The Geological Characteristics And Hydrocarbon Accumulation Model Of The Paleozoic Oil Sand In The Northern Longmen Mountain Zone Of The Northwest Of Sichuan

Oil sand is an important unconventional hydrocarbon resource and complement forconventional hydrocarbon resource. With the increasing both demand and shortage forconventional hydrocarbon resource, the oil sand will play an important role in the oil and gasresource in the future. The oil sand is abundant in China, but the overall level of oil sandexploration is low.The Paleozoic oil sand is study object in the Northern Longmen Mountain Zone of theNorthwest of Sichuan in this paper that has great significance to promote the exploration anddevelopment of oil sand. The Paleozoic oil sand main distribute in the Kuangshanliang, Tianjingshan and Erlangmiao oil sandstone metallogenic zone in the Northern Longmen Mountain Zoneof the Northwest of Sichuan. In this paper the author analyses the oil sand outcrop geologicalfeatures, petrology, sedimentary characteristics and reservoir space types by field reconnaissance,measured section, microscopic image analysis and grain size analysis. The reservoir propertiesare studied through testing. The favorable accumulation conditions to further explore thereservoir-forming rule and hydrocarbon accumulation model of the Paleozoic oil sand in theNorthern Longmen Mountain Zone are studied by Combining with previous research. On thebasis, the oil sand resources of Ping Yipu formation and Chang Jianggou formation are estimatedin study region.The Paleozoic oil sand was formed under marine environment in the Northern LongmenMountain Zone. The lithology of Ping Yipu formation is main quartz sandstone which formsunder coastal environment. Its subfacies include shoreface subfacies and lower beach subfaciesand which microfacies include under shoreface microfacies and middle shorefacemicrofacies.However, the lithology of Chang Jianggou formation is main litharenite which formsunder offshore continental shelf environment. Its subfacies include transition subfacies and coastcontinental shelf outer subfacies through analyzing. The primary intergranular pore, secondary intergranular dissolution pore, secondarydissolution intraparticle pore and structural fracture are chief reservoir space types in region ofinterest. Reservoir space type of Ping Yipu formation is main primary intergranular pore, butreservoir space type of Chang Jianggou formation is main secondary dissolution pore.Reservoir of Ping Yipu formation is middle-low porosity and middle permeability reservoir, butreservoir of Chang Jianggou formation is especially low porosity and ultra-low permeabilityreservoir through lab testing.They are the favorable accumulation conditions of the Paleozoic oil sand in the NorthernLongmen Mountain Zone. Oil origins form black mudstone and shale of Doushantuo formation.These are a variety of reservoir space types,with good reservoir properties.Different structuraltypes play important controlling role in accumulation of the oil sand.Paleo-reservoir of Cambrianhas good conditions for regional seal.The hydrocarbon accumulation models of oil sands are established, which believe thathydrocarbon accumulation model of Chang Jianggou formation is Uplifted and reformed modelin Kuangshanlian area and Nianziba area, as well as hydrocarbon accumulation model of PingYipu formation is remigration model in Tianjingshan area.By calculation, the total geologicalresource of oil sand of Kuangshanliang, Tianjingshan and Erlangmiao oil sandstone metallogeniczone in the Northern Longmen Mountain Zone is3622.466×104t.