Discussion on Is a starting pressure gradient necessary for flow in porous media?

Whether a threshold pressure gradient (TPG) of percolation exists in low-permeability reservoirs has been a hot topic in development theories of low-permeability reservoirs, from which a good many arguments arise in academic circles. For instance, a paper that discusses an identical percolation problem under stable or unstable percolation conditions, which made readers confused. Another unreasonable opinion that percolation of porous media has no threshold pressure gradient in low- or extralow-permeability reservoirs was proposed by using a reservoir limit testing equation to calculate distance to a reservoir boundary that fluid can affect and by wrongfully associating skin effect with a threshold pressure gradient.