Shale gas preservation conditions in the Lower Paleozoic, Yangtze block

Two sets of organic-rich shale developed in the Yangtze block during the Early Paleozoic. The first set was in the Lower Cambrian Niutitang Formation, while the second set was in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation. The shales experienced four stages of orogenic events, including the Guangxi, Indosinian, Yanshanian and Himalayan. Shales are well-preserved in the Upper Yangtze region and to the west of the middle Yangtze region, where only two or three phases of deformation took place. The shale gas content is high, showing a good potential for exploration. In the east of the middle Yangtze region and the west of the lower Yangtze region, shale gas preservation conditions are poorer due to three or four phases of deformation. As a result, the shale gas content is lower as is the exploration potential. In the east of the lower Yangtze region and in the periphery orogenic front of the Yangtze block, four phases of deformation took place, which led to the poorest preservation conditions for shale gas. As to the whole Yangtze block, the residual synclines are most favorable for shale gas preservation.