Start-up pressure gradient of the tight gas reservoirs in Daniudi gas field decreases with increasing effective permeability under constant water saturation

and increases with increasing water saturation.The calculation formula for the drainage radius of gas well at production plateau is deducted from unstable percolation(theory).If start-up pressure is taken into consideration and gas well production is identical

the drainage radius of gas well at production plateau increases with effective permeability.If effective permeability is identical

the drainage radius of gas wells at production plateau decreases with increasing gas well production.The minimum well spacing at a certain proration condition can be calculated by the drainage radius of gas well at production plateau.The production plateau of gas well will not be shortened by well interference only when the real well spacing is larger than minimum well spacing.