Sequence Stratigraphic Features Of Paleogen And Their Control On Reservoir Formation In The West Of Liaohe Beach Area

Shiwu rift lies in the southeast of the southeasten uplift of Songliao basin which is a graben basin controlled by Sangshutai arc fault in the west since early Cretaceous. Based on high-resolution sequence stratigraphy, sedimentary characteristics of the source and tectonic evolution stages in studying area, the paper tells how tectonic geomorphology controlled sequence development and distribution of deposition system during the fault time then summarises sequence configuration and sedimentary evolution at different tectonic stages. Finally it forecasts spatial and temporal distribution of favorable reservoir sands combined with slope topography control sand mechanism.Using high-resolution sequence stratigraphy, drilling cores, well logs and high-resolution seismic response characteristics, sequence-interfaces of the fault time are identified and high-resolution sequence stratigraphic framework including five third sequences is built in the deep of Shiwu rift. The overall layers are thick in north and south but thin in center as well as they are thicker in west than in east because the layers in south, north and eastern edge are seriously denuded.Alluvial fan, fan delta, braid delta, nearshore subaqueous fans and lake facies are found according to a variety of sedimentary marks. In Qikeshu oilfield the supplycation came from east in the fifith formation of Yingcheng group; the sources in east, south and north countered-balance during Huoshiling group and Yingcheng group; the western source grew in Denglouku group. Nine seismic phases are identified and drawn out. The planes of sedimentary facies distribution of each sequence cycle phase are completed combined with lithology statistical law.By analysing structural fault evolution, six kinds of structural styles and three stages of tectonic evolution including Initial rift in Huoshiling group, quick stretch in Shahezi and Yingcheng group and rift atrophy in Denglouku group and Quantou group are divided. Three sequence configuration modes are described as that dual structure was significant in initial rift and rift atrophy time but it was trichotomy in quick stretch time. There are also three sedimentary evolution modes such as alluvial fan - subaqueous fan -lake - fan delta facies pattern in initial rift time, alluvial fan - subaqueous fan - fan lake - Lake - braided river delta - fan delta depositional system in quick stretch time and braided river delta - subaqueous fan - lake facies combination features in rift atrophy time. The paper describs slope control sand mechanism, identifies structural flexure slope break and synsedimentary fault slope and shows horizontal distribution of geomorphological features of slope.Four sets of reservoir sand vertically developed in the deep rift. Their accumulation was controlled by sequence cycles; their types were controlled by sedimentary facies; their distribution was controlled by geomorphological slop; their development was controlled by tectonic movement. Plane distribution of favorable reservoir sands is predicted in key sequences.