川西南地区中二叠统茅口组一段沉积微相特征及有机质富集模式  

Sedimentary microfacies characteristics and organic matter enrichment pattern of the 1st member of the Middle Permian Maokou Formation,southwestern Sichuan Basin

作　　者：翟常博 林良彪[3,4] 尤东华 刘冯斌 刘思雨 ZHAI Changbo;LIN Liangbiao;YOU Donghua;LIU Fengbin;LIU Siyu(Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 102206,China;State Energy Key Laboratory for Carbonate Oil and Gas,Beijing 102206,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]中国石化石油勘探开发研究院,北京102206 [2]国家能源碳酸盐岩油气重点实验室,北京102206 [3]油气藏地质及开发工程全国重点实验室(成都理工大学),四川成都610059 [4]成都理工大学沉积地质研究院,四川成都610059

出　　处：《石油与天然气地质》2024年第2期440-456,共17页Oil & Gas Geology

基　　金：国家自然科学基金面上项目(41872115)。

摘　　要：为了研究四川盆地中二叠统茅口组一段(茅一段)沉积微相和有机质富集规律,开展了岩石学、沉积微相分析。将川西南乐山沙湾剖面茅一段划分为生物碎屑含灰泥岩(MF1)、生物碎屑泥灰岩(MF2)、生物碎屑含泥灰岩(MF3)、灰泥灰岩(MF4)、生物碎屑粒泥灰岩(MF5)、钙藻粒泥灰岩(MF6)、生物碎屑泥粒灰岩(MF7)和钙藻泥粒灰岩(MF8)共8个沉积微相。结合沉积古环境及地球化学分析认为:①茅一段早、中期,主要发育MF2沉积微相,其次为MF7和MF8沉积微相。该期整体为海侵、缺氧环境,发育上升洋流,初级生产力较高。中、晚期主要发育MF6、MF7和MF8沉积微相,为相对海退环境,含氧量略有上升,上升洋流强度减弱,初级生产力下降。末期以MF2沉积微相为主,含氧量略有上升,初级生产力增强。②茅一段的有机质富集主要受海洋初级生产力与缺氧环境的调控,同时受上升洋流的间接影响。较高的初级生产力与较低的含氧量有利于有机质富集与保存。上升洋流可带来深层营养成分,从而增强海洋初级生产力。③MF2与MF7沉积微相在区域上稳定分布,且具有较高初级生产力和较低含氧量沉积环境,是茅一段有机质富集的有利沉积微相。This study aims to investigate the sedimentary microfacies and organic matter enrichment pattern of the 1st member of the Middle Permian Maokou Formation(hereafter referred to as the Mao 1 Member)in the Sichuan Basin.Based on petrological and sedimentary microfacies analyses,we summarize eight sedimentary microfacies(MF1-MF8)in the Mao 1 Member on the Shawan outcrop in Leshan,southwestern Sichuan Basin,encompassing bioclastic calcareous mudstone(MF1),bioclastic marl(MF2),bioclastic argillaceous limestone(MF3),marly limestone(MF4),bioclastic wackestone(MF5),calcareous algal wackestone(MF6),bioclastic packstone(MF7),and calcareous algal packstone(MF8).The sedimentary paleoenvironment and geochemical analyses result in the following conclusions.(1)In the early to middle stages of the Mao 1 Member’s deposition,MF2 was predominantly formed,followed by MF7 and MF8.This period was characterized by a transgressive and anoxic environment overall,marked by the presence of upwelling ocean currents and high primary productivity.The middle to late stages of the Mao 1 Member’s formation primarily witnessed the occurrence of MF6,MF7,and MF8.This period featured relative regression,with slightly increased oxygen content,weakened upwelling ocean currents,and decreased primary productivity.In the final stage of its deposition,the Mao 1 Member was dominated by MF2,with slightly increased oxygen content and enhanced primary productivity.(2)The organic matter enrichment in the member was predominantly influenced by marine primary productivity and anoxic environment,while under the indirect influence of upwelling ocean currents.Specifically,a setting of higher primary productivity and lower oxygen content is conducive to the enrichment and preservation of organic matter.Furthermore,upwelling ocean currents facilitate the transport of nutrients from deeper parts,thus enhancing the marine primary productivity.(3)MF2 and MF7,characterized by stable regional distributions and depositional environments with higher primary productivity

关 键 词：有机质富集 地球化学特征 古环境 沉积微相 茅口组一段 中二叠统 川西南地区 

分 类 号：TE121.3[石油与天然气工程—油气勘探]