Paleogeomorphology Character of Pre-Jurassic and Its Implications for Hydrocarbon Accumulation Research in Maling Area

In order to clarify the reservoir formation model of Jurassic in Malin area of Ordos basin , Based on logging, seismic and core geological data, by the combination of well seismic and 3D modeling , the prejurassic Palaeogeomorphology has been accurately restored. The palaeogeomorphology in study area is overall characterized by “a plateau between two ancient rivers,many furrows and slopes”. A comprehensive study on the relationship between palaeogeomorphology and reservoir shows that paleogeomorphology controlled the distribution of sedimentary microfacies and indirectly affected the distribution of favorable reservoirs in Fuxian formation and Yan 10 section of Yan’an formation. The Jurassic oil source in Malin area is sufficient which come from the Chang7 section of Yanchang formation source rock. The fissure, ancient river and unconformity surface providing three channels for oil and gas migration. The interdistributary bay microfacies mudstone widely developed as thick caprocks in Yan8–Yan9 formation provided the sealing conditions for Jurassic reservoir trap, The slopezone and the interfluvial are the most favorable position for reservoir accumulation, followed by the ancient river which is near the slopezone and the old upland which is develop branch ditch and river. Established the paleogeomorphic reservoir vertical multi–layer system composite reservoir formation model accumulation model of Jurassic, the study area is composed of vertical multilayer system under the action of vertical migration. The research results point out the direction exploration of Jurassic reservoirs in Malin area for the further.