吐哈盆地雁木西油田天然气的选择性生物降解作用

对吐哈盆地雁木西油田原油与原油溶解气地球化学特征进行了对比和分析,探讨了微生物对天然气降解作用的选择性.雁木西油田的天然气均为湿气,不同组分的相对含量和烃类组分碳同位素比值都有较大的变化范围,部分天然气的烃类组分碳同位素比值明显地变大.生物降解作用的选择性与这些变化有极为密切的关系.由于不同的微生物对不同组分的降解能力和强度不同,因而造成了不同剩余烃类组分的碳同位素比值不同,部分烃类碳同位素比值甚至发生倒转.烃类碳数越小,越易发生生物降解作用,较容易发生生物降解作用的组分是甲烷、乙烷和丙烷等较轻的烃类,其次是正丁烷、正戊烷等较重烃类,发生生物降解作用的烃类最高碳数可以达到14.异丁烷、异戊烷等异构烷烃抵抗生物降解作用的能力较强.

Analysis on selectivity biodegradation of natural gas in Yanmuxi Oilfield of Tuha Basin

The geochemical characteristics of oil and oil dissolved gases in Yanmuxi Oilfield of Tuha Basin were analyzed. The selectivity biodegradation of natural gas was studied. All of natural gases are wet gas in this oilfield. The distribution scopes of the relative content of various components and carbon isotope ratio of hydrocarbons are broad. 13C in weight hydrocarbons increases distinctly. The variation scopes of component content and carbon isotope have the considerable relation with the selectivity biodegradation. The different hydrocarbon components have different biodegradation action and degree in Yanmuxi Oilfield. The smaller the carbon number of hydrocarbon molecules, the easier the biodegradation. The first order of biodegradation from easy to difficult is light hydrocarbons such as methane, ethane and propane, and the secondary is heavier hydrocarbons such as normal butane and pentane. The largest carbon number of normal hydrocarbons under action of biodegradation is 14. Isomerization alkyls such as isobutene and isopentane have the stronger ability to resist biodegradation. 