吐哈盆地烃源岩研究进展与低演化油气的形成

Research Progress of Source Rocks and Formation of Low Evolution Oil and Gas in Turpan-Hami Basin

通过对吐哈盆地中、下侏罗统6块源岩抽提物的饱和烃和芳烃馏分进行有机地球化学研究,除进一步印证了前人一些主要结论(如母源输入以高等植物为主、有机质类型以Ⅲ型为主和源岩演化程度低等)外,还发现了一些富有科学意义的新的现象与特征,主要包括:源岩样品中含较高丰度的树脂体类化合物;样品中存在八硫环形式的单质硫;源岩有机质经受过较明显的生物降解作用。认为树脂体类化合物是低演化烃的重要母质,单质硫八硫环和生物降解作用都会导致有机质成烃活化能降低,从而促使有机质在较低的热演化阶段形成油气;这些新的发现对于认识源岩在低演化阶段形成商业性的低熟气储层具有重要意义;吐哈盆地有机质成熟度主体处于RO<0.8%的演化阶段,所生成的原油应为低演化阶段的油,天然气则相应为低熟气。

Geochemical studies were carried out on the saturated and aromatic hydrocarbon fraction of six source-rocks collected from the Middle to Lower Jurassic of Turpan-Hami basin. In the study, we proved some views proposed by the predecessors （1. the organic matter input is mainly higher plants; 2. the organic matter types of source rock are mainly type Ill ; 3. the source rocks evolution degree is low）. At the same time, some new significant findings were revealed （for instance, the Turpan-Hami Basin source rock samples have a high abundance of resin compounds, the organic matter in source rocks suffered a significant biodegradation, and 8S （sulfur） ring substance is also found in the samples）. These substances and the geological action will ultimately lead the activation energy to be greatly reduced, which make it easily to form oil and gas at the lower stage of thermal evolution. The research indicates that the thermal evolution degree of organic matter is less than 0.8% （Ro）, and the resulting oil ＆ gas are categorized as immature oil and low mature gas, respectively. These findings may have important significance to understand the mechanism of oil ＆ gas formation and accumulation,especially for the low-mature gas.