Theoretical Study Of Nonlinear Seepage Well Testing Low Permeability Gas Reservoirs

The past researches show there are threshold pressure gradients’and stress-sensitivity’s effects in the low-permeability gas reservoirs, which results in that the conventional seeping law couldn’t be applied on the low-permeability gas reservoir,and raises the difficulty of production evaluation and well test interpretation.Based on the non-Darcy seeping mechanism of low-permeability gas reservoir,this pape has established gas-water deliverability model and well test model on the effects of threshold pressure and stress-sensitivity,the achivements are as follows:(1) Analyze factors, types, mechanism of deformation, and effective stress.(2) Study stress-sensitivities’ effects on physical parameters (permeability, compressibility, porosity),analyze the permeability hysteresis effects, and take stress-sensitive evaluation.(3) Establish the deliverability model of considering gas-water threshold pressure gradient, stress sensitivity, skin and turbulent effects, and take capacity evaluation under different sensitive parameters.(4) Deduced by material balance equation, establish the gas-water numerical well test model and analyze some factors’influences on wellbore pressure,such as gas-water ratio, threshold pressure gradient, stress sensitivity, wellbore storage coefficient and skin effects.(5) The numerical well test results prove that the threshold pressure gradient and stress sensitivity will increase seepage resistance, both pressure drop and the pressure derivative curves upwarp, while gas-water ratio has greater impacts on the wellbore dynamic pressure.Through non-linear flowing features’ studies, this paper will be of great significance to take capacity assessment and well test interpretation of low-permeability gas reservoirs...