(re)fracturing Austin Chalk Changning shale gas Cyclic CH4 injection EDFM EUR Eagle Ford shale bottomhole pressure bubble point pressure cluster efficiency discrete fracture model drained rock volume embedded discrete fracture model enhanced oil recovery enhanced permeability flow modeling flow models fracture modeling fracture porosity fracture properties fractured reservoir hydraulic fracture closure hydraulic fractures hydraulic fracturing hydraulic fracturing test site infill wells line detection low-permeability reservoir microseismic midland basin