Abstract:

Lithologic traps are the main play for the further exploration in western Dongying Depression. But the knowledge about sedimentary characteristics in this area is disputed. Based on the former views, sedimentary characteristics are reidentified through facies types, provenance systems, facies distribution and facies model. The new understandings are as follows. The main facies types are  braided delta, nearshore sublacustrine fan, turbidite fan and lake. There are three provenance systems which are southern Jinjia, western Gaoqing and southeast provenance systems. The southern Jinjia provenance system is the main one, which formed largescale braided delta （Jinjia sandbody and Gaoqing sandbody） and turbidite fans located at toe of the delta. The western Gaoqing provenance system formed nearshore sublacustrine fan along fault throw wall, which is located in limited area. The southeast provenance system entered into the study area in the late of Sha 3 period, which converge with the southern provenance system. Sedimentary facies model of braided delta to turbidite is constructed in light of sedimentary characteristics which is similar to the delta model in the Gulf of Mexico. Based on this, we draw a conclusion that turbidite fans are the main play for lithologic traps in this area.

Key words: Dongying Depression, the 3rd Member of Shahejie Formation, provenance system, sedimentary facies, lithologic trap