Research On Geological-structure Styles Of Shajingzi Area On The Western Margin Of Ordos Plateau

Preliminary prospecting well Sha-1 located in the Shajingzi district of Huan County, belong to the joint area of overthrust fault belt and Tianhuan depression, with the large potential of petroleum exploration. Different structural layers of different stages of tectonic evolution superimposed with different structural layers in the same stage, controlling the tectonic character and evolution in the district of Shajingzi-Pingliang. Deployment of well Sha-1 and seismic data processing and interpretation, were all basing on the double layers overthrust nappe model, which are not in accordance with those from the drilling and observation of geology section.Study the character of the tectonic is of great practical significance in discussing tectonic patterns, hydrocarbon accumulation models, and hydrocarbon prospective evaluation in the Shajingzi district. On the basis of field investigation and laboratory analysis, this study use abundant geology, geophysical and well data comprehensively. Through mapping the geology section and interpreting the seismic data, we want to reconstruct the structural deformation shapes of Yanshan movement.The result show that the deformation shape is not a double layer overthrust tectonic type, and do not exist a detachment surface in the Permian or Carboniferous formation. Different tectonic zone are divided by imbricate-type thrust faults dip toward west, and in coordinately the Jixian-Ordovician formations deformed with the imbricate-type thrust faults dip toward west under the Cenozoic erathem and Cretaceous formation. All these show that imbricate-type thrust faults dip toward west may be the main tectonic type of the study area. Cretaceous formation overlay discordantly on different formation inferred that the tectonic pattern of Jixian-Ordovician formations was an undependent tectonic zone. Therefore the monoclinal structures of Jixian-Ordovician formations were formed in late Jurassic, and the main pattern is the decollement between basements with imbricate-type thrust faults in the plate structure model in Yanshan movement superimposed with dextral shear slip fault during Himalaya movement.