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. 4. Lamina combinations in the Yangchang Formation Chang 73 sub-member shale of the Ordos Basin. (a) Well Feng 61, 2482.98 m, massive mudstone; (b) Well Cai 30, 1964.88 m, “organic-rich + silt-grade feldspar-quartz” lamina combination; (c) Well Ning 70, 1711.80 m, “organic-rich + tuff-rich” lamina combination.