四川盆地高石梯-磨溪地区栖霞组沉积模式研究

Sedimentary Models of Qixia Formation in Gaoshiti-Moxi Area of Sichuan Basin

近年来,川中地区二叠系栖霞组油气勘探持续取得突破,成为重点勘探领域。然而,目前对栖霞组沉积格局的认识尚存在较大的争议,为厘清川中高石梯-磨溪地区栖霞组的沉积特征,结合沉积古地貌,根据岩心、岩屑、常规测井、成像测井和地球化学资料,开展了沉积相和沉积模式研究。结果表明:栖霞期发育开阔台地相,台内滩和台坪亚相,滩、滩间、灰坪微相;滩相以生屑灰岩、微亮晶球粒灰岩、亮晶砂屑灰岩为主,发育砂屑滩和生屑滩;滩间岩性为泥晶生屑灰岩;灰坪相岩性为泥晶灰岩和硅质灰岩。滩相存在局部白云岩化特征,发育白云质灰岩、灰质白云岩、细-中晶白云岩在、中-粗晶白云岩。栖一段沉积期相对局限,海水相对较深,滩相与滩间交互发育,滩相主体沉积于古地貌相对较高的古隆起高部位,沉积相受古地貌的影响较大;栖二段沉积期相对开阔,古地貌对滩相的影响变弱,滩相连片发育。结合沉积背景,建立了开阔台地滩相模式,研究成果为高石梯-磨溪地区栖霞组的下一步开发部署提供了地质依据。

In recent years,the oil and gas exploration of the Permian Qixia Formation in central Sichuan has made continuous breakthroughs and become a key exploration area.However,there is still a great controversy about the sedimentary pattern of Qixia Formation,especially the influence of the Middle Uplift of the Sichuan Basin on the sedimentation,which is not clear.To clarify the sedimentary characteristics of the Qixia Formation in Gaoshiti-Moxi area of the central Sichuan Basin,based on core,debris,conventional logging,imaging logging and geochemical data,sedimentary facies and sedimentary model were studied in combination with sedimentary paleogeomorphology.The results show that open platform facies,intraplatform shoal and platform subfacies,and shoal,intershoal and grayflat microfacies develop in the Qixia stage.The beach facies is dominated by bioclastic limestone,microsparry pelletic limestone and sparry sand-clastic limestone.The interbeach lithology is micritic bioclastic limestone.The lithologies of grayflat facies is micritic limestone and siliceous limestone.The beach facies are characterized by local dolomitization,including dolomitic limestone,calcite dolomite,fine-mesocrystalline dolomite,and middle-coarse-crystalline dolomite.In the first member of the Qi Formation,the sedimentary period is relatively limited,the sea water is relatively deep,and the beach facies develop interactively.The main part of the beach facies is deposited on the high part of the paleo-uplift with relatively high paleo-geomorphology,and the sedimentary facies is greatly influenced by the paleo-geomorphology.The sedimentary period of the second member of the Qi Formation is relatively open,the influence of paleogeomorphology on beach facies become weak,and the beach connected segments developed.Combined with the sedimentary background,the open platform beach facies model under the control of paleo-uplift was established.The research results provide a geological basis for the next development and deployment of the Qixia Formation in Gaoshiti-Moxi area.