摘要:
草湖凹陷位于塔里木盆地的东北部,其构造运动的多旋回特征十分显著,目前已在草2、草4等井发现了油气。剖析草湖凹陷的构造-地层特征与演化是深入认识研究区的含油气潜力、持续拓展油气发现的基础。基于研究区最新的探井和地震资料,结合周缘1:200 000区域地质填图成果,建立了研究区内的地层系统;依据不整合面的发育特征,划分了构造-地层层序及形成演化阶段。研究认为,草湖凹陷自震旦纪以来经历了多次构造运动,形成规模不等的角度不整合和平行不整合,通过井震标定和地震剖面的解释,识别出10个不整合面,分别是震旦系底界、上奥陶统底界、上泥盆统底界、石炭系底界、三叠系底界的角度不整合和寒武系底界、侏罗系底界、白垩系底界、古近系底界的平行不整合。据此将草湖凹陷自下而上划分为4个构造层、10个构造亚层。在遵循构造演化阶段划分依据的前提下,利用平衡剖面软件,恢复了草湖凹陷的形成演化,将其演化划分为4个阶段:前震旦纪基底形成期;震旦纪-志留纪发育期;泥盆纪-二叠纪定型期;三叠纪至今调整、改造期。
Abstract:
The Caohu Sag is located in the northeast of Tarim Basin. There are multiple cycles of tectonic movement in the region, and oil and gas have been discovered in the well Cao 2 and well Cao 4. Study of its tectono-stratigraphic characteristics and evolution history are critical for further exploration of oil and gas resources in the sag. In this study, the stratigraphic system is established based on the data from drilling wells, seismic survey and 1∶200 000 regional geological mapping. Unconformities are critical to the division of evolutionary stages and the establishment of the basin history. Since the Sinian, 10 unconformities have been recognized in the Caohu Sag,including the angular unconformities under the bottoms of the Sinian, the Upper Ordovician, the Upper Devonian, the Carboniferous, the Triassic, and disconformities on the top boundary of the Cambrian, the Jurassic, the Cretaceous and the Paleogene. Upon these unconformities, we have recognized 4 structural layers and 10 structural sub-layers in the Sag. Based on the tectonic evolution stages, using equilibrium profile software, the tectonic evolution of the Caohu Sag is restored, and the tectonic evolution is divided into four periods: the basement forming period before Sinian, the development period from Sinian to Silurian, the final formation period from Devonian to Permian, and the adjustment period from Triassic to the present.
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