System and method for metering carbon dioxide output in well site

Abstract

The invention relates to a well site carbon dioxide output metering system and method, and the system comprises a multiphase flowmeter which is used for measuring the three-phase total flow and the three-phase fraction of oil, gas and water; the sampling device is used for sampling from the multiphase flowmeter to obtain a sample liquid containing oil, gas and water, and separating out carbon dioxide from a liquid phase of the sample liquid to obtain a mixed gas containing carbon dioxide; the carbon dioxide concentration detector is used for detecting the volume concentration of carbon dioxide in the mixed gas; and the upper computer is used for obtaining the volume of each phase of the oil-gas-water in the period of time according to the total flow of the three phases of the oil-gas-water collected in the preset period of time, and further obtaining the total mass of the carbon dioxide in the oil-gas-water in the period of time, so that the function of accurately calculating the total content of the carbon dioxide in the well site output liquid is realized.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field development, and in particular to a system and method for measuring carbon dioxide output in a well site. Background Art

[0002] CO 2 Capture, oil recovery and storage (CCUS-EOR) can achieve the dual purpose of geological storage of greenhouse gases and improving the recovery rate of crude oil in low-permeability tight oil reservoirs. It is a realistic and feasible large-scale carbon reduction technology. Therefore, CO 2 The research on output measurement system is of great strategic significance.

[0003] Domestic and foreign scholars have studied the CCUS-EOR flooding mechanism, CO 2 Injection technology, CO 2 A lot of research has been done on measurement methods, storage mechanism and effect analysis, storage influencing factors and storage efficiency. It mainly includes the following aspects:

[0004] (1)CO 2 Research on the mechanism of enhanced oil recovery: A large number of studies have shown that CO 2 The flooding has the advantages of reducing crude oil viscosity, expanding crude oil volume, reducing oil-water interfacial tension, and extracting light hydrocarbons to increase the utilization rate of crude oil in tiny pores. The Chinese invention patent with the authorization announcement number CN112304842B provides a shale oil CO 2 / N 2 Alternating displacement injection volume simulation analysis method. This method obtains CO based on the changes in the porosity and oil recovery efficiency of the shale core before and after displacement. 2 / N 2 The injection amount adjustment expression of alternate displacement shale oil is used to improve the CO 2 / N 2 The overall oil recovery efficiency can be improved, thereby increasing the recovery rate of shale oil.

[0005] (2) Research on the calculation method of minimum miscible pressure: mainly including the capillary test method, droplet suspension method, minimum interfacial tension method, etc. The Chinese invention patent with the authorization announcement number CN107939356B provides a method and system for determining the pressure range of gas injection near-miscible drive. The method first obtains the relationship curve between different injection pressures and interfacial tensions, then performs a semi-logarithmic coordinate transformation on the relationship curve, and performs segmented fitting to obtain the non-miscible segment relationship line and the near-miscible segment relationship line. Finally, based on the non-miscible segment relationship line, the near-miscible segment relationship line and the ultra-low interfacial tension, the gas injection near-miscible drive pressure range is determined, and the error can be reduced, the accuracy of the results can be improved, and the method is easy to implement with a high success rate.

[0006] (3)CO 2Research on oil recovery technology: Due to the strong heterogeneity of the reservoir, CO 2 The oil displacement process is easily affected by viscous fingering and gravity differentiation, and gas channeling is likely to occur, resulting in poor oil displacement effect. 2 A qualitative and quantitative analysis method for oil displacement law. 2 The output characteristic curve is established by combining the injection volume, crude oil production volume and gas production volume. 2 The oil recovery process is divided into three different stages: gasless oil recovery stage, gas discovery stage and gas breakthrough stage. Then the CO2 emission can be judged according to the changes of parameters in different stages. 2 Oil displacement, gas breakthrough rules and enhanced oil recovery mechanism, CO 2 Oil recovery has important guiding significance.

[0007] (4)CO 2 Storage related research: The Chinese invention patent with application publication number CN114544463A provides a fractured reservoir geological body CO 2 The method and device for burial assessment. The method obtains the core obtained from the target reservoir geological body; obtains the matrix permeability Km of the core through the formation water core displacement experiment; obtains the core with fractures, calculates the conductivity K of the fractures, and calculates the CO 2 The storage rate is CO 2 Quantitative relationship between burial rate and fracture parameters.

[0008] (5)CO 2 Study on the calculation model of solubility in oil and water: Chen Yanfang et al. studied CO 2 The solubility coefficient determination method involved in the storage volume calculation formula determined the solubility calculation model and obtained the CO 2 The solubility coefficients in oil and water were evaluated for CO in a domestic oil field. 2 Theoretical storage potential and effective storage potential. The solubility coefficient in water uses the prediction model of Duan et al., and the solubility coefficient in oil uses the calculation model proposed by Xue Haitao et al. These two basic models are used to calculate CO 2 The solubility coefficient in oil and water is substituted into the theoretical storage calculation formula to obtain CO 2 The theoretical storage capacity in the reservoir is close to the result calculated by analogy method, which verifies the reliability and correctness of this method.

[0009] Most of the above research results involve CO 2 However, only a few studies have involved CO 2 Studies on storage efficiency assessment, regarding CO2 Even less research has been done on systems that precisely measure output. Summary of the invention

[0010] In view of the above problems, the present application provides a system and method for measuring the carbon dioxide output in a well site to solve the existing problem of lack of CO in oil wells. 2 The problem of accurately measuring output.

[0011] To achieve the above purpose, the inventor provides a carbon dioxide output metering system in a well site, comprising:

[0012] A multiphase flow meter, which is connected to the liquid outlet pipeline at the wellhead of the oil production well and is used to measure the total flow rate and phase fraction of the three phases of oil, gas and water;

[0013] A sampling device, wherein the sampling port of the sampling device is connected to the rear main line of the multiphase flowmeter, and the sampling device is used to sample from the multiphase flowmeter to obtain a sample liquid containing oil, gas and water, and precipitate carbon dioxide from the liquid phase of the sample liquid to obtain a mixed gas containing carbon dioxide;

[0014] A carbon dioxide concentration detector, the carbon dioxide concentration detector is connected to the sampling device, and the carbon dioxide concentration detector detects the volume concentration of carbon dioxide in the mixed gas;

[0015] The host computer is connected to the multiphase flow meter, the sampling device and the carbon dioxide concentration detector. The host computer is used to calculate the volume of carbon dioxide in the mixed gas according to the obtained carbon dioxide volume concentration, obtain the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide, calculate the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water, and then obtain the total mass of carbon dioxide in the sample liquid, and calculate the total mass of carbon dioxide produced by the oil well in the preset time period according to the total flow rate of the three phases of oil, gas and water in the preset time period.

[0016] In some embodiments, an air filter is also included. The air filter is arranged between the sampling device and the carbon dioxide concentration detector, and the air filter is used to filter moisture in the mixed gas.

[0017] In some embodiments, a pressure reducing valve is also included. The pressure reducing valve is arranged between the sampling device and the carbon dioxide concentration detector, and the pressure reducing valve is used to stabilize the pressure of the gas source.

[0018] In some embodiments, a temperature sensor and a pressure sensor are also included, wherein the temperature sensor is used to obtain the temperature in the sampling device, and the pressure sensor is used to obtain the pressure in the sampling device;

[0019] The host computer is connected to the pressure sensor and the temperature sensor, and is also used to obtain the density corresponding to the carbon dioxide according to the temperature and pressure of the sampling device.

[0020] In some embodiments, the host computer is also used to determine whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold value when calculating the mass of carbon dioxide in the liquid phase of the sample liquid based on the saturated solubility of carbon dioxide in oil and water. If it is greater than the threshold value, the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the temperature and pressure of the sampling device, and then the total mass of carbon dioxide in the liquid phase of the sample liquid is calculated based on the obtained saturated solubility; if it is less than the threshold value, the pressure in the sampling device is reduced; when the pressure of the sampling device is greater than a preset value, the volume concentration of the precipitated carbon dioxide is greater than the threshold value, and the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the current temperature and pressure of the sampling device; when the pressure in the sampling device is less than the preset value, the volume concentration of the precipitated carbon dioxide is less than the threshold value, and it is determined that the sample liquid does not contain carbon dioxide.

[0021] Another technical solution is provided, a method for measuring the carbon dioxide output in a well site, comprising the following steps:

[0022] Under the conditions of operating temperature and pressure, the multiphase flowmeter measures the total flow rate and three-phase fraction of oil, gas and water in the oil well;

[0023] The uniformly mixed three-phase fluid in the multiphase flowmeter is sampled by a sampling device to obtain a sample liquid, and carbon dioxide in the liquid phase of the sample liquid is precipitated, and then the sampling device is left to stand for a period of time to obtain a mixed gas containing carbon dioxide;

[0024] The volume concentration of carbon dioxide in the mixed gas is detected by a carbon dioxide concentration detector;

[0025] The volume of carbon dioxide in the mixed gas is calculated according to the obtained carbon dioxide volume concentration;

[0026] The mass of carbon dioxide in the mixed gas is obtained according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide;

[0027] The mass of carbon dioxide in the liquid phase of the sample liquid is calculated according to the saturated solubility of carbon dioxide in oil and water, thereby obtaining the total mass of carbon dioxide in the sample liquid;

[0028] The total mass of carbon dioxide produced by the oil well during the preset time period is calculated based on the total flow rate of the three phases of oil, gas and water during the preset time period.

[0029] In some embodiments, the following steps are also included:

[0030] The mixed gas in the sampling device is sent to the carbon dioxide concentration detector after being filtered out of moisture through an air filter and stabilized by a pressure reducing valve.

[0031] In some embodiments, obtaining the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide specifically comprises the following steps:

[0032] Obtain the density corresponding to carbon dioxide according to the temperature and pressure in the sampling device;

[0033] The mass of carbon dioxide in the mixed gas is calculated based on the volume of carbon dioxide in the mixed gas and the obtained density of carbon dioxide.

[0034] In some embodiments, the step of calculating the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water specifically comprises the following steps:

[0035] Determine whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold value;

[0036] If it is greater than the threshold, the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the temperature and pressure of the sampling device;

[0037] The total mass of carbon dioxide in the liquid phase of the sample liquid is calculated based on the obtained saturated solubility.

[0038] If it is less than the threshold, the pressure in the sampling device is reduced;

[0039] When the pressure of the sampling device is greater than a preset value, the volume concentration of the precipitated carbon dioxide is greater than a threshold value, and the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the current temperature and pressure of the sampling device;

[0040] When the pressure in the sampling device is lower than a preset value and the volume concentration of the precipitated carbon dioxide is lower than a threshold value, it is determined that the sample liquid does not contain carbon dioxide.

[0041] In some embodiments, a calibration step of the carbon dioxide concentration detector is also included, specifically the following steps:

[0042] Place the carbon dioxide concentration detector in clean air and perform automatic zero adjustment;

[0043] A 50% concentration of carbon dioxide standard gas is introduced into the carbon dioxide concentration detector, and the target point concentration is set to 50%;

[0044] Perform target point calibration, wait for the concentration value detected by the carbon dioxide concentration detector to stabilize, and complete the target point calibration;

[0045] High-purity nitrogen is introduced into the carbon dioxide concentration detector to purge the gas pipeline to return the carbon dioxide concentration value to zero.

[0046] Different from the prior art, the above technical scheme uses a multiphase flowmeter to measure the three-phase total flow rate and three-phase phase fraction of oil, gas and water collected from the oil production well; uses a sampling device to sample the three-phase fluid of oil, gas and water uniformly mixed in the liquid outlet pipeline of the three-phase flowmeter to obtain a sample liquid, and precipitates carbon dioxide in the liquid phase of the sample liquid to obtain a mixed gas containing carbon dioxide, and then sends the mixed gas to a carbon dioxide concentration detector to detect the volume concentration of carbon dioxide in the mixed gas, calculates the volume of carbon dioxide in the mixed gas according to the obtained volume concentration of carbon dioxide, obtains the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide, calculates the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water, and adds the mass of carbon dioxide in the mixed gas and the mass of carbon dioxide in the liquid phase to obtain the total mass of carbon dioxide in the sample liquid, and then according to the three-phase total flow rate of oil, gas and water collected within a preset time, the three-phase total volume of oil, gas and water during this period can be obtained, and then the total mass of carbon dioxide in oil, gas and water during this period can be obtained, thereby realizing accurate calculation of the total content of carbon dioxide in the well site production fluid.

[0047] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the text of the specification and the contents recorded in the drawings, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the following is an explanation in combination with the specific implementation mode and drawings of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and shall not be considered as limitations of the present application.

[0049] In the drawings of the specification:

[0050] Figure 1 A structural schematic diagram of a carbon dioxide output metering system in a well site according to a specific implementation method;

[0051] Figure 2 It is another structural schematic diagram of the carbon dioxide output metering system in the well site described in the specific implementation method;

[0052] Figure 3 A schematic diagram of a flow chart of a carbon dioxide output metering system in a well site according to a specific implementation method;

[0053] Figure 4A flowchart of step S360 described in the specific implementation method;

[0054] Figure 5 A flow chart of the steps for calibrating a carbon dioxide concentration detector according to a specific implementation method.

[0055] The reference numerals in the above drawings are described as follows:

[0056] 110. Multiphase flow meter,

[0057] 120. Sampling device,

[0058] 130. Carbon dioxide concentration detector,

[0059] 140. Host computer,

[0060] 150. Air filter,

[0061] 160. Pressure reducing valve,

[0062] 170, one-way valve,

[0063] 180. Solenoid valve. DETAILED DESCRIPTION

[0064] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0065] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0066] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0067] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0068] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0069] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0070] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0071] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0072] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0073] See also Figure 1-2 This embodiment provides a carbon dioxide output metering system in a well site, including:

[0074] The multiphase flowmeter 110 is connected to the liquid outlet pipeline at the wellhead of the oil production well. The multiphase flowmeter 110 is used to measure the total flow rate of the three phases of oil, gas and water and the three-phase phase fraction; the multiphase flowmeter 110 is connected to the wellhead liquid outlet pipeline flange to measure the total flow rate of the three phases of oil, gas and water and the three-phase phase fraction, wherein the phase fraction measurement range is 0-100%; the multiphase flowmeter 110 is equipped with a temperature sensor and a pressure sensor to measure the fluid temperature and pressure in real time. The three-phase phase fraction refers to the volume gas content, water content and oil content, and the gas content range is 0%-100%.

[0075] The sampling device 120 has a sampling port connected to the rear main line of the multiphase flowmeter 110. The sampling device 120 is used to sample the sample liquid containing oil, gas and water from the multiphase flowmeter 110, and precipitate carbon dioxide from the liquid phase of the sample liquid to obtain a mixed gas containing carbon dioxide. The mixed gas is the gas originally contained in the sampling device 120 and the gas precipitated after the liquid phase is depressurized. The sampling device 120 samples the rear main line of the multiphase flowmeter 110, and is controlled by a one-way valve 170 in the middle, so that only the fluid is allowed to flow from the main line to the sampling device 120. The sampling volume (L) of the sampling device 120 is determined by the gas content measured by the multiphase flowmeter 110, and the calculation formula is as follows:

[0076] V s =(L-0.1)α gas +0.1

[0077] Where: V s is the total volume of the sample, in liters, α gas is the gas content.

[0078] The volume of the sampling device 120 can be controlled by the internal piston rod. If the gas content is not 100%, the piston rod is controlled to increase the internal volume of the sampling device 120, thereby reducing the internal pressure and allowing part of the CO 2The increase in gas volume is also beneficial to the subsequent CO 2 The concentration is measured and then the sampling device 120 is left to stand for a period of time.

[0079] The carbon dioxide concentration detector 130 is connected to the sampling device 120 and detects the volume concentration of carbon dioxide in the mixed gas. The carbon dioxide concentration detector 130 is part of the gas detection system and can simultaneously record the carbon dioxide concentration. 2 Parameters such as volume concentration, cumulative flow and cumulative mass.

[0080] The host computer 140 is connected to the multiphase flow meter 110, the sampling device 120 and the carbon dioxide concentration detector 130. The host computer 140 is used to calculate the volume of carbon dioxide in the mixed gas according to the obtained carbon dioxide volume concentration, obtain the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide, calculate the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water, and then obtain the total mass of carbon dioxide in the sample liquid, and calculate the total mass of carbon dioxide produced by the oil well in the preset time period according to the total flow rate of oil, gas and water three phases in the preset time period.

[0081] The multiphase flowmeter 110 is used to measure the three-phase total flow rate and three-phase phase fraction of oil, gas and water collected from the oil production well; the sampling device 120 is used to sample the three-phase fluid of oil, gas and water uniformly mixed in the liquid outlet pipeline of the three-phase flowmeter to obtain a sample liquid, and the carbon dioxide in the liquid phase of the sample liquid is precipitated to obtain a mixed gas containing carbon dioxide, and then the mixed gas is sent to the carbon dioxide concentration detector 130 to detect the volume concentration of carbon dioxide in the mixed gas, and the volume of carbon dioxide in the mixed gas is calculated according to the obtained volume concentration of carbon dioxide, and the mass of carbon dioxide in the mixed gas is obtained according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide. The mass of carbon dioxide in the liquid phase of the sample liquid is calculated according to the saturated solubility of carbon dioxide in oil and water, and the mass of carbon dioxide in the mixed gas and the mass of carbon dioxide in the liquid phase are added to obtain the total mass of carbon dioxide in the sample liquid, and then the total volume of the three phases of oil, gas and water within a certain period of time can be obtained according to the total three-phase flow rate of oil, gas and water collected within a certain period of time, and then the total mass of carbon dioxide in the oil, gas and water within this period of time can be obtained, so that the total content of carbon dioxide in the well site production fluid can be accurately calculated.

[0082] See also Figure 2In some embodiments, an air filter 150 is further included. The air filter 150 is disposed between the sampling device 120 and the carbon dioxide concentration detector 130. The air filter 150 is used to filter moisture in the mixed gas. The air filter 150 is used to clean the gas source and can filter moisture in the compressed gas to prevent moisture from entering the carbon dioxide concentration detector 130 along with the gas.

[0083] See also Figure 2 In some embodiments, a pressure reducing valve 160 is further included. The pressure reducing valve 160 is disposed between the sampling device 120 and the carbon dioxide concentration detector 130. The pressure reducing valve 160 is used to stabilize the pressure of the gas source. The pressure reducing valve 160 can stabilize the pressure of the gas source, so that the gas source is in a constant pressure state, and reduce the damage to hardware such as valves or actuators caused by sudden changes in air pressure. Among them, the pressure stabilization pressure of the pressure reducing valve 160 is less than 0.5MPa.

[0084] The mixed gas of the original gas and the precipitated gas in the sampling device 120 passes through the gas pipeline and the solenoid valve 180, enters the filter pressure reducing controller, and passes through the air filter 150 and the pressure reducing valve 160 in sequence.

[0085] See also Figure 2 In some embodiments, a temperature sensor P and a pressure sensor T are further included, wherein the temperature sensor P is used to obtain the temperature in the sampling device 120, and the pressure sensor T is used to obtain the pressure in the sampling device 120;

[0086] The host computer 140 is connected to the pressure sensor P and the temperature sensor T. The host computer 140 is also used to obtain the density corresponding to the carbon dioxide according to the temperature and pressure of the sampling device 120 .

[0087] Since the density of carbon dioxide is different under different temperatures and pressures, in order to accurately obtain the mass of carbon dioxide in the mixed gas, the temperature and pressure in the sampling device 120 are obtained through the temperature sensor P and the pressure sensor T, and then the corresponding density of carbon dioxide can be obtained by looking up the table, and then the mass of carbon dioxide in the mixed gas can be accurately calculated. The specific method for calculating the mass of carbon dioxide in the mixed gas is as follows:

[0088] ①According to CO 2 Concentration detector and mixed gas volume V sg , calculate the CO in the gas phase under the temperature and pressure conditions of the sampling device 120 2 volume:

[0089] V sgco2 =V sg *VOL co2

[0090] Where: V sgco2CO in the mixed gas 2 Volume, V sg is the total volume of the mixed gas after the sampling device 120 is depressurized, VOL co2 For CO 2 Volume concentration.

[0091] ② Calculate the CO in the mixed gas 2 Pressure division:

[0092] P co2 =P 0 *VOL co2

[0093] Where: P co2 CO in the mixed gas 2 The partial pressure, P 0 is the internal pressure of the sampling device 120, VOL co2 For CO 2 Volume concentration.

[0094] ③ Look up table P co2 T 0 Under the condition of CO 2 Density value. Pure CO 2 The density data is calculated based on the gas state equation, see Table 1 for details:

[0095] Table 1: Pure CO 2 Density data under different temperature and pressure conditions (kg / m3)

[0096]

[0097] Pressure range 0-10MPa, step size 0.1MPa, temperature range 280K-400K, step size 1K;

[0098] ④ Calculate the CO in the mixed gas 2 quality:

[0099] m sgco2 =ρ co2 *V sgco2

[0100] Where: m sgco2 CO in the mixed gas 2 Mass, ρ co2 P co2 T 0 Under the condition of CO 2 Density, V sgco2 CO in the mixed gas 2 volume.

[0101] In some embodiments, the host computer 140 is also used to determine whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold value when calculating the mass of carbon dioxide in the liquid phase of the sample liquid based on the saturated solubility of carbon dioxide in oil and water. If it is greater than the threshold value, the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the temperature and pressure of the sampling device 120, and then the total mass of carbon dioxide in the liquid phase of the sample liquid is calculated based on the obtained saturated solubility; if it is less than the threshold value, the pressure in the sampling device 120 is reduced; when the pressure of the sampling device 120 is greater than a preset value, the volume concentration of the precipitated carbon dioxide is greater than the threshold value, and the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the current temperature and pressure of the sampling device 120; when the pressure in the sampling device 120 is less than the preset value, the volume concentration of the precipitated carbon dioxide is less than the threshold value, and it is determined that the sample liquid does not contain carbon dioxide.

[0102] When calculating the mass of carbon dioxide in the liquid phase of the sample solution based on the saturated solubility of carbon dioxide in oil and water, first determine VOL co2 Is it greater than the preset threshold?

[0103] 1) is greater than the threshold. It is considered that the liquid phase is saturated with dissolved CO 2 , and then use CO 2 Calculation of CO in the liquid phase from saturated solubility data in oil and water 2 quality:

[0104] ① Calculate the volume of oil and water in the liquid phase respectively:

[0105] V slo =V s *α oil ,V slw =V s *α water

[0106] Where: V slo and V slw are the volume of oil and the volume of water in the liquid phase of the sampling device 120, V s is the original sampling volume, α oil and α water They are the oil content and water content measured by the multiphase flow meter 110 respectively.

[0107] ② Look up table P co2 T 0 Under the condition of CO 2 Saturated solubility in oil and water. CO 2The solubility data of is obtained by interpolation of some known experimental data. The result data table includes the temperature range of 280K-400K, the step size is 1K, the pressure range of 0-10MPa, the step size is 0.1MPa, and the data table size is 101*121, as shown in Table 2 and Table 3 below:

[0108] Table 2: CO 2 Saturated solubility data table in crude oil (mol / L)

[0109]

[0110]

[0111] Table 3: CO 2 Saturated solubility data table in formation water (mol / L)

[0112]

[0113] ③ Calculate the CO in oil and water separately 2 Molar amount:

[0114] n o =V slo *S o ,

[0115] n w =V slw *S w ;

[0116] Where: n o and n w CO dissolved in oil and water 2 The molar amount, V slo and V slw are the volumes of oil and water in the liquid phase of the sampling device 120, S o and S w are the oil content and water content respectively.

[0117] ④ Calculate the CO in oil and water separately 2 Quality:

[0118] m soco2 =n o *M co2 ,m swco2 =n w *M co2

[0119] Where: m soco2 and m swco2 CO dissolved in oil and water 2 The quality of o and n wCO dissolved in oil and water 2 The molar amount, M co2 For CO 2 The molar mass is taken as 44.1 g / mol.

[0120] ⑤ Calculate the CO in the sample liquid 2 Total mass:

[0121] m s =m sgco2 +m soco2 +m swco2

[0122] Where: m s CO in the sampled liquid 2 Total mass, m sgco2 、m soco2 and m swco2 The mixed gas, oil and CO in water are 2 quality.

[0123] ⑥ Calculate the CO output within the preset time period 2 Total mass:

[0124]

[0125] Where: m is the CO output in the preset time period 2 Total mass, m s CO in the sample liquid 2 The total mass, V t is the total three-phase flow rate measured by the multiphase flow meter 110 within a preset time period, V s is the original sampling volume.

[0126] 2) is less than the threshold. It is considered that CO in the liquid phase 2 In an unsaturated state, the piston rod in the sampling device 120 is controlled to stretch to reduce the internal pressure of the container.

[0127] ① If CO in the precipitated gas 2 If the concentration is always less than the preset threshold and the internal pressure of the sampling device 120 is greater than 0.1 MPa, the pressure reduction process is repeated until the CO in the precipitated gas is 2 If the concentration is greater than the threshold, then calculate the output CO according to step 1) above. 2 Total amount;

[0128] ② If CO in the precipitated gas 2 If the concentration is always less than the preset threshold and the internal pressure of the sampling device 120 is less than 0.1 MPa, the sampling analysis is terminated and it is considered that the sample liquid does not contain CO. 2 , you can proceed to the next sampling analysis.

[0129] In some embodiments, the carbon dioxide concentration detector 130 needs to be calibrated to zero and 50% CO before use. 2 The calibration steps of the calibration gas are as follows:

[0130] ①Place the carbon dioxide concentration detector 130 in clean air and automatically adjust to zero with one button;

[0131] ② The carbon dioxide concentration detector 130 passes 50% concentration CO 2 Standard gas, and set the target point concentration to 50.0%;

[0132] ③ Perform target point calibration, wait for the measured concentration value to basically stabilize, and after the AD value remains basically unchanged, press the confirmation key to complete the target point calibration;

[0133] ④Introduce high-purity nitrogen to purge the gas pipeline to make CO 2 The concentration indication is reset to zero to facilitate the next measurement.

[0134] The multiphase flowmeter 110 accurately measures the oil, gas and water three-phases over the full range to obtain the three-phase phase fraction, and then a sampling device 120 with a piston rod is used to precipitate part of the CO in the liquid phase. 2 , CO in gas and liquid 2 The contents are calculated separately and then summarized, taking full account of CO 2 The solubility parameters in crude oil and formation water are expanded with high resolution using the 'S-type' curve fitting algorithm based on nonlinear least squares and the cubic spline surface interpolation algorithm, which effectively improves the calculation efficiency and accuracy. The quantitative calculation of CO in the well field production fluid is realized. 2 The total content, combined with CO 2 The injection volume is important for the later evaluation of CO 2 The sealing efficiency provides a scientific basis.

[0135] See also Figure 3 In another embodiment, a method for measuring carbon dioxide output in a well site is applied to the carbon dioxide output measuring system in the well site in the above embodiment, and the method comprises the following steps:

[0136] Step S310: Under the conditions of operating temperature and pressure, the multiphase flowmeter measures the total three-phase flow rate and three-phase phase fraction of oil, gas and water in the oil production well; wherein the operating temperature and operating pressure are both measured in real time by the temperature sensor and pressure sensor provided in the multiphase flowmeter.

[0137] Step S320: sampling the uniformly mixed three-phase fluid in the multiphase flowmeter by means of a sampling device to obtain a sample liquid, and precipitating carbon dioxide in the liquid phase of the sample liquid, and then leaving the sampling device to stand for a period of time to obtain a mixed gas containing carbon dioxide;

[0138] Step S330: detecting the volume concentration of carbon dioxide in the mixed gas by a carbon dioxide concentration detector;

[0139] Step S340: Calculating the volume of carbon dioxide in the mixed gas according to the obtained carbon dioxide volume concentration;

[0140] Step S350: obtaining the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide;

[0141] Step S360: Calculate the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water, and then obtain the total mass of carbon dioxide in the sample liquid;

[0142] Step S370: Calculate the total mass of carbon dioxide produced by the oil well in a preset time period according to the total flow rate of the three phases of oil, gas and water in the preset time period.

[0143] The multiphase flowmeter is used to measure the three-phase total flow rate and three-phase phase fraction of oil, gas and water collected from the oil production well; the sampling device is used to sample the three-phase fluid of oil, gas and water mixed evenly in the liquid outlet pipeline of the three-phase flowmeter to obtain a sample liquid, and the carbon dioxide in the liquid phase of the sample liquid is precipitated to obtain a mixed gas containing carbon dioxide, and then the mixed gas is sent to a carbon dioxide concentration detector to detect the volume concentration of carbon dioxide in the mixed gas, the volume of carbon dioxide in the mixed gas is calculated according to the obtained volume concentration of carbon dioxide, the mass of carbon dioxide in the mixed gas is obtained according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide, the mass of carbon dioxide in the liquid phase of the sample liquid is calculated according to the saturated solubility of carbon dioxide in oil and water, the mass of carbon dioxide in the mixed gas and the mass of carbon dioxide in the liquid phase are added to obtain the total mass of carbon dioxide in the sample liquid, and then the total volume of the three-phase of oil, gas and water within the preset time can be obtained according to the total three-phase flow rate of oil, gas and water collected within the preset time, and then the total mass of carbon dioxide in the oil, gas and water within the period can be obtained, thereby realizing the accurate calculation of the total content of carbon dioxide in the well site production fluid.

[0144] In some embodiments, the following steps are also included:

[0145] The mixed gas in the sampling device is sent to the carbon dioxide concentration detector after being filtered out of moisture through an air filter and stabilized by a pressure reducing valve.

[0146] The mixed gas of the original gas and the precipitated gas in the sampling device passes through the gas pipeline and the solenoid valve, enters the filter pressure reducing controller, and passes through the air filter and the pressure reducing valve in turn. The air filter is used to clean the gas source and can filter the moisture in the compressed gas to prevent the moisture from entering the carbon dioxide concentration detector with the gas. The pressure reducing valve can stabilize the gas source to keep the gas source at a constant pressure state, reducing the damage to hardware such as valves or actuators caused by sudden changes in air pressure. Among them, the pressure regulating pressure of the pressure reducing valve is less than 0.5MPa.

[0147] In some embodiments, obtaining the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide specifically comprises the following steps:

[0148] Obtain the density corresponding to carbon dioxide according to the temperature and pressure in the sampling device;

[0149] The mass of carbon dioxide in the mixed gas is calculated based on the volume of carbon dioxide in the mixed gas and the obtained density of carbon dioxide.

[0150] Since the density of carbon dioxide is different under different temperatures and pressures, in order to accurately obtain the mass of carbon dioxide in the mixed gas, the temperature and pressure in the sampling device are obtained through the temperature sensor and the pressure sensor, and then the corresponding density of carbon dioxide can be obtained by looking up the table, and then the mass of carbon dioxide in the mixed gas can be accurately calculated. The specific calculation method of the mass of carbon dioxide in the mixed gas is as follows:

[0151] ①According to CO 2 Concentration detector and mixed gas volume V sg , calculate the CO in the gas phase under the temperature and pressure conditions of the sampling device 2 volume:

[0152] V sgco2 =V sg *VOL co2

[0153] Where: V sgco2 CO in the mixed gas 2 Volume, V sg VOL is the total volume of the mixed gas after the sampling device is depressurized. co2 For CO 2 Volume concentration.

[0154] ② Calculate the CO in the mixed gas 2 Pressure division:

[0155] P co2 =P 0 *VOL co2

[0156] Where: P co2CO in the mixed gas 2 The partial pressure, P 0 is the internal pressure of the sampling device, VOL co2 For CO 2 Volume concentration.

[0157] ③ Look up table P co2 T 0 Under the condition of CO 2 Density value. Pure CO 2 The density data is calculated according to the gas state equation, see Table 1 for details;

[0158] ④ Calculate the CO in the mixed gas 2 quality:

[0159] m sgco2 =ρ co2 *V sgco2

[0160] Where: m sgco2 CO in the mixed gas 2 Mass, ρ co2 P co2 T 0 Under the condition of CO 2 Density, V sgco2 CO in the mixed gas 2 volume.

[0161] See also Figure 4 In some embodiments, the step of calculating the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water specifically comprises the following steps:

[0162] Step S410: determining whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold;

[0163] If it is greater than the threshold, then executing step S420: obtaining the corresponding saturated solubility of carbon dioxide in oil and water according to the temperature and pressure of the sampling device;

[0164] Step S430: Calculate the total mass of carbon dioxide in the liquid phase of the sample liquid according to the acquired saturated solubility;

[0165] If it is less than the threshold, executing step S440: reducing the pressure in the sampling device;

[0166] Step S450: determining whether the volume concentration of the precipitated carbon dioxide is greater than a threshold value when the pressure of the sampling device is greater than a preset value;

[0167] If yes, then execute step S460: obtain the corresponding saturated solubility of carbon dioxide in oil and water according to the current temperature and pressure of the sampling device, and obtain the corresponding saturated solubility of carbon dioxide in oil and water according to the temperature and pressure of the sampling device;

[0168] If not, that is, when the pressure in the sampling device is less than the preset value and the volume concentration of the precipitated carbon dioxide is less than the threshold value, step 470 is executed: determining that the sample liquid does not contain carbon dioxide.

[0169] When calculating the mass of carbon dioxide in the liquid phase of the sample solution based on the saturated solubility of carbon dioxide in oil and water, first determine VOL co2 Is it greater than the preset threshold?

[0170] 1) is greater than the threshold. It is considered that the liquid phase is saturated with dissolved CO 2 , and then use CO 2 Calculation of CO in the liquid phase from saturated solubility data in oil and water 2 quality:

[0171] ① Calculate the volume of oil and water in the liquid phase respectively:

[0172] V slo =V s *α oil ,V slw =V s *α water

[0173] Where: V slo and V slw are the volume of oil and water in the liquid phase of the sampling device, V s is the original sampling volume, α oil and α water They are the oil content and water content measured by the multiphase flow meter respectively.

[0174] ② Look up table P co2 T 0 Under the condition of CO 2 Saturated solubility in oil and water. CO 2 The solubility data of is obtained by interpolation of some known experimental data. The result data table includes the temperature range of 280K-400K, the step size is 1K, the pressure range of 0-10MPa, the step size is 0.1MPa, and the data table size is 101*121, as shown in Table 2 and Table 3;

[0175] ③ Calculate the CO in oil and water separately 2 Molar amount:

[0176] n o =V slo *S o ,

[0177] n w =V slw *S w ;

[0178] Where: n o and n w CO dissolved in oil and water 2 The molar amount, V slo and V slw are the volumes of oil and water in the liquid phase of the sampling device, S o and S w are the oil content and water content respectively.

[0179] ④ Calculate the CO in oil and water separately 2 Quality:

[0180] m soco2 =n o *M co2 ,m swco2 =n w *M co2

[0181] Where: m soco2 and m swco2 CO dissolved in oil and water 2 The quality of o and n w CO dissolved in oil and water 2 The molar amount, M co2 For CO 2 The molar mass is taken as 44.1 g / mol.

[0182] ⑤ Calculate the CO in the sample liquid 2 Total mass:

[0183] m s =m sgco2 +m soco2 +m swco2

[0184] Where: m s CO in the sample liquid 2 Total mass, m sgco2 、m soco2 and m swco2 The mixed gas, oil and CO in water are 2 quality.

[0185] ⑥ Calculate the CO output within the preset time period 2 Total mass:

[0186]

[0187] Where: m is the CO output in the preset time period 2 Total mass, m s CO in the sample liquid 2 The total mass, V t V is the total three-phase flow rate measured by the multiphase flowmeter within the preset time period, s is the original sampling volume.

[0188] 2) is less than the threshold. It is considered that CO in the liquid phase 2 In an unsaturated state, the piston rod in the sampling device is controlled to stretch to reduce the internal pressure of the container.

[0189] ① If CO in the precipitated gas 2 If the concentration is always less than the preset threshold and the internal pressure of the sampling device is greater than the preset value, which is 0.1 MPa, the pressure reduction process is repeated until the CO in the gas is precipitated. 2 If the concentration is greater than the threshold, then calculate the output CO according to step 1) above. 2 Total amount;

[0190] ② If CO in the precipitated gas 2 If the concentration is always less than the preset threshold and the internal pressure of the sampling device is less than 0.1 MPa, the sampling analysis is terminated and it is considered that the sample liquid does not contain CO. 2 , you can proceed to the next sampling analysis.

[0191] See also Figure 5 In some embodiments, the method further includes the step of calibrating the carbon dioxide concentration detector, which includes the following steps:

[0192] Step S510: placing the carbon dioxide concentration detector in clean air and automatically adjusting to zero;

[0193] Step S520: introducing 50% concentration of carbon dioxide standard gas into the carbon dioxide concentration detector, and setting the target point concentration to 50%;

[0194] Step S530: perform target point calibration, wait for the concentration value detected by the carbon dioxide concentration detector to stabilize, and complete the target point calibration;

[0195] Step S540: high-purity nitrogen is introduced into the carbon dioxide concentration detector to purge the gas pipeline to return the carbon dioxide concentration value to zero.

[0196] The carbon dioxide concentration detector needs to be calibrated to zero point and 50% CO before use. 2 The calibration steps of the calibration gas are as follows:

[0197] ①Place the carbon dioxide concentration detector in clean air and automatically adjust to zero with one button;

[0198] ② The carbon dioxide concentration detector introduces 50% concentration CO 2 Standard gas, and set the target point concentration to 50.0%;

[0199] ③ Perform target point calibration, wait for the measured concentration value to basically stabilize, and after the AD value remains basically unchanged, press the confirmation key to complete the target point calibration;

[0200] ④Introduce high-purity nitrogen to purge the gas pipeline to make CO 2 The concentration indication is reset to zero to facilitate the next measurement.

[0201] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A carbon dioxide output metering system in a well site, characterized in that: include: A multiphase flowmeter, which is connected to the liquid outlet pipeline at the wellhead of the oil production well and is used to measure the total flow rate and phase fraction of the three phases of oil, gas and water; A sampling device, wherein the sampling port of the sampling device is connected to the rear main line of the multiphase flowmeter, and the sampling device is used to sample from the multiphase flowmeter to obtain a sample liquid containing oil, gas and water, and precipitate carbon dioxide from the liquid phase of the sample liquid to obtain a mixed gas containing carbon dioxide; A carbon dioxide concentration detector, the carbon dioxide concentration detector is connected to the sampling device, and the carbon dioxide concentration detector detects the volume concentration of carbon dioxide in the mixed gas; The host computer is connected to the multiphase flow meter, the sampling device and the carbon dioxide concentration detector. The host computer is used to calculate the volume of carbon dioxide in the mixed gas according to the obtained carbon dioxide volume concentration, obtain the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide, calculate the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water, and then obtain the total mass of carbon dioxide in the sample liquid, and calculate the total mass of carbon dioxide produced by the oil well in the preset time period according to the total flow rate of the three phases of oil, gas and water in the preset time period.

2. The carbon dioxide output metering system in a well site according to claim 1, characterized in that: It also includes an air filter, which is arranged between the sampling device and the carbon dioxide concentration detector, and is used to filter moisture in the mixed gas.

3. The carbon dioxide output metering system in a well site according to claim 1, characterized in that: It also includes a pressure reducing valve, which is arranged between the sampling device and the carbon dioxide concentration detector, and is used to stabilize the pressure of the gas source.

4. The carbon dioxide output metering system in a well site according to claim 1, characterized in that: It also includes a temperature sensor and a pressure sensor, wherein the temperature sensor is used to obtain the temperature in the sampling device, and the pressure sensor is used to obtain the pressure in the sampling device; The host computer is connected to the pressure sensor and the temperature sensor, and is also used to obtain the density corresponding to the carbon dioxide according to the temperature and pressure of the sampling device.

5. The carbon dioxide output metering system in a well site according to claim 1, characterized in that: The host computer is also used to determine whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold value when calculating the mass of carbon dioxide in the liquid phase of the sample liquid based on the saturated solubility of carbon dioxide in oil and water. If it is greater than the threshold value, the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the temperature and pressure of the sampling device, and then the total mass of carbon dioxide in the liquid phase of the sample liquid is calculated based on the obtained saturated solubility; if it is less than the threshold value, the pressure in the sampling device is reduced; when the pressure of the sampling device is greater than a preset value, the volume concentration of the precipitated carbon dioxide is greater than the threshold value, and the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the current temperature and pressure of the sampling device; when the pressure in the sampling device is less than the preset value, the volume concentration of the precipitated carbon dioxide is less than the threshold value, and it is determined that the sample liquid does not contain carbon dioxide.

6. A method for measuring carbon dioxide output in a well site, characterized in that: The following steps are involved: Under the conditions of operating temperature and pressure, the multiphase flowmeter measures the total flow rate and three-phase fraction of oil, gas and water in the oil well; The uniformly mixed three-phase fluid in the multiphase flowmeter is sampled by a sampling device to obtain a sample liquid, and carbon dioxide in the liquid phase of the sample liquid is precipitated, and then the sampling device is left to stand for a period of time to obtain a mixed gas containing carbon dioxide; The volume concentration of carbon dioxide in the mixed gas is detected by a carbon dioxide concentration detector; The volume of carbon dioxide in the mixed gas is calculated according to the obtained carbon dioxide volume concentration; The mass of carbon dioxide in the mixed gas is obtained according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide; The mass of carbon dioxide in the liquid phase of the sample liquid is calculated according to the saturated solubility of carbon dioxide in oil and water, thereby obtaining the total mass of carbon dioxide in the sample liquid; The total mass of carbon dioxide produced by the oil well during the preset time period is calculated based on the total flow rate of the three phases of oil, gas and water during the preset time period.

7. The method for measuring carbon dioxide output in a well site according to claim 6, characterized in that: The following steps are also included: The mixed gas in the sampling device is sent to the carbon dioxide concentration detector after being filtered out of moisture through an air filter and stabilized by a pressure reducing valve.

8. The method for measuring carbon dioxide output in a well site according to claim 6, characterized in that: The method of obtaining the mass of carbon dioxide in the mixed gas according to the volume of carbon dioxide in the mixed gas and the density of carbon dioxide specifically comprises the following steps: Obtain the density corresponding to carbon dioxide according to the temperature and pressure in the sampling device; The mass of carbon dioxide in the mixed gas is calculated based on the volume of carbon dioxide in the mixed gas and the obtained density of carbon dioxide.

9. The method for measuring carbon dioxide output in a well site according to claim 6, characterized in that: The method of calculating the mass of carbon dioxide in the liquid phase of the sample liquid according to the saturated solubility of carbon dioxide in oil and water specifically comprises the following steps: Determine whether the volume concentration of carbon dioxide in the mixed gas is greater than a threshold value; If it is greater than the threshold, the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the temperature and pressure of the sampling device; The total mass of carbon dioxide in the liquid phase of the sample liquid is calculated based on the obtained saturated solubility; If it is less than the threshold, the pressure in the sampling device is reduced; When the pressure of the sampling device is greater than a preset value, the volume concentration of the precipitated carbon dioxide is greater than a threshold value, and the corresponding saturated solubility of carbon dioxide in oil and water is obtained according to the current temperature and pressure of the sampling device; When the pressure in the sampling device is lower than a preset value and the volume concentration of the precipitated carbon dioxide is lower than a threshold value, it is determined that the sample liquid does not contain carbon dioxide.

10. The method for measuring carbon dioxide output in a well site according to claim 6, characterized in that: It also includes the calibration steps for the carbon dioxide concentration detector, which are as follows: Place the carbon dioxide concentration detector in clean air and perform automatic zero adjustment; A 50% concentration of carbon dioxide standard gas is introduced into the carbon dioxide concentration detector, and the target point concentration is set to 50%; Perform target point calibration, wait for the concentration value detected by the carbon dioxide concentration detector to stabilize, and complete the target point calibration; High-purity nitrogen is introduced into the carbon dioxide concentration detector to purge the gas pipeline to return the carbon dioxide concentration value to zero.

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