扎格罗斯盆地新生界Asmari-Gachsaran成藏组合地质特征及成藏模式

Geological characteristics and hydrocarbon accumulation model of the Cenozoic Asmari-Gachsran play,Zagros Basin

张震 李浩武 段宏臻 徐祥恺 蒋思芹

Zhang Zhen Li Haowu Duan Hongzhen Xu Xiangkai Jiang Siqin

Asmari-Gachsran成藏组合是扎格罗斯盆地重要的成藏组合。通过对该成藏组合古地理演化、烃源岩、储层、盖层、成藏过程和模式的分析认为,新近纪至第四纪的扎格罗斯褶皱作用使白垩系Kazhdumi组烃源岩埋深加大,大面积进入生烃高峰;同时,构造作用形成了贯穿新生界Asmari组灰岩、Pebdeh组泥岩和白垩系Sarvark组灰岩的开放性裂缝网络,构成油气自烃源岩向储层运移的垂向通道。在大部分地区,Asmari组成藏组合内的油气都是Kazhdumi组烃源岩直接一次充注,而不属于由Sarvark组圈闭中纵向调整而来的次生油气藏。由于裂缝的沟通,Asmari组合Sarvark组储层具有统一的油水界面,在浮力的作用下,浅部的Asmari组储层要比深部的Sarvark组储层更早地充注油气,油气充满度也更高。优质烃源岩、沟通烃源岩与储层的大量开放性垂直裂缝、厚度大的蒸发岩盖层及烃源岩生烃期与构造和裂缝形成期的良好配合是油气富集的主控因素。

The Asmari-Gachsran play is an important play in Zagros Basin.We studied the paleogeography evolution,hydrocarbon source rocks,reservoir rocks,cap rocks and hydrocarbon accumulation process and model of the Asmari-Gachsran play.The Cretaceous Kazhdumi source rocks was more deeply buried due to the Noegene-Quarternary Zagoros folding and mostly reached peak hydrocarbon generation.Meanwhile,open fracture networks that penetrate the Cenozoic Asmari limestone,Pebdeh mudstone and the Cretaceous Sarvark limestone were also formed due to the tectonics,and they constitute vertical pathways for hydrocarbon migration the Kazhdumi source rocks to the above reservoirs.In most areas,the hydrocarbons in the Asmari play were directly charged from the Kazhdumi source rocks instead of the Sarvark play.The Asmari and the Sarvark reservoir share the same oil-water contact due to the connection of fractures,thus the shallow Asmari reservoirs were charged earlier than of the deeper Sarvark reservoir,and have higher filling degree.High quality source rocks,vertical open fractures connecting the source rocks and reservoirs,thick evaporate cap rock,and the good timing between peak hydrocarbon generation and trap-fracture development are the key factors controlling hydrocarbon accumulation in Asmari-Gachsran play.

10.11743/ogg20120205