A new transient well-testing procedure, which extends "pulse-testing" technology, has been developed for determining the hydraulic diffusivity (K/[μcϕ]) in underground-storage reservoirs. The method depends on the availability of cyclic pressure data from a pair of adjacent and communicating wells: A, the upstream or "forcing-function" well, and B, the downstream or "observation" well.

In general, the pressure fluctuations at well B will exhibit both an attenuated amplitude and a phase lag when compared with those at well A. The theory, which relates the two sets of fluctuations, relies on a solution of the diffusion equation, which governs pressure or potential variations with time and distance in a compressible medium.

To apply the theory to experimental observations, a Fourier analysis is performed on the transient pressures at both A and B. The method has been tested with field data and indicates good success in predicting the pressures at offset wells.

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