Quartz Cementation in the Lower Paleozoic Shales,Middle Yangtze Region,South China:Implications for Shale Reservoir Properties  

作　　者：Tian Dong Jian Gao Shuangjian Li Chuan Wang 

机构地区：[1]State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development,Beijing,102206,China [2]SINOPEC Key Laboratory of Geology and Resources in Deep Stratum,Beijing,10220,China [3]School of Earth Resources,China University of Geosciences,Wuhan,430074,China

出　　处：《Journal of Earth Science》2024年第6期1918-1933,共16页地球科学学刊（英文版）

基　　金：financially supported by the SINOPEC Key Laboratory of Geology and Resources in Deep Stratum Foundation(No.33550000-22-ZC0613-0252);the National Natural Science Foundation(Nos.U19B6003,U20B6001 and 42002137)。

摘　　要：As one of the most important constitutes of shales/mudstones,quartz has received increasing interests in the last decades,because productive shale gas successions are generally rich in quartz content.This study critically documents quartz types,silica source for quartz cementation and effect of quartz cementation on reservoir quality in the Lower Paleozoic shales,Middle Yangtze region,South China,including the Lower Cambrian Niutitang Formation and the Upper Ordovician-Lower Silurian Wufeng-Longmaxi formations.Our results suggest that high-resolution scanning electron microscopy combined with cathodoluminescene techniques are necessary for identifying quartz types in shales.Integrations of high-resolution imaging technique and detailed geochemical analysis are able to document silica source for quartz cementation and silica diagenetic processes.Six types of quartz can be identified in the Paleozoic shales,primarily including detrital quartz silt,siliceous skeletons,quartz overgrowth,microcrystalline quartz(matrix-dispersed microquartz and aggregated microquartz),silica nanospheres and fracture-filling quartz veins.Dissolution of siliceous skeletons provides the principal silica sources for authigenic quartz formation in the Paleozoic shales.Authigenic quartz has dual effects on porosity development.Quartz overgrowth definitely occupies interparticle pores and possibly squeeze spaces,whereas aggregated microquartz can form rigid framework that is favorable for generating and preserving intercrystalline pores and organic pores.

关 键 词：shale gas QUARTZ shale reservoir properties Paleozoic shales Middle Yangtze region 

分 类 号：P618.13[天文地球—矿床学]