Liangjialou oilfield in Dongying sag

Bohai Bay basin

was previously thought to be an"indigenously generating and accumulating"oil reservoir

i.e.hydrocarbons generated in the mudstones in the middle 3

rd

member of Shahejie Formation have migrated upward into the adjacent turbidite glutinite.This view

however

is not supported by the latest achievements in hydrocarbon source rock studies in Dongying sag.Oil-to-source correlation

hydrochemical characteristics of oil reservoir and reservoir pressure show that oil reservoirs in southern Liangjialou oilfield

mostly characterized by superpressure and chloride-calcium type water

have been sourced by the upper 4

th

member of Shahejie Formation

i.e.hydrocarbons have firstly migrated laterally along the pathways in the rocks

and then migrated vertically upward through faults and become oil reservoirs either of "both generated and accumulated indigenously"or"generated below and accumulated above";while those in middle and northern Liangjialou oilfield

characterized by normal pressure and sodium bicarbonate water

hydrocarbons have been generated in the lower 3

rd

member of Shahejie Formation

and then directly migrated vertically through faults in the source rock

so the oil reservoirs are of the type of "generated below and accumulated above". The knowledge enlightened us to reevaluate the source rocks in the middle 3

rd

member of Shahejie Formation and restudy the pool-forming patterns in the similar pools around the center of the sag.