The Main Control Factors of Sandbody Reservoir Development in Rift-Subsidence Lake Basin: An Example from the Paleogene West Sag of Liaohe Basin

Rift-subsidence lake basins are important oil-bearing basin of Eocene in the eastern China.The research of the main controlling factors of sandbody development has great practical significances for the prediction of hydrocarbon reservoirs.The characteristic research of the Paleogene sandbody distribution in west sag of Liaohe Basin shows that sedimentary environment,palaeogeomorphology and lake surface and base level fluctuation are the dominant controlling factors of sandbody development,among which the palaeogeomorphology is the most obvious one except for the sedimentary environment.The palaeogeomorphology of west sag includes palaeo-high,palaeo-ditch and valley,palaeo-platform,palaeo-break in-slope and palaeo-trough fault,which affect the distribution of depositional system and the development of sandbodies.The palaeo-break in-slope is divided into three types,i.e.faulted terrace type break in-slope,faulted scarpe type break in-slope and steep slope type break in-slope.Alluvial fan,fan-deltas and far-shore turbidite fan are developed on faulted terrace type break in-slope;Alluvial fan and nearshore turbidite fan are developed on faulted scarp type break in-slope;Alluvial fan,fan-deltas and nearshore turbidite fan are developed on steep slope type break in-slope.