四川盆地东北部三叠系飞三段沉积特征及油气地质意义

近年来,四川盆地东北部三叠系飞三段天然气勘探持续获得新发现.通过钻井岩心观察、测井解释、相标志鉴定和颗粒岩优势相分析,系统研究了四川盆地东北部三叠系飞三段沉积特征及油气地质意义.研究结果表明:①研究区飞三段主要发育开阔台地和局限—蒸发台地,可进一步识别出台内滩、滩间海、潮坪和瀉湖等4种沉积亚相.②台内滩以颗粒岩沉积为主...

Sedimentary characteristics and petroleum geological significance of the third member of Triassic Feixianguan Formation in northeastern Sichuan Basin

In recent years， new discoveries have been made in natural gas exploration of the third member of Triassic Feixianguan Formation（T₁f³）in northeastern Sichuan Basin. The sedimentary characteristics and petroleum geological significance of T₁f³ in northeastern Sichuan Basin were studied through drilling core observation，logging interpretation，facies marker identification and analysis of dominant facies of granular rock. The results show that： （1）The T₁f³ in the study area is dominated by open platforms and restricted-evaporate platforms，and four sedimentary subfacies can be identified，including intra-platform shoal，interbank sea，tidal flat and lagoon.（2）The intra-platform shoals are mainly composed of granular rock deposits，which can be further divided into oolitic shoal microfacies and bioclastic shoal microfacies. Oolitic shoals formed in micro-topographic highlands of open platforms or restricted-evaporate platforms，and bioclastic shoals formed in open platforms，both of which had high energy sedimentary water，with upward coarsening reverse grain sequence.（3）The interbank seas and lagoons were mainly developed in the low-lying areas inside the platform，with low depositional environment energy. They can be further divided into calcite interbank seas（calcite lagoons）and dolomitic lagoon microfacies， which belong to semi-restricted to restricted interbank seas（lagoons） . The tidal flats were developed near the mean sea level inside the platform in the late stage of multi-level sea level decline，corresponding to the sedimentary response of sedimentary water shallowing and hydrodynamic weakening，and they can be further divided into gypsum flat microfacies and dolomitic flat microfacies.（4）The thickness of granular rocks is greater than 15 m and the thickness of gypsum rocks is 15-20 m in the northeastern P6-L1-L5 well areas in the study area， and this area can be a key area for exploration of natural gas reservoirs of T₁f³.