Study On Structural Evolution Characteristics And Sand Control Mechanism Of Banqiao Slope

The slopes of the Qikou Depression are developed,among which the slopes of Banqiao are typical rotational lift-slope slopes,mainly controlled by the Cangdong Fault on the western edge of the Qikou Depression.The internal fracture characteristics of Banqiao slope are complex,and the fracture characteristics of the slope are analyzed from three aspects,including geometry,kinematics and dynamics,through the interpretation of seismic data.Research analysis shows that three different groups of fracture systems are mainly developed within the Banqiao slope,they are the Dazhangtuo parallel fault system,which is dominated by differential extension on the west side,striking NE,with a series of positive faults arranged in parallel,and the profile shows a plate-like positive faults arranged at a high angle in a downward direction.On the east side,the Changlu pinnate fault system and Gaoshaling broom fault system jointly controlled by extensional strike slip strike are NNE and NEE respectively.The secondary fault of Changlu fault system and the main fault are pinnately oblique,while the west side of Gaoshaling fault system converges and spreads eastward.By analyzing the activity of the main fracture and secondary fracture,the tectonic evolution of Banqiao slope is divided into three stages: initial rifting period,rotational lift-off period and depressional subsidence period.In order to further clarify the sand control mechanism in the slope area,the data from seismic,logging and core testing and assaying were used to comprehensively analyze the physical source,paleo morphology,sedimentary characteristics and sand body spreading characteristics of the study area.The study shows that the Cangxian Uplift has developed a number of undercutting fracture conversion trenches on the side of the basin,such as Shenqingzhuang,Zengfutai,Xiaozhan and Gegu,and these trenches provide important channels for the transport of clastic materials from the Cangxian Uplift into the basin.Among them,the fan corresponding to the Xiaozhan source and the Gegu source mouth is widely distributed and is the main sedimentary body in the Banqiao slope area.The Banqiao slope is a fan delta-distant shore submerged fan-deep lake phase sedimentary sequence,and the difference in paleo morphology determines the different patterns of sand body development in different periods.The boundary fault activity intensifies during the rotational lift-slope period,and the steep slope zone pattern develops,the sand body phase changes quickly,and the wave area is small;the overall subsidence period of the paleo-geomorphology is slow,and the debris material from the Cangxian uplift source is transported along the slope for a long distance.Multi-phase sand bodies are distributed in a large stacked contiguous area in the middle slope.It was finally determined that the sand control mechanism of the Banqiao slope is mainly two kinds of sand control mechanisms,namely,sand control by broken grooves and sand control by trenches.