Breakthroughs in hydrocarbon exploration in the Ganchaigou area,Qaidam Basin and their implications
No significant hydrocarbon exploration discoveries were achieved for over 60 years of efforts,and breakthroughs have ultimately been made since 2019 when seismic survey targeting mountainous regions was performed and study on the formation of and hydrocarbon accumulation in mixed siliciclastic-carbonate reservoirs developed in plateau salinized lacustrine environment went further.The discovery of structural reservoirs located in the Lower Ganchaigou Formation of the Paleogene,along with great potentials shown in the exploration and development of Yingxiongling shale oil and lacustrine carbonate lithological reservoirs in this area,can be attributed to the following factors.First,high-quality 3D seismic data serve to reveal the underground structure geometry in the Ganchaigou area,where a faulted anticline favorable for hydrocarbon accumulation as a trap is detected in the east;Second,large-scale mixed carbonate rocks of salinized lacustrine facies have storage capacity,while clastic rocks,lacustrine carbonate rocks and gypsolyte are well-aligned both laterally and vertically,thus being of a good source rock-reservoir-caprock assemblage as a whole;Third,both conventional(out of source rocks)and unconventional(within source rocks)hydrocarbon are generated and accumulate as a total petroleum system(TPS)in the study area.In investigating the exploration process in the study area,we confirm that the progress in seismic exploration technology lays a solid foundation for the discovery of the complex structural trap underground and its petroleum geological characteristics.The mixed carbonate rocks developed in large scale in the dry salinized lacustrine environment function as both source rocks and reservoirs,a finding that has extended our understanding in exploration and been a key in fulfilling the breakthroughs.The adoption of the TPS concept serves to push hydrocarbon exploration to go further into the source rocks while revealing the great potentials of Yingxiongling shale oil to be developed.
seismic explorationbasic geologytotal petroleum system(TPS)unconventional oil and gasGanchaigou areaQaidam Basin
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