In Bonan sag

the deep source rocks are predominantly dark shale

sandy shale and evaporites in the 4

th

member of Paleogene Shahejie Fm

with the TOC content of 0.9%-2.39% and kerogens of type iv and

1

;the deep reservoir rocks are mainly composed of glutinite

fine sandstone and muddy limestone in the 4

th

member of Shahejie Fm

with the porosity of 1.18%-23.5% and permeability of 0.1×10

-3

-36.67×10

-3

μm

2

.According to trap types

the deep oil-gas pools in Bonan sag can be divided into lithologic trap and composite trap oil-gas pools;based on types of source rock

they can be divided into oil-gas pools sourced by Paleogene sapropel-type source rocks and sourced by Paleo-Mesozoic coal measures(i.e.coal-derived gas pools);in the light of source-reservoir-cap rock combinations

they can be divided into "self-sourcing and self-reservoring"type oil-gas pools(i.e.both the source rocks and reservoir rocks are in the 4

th

member of Shahejie Fm)

and "upper-sourcing and lower-reservoiring"type oil-gas pools(i.e.the oil-gas pools with the source rocks in the 3

rd

member of Shahejie Fm and reservoir rocks in the 4

th

member of Shahejie Fm). Their reservoiring process is controlled dominantly by charging stages

fluid dynamic systems and evaporite layers.The continuous late-stage charging has provided huge quantities of hydrocarbons for deep reservoiring.The unique dynamic systems of overpressure fluid in deep strata have provided the driving force for hydrocarbons migration and accumulation.The control of evaporites on oil and gas accumulations is represented by (1) acting as regional seal rocks

(2) delaying the diagenetic process of underlying strata and improving the poroperm characteristics of reservoir rocks and(3) conducing to the formation of overpressure fluid systems.Therefore

the strata overlain by evaporites are favorable targets for deep oil and gas exploration.