Pore Structures of the Lower Permian Taiyuan Shale and Limestone in the Ordos Basin and the Significance to Unconventional Natural Gas Generation and Storage

Figure 3

Examples of Taiyuan Formation limestones: (a) core of bioclastic limestone, 2172.1~2172.4 m; (b) core of limestone, 2195~2195.4 m; (c) micrograph of limestones with sea urchin fossil, 2172.2 m; (d) micrograph of limestone with bryozoan, 2172.3 m; (e) micrograph of limestone with typical stylolite structure, 2195.0 m; (f) micrograph of limestones with microfractures filled by pyrites and organic matter, 2195.1 m; and examples of Taiyuan Formation shales: (g) core of calcareous shale and calcareous siltstone, 2191.9~2192.2 m, with irregular calcareous-silty beddings with abundant bioturbations; (h) core of massive shale and its top and bottom surface, 2181.6~2181.8 m; (i) micrograph of shale with silty laminations consisting of quartz and feldspars, 2191.9 m; (j) photomicrograph of shale with silty laminations disturbed by bioturbations, 2192.0 m; (k) micrograph of shale with pyrites, 2169.2 m; (l) micrograph of shale with clustered pyrite grains.

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