The Significance of the Intrabed Turbidite Sandstone in the Lower Segment Black Shale of Longmaxi Formation, the Lower Silurian, Nanchuan, Sichuan Basin, China
Chengdu University of Technology, Chengdu City, Sichuan, China
With big thickness, organic-rich, high maturity, brittleness, the black shale of the lower segment of the Longmaxi Formation Lower Silurian is one of the best source rock and the most important exploration target of shale gas in Sichuan basin and its adjacency. The black shale of the lower segment of the Longmaxi Formation depositional environment is deep-water shelf.
Nanchuan field is located at southeast of Sichuan basin, and 13 outcrop sections of the black shale of the lower segment of Longnaxi Formation are studied. There are 3 outcrop sections bearing intrabed sandstone, Dahe section, Shanquan section, Jinjiagou section in the north-west of Nanchuan field(Figure 1). There are 2 to 4 beds of sandstone, and its thickness is 0.3m to 0.6m. The componential maturities of the intrabed sandstone is higher, and textural maturities of the intrabed sandstone is lower, and lithological types are mostly fine -grained quartzose sandstone. By the stratigraphic correlation and division, the intrabed turbidite sandstone body distribution range is big, and the buried depth of the body in the north-west of Nanchuan field reaches to 4500m.
The intrabed turbidite sandstone in the lower segment black shale of Longmaxi Formation in Nanchuan field is similar to the intrabed limestone of the Barnett shale and Marcellus shale. The intrabed turbidite sandstone in the lower segment black shale of Longmaxi Formation in Nanchuan field is the main shale gas exploration target because of its good reservoir physical condition ,good source reservoir cap assemblage configuration.
AAPG Datapages/Search and Discovery Article #90180©AAPG/SEPM/China University of Petroleum/PetroChina-RIPED Joint Research Conference, Beijing, China, September 23-28, 2013