Sedimentary facies and subtle petroleum reservoirs ofthe upper submember of Member 3 of Paleogene Shahejie Formation in Liuxi area of Raoyang Sag， Jizhong Depression
Zhang Dazhi Ji Youliang Han Chunyuan Chu Lilan
1 Research Institute of Petroleum Exploration and Development，PetroChina，Beijing100083
2 Faculty of Resource and Information Technology, China University of Petroleum(Beijing)，Beijing102249
3 PetroChina Huabei Oilfield Company， Renqiu062552，Hebei
4 Daqing Oilfield Exploration and Development Research Institute，Daqing163712，Heilongjiang
Through core observations and single well sedimentary facies analysis， combined with the sedimentary setting， it is concluded that braided fluvial delta and lacustrine facies were developed during the deposition of the upper submember of the Member 3 of Paleogene Shahejie Formation in Liuxi area， and mainly the braided fluvial delta front and shoreshallow lacustrine subfacies were developed. The microfacies mainly include braided fluvial distributary channel， overbank deposit， subaqueous distributary channel， mouth bar and sheetlike sandbody. Based on the principles of sequence stratigraphy and the previous researches， the upper submember of the Member 3 of the Shahejie Formation in the study area is a complete thirdorder sequence which can be divided into lowstand systems tract， transgressive systems tract and highstand systems tract respectively corresponding to the early， the middle and the late depositional periods of the upper submember. The sedimentary facies maps of each period were compiled and the distribution characters of the sedimentary systems were investigated. The high in north and low in south topography in the depositional period of the upper submember matched well with the eastwest trending sandbodies of the braided fluvial delta. The sands, combined with favorable hydrocarbon sources， thus can create profitable conditions for hydrocarbon accumulation in the late period. The main reservoirs include the subaqueous distributary channel and mouth bar sandbodies of the braided fluvial delta developed during the early depositional period of the upper submember of the Member 3 of the Shahejie Formation which form a very profitable source rockreservoircap rock assemblage together with the source rocks developed in the middle depositional period， and are favorable for the formation of subtle hydrocarbon accumulations. Four types of patterns for subtle hydrocarbon accumulations development were established. The analyses indicate that the braided fluvial delta front sandbodies developed during the early depositional period of the upper submember of the Member 3 of Shahejie Formation are the favorable targets for further exploration of subtle hydrocarbon accumulations.
. Sedimentary facies and subtle petroleum reservoirs ofthe upper submember of Member 3 of Paleogene Shahejie Formation in Liuxi area of Raoyang Sag， Jizhong Depression[J]. JOPC, 2008, 10(6): 571-582.
