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

13

C 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

13

C

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.