Abstract:

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.