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通过综合分析天然气组分、碳同位素组成和伴生原油的碳同位素组成、饱和烃色谱、色谱-质谱等资料,对准噶尔盆地三台地区天然气特征及其形成机制进行了研究。三台油气田侏罗系天然气乙烷碳同位素组成普遍较轻,原油碳同位素组成较轻、姥植比较小,甾烷分布以C29和C28甾烷含量较高、C27甾烷含量较低为特征,油、气主要来自阜康凹陷二叠系平地泉组腐泥型烃源岩。天然气组成以甲烷为主,甲烷碳同位素组成较轻,比典型的生物气重,但比热成因气轻;气藏埋藏较浅,与稠油伴生或邻近;伴生的稠油遭较强生物降解,出现25-降藿烷,表明三台油气田侏罗系天然气属于典型的原油菌解气。微生物降解原油的过程是在细菌和热力学作用下由微生物参与的一种水-烃反应,产甲烷菌利用CO2和H2优先对轻碳同位素进行还原反应产生碳同位素组成较轻的甲烷气。含油气盆地中遭生物降解的稠油和油砂分布广泛,原油菌解气藏具有良好勘探前景。
Through the comprehensive analysis of natural gas components, carbon isotope composition and carbon isotope composition of associated crude oil, saturated hydrocarbon and chromatographic - mass spectrometry data, the natural gas in Santai area of Junggar Basin and its formation mechanism were studied. The carbon isotope composition of natural gas of Jurassic in Santai oil and gas field is generally lighter, the carbon isotope composition of crude oil is lighter, the proportion of grandmas is smaller, the content of sterane is higher with C29 and C28 steranes and C27 steranes is lower, Oil and gas mainly come from the sag-type source rocks of Permian Pingdiquan Formation in Fukang Sag. The composition of natural gas is mainly methane. Methane has a relatively low carbon isotope composition, which is heavier than typical biogas, but lighter than the pyrogenic gas. The shallow gas buries are associated with or near heavy oil, and the associated heavy oil is strongly biodegraded , 25-norhopane appears, which indicates that the Jurassic natural gas in Santai oil-gas field belongs to the typical crude oil bacteria. The process of microbial degradation of crude oil is a water-hydrocarbon reaction involving microbes under the action of bacteria and thermodynamics. Methanogenic bacteria use CO2 and H2 preferentially to reduce light carbon isotopes to produce lighter carbon isotopes. Biodegradable heavy oil and oil sands are widely distributed in petroliferous basins, and the crude oil pyrolysis gas reservoirs have good exploration prospects.