Hydrocarbon Source Rock Characteristics And Shale Gas Resource Potential In Changdu Basin During The Upper Permian Series-upper Triassic Series

Changdu basin is a petroliferous basin with the oil and gas resource potential in the Tibetan region.Due to short of in-depth study in oil and gas geological conditions and structure preservation condition of this basin,we do not have a high level of understanding at the presentant.This paper aimed at not only critical geological but also oil and gas geological problems in this basin,through the combination of field construction route,the measured stratigraphic section and indoor analysis of hydrocarbon source rock,evaluate hydrocarbon source rocks geological characteristics,oil and gas geological conditions in the Tuoba formation,Adula formation and the Duogaila formation during the upper Permian series-upper Triassic series and forecast the potential of hydrocarbon source rocks,achieve the following:1,In the late Permian-late Triassic,the basin generally belong to the marina shallow sea-delta sedimentary environment,and has experienced several transgression-regression process.Late Permian-the early late Triassic,from the marginal seas change into shallow sea shelf into terrestrial delta.In the Late late Triassic,block uplift,the depth of the water becomes shallow,appeared terrigenous delta.Faults and folds developed in the internal basin.Lancang river fault is the western boundary of the basin,while the eastern is Zixia-Deqin fracture.North boundary and south boundary are no clear.2.We has cleared about the main hydrocarbon source rock layer in the basin including Tuoba formation,Adula formation and Duogaila formation.These formations's main lithology is mud shale,thickness of hydrocarbon source rock is great.The three formations of hydrocarbon source rock has good potential.The results of all samples of the tuoba formation,the adula formation are ?₂ type,the results of all samples of the Duogaila formation are ?₂ type and ?I type,all of the samples are the type which tend to produce gas.The vitrinite reflectance of all sample of The three formations are greater than 1.3,shows the thermal evolution in the hydrocarbon source rock in upper Permian series-upper Triassic series in Changdu basin has reached high mature to over mature stage.Tuoba formation,Adula formation and Duogaila formation rock have a good brittleness,is advantageous to the artificial fracturing.Clay mineral content is not absolute influence on their production.3,By volume method,We can get the recoverable resources of Tuoba formation,Adula formation and Duogaila formation is about 10.51 x 10⁸ m³,the future resource is about 70.1 x 10⁸m³.The resource totally up to advantageous standard.