| The organic matter content of Lower Cambrian shale in Cengong Block,Guizhou is relatively high,the burial conditions are good,and the exploration and development prospect of shale gas is broad.The study on the structural characteristics and evolution process of the Lower Cambrian in this block has important guiding significance for the exploration and development of shale gas in this area.However,predecessors only carried out regional research work in this area,and the structural research is rough.Isochronous sequence stratigraphic analysis has not been carried out in the area before,and there may be diachronic phenomenon,The research on the structural characteristics of small layers is not fine enough,and the predecessors have not carried out detailed work on the structural evolution characteristics of small layers in the area.In this study,the isochronous stratigraphic framework of the target layer in the work area is established by using the theory and method of Sequence Stratigraphy,through the observation of field geological outcrops and cores,combined with logging data and seismic interpretation data.On this basis,the fine interpretation of Lower Cambrian structure in Cengong Block is carried out,the structural characteristics of small layers are determined,and the characteristics of structural evolution are studied.This paper has obtained five research results:(1)based on core,logging and seismic data,the sequence stratigraphic framework of the lower Cambrian in Cengong Block,Guizhou Province is established.The target interval of the lower Cambrian in the study area is divided into one second-order sequence,five third-order sequences and nine fourth-order sequences.(2)The high-precision interpretation of seismic data was carried out.The faults in the study area were classified according to the fault displacement and extension length,and 22 V grade faults and 13 VI grade faults are divided.(3)High and steep reverse faults are mainly developed in the study area.The strike of the faults is mainly north-west,which is consistent with the strike of the regional large faults.It also develops NW trending faults cut by NE trending faults.In the study area,there are many small number faults with small displacement,short extension length,which are mainly developed at the edge of syncline wing and the turning part from axis to wing of syncline.(4)The structure of the study area is a syncline structure,in which many small-scale faults are developed.The low structure is located in the east of the 3D work area and gradually rises to the periphery.The dip angle of the stratum in the east is steep and in the west is gentle.(5)The depositional period of the lower Cambrian is during the Xuefeng movement,and the tectonic movement is weak.Therefore,the thickness change of the stratum is small and the stratum is fully developed.There are few faults developed and most of them are parallel single faults with high angle thrust.In the Late Early Cambrian,affected by the Yanshan and Himalayan movements,the study area was uplifted and subjected to denudation and fold deformation,forming the current structural style.The results of this paper provide reliable basic data for the next comprehensive evaluation of shale gas structural favorable areas in Cengong Block and guiding the deployment of shale gas well locations.It can effectively improve the accuracy of shale gas exploration,and lay a good foundation for the next step of shale gas exploration and development. |
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