The Research Of Organic Petrology Characteristics On Source Rock In Northwest Guizhou

Due to long anoxic marine sedimentary environment,black shale with multi-layers formed in the Northwest of Guizhou.After geological exploration and integrated researches,many workers proposed that the fairly good source rock of Lower Cambrian Niutitang Formation has high organic matter abundance.Therefore,rich resources of oil and gas must have been contained in this region,and is expected to become a favourable hydrocarbon explorating area in recent years.Using whole rock analysis,organic petrology characteristics of source rocks of the lower Cambrian Niutitang formation,upper Ordovician Wufeng formation-lower Silurian Longmaxi formation,lower Permian Longtan formation in northwestern Guizhou province have been studied in this paper,including the maceral composition,types of organic matter and hydrocarbon generating characteristic.Organic maceral is relatively low in the lower Cambrian Niutitang formation,upper Ordovician Wufeng formation-lower Silurian Longmaxi formation,4.95%and 5.63%on average respectively.On the other hand,organic maceral of lower Permian is very high,average 23.2%.For the lower Cambrian Niutitang formation and upper Ordovician Wufeng formation-lower Longmaxi formation,sapropelite is rich in the maceral composition,and exinite is relatively developed,and vitrinite and inertinite are absent.For lower Permian,inertinite and sapropelite are relatively developed,exinite is absent.Lower Cambrian Niutitang formation has the best kerogen type with dominant Type ? contributed by algae and bacteria.Kerogen type of upper Ordovician Wufeng formation-lower Longmaxi formation is inferior and lower Permian Longtan formation is worst with type ?.The source rocks in Northwest of Guizhou from the Cambrian to the Permian are at a mature stage to high maturity.Almost all of the organic matter of hydrocarbon source rocks in Lower Cambrian niutitang formation are in the mature stage,hydrocarbon generation of organic matter have largely ceased,no new generation of natural gas as a supplementary source,shale gas reservoirs into already-built natural gas lost-dominated process.Due to angry mode in the area primarily for heat formation caused by high maturity does not therefore affect the quality of source rock,seal of caprock has become particularly important.