THE STRUCTURAL TRAPS AND OIL-GAS ACCUMULATIONS ON WEN' AN SLOPE OF BAXIAN SAG

Fault-blocks and fault-nose traps could be easily seen on the Wen'an slope of Baxian Sag.The formation and development of traps were controlled by tectonic movement.From the Kongdian Formation to the forth segment of the Shahejie Formation,the Jizhong sag were influenced by the late Yanshan movement.The shape of traps was controlled by the movement in the beginning of deformation of the basin.From the third segment to the first segment of the Shahejie Formation,Himalayan Ⅰ movement dominated the formation of traps.In Quaternary,strong tectonic movement stopped,and no influence on traps could be seen.In conclusion,structural traps in the study area were mainly formed during the third to the first stage of the Shahejie Formation in Shigezhuang Suqiao horst and graben fault zone.Structural reservoirs are divided into 4 types,namely,the fault block reservoirs,broken nose reservoirs,anticline reservoirs,broken anticline reservoirs.The traps formed in the Kongdian Formation to the forth,third and second segment of the Shanhejie Formation were the most favorable reservoirs to oil accumulation.Hydrocarbon exploration on Wen'an slope of the Baxian Sag should be focused more on fault block traps and broken nose traps formed during Late Tertiary in the middle and west part of Shigezhuang-Suqiao horst and graben fault zone and in the middle and west part of Zhaogezhuang-Zuogezhuang horst and graben fault zone.