Abstract:

The two factors of TPR（threshold pressure gradient）and stress sensitivity should be considered in low permeability reservoir development.Because of strong nonlinear property of control equation and nonconstant boundary of fluid flow,the mathematical model used now is very tedious.In order to simplify calculation process，the characteristic of instability,low speed and nonlinear flow pressure distribution are obtained with reservoir pressure distribution approximate formula.Meanwhile,the motion law of flowing boundary and the distribution of formation pressure,as well as variation law of production rate are gained based on material balance principle under the condition of constant flow rate.Calculation results show that TPR increase flow resistance in porous media and media deformation decreases conductivity near the well bore formation,which result in formation energy can not be released and add to the difficulty of lowpermeability reservoir exploitation.

Key words: low permeability, TPR（threshold pressure gradient）, stress sensitivity, nonsteady flow, approximate solution