新疆三塘湖盆地马朗凹陷石炭系原油形成过程及勘探意义

新疆三塘湖盆地马朗凹陷牛圈湖构造带马25井石炭系火山岩储层中发现了原油和固体沥青共存,通过储层多级分离抽提和原油地球化学分析,并对这些原油(或固体沥青)的形成过程与其勘探意义进行了研究,结果表明这些原油和沥青可能主要来自下石炭统烃源岩,具有较低姥植比和伽玛蜡烷含量、高丰度三环萜、高Ts/Tm比值和重族组分碳同位素(δ13C-28.0‰)特征;现今油藏原油富含生物降解标志物(25-降藿烷),同时却无明显其它生物降解特征(正构烷烃、甾藿烷等保存完整),反映多期充注特征,即二叠纪中晚期成藏后遭受生物降解,白垩纪后期又再次充注形成;下石炭系有效烃源岩的存在预示着本区具有深部下石炭统源岩贡献的油气藏勘探前景。

Crude Oil Forming Processes and Exploration Significance of Carboniferous in Malang Sag,Santanghu Basin

Crude oil and solid bitumen coexist in the volcanic reservoirs of the Well Ma25 in the Niuquanhu structure zone in the Malang depression in the Santanghu Basin, Xingjiang. Through multistage separation and extraction, and geochemical analysis of the reservoirs, the formation processes and exploration significance of these crude oil (or solid bitumen) have been discussed. The results show that the crude oil / bitumen may mainly come from the source rocks of Lower Carboniferous, with lower Pr/Ph and gammacerane index, high abundance of tricyclic terpane, high Ts/Tm ratio and the heavy aromatic component carbon isotope (δ13C>-28.0‰). Crude oil in the reservoirs is now rich in biological degradation markers (25-norhopane) with no other significant biodegradation characteristics (n-alkanes, steranes and hopanes is intact), reflecting the characteristics of the multi filling stages, that is, oil reservoirs suffered biodegradation after accumulation in the Late Permian and were filled again in the Late Cretaceous. The existence of the Lower Carboniferous source rocks in this area indicates that there are potentials for oil and gas exploration from reservoirs in the deep Lower Carboniferous source rocks.