Based on characteristics and spatial distribution patterns of single-well sedimentary microfacies

gross-to-net ratio and thickness of single sandstone layer of the Putaohua reservoir in south Gulong sag of Songliao Basin

we studied the spatial distribution pattern of sedimentary microfacies and predicted favorable sand bodies.The Putaohua reservoir consists of various sedimentary microfacies including distributary channels

interdistributary channels

mouth bars

front sheet sand

front delta mud and shallow lake mud

with sediments mainly sourced from the north and the west.It is of a typical shallow-delta deposit characterized by poor-developed mouth bars but wide front sheet sandstones.From bottom to top

the thickness and the grain size of sandstone layers increase with the lake level dropping

indicating a progradational stratigraphic sequence.In addition

the areas of front sheet sandstones also enlarge upwards and their shapes change from EW-trending strips in the lower part into large sheets in the upper part.The provenance is mainly located in the north at the early stage

while is mainly located in the west at the late stage.The early banded sand layers and the later large sheet-shape lenticular sand layers at the center of the sag are favorable sandbodies.