Reconstruction of the sedimentary microfacies and palaeogeomorphology in early Jurassic of Wangwazi Area of Wuqi County,Ordos Basin

The palaeogeomorphic shape of the pre-Jurassie, which is mainly composed of paleochannel, slope ridge and trench, was reconstructed with the mold method. The sedimentation of early Jurrasic was controlled by pre-Jurassic palaeogeomorphology. In the period of Yan 10 deposition, the microfacies were mostly channel sandbar and overbank swamp of braided river subfacies, and in the period of Yan 9 deposition, the microfacies were distributary channels, overbank swamp of delta plain subfacies. In general, the channel sand body was mainly in direction of NW-SE, influenced by the northwest provenance. The relationship of pre-Jurassic sedimentary paleogeomorphology with Yan 10 and Yan 9 petroleum reservoir was analyzed, and the reservoir was mainly distributed in relatively high zone such as slope being adjacent to elevation. The formation and distribution of the reservoir is controlled by the development of channel sand bodies and the exploration area is located in the palaeogeomorphic slope position. The incised valleys of the north paleochannel can serve as the passageway for gas and upward oil migration, produced by Yanchang formation source rocks. Thus, Jurassic petroleum pool may have been well developed in study area and the overlapping area of the pre-Jurassie slope ridge and channels sandbody of Yan 10 and Yan 9 should be the exploration targets in the near future.