Volcanic clastic rock reservoir formation control factors analysis of Jiufotang formation in Lujiapu sag,Kailu basin

Volcanic clastic rocks of Jiufotang formation in Lujiapu sag,Kailu basin mainly include five lithology categories,namely volcanic breccia lava,volcanic breccias,tuff(welded tuff),sedimentary tuff and tuffaceous sandstone(gravel),and from bottom to top,the pyroclastic content has a tendency to reduce.In volcanic clastic rock,four kinds of reservoir space were developed,namely primary pore,secondary pore,primary and secondary cracks.The favorable reservoir space of volcanic clastic rock reservoir is the "primary and secondary" combination type.Volcanic clastic rock reservoir formation is controlled by multiple factors:fast fault depression Jiufotang period in lower cretaceous.Jiufotang period is the deep lacustrine- half deep lacustrine facies mudstone and shale period and it is theresource base for volcanic clastic rock reservoir accumulation.Good reservoir property is a favorable condition for volcanic clastic rock reservoir accumulation.This kind of reservoir distribution is determined by volcanic mechanism characteristics.The tectonic stress can increase the accumulation probability of pyroclastic rock.The period of volcanic activity is related to volcanic clastic rock reservoir transformation,and finally can determine the oil and gas enrichment degree.