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

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.