YI Ting, ZHOU Wen*, YANG Fan, CHEN Wen-ling, ZHANG Hao-tian, XU Hao, LIU Rui-yin, ZHAO Xin, JIANG Ke

（Chengdu University of Technology, Chengdu 610059, China）

Abstract: In order to analyze types and characteristics of quartzs in shale gas reservoirs, the Longmaxi Formation shale in Sichuan Basin was taken as the main object of this study. The samples were observed by using thin section identification and scanning electron microscopy (SEM) of argon ion polishing-field emission environment, analyzed by using energy spectrum analysis and X-ray diffraction analysis, and analyzed for their organic carbon contents. The quartz contents of the Longmaxi Formation shale range from 23% to 83% with an average of 52%. The quartz can be classified into five types including the terrigenous clastic quartz, bio-skeletal related quartz, mixture of sedimentary and early diagenetic quartzs, diagenetically authigenic quartz, and quartz veins in fissures. Quartz contents are positively correlated with organic carbon contents. Especially, organic quartz can be used to betterly indicate the development of organic matter in the reduced environment. Organic quartz refers to the bio-skeletal quartz which retains kerogen evolved from soft matters, quartz for replacing bio-skeletons, and quartz associated with bitumen. The accumulation of bitumen-associated quartz in primary pores of the shale resulted in the reduction of the porosity of reservoir, but the inhibition of the late diagenesis to a certain extent, the reservation of pores for infilling bitumen, and the formation of a connected pore network by organic pores and gaps between quartz and bitumen.

Keywords: quartz types; quartz characteristics; organic quartz; pore

ACTA MINERALOGICA SINICA Vol. 40, No.2, 2020, page 127-136