Morphology and genesis of the solid bitumen from the Changxing Formation-Feixianguan Formation in northeastern Sichuan

The SEM examination of the solid bitumen from the Upper Permian to the Lower Triassic reservoirs in northeastern Sichuan shows the morphological features of the solid bitumen including crustiform, botryoidal, nodular, vermiform and dried persimmons-like features, of which the crustiform and botryoidal solid bitumen is dispersed in the Triassic reservoirs, while the nodular, vermiform and dried persimmons-like solid bitumen occurs in the Permian reservoirs. The differences in occurrence represent distinct genesis and evolutionary phases of the bitumen. It is inferred from the scaly textures and pelleted mesophase textures that the bitumen has entered into high-grade evolutionary stages.