四川超级盆地天然气富集规律与勘探方向OA

In order to clarify the natural gas enrichment patterns and exploration targets in the Sichuan Basin,a systematic study was conducted under the framework of tectonics controlling basins,basins controlling sedimentation,and tectonics and sedimentation controlling reservoir-forming assemblages.The study comprehensively analyzed the geological conditions for the formation of this super basin,summarized the natural gas enrichment patterns controlled by tectonic sequence,and proposed key targets for future exploration.The following results are obtained.(i)Controlled by the evolution of the Tethyan tectonic domain,the Sichuan Basin underwent three major evolutionary stages:the Nanhuaian intracontinental rift basin,the Ediacaran-Middle Triassic cratonic basin,and the Late Triassic-Jurassic foreland basin.The basin-wide gas-bearing potential in planar distribution and the vertical superposition of multiple petroleum systems are key factors controlling the formation of the gas-rich super basin.(ii)Intense intracratonic tectonic differentiation governs the spatial distribution of paleo-rifts,paleo-platform margins,and paleo-uplifts,thereby shaping the distribution pattern of large-scale gas reservoir-forming elements.Deep to ultra-deep carbonate reservoirs are characterized by multi-stage hydrocarbon accumulation,near-source hydrocarbon enrichment,and tectonic differentiation controlling zone.(iii)The migration of depositional and subsidence centers in the foreland basin forms a"sandwich-type"proximal reservoir-forming assemblage.Shallow to medium tight gas reservoirs exhibit the features of fault-sandstone coupling,near-source migration,and multi-layer accumulation.The Upper Triassic Xujiahe Formation in the foreland depression-slope zone demonstrates the characteristics of full-sequence hydrocarbon accumulation.Key targets for gas exploration are proposed as follows:from the practical perspective,deep to ultra-deep carbonate rocks,tight gas in the Xujiahe Formation-Middle Jurassic Shaximiao Formation in the foreland depression-slope zone,and shale gas in shelf facies are critical to supporting the Sichuan Basin's gas production breakthrough of 100 billion cubic meters by 2030;from the potential perspective,the ultra-deep Neoproterozoic Qingbaikou-Nanhua rift systems in the central basin,deep layers or nappe footwall in the foreland thrust belts along the basin margin,and the Lower Paleozoic shale gas in central Guizhou-western Hubei areas outside the basin should be evaluated as soon as possible.