Abstract: Gas field development and indoor experiment indicate that start-up pressure gradient exists in low permeability gas reservoirs owing to influence of narrow pore throats, poor connectivity, extremely low permeability, and the effect of interfacial tension among gas, liquid and solid, etc. The impact of rock deformation on permeability is significantly obvious. Conventional gas reservoir simulation technique is based on Darcy's Law, and cannot accurately describe the percolation with start-up pressure gradient and rock deformation. On the basis of the predecessors' research work, a mathematical model of non-linear percolation in gas reservoir is developed, and a case is given in this paper. The results show that the star-up pressure gradient and rock media deformation have serious effect on the performance for gas reservoir development.

Key words: low permeability gas reservoir, start-up pressure, pressure gradient, media, deformation, numerical simulation