Formation Mechanism of the Sinian Natural Gas Reservoir in the Leshan-Longnvsi Paleo-uplift, Sichuan Basin
Sinian deep-buried carbonate gas reservoir has been discovered in the Leshan-Longnvsi Paleo-uplift,Sichuan Basin.In this paper,we discuss the formation mechanism of this reservoir based on an integrated analysis of multiple characteristics of the gas formation,including gas reservoir type,fluid nature,origin and source of gas,gas charge phase,and evolution of gas formation.Results show that the Sinian Dengying Formation gas reservoir includes diversified types,such as structural,lithological,and stratigraphic-lithological.The fluid nature varies in different gas reservoirs.The gas is of mixed origin and sourced from Sinian and Lower Cambrian rocks,and the mixed ratio varies in different reservoirs.The gas formation has subjected to three phases,including the primary formation of paleo-oil reservoir,subsequent oil-cracking,and final alteration and accumulation of gas reservoir.The gas formation has three mechanisms,including the remigration and accumulation of the cracking paleo-oil,in-situ or intact accumulation of the cracking paleo-oil,and late accumulation of dry gas.Of these three mechanisms,the second one may be the most significant for the exploration of deep-buried carbonate reservoir under high maturation condition,as exemplified by the most-recently discovered giant gas reservoir in the central basin.
Sichuan BasinLeshan-Longnvsi Paleo-upliftDengying FormationOil-cracking gasEvolution of hydrocarbon accumulationHydrocarbon accumulation mechanism
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