Lacustrine carbonate rocks

distributed mainly at the upper part of the 4th Member and the middle and lower parts of the 1st Member in the Shahejie Formation

are impor-tant Eogene reservoirs in Bohai Bay Basin.They can be divided into framework

granular and micritic carbonate rocks.The framework carbonate rock bodies consists of reef

mound and framework organism layer.Reefs are predominently distributed in the clear water area on the subaqueous platforms or uplifts

the reef-core and front reef microfacies of which have the best hydrocarbon reserving condition with framework pores

organic visceral pores and solution pores.Mounds are distributed in the steep slope areas of fossilis lands or basins

the cores of which are the greatest in thickness

and the best in pores.Biobeds are distributed in the gentle slope areas of the basin or fossil islands

or in the deep water areas with terrigenous debris.These beds are usually not so thick and the pores are homogenous.The granular carbonate rock bodies

composed of beach

barrier

bar

sandpit and algal beach

etc.with fine primary and secondary pores

are distributed in shoreand shllow lake areas.The micritic carbonate rocks that are formed by chemical and bio-chemical deposition are distributed in shallow to deep lake areas

the reserving spaces in-clude interlayer fractures and solution channels.