Multistage petroleum charges in the Silurian of Tazhong north slope of the Tarim basin, northwest China: evidence from fluid inclusions and organic geochemistry

摘要

Well S provides a good opportunity to investigate the petroleum filling history in Tazhong North Slope. Petrographic investigations suggest that bitumen, oil, and petroleum inclusions coexist in Silurian sandstones from well S, reflecting a complicated reservoir filling history in the study area. Integration of organic geochemistry and fluid inclusion analysis shows that the Silurian reservoir has experienced three episodes of petroleum charge, that is from the late Silurian to the early Devonian, the early-middle Triassic and the Paleogene, respectively. The present-day reservoir fluids in the Silurian are the mixtures generated in multiple (at least two) episodes of petroleum charge. The oil charging into Silurian resevior in the early period had experienced considerable degradation, and was mixed with later non-degraded oil.