Arifur Rahman
Modern type curve analysis involves matching the pressures and their semi log derivative on a set of dimensionless type curves, and selecting a match point. Using this point and a specified matching curve, reservoir parameters such as permeability, skin factor, wellbore storage, areal extent etc. can be calculated. This paper shows that the same parameters can be obtained by using derivative analysis and type curve analysis. There are many graphical techniques that can be used to analyze well test data. These techniques include Cartesian, semi-log, and log-log plots of pressure and pressure drop functions. The particular analysis technique to be used depends uniquely on the reservoir flow model. In this paper first, semi-log plot of pressure versus the logarithm of some time function is used. Log-log plots are used, as a diagnostic tool to determine the reservoir model and to identify analogous data trends. In fact only the semi log derivative of the data is needed on log-log coordinates. Finally, pressure derivative and type curve values are used to construct a vertical model of the reservoir. In addition to the semi log derivative data, it is advisable to superimpose a plot of PPD (primary pressure derivative). This enables the analyst to differentiate between reservoir and wellbore effects.
Share this article