Abstract: Lacustrine carbonate rocks are widely distributed in the lower part of the first member of Shahejie Formation of Palaeogene in southwest margin of Qikou sag. Comprehensive analysis revealed that it had favorable accumulation conditions, good space configuration of source-reservoir-cap rock associations. Oil shale and dark mudstone stably distributed in the lower part deposited with carbonate reservoir interactively, and they were both source bed and favorable regional cap rocks. This was favorable for large-area accumulation of carbonate reservoir and owned certain potential for exploration. Currently, oil and gas discovered through exploration are mainly distributed in fracture development belts and fold deformation zones, which proves that hydrocarbon accumulation is closely related to the degree of fracture development, and reservoir types are mainly structural-lithologic ones. This paper pointed out that exploration should be mainly carried out in the fracture development zone and the transitional zone of dolomite and sandstone, based on strengthening engineering technology research. And plane fracture prediction should be conducted in carbonate reservoirs in these areas without fractures

Key words: Qikou sag, lacustrine carbonate rock, reservoir feature, fracture, generating rock, accumulation pattern, hydrocarbon exploration