The Structural Feature And Prototype Basin Research Of The Red Beds In Dongying Sag

Ek1-Es4x formations in the southern slope of Dongying Sag is deposited a set of alluvial fan-fluvial facies and is called"red beds"because it's red in color. With further exploration, the"red beds"gradually becomes an important backup area for petroleum exploration. It is of great significance for the reservoir exploration of"red beds"to analyze the characteristics of structural evolution of"red beds"in Dongying Sag and to restore the prototype of structural framework in the period the"red beds"deposited.Based on detailed analysis and interpretation on various geological data of cores, logging, well logging, seismic and geochemical data etc., the prototype of structural framework in the period that"red beds"deposited was recovered by the detailed description of faulted structures firstly and by the analysis of the controlling effect of faulted structures to deposition and erosion combined with the restored denuded thickness and original thickness of strata.It is shown by analysis on geometrical characteristics of structures that the"red beds"is the main structural styles in the southern slope of Dongying Sag. Fault systems that distribute in the"red beds"are divided into three groups: some faults are in NE direction, some are in E-W direction and others are in NW direction. Faults assemblages on the plane are parallel, en echelon, pinnate and oblique in arrangement. On the profile, strench structural style is the most developed, which include concordant and antithetic titled fault blocks, Y-shape assemblage, horst and graben as well as reverse drag anticline etc..Based on the period that faults formed, faults that affected the"red beds"in Dongying Depression can be divided three faults systems: fault systems developed before"red beds"deposited, during"red beds"deposited and after"red beds"deposited. Before the deposition of"red beds", the NW-trending faults controlled the basin. The east section of the Chennan fault and Shicun fault divided the present depression into two sub-basins, i.e. the main depositional body in the north and Boxing area in the south. The characteristics of the fault systems during the period that"red beds"deposited are that the inherited development and reconstruction of NW-trending fault system that developed before"red beds"deposited, which includes the east section of the Chennan fault, Shicun fault and so on and the formation of the Gaoqing-Pingnan fault,western of Chennan fault,Binnan fault,Boxing fault and other faults with NEE direction. Fault system formed after"red beds"deposited are mainly in NEE or E-W direction, which cut and reconstruct the"red beds"formations. The denuded areas lie in NEE (or NE) -trending positive element zones and southern gentle slope.Based on the cognitions of structures, sedimentation, and strata denudation, the overall framework of prototype basin in the depositional period of"red beds"formation shows that it is a faulted basin with a fault in the north-east and an overlap in the south-west in Dongying Sag. The Sag is divided into two secondary sags by the eastern part of Chennan fault and Shicun-yangxin fault zone etc. The depositional center locates on the downcast side of the east Chennan fault. Secondary depositional centers distributed like a string of beads along Shicun-Binnan-Linfanjia-Xinyang in NW direction.