The pressure causes tiny cracks to form that allow the gas to escape. This entire fracture system connects the well to the productive parts of the reservoir away from the bottomhole.

Environmental impacts of shale gas production in the US
One of the 2 basic technologies for shale gas production is Hydraulic fracturing.
The pressure causes tiny cracks to form that allow the gas to escape. This entire fracture system connects the well to the productive parts of the reservoir away from the bottomhole.