Abstract: Reservoir spaces in shale controls not only the shale gas reserves, but also the production capacity of shale gas wells, thus the study of reservoir space characteristics and charging process of lacustrine shale gas helps greatly to determine exploration targets.This paper integrates various technologies, such as field outcrops, core observation, thin section and SEM Pore Imaging, to study the reservoir space types and their features of Chang 7 shale of the Yanchang Fm in Yanchang Block of Shanbei slope zone, Erdos Basin.Combined with the experimental results of shale gas components, this paper simulates the shale gas charging process.The results show that, the reservoir spaces of Chang 7 shale are dominated by primary intergranular pores, secondary dissolved pores, organic pores, structural fractures and lamellation fractures.In the desorption process, the methane gas with relatively small molecule size is the first to be released from shale.However, the methane gas containing ¹³C is relatively more difficult to be released from the shale.In the early gas generating stage, the small portion of heavy gas generated from Chang 7 shale mainly adsorbed on the organic surface and micropores.In the main gas generating stage, heavy gas and ¹³C_CH4-containing methane had priority over other gas components to be absorbed in the shale reservoir.Only when the adsorption capacity and dissolution capacity of shale were met, could the free gas exist in the shale reservoir.

Key words: desorption experiment, pore and fracture feature, shale gas charging, Chang 7 member, Erdos Basin