Types of biogenic quartz and its coupling storage mechanism in organic-rich shales: A case study of the Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation in the Sichuan Basin, SW China

GUAN Quanzhong,DONG Dazhong,ZHANG Hualing,SUN Shasha,ZHANG Surong,GUO Wen

Table 2 Statistics on the proportions of organic matter pores in shale samples from Wufeng-Longmaxi Formation, the Sichuan Basin.

Well name Lithology Sample number Silica content/ % TOC/ % Whole-rock specific surface area/ (m2·g-1) Whole- rock pore volume/ (mL·g-1) Extracted organic matter specific surface area/(m2·g-1) Extracted organic matter pore volume/(mL·g-1) Proportion of organic matter specific surface area/% Proportion organic pore volume/% W202 Siliceous- calcareous shale 3 0.22 2.54 21.23 0.08 96.48 0.30 13.85 11.11 Calcareous shale 2 1.78 1.95 19.96 0.08 65.78 0.26 7.71 7.76 Siliceous shale 3 28.78 6.06 27.06 0.09 163.01 0.28 43.81 23.32 W204 Calcareous shale 2 9.66 2.29 25.97 0.14 121.42 0.27 12.85 5.48 Argillaceous shale 3 0.15 1.05 15.25 0.05 60.13 0.22 4.97 4.98 Siliceous shale 3 3.21 2.84 28.68 0.07 105.40 0.37 12.53 18.46