Occurrence conditions and exploration targets of deep coal-rock gas in the Huhehu Sag,Hailar Basin
Hydrocarbon reservoirs have been identified in the 2nd member of the Cretaceous Nantun Formation(also referred to as the Nan 2 Member)in the Huhehu Sag,Hailar Basin.However,limited studies have been conducted on the occurrence conditions and exploration targets of deep coal-rock gas therein.In this study,we analyze the fundamental conditions for hydrocarbon accumulation,including source rocks,deposits,and structures,in the Huhehu Sag and examine the developmental characteristics and gas-bearing features of deep coal reservoirs.Accordingly,we explore the occurrence conditions of deep coal-rock gas in the sag and propose potential exploration targets.The findings reveal that in Nantun Formation there are two suites of mature source rocks in the mudstones and coals,which provide a favorable material basis for the deep coal-rock gas generation and accumulation.During the deposition of the Nan 2 Member,Hailar Basin,a faulted lacustrine basin,exhibits swamps,which create a favorable coal-forming setting.The initial extension stage of the basin witnessed the formation of thick coals and coal-mudstone coexistence,while its stable extension and contraction stages featured thin coals and sandstone-coal coexistence.The ramp-faulted terrace zone exhibits thin coals and low gas content.In contrast,the trough and steep slope zones are characterized by thick coal rocks and well-developed cleats,with organic pores interconnected by microfractures,contributing to high connectivity and a well-developed pore-fracture system.So it is rich in free gas.The fault system formed in the early extension stage provides pathways for the vertical and lateral migration of deep coal-rock gas.The Huhehu Sag exhibits deep coal-rock gas resources predicted at 1.79×1012 m3,suggesting considerable exploration potential and establishing this sag as an important new risk exploration target in the faulted lacustrine basin.Additionally,the trough and steep-slope zones are identified as the most favorable exploration targets for deep coal-rock gas.
risk explorationtrough zonesteep-slope zonedeep coal-rock gasthe 2nd member of the Nantun Formation(Nan 2 Member)Huhehu SagHailar Basin
万方数据
维普
