During the whole process of petroleum exploration and development

the prediction of sandbodies in any target area

especially those in wellblocks of horizontal wells

is always dependent upon an analysis of reservoir deposition systems.The well Zhou-57 produces from the Putaohua Formation

which was deposited within the transition zone from a large-scale delta front to lake in northern Songliao Basin.The formation features in thin single sand bodies with a thickness of less than 2 m.The spatial distribution of these sandbodies is controlled by the variation and evolution of deposition systems during different geological times.The distribution and strike of sandboies are strictly controlled by lake transgression and regression.Therefore

a fine description of these sandbodies requires firstly a detailed geological study and then a prediction of sandstone sublayers through seismic wave impedance inversion.The prediction results can be used as important reference factors to adjust the injection-production pattern and improve the recovery ratio during the later phase of development.