三湖坳陷第四系七个泉组层序地层及有利目标预测

Sequence stratigraphy of Quaternary Seven Spring Group of the Sanhu depression and prediction for prospective targets for hydrocarbons

采用钻/测井、地震及米兰科维奇旋回相结合的方法,对柴达木盆地三湖坳陷第四系七个泉组进行了高分辨率层序地层学研究,在七个泉组可识别出6个层序界面,进而划分出5个三级层序。根据蒿藜花粉含量、碳酸盐含量、δ18O、GR、氯离子含量等对比分析,本区气候总体上由温暖变为干冷,存在5次温湿与干冷气候的次级旋回,分别对应sq1、sq2、sq3、sq4、sq5五个层序,每个旋回内部波动与基准面上升半旋回和基准面下降半旋回相一致。层序Ⅱ(sq2)基准面上升半旋回时期发育的三角洲前缘砂体尖灭及砂岩透镜体圈闭是进一步勘探的有利目标。

By combining drilling, logging and seismic data with the Milankovitch cycle, we have carried out a high-resolution sequence stratigraphy research on the Sanhu depression Seven Spring Group in the Qaidam Basin. We identified six sequence surfaces in the Seven Spring Group, and further divided the Group into five triple-pole sequences. Based on the comparative analysis of the contents of the Artemisiaepollenites pollen and carbonates, δ^18 O composition, the GR（Gamma Ray） curves, and the contents of chlorine ions, we could draw the following conclusions. Overall, the climate in this area has changed from warm to cold. There are five secondary cycles of this climate change, from warm and humid to cold and dry. These five cycles correspond to the five stratigraphic sequences of the sq1, sq2, sq3, sq4 and sq5. In each cycle, the inner fluctuations are coincident with the rise of the base level in upper half cycles and the fall of the base level in lower half cycles. The delta-front sandstone out-pinch and the sandstone lens traps developed during the upper half cycles of the rise of the base level of Sequence （sq2） are prospective targets for the further exploration for hydrocarbons.