Study of Desorption in a Vapor Dominated Reservoir with Fractal Geometry

Abstract

This paper is an attempt to model well decline in a vapor dominated reservoir with fractal geometry. The fractal network offractures is treated as a continuum with characteristic anomalous diffusion ofpressure. A numerical solver is used to obtain the solution of the partial differential equation including adsorption in the fractal storage space. The decline of the reservoir is found to obey the empirical hyperbolic type relation when adsorption is not present. Desorption does not change the signature of the flow rate decline but shifts it on the time/flow rate axis. Only three out ofsix model parameters can be estimated from field data, due to the linear correlation between parameters. An application to real well data from The Geysers field is presented together with the estimated reservoir, fractal space and adsorption parameters. Desorption dominated flow is still a questionable approximation for flow in fractal objects.