Organic-rich formation and hydrocarbon enrichment of lacustrine shale strata:A case study of Chang 7 Member  

作　　者：Quanyou LIU Peng LI Zhijun JIN Yuewu SUN Guang HU Dongya ZHU Zhenkai HUANG Xinping LIANG Rui ZHANG Jiayi LIU 

机构地区：[1]State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,SINOPEC,Beijing 102206,China [2]Petroleum Exploration and Production Research Institute,S1NOPEC,Beijing 102206,China [3]Institute of Energy,Peking University,Beijing 100871,China [4]Research Center of Palaeontology and Stratigraphy,Jilin University,Changchun 130026,China [5]School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China

出　　处：《Science China Earth Sciences》2022年第1期118-138,共21页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41625009,U20B6001,42002139,42090025);the Strategic Priority Research Program of the Chinese Academy of Sciences,China(Grant No.XDA14010404);Tencent Xplorer Prize。

摘　　要：Lacustrine shale is an important target for the exploration of unconventional oil and gas in China beyond marine shale gas.However,the formation environment of lacustrine shale differs from that of marine shale,resulting in a different reservoir composition,organic matter,oil and gas content,and hydrocarbon mobility.In this study,the Chang 7 shale of the Yanchang Formation in the Ordos Basin was used to analyze the effect of volcanic activity on the paleoproductivity and preservation conditions during the formation of lacustrine shale.The results show that algae and bacteria were developed before the eruption.After the eruption,the number of bacteria declined,but the increased prosperity of algae reflects that the volcanic activity enhanced ancient productivity.The sulfate generated by volcanic activity promotes bacterial sulfate reduction,and the produced H_(2)S leads to a strong reducing environment in the waterbody,which is conducive to the preservation of organic matter.Organic geochemical analysis shows that the black shale in the shale strata has a high total organic carbon(TOC)content and strong hydrocarbon generation potential,whereas the tuff has a low TOC content and can scarcely generate hydrocarbons,indicating that the tuff deposited by volcanic activity cannot be considered as effective source rock.In terms of storage space,shale is mainly laminar and dispersed,and it includes organic and inorganic pores.The development of organic pores is affected by thermal maturity,whereas inorganic pores mainly occur between detrital particles and crystals.Tuff is mainly supported by heterogeneous matrix and associated with alteration.Its pores include inter-and intragranular mineral pores.The development of tight sandstone pores is affected by compaction,cementation,and dissolution,which mainly consist of intra-and intergranular pores.The Chang 7 lacustrine shale generally contains oil,but different lithologies have different oil drainage efficiencies.Sandstone and shale exhibit the best and worst oil drainage e

关 键 词：Lacustrine shale Organic-rich Volcanic activity Pore structure OILINESS 

分 类 号：P618.13[天文地球—矿床学]