A method is presented to analyze variable rate tests in gas wells considering the effect of damage and high-velocity flow. This is a direct method that allows an estimation of the turbulent term coefficient D and the skin factor without using a trial and error procedure. The methods are applicable to infinite acting radial flow.

The method considers a step-function approximation of the flow rate. It consists of two parts: a) a graph of
Δpp(p)tj=1N(qiqj1ttj1)
is made from which we can estimate the formation conductivity kh and b) a graph of
1.1513[Δpp(p)m1qN[j=1N(qjqj1qN)log(ttj1)+log(1ϕμ(pi)ct(pi)rw2)+log(4βtγ1)]vsqN

is made that yields an estimate of the parameter D and of the skin factor s. This method can also be applied to continuosly varying rate flow tests.

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