Reservoir characteristics and genetic mechanisms of gas-bearing shales with different laminae and laminae combinations: A case study of Member 1 of the Lower Silurian Longmaxi shale in Sichuan Basin, SW China

SHI Zhensheng,DONG Dazhong,WANG Hongyan,SUN Shasha,WU Jin

Fig. 11. SEM photos showing lamina combination types and gas-bearing shale in Long-1 Member, Sichuan Basin. (a) Shuanghe outcrop, Long 111, siltstone bearing laminae; the silty laminae are lenticular; the interfaces are intermittent, planar and parallel; the top and bottom interfaces are in abrupt contact; (b) Shuanghe outcrop, Long 111, siltstone bearing laminae; the silty laminae are banded; the interfaces are continuous, planar and parallel; the top and bottom interfaces are in abrupt contact; (c) Well Zu 201, 4365.8 m, gradating sand-mud combination; the top interface of the silty laminae is in abrupt contact; and the bottom interface is in graded contact, forming reversed grading; interfaces are generally intermittent, planar and parallel; (d) Well Zi-201, 3670.5 m, gradating sand-mud combination; silty laminae and clayey laminae form reversed grading or normal grading; interfaces are generally continuous, planar and parallel; (e) Well Yanjin-1, 1534.6 m, siltstone and claystone interlaminated laminae; the top and bottom interfaces of silty laminae and clayey laminae are all in abrupt contact; the lower lamina interface is continuous, planar and parallel, while the upper lamina interface is continuous, planar and nonparallel; (f) Well Wei-204, 3529.9 m, siltstone and claystone interlaminated laminae; the top and bottom interfaces of silty laminae and clayey laminae are all in abrupt contact; the lamina interfaces are intermittent, planar and parallel.