Study on shale facies sedimentary environment of lower Es3-upper Es4 in Dongying sag

Key words:  Dongying sag  shale facies  sedimentary environment  climate

Abstract:

According to the core color, component, structure organic matter abundance of system cored wells, shale facies of the lower Es₃-upper Es₄ in Dongying sag were divided. The ancient environment was analyzed by climate, provenance, water depth, salinity, oxidation and reduction, and a standard of classification and quantification was established. The findings include: climate from arid to semiarid to semi-humid, water from semi-deep to deep and strong reduction to reduction, salinity from saline to salt to brackish, and provenance from less to more. The ancient environment can be divided into six environmental combinations. This study establishes the following relationships between the sedimentary environment and facies. The organic matter content of shale facies are mainly affected by salinity:saline range develops less organic matter facies, and salt and brackish range develops rich organic matter facies. Structure of shale facies are mainly controlled by climate and water depth:arid and semiarid climate and semi-deep water environment develops lamina facies, and semi-humid climate and deep water develops stratiform facies. Lithology of shale facies are mainly affected by climate and provenance:arid climate and less provenance environment develops argillaceous limestone and limestone, and demi-humid climate and more provenance environment develops lime mudstone.