Most of the procedures available in the literature for well tests analysis assume a uniform initial pressure distribution. In this paper the influence of a non-uniform initial condition in pressure data is presented.

Several solutions, which consider a non-uniform initial distribution and different conditions at the inner and outer boundaries, are presented. These solutions were obtained by using a combination of Laplace transformation and Green's function methods. Integral equations relating the well response to the initial distribution function are obtained. These equations, which represent inverse problems, are solved recursively by using Backus and Gilbert solution.

Numerical experiments of the pressure response in homogeneous and naturally fractured reservoirs with different initial pressure distributions are presented. The theory and numerical results are compared and found good agreement demonstrating the applicability of the proposed method.

For radial systems it is found that the semilogarithmic straight line is not generally evident during the transient period. Also during the boundary dominated flow period, with no-flow outer boundary, it is found that an additional pressure drop is present for the case of a non-uniform initial distribution. An expression for this additional pseudo-skin is provided.

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