7; 208. Port 8; 209. Port 9;

[0074] 21. Second quantitative loop;

[0075] 22. High-carbon pre-column;

[0076] 23. Air resistance;

[0077] 24. Mass spectrometry detection module;

[0078] 25. Sample outlet pipe;

[0079] 26. Third carrier gas;

[0080] 27. Fourth carrier gas. Detailed Implementation

[0081] The present application will be further described in detail below with reference to the accompanying drawings.

[0082] This application first discloses a system for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS), referring to... Figure 1 and Figure 2 The system includes a low-carbon component analysis unit 1 and a high-carbon component analysis unit 2. The low-carbon component analysis unit 1 performs gas chromatography analysis on C1-C5 low-carbon components, and the high-carbon component analysis unit 2 performs gas chromatography-mass spectrometry analysis on C6-C8 high-carbon components.

[0083] The low-carbon component analysis unit 1 includes a first valve 10, a first quantitative ring 11, a low-carbon pre-column 12, a low-carbon separation column 13, and a chromatographic detection module 14.

[0084] The high-carbon component analysis unit 2 includes a second valve 20, a second quantitative ring 21, a high-carbon pre-column 22, a gas resistance 23, and a mass spectrometry detection module 24.

[0085] The first valve 10 is a 10-way valve with ports 1 to 10, and the second valve 20 is a 10-way valve with ports 1 to 10. For example, the first valve 10 and the second valve 20 can be VICI pneumatic 10-way valves. Different gas paths are connected by switching the connection states of ports 1 to 10 of the first valve 10 and ports 1 to 10 of the second valve 20. The first valve 10 in the low-carbon component analysis unit 1 and the second valve 20 in the high-carbon component analysis unit 2 are connected through a gas path formed by the sample inlet pipe 15 and the sample outlet pipe 25.

[0086] Specifically, when the first valve 10 and the second valve 20 are simultaneously in the first state, port 101 of the first valve 10 is connected to the sample inlet pipe 15. The sample sequentially passes through port 202 of the first valve 10, the first metering ring 11, port 9 of the first valve 10, port 100 of the first valve 10, port 101 of the second valve 20, port 202 of the second valve 20, the second metering ring 21, port 9 of the second valve 20, and port 10 of the second valve 20 before connecting to the sample outlet pipe 25, forming a sampling gas path. When the sample is charged into the low-carbon component analysis unit 1, the sample can be simultaneously charged into the high-carbon component analysis unit 2 via the sampling gas path. The charged sample is stored in the first metering ring 11 and the second metering ring 21.

[0087] When the first valve 10 is in the first state: port 5 105 of the first valve 10 is connected to the first carrier gas 16. After port 6 106 of the first valve 10 is connected to port 5 105, it is sequentially connected to the low-carbon separation column 13 and the chromatographic detection module 14. Port 8 108 of the first valve 10 is connected to the second carrier gas 17. The second carrier gas 17 sequentially passes through port 7 107 of the first valve 10, the low-carbon pre-column 12, port 3 103 of the first valve 10, and port 4 104 of the first valve 10 before being discharged, forming a backflush gas path.

[0088] When the second valve 20 is in the first state: the third carrier gas 26 is sequentially connected to ports 3 (203) and 4 (204) of the second valve 20, and the connecting gas resistance 23 is vented. Port 7 (207) of the second valve 20 is connected to the fourth carrier gas 27, which sequentially passes through port 8 (208) of the second valve 20, the high-carbon pre-column 22, port 5 (205) of the second valve 20, port 6 (206) of the second valve 20, and the mass spectrometry detection module 24, forming a high-carbon detection gas path.

[0089] When the first valve 10 and the second valve 20 are both in the second state: the sample inlet pipe 15 is connected to port 101 of the first valve 10, and port 101 of the first valve 10 is connected to port 100 of the first valve 10, port 201 of the second valve 20, and port 200 of the second valve 20 in sequence, and then connected to the sample outlet pipe 25 for discharge.

[0090] When the first valve 10 is in the second state, the first carrier gas 16 passes through port 5 105 and port 4 104 of the first valve 10 in sequence and is then discharged. Port 8 108 of the first valve 10 is connected to the second carrier gas 17, which passes through port 9 109 of the first valve 10, the first metering ring 11, port 2 102 of the first valve 10, port 3 103 of the first valve 10, the low-carbon pre-column 12, port 7 107 of the first valve 10, port 6 106 of the first valve 10, the low-carbon separation column 13, and the chromatographic detection module 14 in sequence, forming a low-carbon detection gas path.

[0091] When the second valve 20 is in the second state, port 3 203 of the second valve 20 is connected to the third carrier gas 26. The third carrier gas 26 passes sequentially through port 2 202 of the second valve 20, the second metering ring 21, port 9 209 of the second valve 20, port 8 208 of the second valve 20, the high-carbon pre-column 22, port 5 205 of the second valve 20, port 4 204 of the second valve 20, and the gas resistance 23, forming a high-carbon separation gas path. The fourth carrier gas 27 passes sequentially through port 7 207 and port 6 206 of the second valve 20 before being connected to the chromatographic detection module 24.

[0092] In this embodiment, a shut-off valve 150 is installed on the sample inlet pipe 15. The first carrier gas 16 and the second carrier gas 17 are hydrogen. A flow controller is installed on the gas path between the first carrier gas 16 and the first valve 10, and on the gas path between the second carrier gas 17 and the first valve 10, respectively. The flow controller pressure for the first carrier gas 16 is set to 58 ps, and the flow controller pressure for the second carrier gas 17 is set to 42 psi. The low-carbon pre-column 12 and the low-carbon separation column 13 can be 1 / 8 packed columns. The chromatographic detection module 14 is an FID detector. The third carrier gas 26 and the fourth carrier gas 27 are helium. Similarly, a flow controller is installed on the gas path between the third carrier gas 26 and the second valve 20, and on the gas path between the fourth carrier gas 27 and the second valve 20, respectively. The flow controller pressure for the third carrier gas 26 is set to 18 psi, and the flow controller pressure for the fourth carrier gas 27 is set to 8 psi. The first metering ring 11 and the second metering ring 21 are both 1 / 16 stainless steel tubes with a volume of 75 μL. The mass spectrometry detection module 24 is a mass spectrometer. The high-carbon pre-column 22 and the mass spectrometer are connected via a stainless steel capillary column with an inner diameter of 0.25 mm as the transfer line. The mass spectrometer uses an ion source energy of 30 eV.

[0093] The high-carbon pre-column 22 is an HP-1 quartz capillary column, 15m long and 0.25mm inner diameter, packed with a dimethyl polysiloxane stationary phase of 78%–86%. Alternatively, the high-carbon pre-column 22 can be a dimethyl polysiloxane stationary phase of 82%. The high-carbon pre-column 22 is used to separate low-carbon and high-carbon components in the sample. In the high-carbon separation gas path, C1-C5 low-carbon components, due to their small molecular weight, pass through the high-carbon pre-column 22 first and are then discharged via gas resistance 23. C6-C8 high-carbon components require a longer time to pass through the column and are further hindered by gas resistance 23, making them difficult to discharge quickly and temporarily remaining in the high-carbon pre-column 22, thus achieving the separation of C1-C5 low-carbon components and C6-C8 high-carbon components. Meanwhile, the ratio of the stationary phase in the high-carbon pre-column 22, the separation degree of the C6-C8 high-carbon components, and the peak elution time of the mass spectrometry detection module 24 were studied, and the results are shown in Table 1 below.

[0094] Table 1: Separation degree of high carbon components from C6 to C8.

[0095]

[0096]

[0097] As shown in Table 1, a lower proportion of the stationary phase in the high-carbon pre-column 22 shortens the elution time of the mass spectrometry detection module 24, but also reduces the resolution of the components. Lower resolution results in poorer quantification. Since the C1-C5 low-carbon components have small molecular weights and short separation times, the chromatographic detection module 14 typically detects C1-C5 low-carbon components within 30 seconds. For C6-C8 high-carbon components, higher resolution and longer separation time lead to longer elution times. This application utilizes the ion recognition characteristics of mass spectrometry to control the obtained mass spectrometry peaks to be continuous, incompletely separated peak groups, thus shortening the separation time. The retention time is determined by the highest point of the mass spectrometry peak. Then, based on the characteristic ions of the target component at that retention time, a complete ion peak is extracted. The continuous peaks are then used to extract the respective ion spectra of each component using their characteristic ions. The peak area in the ion spectra is used to quantify a component, ensuring accurate detection. This application discovers that by controlling the proportion of the high-carbon pre-column 22 stationary phase to 78%–86%, the separation degree of the C6–C8 high-carbon components can reach 75%–84%. Under this degree of separation, the ion spectra of the continuous, incompletely separated peak groups are easy to identify, and the overall peak elution time is less than 45 seconds, effectively shortening the detection time of the C6–C8 components. Thus, the overall detection time of the C1–C8 components in this system is less than 45 seconds, and the detection results have the highest relative accuracy.

[0098] Of course, in some other implementations, in order to further improve the accuracy of the results, the separation of C6-C8 can be increased accordingly, so that the detection time is greater than 45 seconds.

[0099] This system has only one set of low-carbon component analysis unit 1 and high-carbon component analysis unit 2. The connection between different gas paths and the completion of detection are achieved by switching between the first valve 10 and the second valve 20. The system has a simple structure, is easy to operate, and allows both low-carbon component analysis unit 1 and high-carbon component analysis unit 2 to work simultaneously, resulting in a short detection time. The following will provide a more detailed description of the method for rapid analysis of C1-C8 gas samples using gas chromatography-mass spectrometry (GC-MS) according to this application.

[0100] The method for rapid analysis of C1-C8 gas samples using system gas chromatography-mass spectrometry disclosed in this embodiment includes the following steps:

[0101] S1. Extract oil and gas samples using a gas extraction device, connect them to the sample inlet pipe 15 via a Teflon tube, simultaneously switch the first valve 10 and the second valve 20 to the first state, open the first carrier gas 16, the second carrier gas 17, the third carrier gas 26, and the fourth carrier gas 27, and open the shut-off valve 150 of the sample inlet pipe 15. Fill the first quantitative ring 11 and the second quantitative ring 21 with the sample through the sampling gas path to perform sampling.

[0102] S2, synchronously switch the first valve 10 and the second valve 20 to the second state. The sample in the first quantitative ring 11 is carried by the second carrier gas 17 and sequentially passes through the low carbon pre-column 12 and the low carbon separation column 13 along the low carbon detection gas path to separate the C1-C5 low carbon components into the FID detector.

[0103] Simultaneously with the sample flow in the low-carbon detection gas path, the third carrier gas 26 carries the sample in the second quantitative ring 21 and passes sequentially through the high-carbon pre-column 22 and gas resistance 23 along the high-carbon separation gas path. The low-carbon components C1-C5 in the sample are gradually discharged through the gas resistance 23, while the high-carbon components C6-C8 are temporarily retained in the high-carbon pre-column 22.

[0104] S3, the first valve 10 and the second valve 20 are switched again to enter the first state. When the fourth carrier gas 27 flows through the high carbon pre-column 22, it carries the C6-C8 high carbon components separated in step S2 into the mass spectrometer.

[0105] At the same time, the second carrier gas 17 backflushes the sample in the low-carbon pre-column 12, removing the high-carbon components remaining in the low-carbon pre-column 12.

[0106] The C1-C5 low-carbon components entering the FID detector and the C6-C8 high-carbon components entering the mass spectrometer are used as detection samples for the FID detector and the gas chromatograph-mass spectrometer, respectively. During steps S2 and S3, they are detected simultaneously, generating spectral signals and completing quantification.

[0107] Since this system achieves synchronous detection through the switching of the first valve 10 and the second valve 20, the first carrier gas 16, the second carrier gas 17, the third carrier gas 26, and the fourth carrier gas 27 may have an empty flow state in the first and second states of the first valve 10 and the second valve 20, which serves to clean the gas path. The sample may also flow directly in and out without entering the first metering loop 11 and the second metering loop 21. Of course, in some other embodiments, the shut-off valve 150 of the sample inlet pipe 15 can be closed after sample collection is completed.

[0108] The relationship between the opening time of the shut-off valve 150 in step S1 and the average response value and relative standard deviation (RSD) of the measured component in the FID detector was further investigated. The results are shown in Table 2 and... Figure 3 As shown.

[0109] Table 2: Parameter table for the opening time of the shut-off valve.

[0110] Shut-off valve opening time Average response value of test components Relative standard deviation (RSD) of the response value 1.0s 35432 5.10 1.5s 40018 4.55 2.0s 42350 4.31 2.5s 52089 4.09 3.0s 59105 3.49 3.5s 66435 3.33 4.0s 68408 3.22 4.5s 72303 2.85 5.0s 79421 2.56 5.5s 81134 2.43 6.0s 81953 2.08 6.5s 75567 2.10 7.0s 65431 2.44 7.5s 60235 2.78 8.0s 52648 2.84 8.5s 39461 2.85 9.0s 32211 3.11 9.5s 28615 3.55 10s 27271 3.68

[0111] It was found that when the shut-off valve 150 was open for 6 seconds, the average response value of the measured component of the FID detector was the highest and the relative standard deviation (RSD) of the response value was the lowest, which is beneficial to improving the accuracy of detection. Therefore, in step S1, after sampling for 6 seconds, the shut-off valve 150 was closed, the sampling was completed, and the first valve 10 and the second valve 20 were switched to the second state of step S2.

[0112] The duration of gas path connection before valve switching in step S3 (as described in step S2) is crucial for the separation of C1-C5 low-carbon components in the sample. Too short a time will result in incomplete separation of C1-C5 components, causing interference between the low-carbon and high-carbon signals during mass spectrometry detection. Too long a time will reduce the injection volume, lowering the response and affecting both the final detection time and accuracy. The duration of the second state for the first valve 10 and the second valve 20 in step S2 was investigated, and the results are shown in Table 3 below. Figure 4 As shown.

[0113] Table 3: Opening time parameter table of first valve 10 and second valve 20 in step S2.

[0114] Opening time C5 Average Response Value C6 Average Response Value 2s 3569 16591 3s 3088 16898 4s 2937 17159 5s 2751 17597 6s 2106 18766 7s 1833 18837 8s 1511 19002 9s 1337 19581 10s 1109 19939 11s 997 19567 12s 967 19081 13s 965 18911 14s 957 18736 15s 934 18592 16s 966 18518 17s 954 18320 18s 967 18323

[0115] It was found that during the 10-12 seconds of opening time of the first valve 10 and the second valve 20 in step S2, the average response of C6 was at its highest level, while the average response of C5 was already at a low level. This indicates that the C1-C5 components in the sample were effectively separated within 10-12 seconds of high-carbon separation, and the high-carbon signal response was strong, resulting in accurate detection results. Therefore, further, after the first valve 10 and the second valve 20 switch to the second state for 10-12 seconds in step S2, the valves are closed in step S3.

[0116] Furthermore, the study found significant signal attenuation when the mass spectrometer was used for detection in this application, such as... Figure 5 and Figure 6 As shown, this causes deviations in the mass spectrometry measurement results; the C1-C5 components enhance the attenuation of the mass spectrometry signal. (Reference) Figure 7 It can be observed that the measurement error at the chromatographic end is smaller compared to mass spectrometry. The high-carbon pre-column 22 of this application cannot completely separate the low-carbon components (C1-C5) in the sample; a small amount of C5 will enter the mass spectrometer. The signal attenuation process of C5 in the mass spectrometer is basically the same as that of C6-C8, with both exhibiting the same attenuation rate with increasing working time. Therefore, C5 is used as an internal standard to correct the signal at the mass spectrometer. In this way, without introducing a new internal standard, increasing the difficulty of component resolution, or affecting the analysis cycle, mass spectrometry correction can be performed simultaneously during sample measurement.

[0117] Specifically, during sample measurement, the C5 values ​​of both the chromatographic and mass spectrometric instruments are observed. The C5 chromatographic signal value is denoted as Xc5, and the C5 mass spectrometric signal value is denoted as Yc5. The internal standard coefficient I is calculated using the formula I = Xc5 / Yc5. This internal standard coefficient I is then multiplied by the signal values ​​of components C6-C8 measured by the mass spectrometer to obtain the corrected signal value, thus improving the accuracy of the measurement results. The correction formula is Ya = Ysi * I, where I is the aforementioned internal standard coefficient, Ysi is the signal value measured by the mass spectrometer, and Ya is the actual signal value calculated after correction using the internal standard coefficient I. Figure 8 The diagram shows a comparison of the C6 signal at the mass spectrometer end before and after correction according to the correction method of this application. It can be seen that the signal is basically not attenuated after correction.

[0118] Of course, the above embodiments are the best embodiments of this application, and are only used to illustrate the technical concept and features of this application. Their purpose is to enable those skilled in the art to understand the content of this application and implement it accordingly, and they should not be used to limit the scope of protection of this application. All modifications made in accordance with the spirit of the main technical solution of this application should be included within the scope of protection of this application.

Claims

1. A system for the rapid analysis of C1-C8 gas samples by gas chromatography-mass spectrometry, characterized in that, The system comprises a first valve, a first constant ring, a low-carbon pre-column, a low-carbon separation column, a chromatographic detection module, a second valve, a second constant ring, a high-carbon pre-column, a gas resistance, and a mass spectrometric detection module; The first valve is connected with a sample inlet pipe, and the first valve, the first constant ring, the second constant ring, and the second valve are connected to form a sampling gas path; The first constant ring, the first valve, the low-carbon pre-column, the low-carbon separation column, and the chromatographic detection module are connected to form a low-carbon detection gas path; The second constant ring, the second valve, the high-carbon pre-column, and the gas resistance are connected to form a high-carbon separation gas path; The second valve, the high-carbon pre-column, and the mass spectrometric detection module are connected through a high-carbon detection gas path; The high-carbon separation gas path forms the high-carbon detection gas path through switching of the second valve; Low-carbon components in the high-carbon separation gas path are discharged through the gas resistance, and high-carbon components enter the high-carbon detection gas path; When the first valve and the second valve are in a first state, the system forms the sampling gas path; When the first valve is in the first state, the system forms a backflushing gas path, and when the first valve is switched to a second state, the system forms the low-carbon detection gas path; When the second valve is in the first state, the system forms the high-carbon detection gas path, and when the second valve is switched to the second state, the system forms the high-carbon separation gas path; The first valve has a 1st port to a 10th port, and the second valve has a 1st port to a 10th port; When the first valve and the second valve are in the first state, the 1st port of the first valve is connected with the sample inlet pipe, and the sample sequentially passes through a 2nd port of the first valve, the first constant ring, a 9th port of the first valve, a 10th port of the first valve, a 1st port of the second valve, a 2nd port of the second valve, the second constant ring, a 9th port of the second valve, and a 10th port of the second valve, and is then connected with a sample outlet pipe to form the sampling gas path; When the first valve is in the first state, an 8th port of the first valve is connected with a second carrier gas, and the second carrier gas sequentially passes through a 7th port of the first valve, the low-carbon pre-column, a 3rd port of the first valve, and a 4th port of the first valve, and is then discharged to form the backflushing gas path; When the second valve is in the first state, a 7th port of the second valve is connected with a fourth carrier gas, and the fourth carrier gas sequentially passes through an 8th port of the second valve, the high-carbon pre-column, a 5th port of the second valve, a 6th port of the second valve, and the mass spectrometric detection module to form the high-carbon detection gas path; The high-carbon pre-column is a dimethylpolysiloxane chromatographic column with a stationary phase ratio of 78% to 86%.

2. The system for rapid analysis of C1-C8 gas samples by GC-MS according to claim 1, characterized in that, The system further comprises a backflushing gas path, the low-carbon pre-column, and the first valve are connected to form the backflushing gas path, and the low-carbon detection gas path is formed by switching of the first valve.

3. The system according to claim 2, wherein When the first valve is in the second state, the No. 8 port of the first valve is communicated with the second carrier gas, and the second carrier gas sequentially passes through the No. 9 port of the first valve, the first quantitative ring, the No. 2 port of the first valve, the No. 3 port of the first valve, the low-carbon pre-column, the No. 7 port of the first valve, the No. 6 port of the first valve, the low-carbon separation column and the chromatographic detection module, forming the low-carbon detection gas path. When the second valve is in the second state, the No. 3 port of the second valve is communicated with the third carrier gas, and the third carrier gas sequentially passes through the No. 2 port of the second valve, the second quantitative ring, the No. 9 port of the second valve, the No. 8 port of the second valve, the high-carbon pre-column, the No. 5 port of the second valve, the No. 4 port of the second valve and the air resistance, forming the high-carbon separation gas path.

4. The system for rapid analysis of C1-C8 gas samples by GC-MS according to claim 3, characterized in that, When the first valve is in the first state, the No. 5 port of the first valve is communicated with the first carrier gas, and after the No. 6 port of the first valve is communicated with the No. 5 port, the low-carbon separation column and the chromatographic detection module are sequentially communicated.

5. The system for rapid analysis of C1-C8 gas samples by GC-MS according to claim 4, characterized in that, When the first valve and the second valve are in the second state: the sample inlet pipe is communicated with the No. 1 port of the first valve, and after the No. 1 port of the first valve is sequentially communicated with the No. 10 port of the first valve, the No. 1 port of the second valve and the No. 10 port of the second valve, the sample outlet pipe is communicated; When the first valve is in the second state, the first carrier gas sequentially passes through the No. 5 port and the No. 4 port of the first valve and is discharged; When the second valve is in the second state, the fourth carrier gas sequentially passes through the No. 7 port and the No. 6 port of the second valve and is connected to the chromatographic detection module.

6. The system for rapid analysis of C1-C8 gas samples by GC-MS according to claim 4, characterized in that, The first carrier gas, the second carrier gas, the third carrier gas and the fourth carrier gas are respectively connected with a flow controller, the pressure of the flow controller of the first carrier gas is set to 58 psi, the pressure of the flow controller of the second carrier gas is set to 42 psi, the pressure of the flow controller of the third carrier gas is set to 18 psi, and the pressure of the flow controller of the fourth carrier gas is set to 8 psi.

7. A method for rapid analysis of C1-C8 gas samples by GC-MS using the system according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: Switching the first valve and the second valve to the first state, the sampling gas path is communicated, and the sample is filled into the first quantitative ring and the second quantitative ring; Switching the first valve and the second valve to the second state: The low-carbon detection gas path is communicated, the second carrier gas is input into the low-carbon detection gas path, the second carrier gas carries the sample in the first quantitative ring to pass through the low-carbon pre-column and the low-carbon separation column, and C1-C5 low-carbon components are separated and obtained to enter the chromatographic detection module for detection; The high-carbon separation gas path is communicated, the third carrier gas is input into the high-carbon separation gas path, the third carrier gas carries the sample in the second quantitative ring to pass through the high-carbon pre-column and the air resistance, and C1-C5 low-carbon components in the sample are discharged through the air resistance first, and C6-C8 high-carbon components are temporarily retained in the high-carbon pre-column; After the C1-C5 low-carbon components sample of the chromatographic detection module is completed, the first valve is switched to the first state, the low-carbon detection gas path is cut off, the second carrier gas is communicated with the low-carbon pre-column, and the sample remaining in the low-carbon pre-column is back-flushed and discharged; After the high carbon separation is completed, the second valve is switched to the first state, the high carbon separation gas path is cut off, the fourth carrier gas is communicated with the high carbon pre-column, and the C6-C8 high carbon components temporarily remaining in the high carbon pre-column are carried into the mass spectrum detection module for detection; The low carbon pre-column and the low carbon separation column completely separate the C1-C5 low carbon components, and the high carbon pre-column incompletely separates the C6-C8 high carbon components with a separation degree of 75% to 86%.

8. The method of claim 7, wherein the method is a method of rapid analysis of C1-C8 gas samples by GC-MS. The opening time of the sampling gas path is 6s to 10s; The opening time of the second valve in the second state is 10s to 12s; When the first valve is switched between the first state and the second state, the second valve is synchronously switched.

9. The method of claim 7, wherein the method is a method of rapid analysis of C1-C8 gas samples by GC-MS. The ion source energy of the mass spectrum detection module is 30ev.

10. The method of claim 7, wherein the method is a method of rapid analysis of C1-C8 gas samples by GC-MS. When the mass spectrum detection module quantifies the C6-C8 high carbon components, C5 is used as an internal standard substance, an internal standard coefficient I = Xc5 / Yc5 is obtained according to a C5 chromatographic signal value Xc5 measured by the chromatographic detection module and a C5 mass spectrum signal value Yc5 measured by the mass spectrum detection module, and a signal obtained by the mass spectrum detection module is corrected according to a formula Ya = Ysi*I, wherein Ysi is a signal value measured by the mass spectrum detection module, and Ya is a corrected signal value.

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