GEOCHEMICAL CHARACTERISTICS AND ITS EXPLORATION SIGNIFICANCE IN XIEFENGQIAO OILFIELD OF THE JIANGHAN BASIN

Xiefengqiao Oilfield is located in the south of Wancheng fault zone in the Jiangling Sag,the Jianghan Basin.The traps were divided into two different types,i.e.Fu Ⅰ fault block and Xiefengqiao fault nose by Wancheng fault.In the early time,it was considered that Xiefengqiao reservoirs were consisted of Xiefengqiao fault nose reservoir and Fu Ⅰfault block reservoir,which were of different types and independent reservoirs.However,according to the latest production information and geochemical characteristics of the reservoirs,they were a unified reservoir.The gypsum mudstones were well developed in Xiefengqiao Oilfield.These gypsum mudstones with good plasticity were jointed with each other on both sides of Wancheng fault,so an unified seal was formed.Meanwhile,according to gas chromatography analysis of crude oils from the Neogene Xingouzui Formation of Xiefengqiao fault nose and the Cretaceous Yuyang Formation of FuⅠfault block,it can be concluded that reservoirs in Yuyang Formation in FuⅠfault block and Xingouzui Formaion in Xiefengqiao fault nose were laterally connected.They showed the same oil/water interface and the same pressure system.