Gubei buried hill

with an area of 60km

2

and 1200m thick Paleozoic car-bonite sediments

is situated in the northeast seashore of the Jiyang Depres-sion.5 reverse faults and 2 overturned anticlines have been found here.The formation of the reverse faults and the overtured anticlines wererelated to the sinistral shear-compression of the Tanlu huge fracture andthe obstruction of Chengning uplift.A lot of fissures developed on the top ofthe anticlines due to tensil stress.After long time weathering and erosionfrom the Middle Ordovician to Middle Carboniferous

pores

caves and crevicesdeveloped in the weatherd crust of Ordovician

thus providing favourablespace for hydrocarbon enrichment.Surrounding by source sags

the buried hill has developed into secondaryoil pools with young source beds and old reservoiring beds.Majorproductive bed is the weathering crust of the upper part of the OrdovicianSystem

but the most rich positions are higher levels in the central part ofthe overturned anticlines.