Seepage flow characteristics of single-phase gas in low-permeability gas reservoir

At present,the description of the seepage flow characteristic of single-phase gas in low-permeability gas reservoir is only qualitative.It is held that the seepage flow curve of the single-phase gas in low-permeability gas reservoir is composed of two segments of the convex curve under lower square pressure gradient and the pseudo-straight line under higher square pressure gradient;there are pseudo-initial flow rate,critical square pressure gradient and critical seepage flow.In this paper,the seepage flow characteristic of the single-phase gas is quantitatively described.The effect of permeability on the seepage flow curve is studied by the seepage flow experiments of the cores from Sulige low-permeability gasfield,and the relationships between pseudo-initial flow rate,critical square pressure gradient and the physical parameter of the cores are obtained.It is shown that there is linear relation between the pseudo-initial flow rate and the core coefficient,and there is negative power function relation between the critical square pressure gradient and the core coefficient.The equations for describing the seepage flow characteristic of single-phase gas in low-permeability gas reservoir are shown.The study can provide mathematical basis for recognizing the seepage flow law in low permeability gas reservoirs.