GENETIC TYPES AND DISTRIBUTION RULES OF THIN SAND LAYERS IN THE FOURTH MEMBER OF SHAHEJIE FORMATION IN SHUBEI AREA OF THE WESTREN SAG, LIAOHE DEPRESSION

To determine the genetic types and distribution rules of thin sand layers in the fourth member of Shahejie Formation (Es₄) in Shubei area of the western sag, Liaohe Depression, the paper summarizes the identification marks of thin sand layers of different genesis based on the characteristics of core, logging response and seismic reflection, and predicts the distribution of sand bodies of each sand group, as well as the controlling factors of sand body development and sedimentary models. The results show that the Es₄ in the area belongs to fan delta-lacustrine sedimentary system. The thin sand layers have 4 genetic types, including underwater distributary channel, low-uplift bar, estuary dam and coastal shoal, among which the former two are dominated. The paleo-landform, paleo-provenance and paleo-water depth control the distribution of sand bodies. Divided by Shuguang and Xinglongtai buried hills, the south is the fan delta sedimentary area where the front subaqueous distributary channel and estuary dam are developed; while the north (including low-uplift area) is a semi-closed bay area without obvious water injection where the low-uplift beach bar sand body and limestone/dolomite flat are mainly developed, with coastal shoals along some areas of western coast. The largely developed low-uplift bar sand body outside the reserve area is a potential substitution for the increasing reserves and production of clastic rocks.