Comprehensive study of core

logging and seismic data

and classification of stratigraphic sequence interfaces show that various types of sandbodies

including beach and bar sands

coastal subaqueous fan and gravitational flow channel sands in Shahejie Formation

are developed on the western slope of Qinan sag. Basal overlapping

top denudation

and facies variation between them are evident in Shahejie Formation

thus multiple layer systems and various types of non-structural traps can be formed.The western slope in Qikou depression

an inherent structural slope

is the main directional area of hydrocarbon migration in the depression

and has excellent hydrocarbon supplying conditions. The beach and bar sandbodies in the 3 member of Shahejie Formation are widely distributed

and have an average porosity of 24.8% and average permeability of 175.5×10

-3

μm

2

thus belong to high porosity and high permeability reservoirs.Moreover

these sandbodies have never been disrupted by large tectonic movement since their sedimentation

thus the area would have favorable hydrocarbon preservation conditions. Various types of reservoirs have been discovered during previous exploration

including unconformity reservoirs

upwarping pinch-out reservoirs

and structural-lithologic reservoirs represented by Qi674 well reservoir

Lianmeng reservoir and Qinan 9-1 well reservoir

respectively

indicating that the area possesses the condition of forming certain size subtle reservoirs. According to the study of core

log and seismic facies

it is predicted that the low stand subaqueous fan sandbodies in the 3

rd

member of Shahejie Formation on the western slope of Qinan sag and the slope break zone of the slope in Qibei sag would be the favorable areas in the later exploration; among which

the lithologic traps to the south of Kou 50 well and Zhuang 43 well fault block would firstly be selected as the exploration targets.