A Study On Sedimentary Characteristics Of The East Subsag In Zhagesitai Sag Tengel Depression Of Erlian Basin

The east subsag of Zhagesitai Sag in Tenggel Depression of Erlian Basin is a Mesozoic and Cenozoic rift basin, flares along the north-east trending. The northwest is bounded by Shandan Convex, the south is bounded by Naritu Convex, the east is next to Chagannuoer Convex. The subsag is formed in the background of tension, which performed as the double break single super-type、deep and narrow、graben subsag structure. It developed a set of continental clastic rock series, and clamp a small volcano rocks of the lower Cretaceous Bayanhua group strata.Through the Zhagesitai Sag east subsag of internal basic geological data, core data, logging data, seismic data analysis, combined with Zhagesitai Sag east subsag the middle of subsidence zone belt analysis of single well facies, structural geology, petroleum geology, sedimentary petrology etc.subject as a guide, to analysis the characteristics of sedimentary facies and distribution regularities of the study area.The Zhagesitai Sag east subsag as a rift basin, fault activity controls the sag sedimentary facies type development and the sedimentary facies and its migration.In addition to the normal development of lake facies, fan delta facies and near the underwater fan facies are the important sedimentary facies type of the study area.It has8seismic facies types in the study area:①the low oblique seismic phase--gentle slope type of fan delta facies;②the sheet-plate of strong seismic amplitude phase--shore-shallow lake facies;③the similar S shape progradational seismic facies--steep fan-delta (coarse grain structure);④the Lenticular or hummocky seismic facies--nearly underwater fan facies (coarse grain structure);⑤the sheet-strong seismic amplitude phase--shore-shallow lake, semi-deep lake facies;⑥the (nearly) sheet weak seismic amplitude phase shore shallow lake and deep lake facies;⑦the (nearly) sheet weaker amplitude seismic facies--shallow lake, semi-deep lake facies;⑧and the (nearly) sheet of seismic amplitude phase-shore-shallow lake, shallow lake facies.Sedimentary facies type by the sag margin slope (Shore-shallow lake) development of various underwater fan (fan) and delta transition to bottom groove center of the shallow lake and half deep lacustrine facies.The fan body along the direction of the long axis parallel to the bottom groove arranged, advancing direction is approximately vertical Lake, sediment source comes from the basin around the big drop denudation heights or adjacent areas long-term ancient uplift and denudation area.The analysis of single well facies display that the middle of the study area subsidence zone developed4phase such as fluvial facies, lacustrine facies, alluvial fan and underwater fan, Among them the shore-shallow lake-semi-deep lake facies and shore-shallow lake-half deep lake environment of alluvial fan and the subaqueous fan is most developed.