The identification of superimposed gas-bearing systems in coal measures is the basis for expediting the optimization of coal measure gas co-production.Through the analysis of drill cores and log data of Upper Carbonif...The identification of superimposed gas-bearing systems in coal measures is the basis for expediting the optimization of coal measure gas co-production.Through the analysis of drill cores and log data of Upper Carboniferous Benxi Formation to the member 8 of Middle Permian Lower Shihezi Formation in Daning-Jixian block,eastern margin of Ordos Basin,four distinct superimposed coal measure gas-bearing systems were identified,and their formation mechanism was discussed from the sequence stratigraphic perspective.Type Ⅰ system mainly contains multiple coal seams,shales and sandstone layers.Type Ⅱ system is dominated by multiple coal seams and shales.Type Ⅲ is characterized by multiple sandstone layers,and type Ⅳ system is dominated by limestones and mudstones.In general,the gas-bearing systems deposited in barrier-lagoon are type Ⅱ,those deposited in carbonate tidal flats are type IV,and those deposited in the delta front are types Ⅰ and Ⅲ.The marine mudstone,acting as a key layer near the maximum flooding surface,exhibits very low permeability,which is the main factor contributing to the formation of superimposed gas-bearing systems.The sedimentary environment plays a significant role in controlling the distribution of gas-bearing systems.Notably,the vertical gas-bearing systems in the south-western region,where delta front and lagoon facies overlap,are more complex than those in the north-eastern delta front facies.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42072198 and 42130802)the Fundamental Research Funds for the Central Universities(No.265QZ2021011).
文摘The identification of superimposed gas-bearing systems in coal measures is the basis for expediting the optimization of coal measure gas co-production.Through the analysis of drill cores and log data of Upper Carboniferous Benxi Formation to the member 8 of Middle Permian Lower Shihezi Formation in Daning-Jixian block,eastern margin of Ordos Basin,four distinct superimposed coal measure gas-bearing systems were identified,and their formation mechanism was discussed from the sequence stratigraphic perspective.Type Ⅰ system mainly contains multiple coal seams,shales and sandstone layers.Type Ⅱ system is dominated by multiple coal seams and shales.Type Ⅲ is characterized by multiple sandstone layers,and type Ⅳ system is dominated by limestones and mudstones.In general,the gas-bearing systems deposited in barrier-lagoon are type Ⅱ,those deposited in carbonate tidal flats are type IV,and those deposited in the delta front are types Ⅰ and Ⅲ.The marine mudstone,acting as a key layer near the maximum flooding surface,exhibits very low permeability,which is the main factor contributing to the formation of superimposed gas-bearing systems.The sedimentary environment plays a significant role in controlling the distribution of gas-bearing systems.Notably,the vertical gas-bearing systems in the south-western region,where delta front and lagoon facies overlap,are more complex than those in the north-eastern delta front facies.
