Abstract:

In order to investigate the control of diagenetic environment on diagenetic evolution of red-beds reservoir,we studied the diagenetic environments of the Eocene red-beds in the eastern Dongying Sag Bohai Bay Basin through burial history reconstruction,thin section analysis,scanning electron microscopic observation,routine core analyses.On this basis,we described intensity of diagenesis and established evolutionary patterns of red-bed reservoirs under the control of diagenetic environment.The diagenetic environment of the Eocene red-beds in the eastern Dongying Sag is divided into two types according to the differences of control factor,range of influence and property types,namely original alkaline environment and burial acidic environment,which correspond to penecontemporaneous period-early diagentic stage A,early diagentic stage B-middle diagenetic stage A respectively.The diversity in diagenetic products and intensity is sharp due to the differences of diagentic environment.A diagenetic modification model of the Eocene red-beds reservoir was established based on quantitative description of diagenetic intensity,namely "early strong cementation and weak dissolution-middle and late moderate dissolution and weak compaction" under the control of diagenetic environment with alkality to weak acidity-moderate-strong acidity.Red bed reservoirs under the control of this model feature in a pore evolutionary pattern of "rapid-decreasing of primary porosity,slow-growing of secondary porosity in early stage;slow-decreasing of primary porosity,rapid-growing of secondary porosity in middle and later stages".

Key words: red-bed, diagenetic environment, diagenetic evolutionary process, Dongying Sag, Bohai Bay Basin