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. 8. Occurrence characteristics of crude oil in “organic-rich + tuff-rich” lamina combination shale strata in the Chang 73 sub-member of Ordos Basin. (a) Well Ning 70, 1721.92 m, crude oil filling in intergranular pores in thin sandstone interbed; (b) Well Ning 70, 1718.90 m, crude oil retained in organic-rich lamina in shale; (c) comparison of high-resolution laser Raman curves of positions marked in Fig. 8a and 8b; (d) Well Yangjian 1, overpressure fracture in tuff-rich lamina.