This paper presents a new method for analyzing gas well test data distorted by wellbore storage. The method that we propose in this paper is an explicit deconvolution method which is independent of the reservoir model. As is well known, the deconvolution procedure corrects test data influenced by wellbore storage and yields the pressure profile that would have existed had the afterflow rate been zero. Deconvolved data may then be analyzed using conventional semilog and type curve techniques.
This new deconvolution method has an explicit solution; i.e., a single formula corrects for the wellbore storage effect using measured bottomhole pressure and sandface flowrate. Previously introduced methods are tedious and difficult to apply. This method is much faster, gives equitable accuracy, and is easy to use. In the event the sandface flowrate is not measured, methods to estimate the sandface rate using our proposed wellbore material balance equation are presented.
The method given here is simple enough to be used in hand calculations; algorithms to apply this method are outlined in this paper.