Abstract:

Fluid flowing barrier extends outwards continuously, which is a feature of pressure propagation in low velocity non-darcy percolation. In views of such character, a fixed-boundary mathematical model based on the pattern of low velocity non-darcy percolation with skin effect is presented, and solutions of flow rate and cumulative production in Laplace domain is worked out with Green’s function. The radius of flowing boundary corresponding to different time intervals is determined according to the starting differential pressure needed by fluid from static to flowing condition. The analytical solution of the fixed boundary model is then used to calculate the correlation of flow rate and cumulative production versus time, which is regarded as a numerical approximation of flowing boundary model. Stehfest method is used to obtain the flow rate and cumulative production curves. Discussion is presented on the influence of flowing boundary, starting pressure gradient, skin effect and difference between darcy percolation and nondarcy percolation.

Key words: low permeability pools, non-darcy percolation, starting pressure gradient, flowing boundary, rate performance, skin effect