A method for observing and evaluating methane emissions from offshore oil and gas platforms

Abstract

The present invention discloses an observation and evaluation method for methane emissions from an offshore oil and gas platform, comprising: obtaining and analyzing data information of the offshore oil and gas platform, obtaining influencing factors for the evaluation of methane emissions from the offshore oil and gas platform; sorting out the types of influencing factors for the evaluation of methane emissions; formulating a survey plan for methane emissions from the offshore oil and gas platform by ship cruise observation; performing cruise observation of methane emissions from the offshore oil and gas platform to obtain observation data; based on the basic characteristics of methane emissions from the offshore oil and gas platform, analyzing the correlation and mutual matching between the acquired data, and preliminarily evaluating the quality of the acquired data while eliminating abnormal data; determining the atmospheric methane concentration value of the offshore oil and gas platform; quantitatively evaluating the methane emissions from the offshore oil and gas platform; correcting and adjusting the methane emissions from the offshore oil and gas platform, analyzing and evaluating the influencing factors of the methane emissions from the offshore oil and gas platform, and finally determining the methane emissions from the offshore oil and gas platform.

Description

Technical Field

[0001] The present invention relates to the technical field of marine environment observation, and in particular to a method for observing and evaluating methane (CH4) emissions from marine oil and gas platforms. Background Art

[0002] CH4 is the second most potent greenhouse gas in the atmosphere after CO2, contributing 18.2% to global warming. CH4 has a high warming potential and a short lifespan.

[0003] The existing technology uses the emission factor estimation method to calculate greenhouse gas emissions. This method has the following problems: (1) In oil and gas production, the emission contribution of different components is unclear, and the source of the default value calculation is unclear; (2) The emission factor was formulated based on the Canadian oil and gas industry emission factor, which was relatively early and the process of empirical correction of the emission factor is not transparent; (3) There is a lack of verification and support from measured data, and the calculation results are also subject to great uncertainty. In addition, the operating modes and emission reduction measures of offshore oil and gas platforms are very different from those on land. The diversity and timeliness of emission factors will lead to large differences between the calculation results and actual emissions. In recent years, satellite remote sensing, as an emerging observation method, has been successfully used in the observation and research of CH4 point source emissions on land through signal inversion and ground-based data correction. This method has the advantages of wide coverage and rapid response, but is limited by sea surface reflection and weather and sea conditions. Satellite remote sensing observation and research on CH4 emissions from offshore oil and gas platforms is still in its infancy. Therefore, overall, there is currently a lack of observation and assessment methods for methane emissions from offshore oil and gas platforms, which makes it impossible to accurately assess methane emissions from offshore oil and gas platforms, limiting methane emission reduction and comprehensive management from offshore oil and gas platforms. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention discloses a method for observing and evaluating methane emissions from offshore oil and gas platforms, which specifically includes the following steps:

[0005] S1: Data acquisition and analysis of offshore oil and gas platforms, including: (1) attributes of oil and gas platforms: production scale, production facilities, process flow, oil and gas production, greenhouse gas emissions, and total amount of associated gas combustion; (2) atmospheric and sea conditions of oil and gas platforms: meteorological characteristics, air mass conditions, hydrological characteristics, and other development activities.

[0006] S2: Analysis of factors affecting the assessment of methane emissions from offshore oil and gas platforms. Based on the analysis of offshore oil and gas platform data, the types of factors affecting the assessment of methane emissions are sorted out, including but not limited to land-sea air mass transport, atmospheric methane background, sea-air exchange, and the impact of ship activities.

[0007] S3: Development of a survey plan for methane emissions from offshore oil and gas platforms based on ship-borne observations, including:

[0008] (1) The stage of the ship approaching the oil and gas platform in a straight line from the downwind direction: The distance (generally 10 km) that the observation ship approaches from the downwind direction of the oil and gas platform is determined based on the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc. The observation ship approaches the oil and gas platform at a constant speed of 4-5 knots from the downwind direction of the oil and gas platform, and obtains atmospheric data such as atmospheric methane concentration at different distances from the downwind direction of the oil and gas platform. In addition, data related to the water column profile are collected at 10 km, 5 km, 2.5 km, and 1.0 km respectively based on the seawater thermohaline jump layer.

[0009] (2) Ship orbiting the oil and gas platform: The observation ship orbits the oil and gas platform with a radius of 1-2 km (adjusted according to the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc.) to obtain atmospheric data such as the atmospheric methane concentration around the oil and gas platform.

[0010] (3) The stage of the ship sailing away from the oil and gas platform in an "S" shape from the downwind direction: the observation ship sails away from the oil and gas platform in an "S" shape trajectory at a constant speed of 4-5 knots from the downwind direction of the oil and gas platform (the width and distance of the "S" shape are adjusted according to the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc.), and obtains atmospheric methane concentration and other atmospheric related data in different ranges downwind of the oil and gas platform.

[0011] S4: Underway observation of methane emissions from offshore oil and gas platforms, obtaining observation data, including:

[0012] (1) Atmospheric data observed during ship navigation: longitude, latitude, atmospheric methane concentration, atmospheric temperature, atmospheric humidity, atmospheric pressure, sea surface wind direction, sea surface wind speed, ship speed, etc.;

[0013] (2) Seawater column profile sampling observation data: longitude, latitude, depth, temperature, salinity, dissolved oxygen, and dissolved methane concentration in seawater.

[0014] S5: Observation data quality assessment and quality control. Based on the basic characteristics of methane emissions from offshore oil and gas platforms, analyze the correlation and mutual matching between the acquired data, preliminarily evaluate the quality of the acquired data, eliminate abnormal data, and ensure the scientific nature of the data.

[0015] S6: Determination of atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms, analysis of the impact of land-sea air mass transport and atmospheric methane background on the observed methane concentration of offshore oil and gas platforms, the observed atmospheric methane concentration is X 总 , the concentration of methane transported by the land-sea air mass is X 陆海气团 , atmospheric methane background concentration is X 大气本底 , then the concentration of atmospheric methane X(x,y,z) on the offshore oil and gas platform is:

[0016] X(x,y,z)=X 总 -X 陆海气团 -X 大气

[0017] S7: Methane emissions from offshore oil and gas platforms (Q 油气平台 ), analyze the impact of sea-air exchange and ship activities on the assessment of methane emissions from offshore oil and gas platforms, and build a model to assess the methane emissions Q of offshore oil and gas platforms. 油气平台 :

[0018] Q 油气平台 =Q 总 -Q 海-气交换 -Q 船舶活动

[0019] Where Q 总 is the total amount of methane emissions assessed by atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms, Q 海-气交换 and Q 船舶活动 are the methane emissions from sea-air exchange and ship activities, respectively.

[0020] S8: Correction and adjustment of methane emissions from offshore oil and gas platforms. Comprehensively analyze the impact of different influencing factors, including but not limited to land-sea air mass transport, atmospheric methane background, sea-air exchange, and ship activities, on the assessment of methane emissions from offshore oil and gas platforms. Combined with the basic characteristics of methane emissions from offshore oil and gas platforms, the assessment results are corrected and adjusted to ultimately determine the methane emissions from offshore oil and gas platforms.

[0021] Furthermore, the total amount of methane emissions (Q 总 ) uses the following algorithm:

[0022]

[0023] Where u is the wind speed along the main axis of the CH4 emission plume; σ y and σ z are the horizontal and vertical standard deviations of the atmospheric CH4 concentration distribution, respectively; y is the lateral diffusion distance of the CH4 emission plume; z is the distance between the offshore oil and gas platform and the sea surface; x is the distance between the observation point and the offshore oil and gas platform; h s is the emission source height of the offshore oil and gas platform; X(x, y, z) is the atmospheric methane concentration of the offshore oil and gas platform after eliminating the effects of land-sea air mass transport and atmospheric methane background:

[0024] X(x,y,z)=X 总 -X 陆海气团 -X 大气本底

[0025] Where, X 总is the atmospheric methane concentration observed in the area around the offshore oil and gas platform, X 陆海气团 Concentration of methane transported to land and sea air masses, X 大气本底 is the background concentration of atmospheric methane.

[0026] Furthermore, the impact of sea-air exchange on the assessment of methane emissions from offshore oil and gas platforms (Q 海-气交换 ) uses the following algorithm:

[0027] Q 海-气交换 =0.251u 2 ×(2356.2-166.38t+6.3952t 2 -0.13422t 3 +0.0011506t 4 / 660) -0.5 ×(C g (βRT / V CH4 +V g / V l )-C eq )

[0028] Where: u is the wind speed along the main axis of the CH4 emission plume; t is the seawater temperature; C g is the CH4 concentration in the gas phase after gas-liquid equilibrium; β is the CH4 solubility coefficient in seawater; R is the gas state constant; T is the absolute temperature; V CH4 is the molar volume of CH4 under standard conditions; V g and V l are the volumes of gas and liquid phases in equilibrium in the headspace of seawater, respectively; C eq It is the concentration of dissolved CH4 in seawater when the surface seawater is in equilibrium with the atmosphere.

[0029] Furthermore, the impact of ship activities on the assessment of methane emissions from offshore oil and gas platforms (Q 船舶活动 ) uses the following algorithm:

[0030]

[0031] Where: u is the wind speed along the main axis of the CH4 emission plume; and are the horizontal and vertical standard deviations of the distribution of CH4 emitted from ship activities, respectively; is the elevated atmospheric CH4 concentration caused by ship activity emissions; x0' is the distance between the observation point and the ship; y0' is the lateral diffusion distance of the CH4 emission plume from ship activity; z0' is the distance between the ship and the sea surface; h s ' is the height of the emission source from ship activities.

[0032] Due to the adoption of the above-mentioned technical solution, the present invention provides a method for observing and evaluating methane emissions from offshore oil and gas platforms. This method uses actual measured data from ships during navigation, and is more authentic, representative, and real-time. It can scientifically and accurately realize the observation and evaluation of methane emissions from offshore oil and gas platforms, and its accuracy is significantly improved compared to traditional indirect estimation methods such as emission factor estimation methods. In addition, the present invention classifies different influencing factors for evaluating methane emissions from offshore oil and gas platforms based on the basic characteristics of methane emissions from offshore oil and gas platforms, enhances the ability to express the characteristics of different influencing factor processes, and can comprehensively and efficiently quantitatively evaluate methane emissions from offshore oil and gas platforms, sort out the influence of different influencing factors, and overcome the limitation of traditional methods that require clear emission factors. Therefore, this method can be widely used in the observation and evaluation of methane emissions from offshore oil and gas platforms, and can provide an important technical basis for precise methane emission reduction and comprehensive management of offshore oil and gas platforms, and contribute to the realization of a green and low-carbon transformation of the offshore oil and gas industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 Flowchart of the method of the present invention.

[0035] Figure 2 Schematic diagram of the spatiotemporal variation of atmospheric CH4 observed by a ship circling a typical oil and gas platform in the Bohai Sea in the embodiment. DETAILED DESCRIPTION

[0036] To make the technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention:

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] like Figure 1 The method for observing and evaluating methane emissions from an offshore oil and gas platform includes the following steps:

[0040] S1: Data acquisition and analysis of offshore oil and gas platforms, including: (1) attributes of oil and gas platforms: production scale, production facilities, process flow, oil and gas production, greenhouse gas emissions, and total amount of associated gas combustion; (2) atmospheric and sea conditions of oil and gas platforms: meteorological characteristics, air mass conditions, hydrological characteristics, and other development activities.

[0041] S2: Analysis of factors affecting the assessment of methane emissions from offshore oil and gas platforms. Based on the analysis of offshore oil and gas platform data, the types of factors affecting the assessment of methane emissions are sorted out, including but not limited to land-sea air mass transport, atmospheric methane background, sea-air exchange, and the impact of ship activities.

[0042] S3: Development of a survey plan for methane emissions from offshore oil and gas platforms based on ship-borne observations, including:

[0043] (1) The stage of the ship approaching the oil and gas platform in a straight line from the downwind direction: The distance (generally 10 km) that the observation ship approaches from the downwind direction of the oil and gas platform is determined based on the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc. The observation ship approaches the oil and gas platform at a constant speed of 4-5 knots from the downwind direction of the oil and gas platform, and obtains atmospheric data such as atmospheric methane concentration at different distances from the downwind direction of the oil and gas platform. In addition, data related to the water column profile are collected at 10 km, 5 km, 2.5 km, and 1.0 km respectively based on the seawater thermohaline jump layer.

[0044] (2) Ship orbiting the oil and gas platform: The observation ship orbits the oil and gas platform with a radius of 1-2 km (adjusted according to the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc.) to obtain atmospheric data such as the atmospheric methane concentration around the oil and gas platform.

[0045] (3) The stage of the ship sailing away from the oil and gas platform in an "S" shape from the downwind direction: the observation ship sails away from the oil and gas platform in an "S" shape trajectory at a constant speed of 4-5 knots from the downwind direction of the oil and gas platform (the width and distance of the "S" shape are adjusted according to the scale of the oil and gas platform, the condition of the observation ship, the on-site sea conditions, etc.), and obtains atmospheric methane concentration and other atmospheric related data in different ranges downwind of the oil and gas platform.

[0046] S4: Underway observation of methane emissions from offshore oil and gas platforms, obtaining observation data, including:

[0047] (1) Atmospheric data observed during ship navigation: longitude, latitude, atmospheric methane concentration, atmospheric temperature, atmospheric humidity, atmospheric pressure, sea surface wind direction, sea surface wind speed, ship speed, etc.;

[0048] (2) Seawater column profile sampling observation data: longitude, latitude, depth, temperature, salinity, dissolved oxygen, and dissolved methane concentration in seawater.

[0049] S5: Observation data quality assessment and quality control. Based on the basic characteristics of methane emissions from offshore oil and gas platforms, analyze the correlation and mutual matching between the acquired data, preliminarily evaluate the quality of the acquired data, eliminate abnormal data, and ensure the scientific nature of the data.

[0050] S6: Determination of atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms, analysis of the impact of land-sea air mass transport and atmospheric methane background on the observed methane concentration of offshore oil and gas platforms, the observed atmospheric methane concentration is X 总 , the concentration of methane transported by the land-sea air mass is X 陆海气团 , atmospheric methane background concentration is X 大气本底 , then the concentration of atmospheric methane X(x,y,z) on the offshore oil and gas platform is:

[0051] X(x,y,z)=X 总 -X 陆海气团 -X 大气

[0052] S7: Methane emissions from offshore oil and gas platforms (Q 油气平台 ), analyze the impact of sea-air exchange and ship activities on the assessment of methane emissions from offshore oil and gas platforms, and build a model to assess the methane emissions Q of offshore oil and gas platforms. 油气平台 :

[0053] Q 油气平台 =Q 总 -Q 海-气交换 -Q 船舶活动

[0054] Where Q 总is the total amount of methane emissions assessed by atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms, Q 海-气交换 and Q 船舶活动 are the methane emissions from sea-air exchange and ship activities, respectively.

[0055] S8: Correction and adjustment of methane emissions from offshore oil and gas platforms. Comprehensively analyze the impact of different influencing factors, including but not limited to land-sea air mass transport, atmospheric methane background, sea-air exchange, and ship activities, on the assessment of methane emissions from offshore oil and gas platforms. Combined with the basic characteristics of methane emissions from offshore oil and gas platforms, the assessment results are corrected and adjusted to ultimately determine the methane emissions from offshore oil and gas platforms.

[0056] Example:

[0057] First, obtain and analyze the data of marine oil and gas platforms, including the properties of the oil and gas platforms and the atmospheric and sea conditions of the oil and gas platforms; sort out and analyze the factors affecting the assessment of methane emissions from marine oil and gas platforms, including but not limited to the transport of land-sea air masses, atmospheric methane background, sea-air exchange, and the impact of ship activities; formulate and refine a marine oil and gas platform methane emission survey plan based on ship underway observations applicable to the target marine oil and gas platforms, including: the stage of the ship approaching the oil and gas platform in a straight line downwind, the stage of the ship circling the oil and gas platform, and the stage of the ship leaving the oil and gas platform in an "S" shape downwind; implement underway observations of methane emissions from marine oil and gas platforms to obtain observation data The data include: atmospheric data observed by ships during navigation and seawater column profile sampling observation data; comprehensive analysis of observation data, quality assessment and quality control to ensure the scientific nature of the data; analysis of the impact of land-sea air mass transport and atmospheric methane background on the observed methane concentration of offshore oil and gas platforms, and determination of the atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms; analysis of the impact of sea-air exchange and ship activities on the assessment of methane emissions from offshore oil and gas platforms, construction of a quantitative assessment model, correction and adjustment of the assessment results based on the basic characteristics of methane emissions from offshore oil and gas platforms, and final determination of the methane emissions (Q) of offshore oil and gas platforms. 油气平台 ):

[0058] Q 油气平台 =Q 总 -Q 海-气交换 -Q 船舶活动

[0059] Where Q 总 is the total amount of methane emissions assessed by atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms, Q 海-气交换 and Q 船舶活动 are the methane emissions from sea-air exchange and ship activities, respectively.

[0060] The total amount of methane emissions (Q) estimated by atmospheric methane concentration (X(x,y,z)) of offshore oil and gas platforms 总 ):

[0061]

[0062] Where u is the wind speed along the main axis of the CH4 emission plume; σ y and σ z are the horizontal and vertical standard deviations of the atmospheric CH4 concentration distribution, respectively; y is the lateral diffusion distance of the CH4 emission plume; z is the distance between the offshore oil and gas platform and the sea surface; x is the distance between the observation point and the offshore oil and gas platform; h s is the emission source height of the offshore oil and gas platform; X(x, y, z) is the atmospheric methane concentration of the offshore oil and gas platform after eliminating the effects of land-sea air mass transport and atmospheric methane background:

[0063] X(x,y,z)=X 总 -X 陆海气团 -X 大气本底

[0064] Where, X 总 is the atmospheric methane concentration observed in the area around the offshore oil and gas platform, X 陆海气团 Concentration of methane transported to land and sea air masses, X 大气本底 is the background concentration of atmospheric methane.

[0065] The impact of sea-air exchange on the assessment of methane emissions from offshore oil and gas platforms (Q 海-气交换 ):

[0066] Q 海-气交换 =0.251u 2 ×(2356.2-166.38t+6.3952t 2 -0.13422t 3 +0.0011506t 4 / 660) -0. 5×(C g (βRT / V CH4 +V g / V l )-C eq )

[0067] Where: u is the wind speed along the main axis of the CH4 emission plume; t is the seawater temperature; C g is the CH4 concentration in the gas phase after gas-liquid equilibrium; β is the CH4 solubility coefficient in seawater; R is the gas state constant; T is the absolute temperature; V CH4 is the molar volume of CH4 under standard conditions; V g and V l are the volumes of gas and liquid phases in equilibrium in the headspace of seawater, respectively; C eqIt is the concentration of dissolved CH4 in seawater when the surface seawater is in equilibrium with the atmosphere.

[0068] Impact of ship activities on the assessment of methane emissions from offshore oil and gas platforms (Q 船舶活动 ):

[0069]

[0070] Where: u is the wind speed along the main axis of the CH4 emission plume; and are the horizontal and vertical standard deviations of the distribution of CH4 emitted from ship activities, respectively; is the elevated atmospheric CH4 concentration caused by ship activity emissions; x0' is the distance between the observation point and the ship; y0' is the lateral diffusion distance of the CH4 emission plume from ship activity; z0' is the distance between the ship and the sea surface; h s ' is the height of the emission source from ship activities.

[0071] Example

[0072] Based on the ship navigation observation data of typical oil and gas platforms in Bohai Sea in 2023, the atmospheric methane concentration of marine oil and gas platforms is: 2145-2441ppb, which is significantly higher than the methane concentration of the surface atmosphere of Bohai Sea. The methane emissions of marine oil and gas platforms are 56-216kg / h. The sea-air exchange effect is an important influencing factor in the assessment of methane emissions from marine oil and gas platforms. Based on the inventive method, high-precision observation of atmospheric methane concentrations of marine oil and gas platforms and accurate assessment of methane emissions from marine oil and gas platforms are achieved, which clarifies that the sea-air exchange effect is an important influencing factor in the assessment of methane emissions from marine oil and gas platforms; it is more scientific and accurate than the methane emissions of marine oil and gas platforms assessed by traditional emission factor estimation methods, and is in line with objective reality. Therefore, it can be seen that the inventive method more scientifically and accurately assesses the methane emissions of marine oil and gas platforms, and accurately sorts out the main influencing factors. Such as Figure 2 The figure shows the spatiotemporal changes of atmospheric CH4 observed by a ship circling a typical oil and gas platform in the Bohai Sea in 2023.

[0073] The present invention uses real-time observation data from ship-based navigation, which is more authentic, representative and real-time. It can scientifically and accurately realize the precise assessment of methane emissions from offshore oil and gas platforms, and its accuracy is significantly improved compared with traditional indirect estimation methods such as emission factor estimation.

[0074] Based on the basic characteristics of methane emissions from offshore oil and gas platforms, the present invention classifies different influencing factors for evaluating methane emissions from offshore oil and gas platforms, enhances the ability to express the characteristics of processes involving different influencing factors, and can comprehensively and efficiently quantitatively evaluate methane emissions from offshore oil and gas platforms, sorting out the effects of different influencing factors, thus overcoming the limitation of traditional methods that require clear emission factors.

[0075] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for observing and evaluating methane emissions from offshore oil and gas platforms, characterized in that include: Acquire and analyze offshore oil and gas platform information, including oil and gas platform attribute information and atmospheric and sea conditions information; Obtain the influencing factors of methane emission assessment of offshore oil and gas platforms: sort out the types of influencing factors of methane emission assessment based on offshore oil and gas platform data information; Formulate a survey plan for methane emissions from offshore oil and gas platforms using ship-borne observations; Conduct cruise observations of methane emissions from offshore oil and gas platforms to obtain observation data; Based on the basic characteristics of methane emissions from offshore oil and gas platforms, the correlation and matching between the acquired data are analyzed, and the quality of the acquired data is preliminarily evaluated while eliminating abnormal data; Determine atmospheric methane concentration values ​​on offshore oil and gas platforms; Quantitative assessment of methane emissions from offshore oil and gas platforms; Correct and adjust the methane emissions of offshore oil and gas platforms, analyze and evaluate the factors affecting methane emissions of offshore oil and gas platforms, correct and adjust the evaluation results based on the basic characteristics of methane emissions from offshore oil and gas platforms, and ultimately determine the methane emissions of offshore oil and gas platforms; Quantitative assessment of methane emissions from offshore oil and gas platforms: Analyze the impact of sea-air exchange and ship activities on the assessment of methane emissions from offshore oil and gas platforms, and use the following algorithm to assess methane emissions from offshore oil and gas platforms Q 油气平台 : Q 油气平台 =Q 总 -Q 海-气交换 -Q 船舶活动 Q 总 is the total amount of methane emissions based on the atmospheric methane concentration assessment of offshore oil and gas platforms, Q 海-气交换 is the methane emission from sea-air exchange, Q 船舶活动 methane emissions from ship activities; Evaluate the total amount of methane emissions Q based on the atmospheric methane concentration X(x, y, z) of offshore oil and gas platforms 总 : Where u is the wind speed along the main axis of the CH4 emission plume, σ y and σ z are the horizontal and vertical standard deviations of atmospheric CH4 concentration distribution, y is the lateral diffusion distance of CH4 emission plume, z is the distance between the offshore oil and gas platform and the sea surface, x is the distance between the observation point and the offshore oil and gas platform, and h is the distance between the observation point and the offshore oil and gas platform. s is the height of the emission source of the offshore oil and gas platform, and X(x, y, z) is the atmospheric methane concentration of the offshore oil and gas platform after eliminating the influence of land and sea air mass transport and atmospheric methane background: X(x,y,z)=X 总 -X 陆海气团 -X 大气本底 Where, X 总 is the observed atmospheric methane concentration in the offshore oil and gas platform area, X 陆海气团 The concentration of methane transported to the land-sea air mass, X 大气本底 is the atmospheric methane background concentration; When analyzing and evaluating the factors affecting methane emissions from offshore oil and gas platforms: The impact of sea-air exchange on the assessment of methane emissions from offshore oil and gas platforms 海-气交换 The following algorithm is used: Q 海-气交换 =0.251u 2 ×(2356.2-166.38t+6.3952t 2 -0.13422t 3 +0.0011506t 4 / 660) -0.5 ×(Cg(βRT / V CH4 +V g / V l )-C eq ) Where: u is the wind speed along the main axis of the CH4 emission plume, t is the seawater temperature, C g is the CH4 concentration in the gas phase after gas-liquid equilibrium, β is the CH4 solubility coefficient in seawater, R is the gas state constant, T is the absolute temperature, V CH4 is the molar volume of CH4 under standard conditions, V g and V l are the volumes of gas phase and liquid phase in equilibrium in the headspace of seawater, C eq is the concentration of dissolved CH4 in seawater when the surface seawater is in equilibrium with the atmosphere; The impact of ship activities on the assessment of methane emissions from offshore oil and gas platforms 船舶活动 The following algorithm is used: Where: u is the wind speed along the main axis of the CH4 emission plume, and are the horizontal and vertical standard deviations of the distribution of CH4 emitted from ship activities, respectively; is the increased concentration of atmospheric CH4 caused by ship activities, x0′ is the distance between the observation point and the ship, y0′ is the lateral diffusion distance of the CH4 emission plume from ship activities, z0′ is the distance between the ship and the sea surface, and h s ′ is the height of the emission source of ship activities.

2. The method for observing and evaluating methane emissions from an offshore oil and gas platform according to claim 1, characterized in that: The above-mentioned survey plan for methane emissions from offshore oil and gas platforms for ship-borne observations includes: When the ship approaches the oil and gas platform in a straight line downwind, the distance of the observation ship approaching from the downwind direction of the oil and gas platform is determined based on the scale of the oil and gas platform, the status of the observation ship, and the actual sea conditions on site, and the atmospheric methane concentration and atmospheric related data at different distances downwind of the oil and gas platform are obtained. In addition, data related to the water column profile are collected at different distances downwind of the oil and gas platform based on the seawater thermohaline jump layer; When the ship is circling the oil and gas platform, the observation ship circles the oil and gas platform at a certain radius to obtain the atmospheric methane concentration around the oil and gas platform; When the ship is moving away from the oil and gas platform in an S-shape downwind, data on atmospheric methane concentration in different ranges downwind of the oil and gas platform are obtained.

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