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为评价油气田天然释放CH4对大气CH4源与汇的贡献,采用静态箱法实地监测了新疆塔里木盆地雅克拉凝析油气田油水界面处甲烷的释放通量,并采用在线大气甲烷碳同位素制样系统与稳定同位素质谱仪联机测试了通量箱甲烷碳同位素组成.结果表明,由于油水界面边水活跃程度不同,甲烷通量在空间变化很大,最高的日释放通量达2.28mg/m2.d,最低-1.32mg/m2.d,日平均释放通量0.51mg/m2.d,标准偏差达1.23mg/m2.d.油水界面处甲烷通量日变化规律基本相同,凌晨至清晨时达到相对高点,随后逐渐降低,下午至傍晚时段为释放低值甚至负值,夜晚时分又逐渐增加.通量箱中甲烷δ13C组成白天随甲烷浓度的线性降低而逐渐偏重,夜晚δ13C随着甲烷浓度的线性增加而逐渐偏重.可见,油水界面边水活跃,其上方的土壤形成相对氧化的环境,油气藏甲烷及烃类在向地表运移的过程中不断被土壤吸收氧化,仅有少量运移至地表并逸散到大气中,局部甚至均被吸收氧化,而成为大气甲烷的汇.
In order to assess the natural contribution of CH4 to atmospheric CH4 sources and sinks in the oil and gas fields, the methane fluxes at the oil-water interface of the Jacquai condensate field in the Tarim Basin of the Tarim Basin were monitored by the static chamber method. The online atmospheric methane carbon isotope sampling system and The stable isotope mass spectrometer was used to test the carbon isotope composition of methane in the flux tank.The results showed that the flux of methane varied greatly in space due to the different degree of active water at the interface of oil and water, with the highest daily flux of 2.28mg / m2.d, The minimum average daily flux was -1.32mg / m2.d, the average daily average flux was 0.51mg / m2.d and the standard deviation was 1.23mg / m2.d. The daily variation of methane flux at the oil-water interface was basically the same, reaching relatively high from early morning to early morning Point, and then gradually decreased from afternoon to evening for the release of low or even negative, and then gradually increase at night hours.The flux of methane δ13C composition gradually decreases with the linear decrease of methane concentration during the day and night δ13C with the concentration of methane linear Increasing and gradually biased.It can be seen that the water at the oil-water interface is active and the soil above it forms a relatively oxidized environment. Methane and hydrocarbons in the oil and gas reservoirs are continuously absorbed by the soil during its migration to the surface Only a small amount migrated into surface and escape to the atmosphere, it is absorbed even partial oxidation of methane to the atmosphere to become sinks.