Abstract: Ordovician marine shale gas in the Ordos Basin has its unique geological characteristics. Proper evaluation of hydrocarbon
generation and storage capacities of shale, and accurate prediction of sweet spot distribution will provide guidance for marine
shale gas exploration in the Ordos Basin. Study of sedimentary paleo-bottom shape and tectonic-sedimentary evolution has
been carried out, which indicates that the sedimentary framework of Wulalike Formation in the western Ordos Basin is characterized by “local low-lying areas on the slope, deep water environment in the west and shallow in the east” with a sedimentary system of deep-water slope—open marine shelf—basin. A set of thick and widely distributed source rocks is developed in Wulalike Formation with the characteristics of “low TOC, low gas content, low porosity, low pressure, high maturity, high brittleness, high permeability and great burial depth”. Although the organic carbon content is low, it can effectively generate hydrocarbons and enrich locally, which is different from the high-abundance shale gas in the Sichuan Basin. Integrated logging and geological research have developed a technology of neutron-resistivity composite index for sweet spot prediction specially for marine shale gas in the western Ordos Basin. The sweet spot interval is at the bottom of Wulalike Formation with a thickness of 3-5 m and four sweet spot areas have been identified in the central-north section of western Ordos Basin. At the same time, gas enhanced energy fracturing test has been conducted to increase formation pressure and solve the problem of “low pressure and low abundance”,achieving breakthrough in marine shale gas exploration, which has great significance for the replacement of natural gas exploration in the Ordos Basin.