Dongying sag is the largest petroliferous region in Jiyang depression

Bohai Bay basin

which is the largest reserves distribution region in the lithologic pools

Jiyang depression. The main reservoir rock of lithologic pools in Dongying sag is sandstones in the middle and lower parts of the 3rd member of Shahejie Fm(Es

3

).The main source rock is mudstones deposited in the Es

3

and the lower part of Es

4

. The exploration results of lithologic pools in Dongying sag show that the lithologic traps has a great variation in trap fill in Dongying sag. In order to study the trap fill as well as its distribution and controlling factors in lithologic pools

the methods of statistic analysis and principal factor analysis have been used. In general

the trap fill in the lithologic pools of Dongying sag ranges from 6.8% to 94.1%

with an average value of 46.5%. Among these

50% lithologic traps has less than 40% trap fill; 46.7% lithologic pools is more than 50%

only a few trap fill is more than 80%

with the maximum value of 94.1%.In terms of the types of sandbody

the trap fill in lithologic pools of sandbody isolated by source rock is relatively high

with the average 60%

while the trap fill of the lithologic pools laterally connected with faults is relatively low

with average about 40%. In stratigraphic horizon

the lithologic pools in the lower and middle parts of Es

3

have trap fill as high as 52%

while the lithologic pools in the Es

2

is only 23% trap fill.In the lithologic traps of Dongying sag

the most important factor of controlling the trap fill is hydrocarbon migration conditions

including the distances between lithologic traps and source area

the quantity of faults and the residual pressure within the lithologic traps. The second one is the hydrocarbon charge conditions

i.e. the petrophysical property (average porosity and permeability) and geometry (thickness and area) of sandbody.The oil source condition has a relatively less influence on the trap fill

because of more abundant oil source in Dongying sag.