Sedimentary facies in the Neogene Guantao Formation in the Gaoliu structural zone,Nanpu depression

Sedimentary facies in the Neogene Guantao Formation are examined in order to effectively guide the rolling exploration and development in the Gaoliu structural zone,in which the alluvial fan,braided stream and meandering stream facies are developed.The alluvial fan facies appears at the bottom of the Guantao Formation,followed by the braided stream facies developed in the middle and lower parts,and the meandering stream facies is developed on the top of it.There occurred the mid-fan and fan fringe subfacies of the alluvial fan facies during the IV depositional stage of the Guantao Formation;the channel subfacies and interchannel subfacies of braided stream facies during the Ⅲ and II depositional stages of the Guantao Formation,and the channel and interchannel subfacies of the meandering stream during the I depositional stage of the Guantao Formation.The development of the sedimentary facies outlined above is mainly controlled by the tectonic movement,relatively strong oxidation environment,dry and warm climatic conditions and base-level fluctuation during the deposition of the Guantao Formation.The matching of the flood-plain mudstone and fluvial sandstone may form the favourable source-reservoir-seal associations.