Abstract:

Dongying depression has experienced evolution of blockfaulting,erosion and overlapping during Eogene,resulting,in a gently Waved erosional surface of basement rocks on its north steep slope where lacustrine embayments were separated by basement;noses and subaqueous alluvial fans well developed,These paleomorphological and paleotopographical features have obviously controllcd the size and geometry of fans,which can be divided into three types:1) lacustrine cliff fans;2) faulted scarp fans:and 3) terraced fans,with the first one being the dominant type. They are coalescing each other to form a kind of skirt-hem. The fans are sand and conglomerate bodies formed by rapid deposition of flood turbidite near the source area.It has become a new field for the exploration of oil and gas,since it may contain important stratigraphical types of oil traps. Different parts of these fans form different traps The model roughly is: the innerfans form stratigraphical overlapping traps;the mid-fans lithologic traps sealed by faults;the outerfans lenticular lithologic traps. The basement noses are the prerequisite ground for oil accumulation. The mid-fan front and channels,having a lot of secondary pores and good reservoir properties,may be prolific in oil and gas.