准噶尔盆地三台油气田原油菌解气特征及成因  

Features and origin of oil degraded gas of Santai field in Junggar Basin, NW China

作　　者：路俊刚[1,2] 王力[1] 陈世加[1,2] 韩辉[1,2] 张焕旭[1] 黄囿霖 何晓波[1] 占盼 周世颖[1] 章安然 李啸天[1] 

机构地区：[1]西南石油大学地球科学与技术学院 [2]四川省天然气地质重点实验室

出　　处：《石油勘探与开发》2015年第4期425-433,共9页Petroleum Exploration and Development

基　　金：国家重点基础研究发展计划(973)项目"中国陆相致密油(页岩油)形成机理与富集规律基础研究"(2014CB239005);国家科技重大专项"四川盆地致密油气成藏机理与富集规律"(2011ZX05001-001);中国石油天然气股份有限公司科学研究与技术开发课题"典型油气藏形成机制与模式"(2014A-0214)

摘　　要：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。Based on comprehensive analysis of the natural gas composition, carbon isotopes and associated oil carbon isotopes, saturated hydrocarbon chromatography, and gas chromatography-mass spectrography, the features and formation mechanisms of natural gas in Santai area, Junggar Basin are studied. The Jurassic natural gas in Santai area is characterized by light ethane carbon isotopes, and the features of associated oil are light carbon isotopes, low Pr/Ph ratio, high C29 and C28 sterane value and low C27 sterane value, which shows that the hydrocarbons were mainly derived from the sapropelic source rock of the Permian Pingdiquan Formation in Fukang sag. The natural gas composition is dominated by methane. The methane carbon isotope value of the natural gas is higher than that of biogenic gas, but it is lower than that of thermogenic gas. Natural gas reservoirs were buried shallowly and always associated with or close to heavy oil which was subjected to serious biodegradation, with occurrence of 25-norhopane. All above indicate that the natural gas in Santai area is typical oil degraded gas by bacteria. Biodegradation was a process of water-hydrocarbon reaction which was affected by the bacteria and thermodynamics. The methane bacteria made use of CO2 and H2 to reduce light carbon isotopes preferentially to generate methane of light carbon isotopic compositions. Biodegraded heavy oil and oil sand are widely distributed in the petroliferous basin, therefore, reservoir oil degradation gas has good exploration prospects.

关 键 词：准噶尔盆地 三台油气田 原油菌解气 天然气成因 碳同位素组成 微生物降解作用 水-烃反应 

分 类 号：TE122.2[石油与天然气工程—油气勘探]