Abstract: Based on the conventional core experiments and pressure-sensitive features of gas reservoirs,it is suggested that the "slip flow of gas" and "threshold pressure" may be caused by pressure sensitivity of gas reservoir.This paper takes the overpressured tight gas reservoir in the shallow Upper Jurassic Penglaizhen Formation,Xinchang gas field,Sichuan province,as a research object,analyses the data collected from gas single-phase percolation experiments on its rock samples,and discusses the causes of the sophisticated percolation process with the coexistence of "slip flow of gas" phenomena and "threshold pressure" features.It proposes that the percolation process be induced by pressure sensitivity rather than by traditional Klinkenberg effect or low rate non-Darcy mechanism.The experiments also indicate that the Penglaizhen gas reservoirs in Xinchang gas field shows strong pressure sensitivity,and its fitting factor ranging between 0.3 to 1.9 and permeability reduction magnitude varying from 10% to 80%.

Key words: overpressure, percolation characteristics, Penglaizhen Formation, Xinchang gas field