Sedimentary systems and their influences on gas distribution in the second member and third member of the Permian Xiashihezi Formation in the Daniudi Gas Field, Ordos Basin, China

Based on the study of cores, analytical data and statistics data from the second member and the third member of the Permian Xiashihezi Formation (P(1)x(2) and P(1)x(3)) in the Daniudi Gas Field, Ordos basin, China, the shore-shallow lake deposition can be confirmed in the study area for the first time. The discovery of tempestite deposition and the sandbody reworked by lacustrine waves can be inferred by the observation of cores. The presence of type II1 kerogen indicates stable infralittoral deposits in this area. Also, the analysis of chemical elements indicates that the water depth became deeper from north to south and that the deposition environment changed from onshore to underwater. Moreover, the distribution of mudstone colors reveals that the lake shoreline changed over different periods. Based on the study of sedimentary facies and the statistics of the gas pool, the closed relationship between lake shoreline and the distribution of the gas pools is conformed.