Characteristics and main controlling factors of shale gas reservoirs in transitional facies on the eastern margin of Ordos Basin

In order to study the pore characteristics of shale gas reservoirs on the eastern margin of Ordos Basin, the authors selected the shale in Ye-1, Ye-4 and DT803 wells for experiments including scanning electron microscope, nitrogen sorption-desorption experiments and related geochemical experiments. Meanwhile, the transitional facies shale pore types, characteristics and influencing factors of gas reservoir were analyzed. The results show that inter-granular pore and organic pores are most developed in the shale, the pore morphology of the shale is mainly in the narrow parallel-plate, the pore size distribution range is 1-60nm, and the main pore size distribution is between 1-6nm and 40-60nm. The mesopores make a major contribution to pores specific surface area and pore volume, the contribution of the micro-pores to the surface area cannot be ignored; the values of organic carbon and clay minerals are the main controlling factors of the pore development, and the influence of brittle minerals on the development of pores is not obvious.