西湖凹陷平湖构造带花港组沉积环境与聚煤规律

Sedimentary environment and coal accumulation law of Huagang Formation in Pinghu Structural Zone of Xihu Depression

为了对西湖凹陷勘探区优选、煤系烃源岩生烃潜力进行评价,就西湖凹陷花港组的岩相古地理和煤层富集的控制因素进行研究,根据钻井的岩石学、地球化学、古生物特征及地球物理测井特征进行了分析,利用岩性等值线图恢复了花港组的岩相古地理图,总结了平湖构造带的沉积特征与煤层发育规律。研究结果表明:在西湖凹陷古近系花港组识别出9种岩相类型,主要发育三角洲沉积体系,物源区位于该凹陷区西部的海礁隆起和西南部的渔山隆起,且花港组下段古地理单元包括上三角洲平原和下三角洲平原,上段古地理单元包括上三角洲平原、下三角洲平原和三角洲前缘,整个花港组以下三角洲平原占优势。在花港组沉积期发生持续的湖侵现象,聚煤作用主要发生于下三角洲平原分流间湾,且下段聚煤作用强于上段。

In order to optimize the exploration zone of Xihu depression and an evaluation conducted on the hydrocarbon generating potential of the coal measure source rock,a study was conducted on the control factors of the lithofacies palaeogeography and seam enriched in the Huagang Formation of Xihu depression. According to the petrology,geochemistry,paleontology features and geophysical logging of the borehole drilling,an analysis was conducted. A lithofacies contour map was applied to recover the lithofacies paleogeographic map and to summarize the sedimentary features of Pinghu tectonic zone and the seam development law. The study results showed that the Huagang Formation of the Paleogene in Xihu depression recognized 9 lithology types,the delta sedimentary system was mainly developed and material resources area was located in the sea reef uplift at the west of the study area and the Yushan uplift at the southwest of the study area. The paleogeographic unit at the low section of Huagang Formation would include upper delta plain and the low delta plain. The upper paleogeographic unit would include the upper delta plain,low delta plain and the delta leading edge. The whole Huagang Formation was superiority with the low delta plain. During the sedimentary period,a lake transgression phenomenon was sustainably occurred in Huagang Formation.The coal accumulation function was mainly occurred in a between distributary bay of the delta plain and the low section coal accumulation function would be better than the upper section.