Laminae combination and shale oil enrichment patterns of Chang 73 sub-member organic-rich shales in the Triassic Yanchang Formation, Ordos Basin, NW China

XI Kelai,LI Ke,CAO Yingchang,LIN Miruo,NIU Xiaobing,ZHU Rukai,WEI Xinzhuo,YOU Yuan,LIANG Xiaowei,FENG Shengbin

Fig. 5. Characteristics of reservoir space in “organic-rich + silt-grade feldspar-quartz” lamina combination shale strata of the Yanghcang Formation Chang 73 sub-member in the Ordos Basin. (a) Well Cai 30, 1964.88 m, K-feldspar dissolved pores in silt-grade feldspar-quartz lamina (plane-polarized light); (b) and (c) Well Cai 30, 1964.88 m, K-feldspar dissolved pores filled with authigenic kaolinite in silt-grade feldspar-quartz lamina (SEM); (d) Well Cai 30, 1959.48 m, clay mineral intercrystalline pores in organic-rich lamina (SEM); (e) Well Cai 30, 1964.88 m, pyrite intercrystalline pores in organic-rich lamina (SEM); (f) Well Cai 30, 1962.95 m, overpressured microfractures in silt-grade feldspar-quartz lamina (plane-polarized light); (g) Well Cai 30, 1968.44 m, bedding fractures in shale (SEM); (h) Well Cai 30, 1968.92 m, primary pores and feldspar dissolved pores in thin sandstone interbed (plane-polarized light); (i) Well Li 57, 2340.40 m, primary pores and feldspar dissolved pores in thin sandstone interbed (plane-polarized light).