Lithology Characteristics and Meaning of the Yanchang Formation in the Majiatan Area of the Ordos Basin

Mainly located in the central of the thrusted region of the western Ordos basin, the Mesozoic Erathem in the Majiatan area is favorable to exploration activity. In order to investigate the scale of the depositional system, the sedimentary facies pattern and the reservoir distribution of the Upper Triassic Yanchang formation, based on the regional geology research, the component of clastic grains, lithogenesis and maturity of the Yanchang formation sandstones are studied detailedly. Moreover, the reservoir potentiality and source area are also discussed comprehensively. The result indicates that both the compositional maturity and the textural one of this sandstone are lower, and that although the diagenesis is intensive, but it is favorable to form quality reservoir. Moreover,the Yanchang formation likely originate from the Proterozoic metamorphosized rocks, granite and the Lower-Palaeozoic igneous rock from the northwestern Alanshan plane.