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. 6. Characteristics of reservoir space in “organic-rich + tuff-rich” lamina combination shale strata of the Yangchang Formation Chang 73 sub-member in the Ordos Basin. (a) Well Ning 70, 1718.90 m, clay mineral intercrystalline pores (SEM); (b) Well Ning 70, 1718.90 m, strawberry-like authigenic pyrite intercrystalline pores (SEM); (c) Well Ning 70, 1721.92 m, oil-charged primary pores and a small amount of secondary dissolution-enlarged pores in thin sandstone interbed (plane-polarized light).