Analyzing the Pressure Response during the Afterfl ow Period: Determination of the Formation Permeability and Skin Factor

As we mentioned in Chapter 9, in some cases the afterfl ow period can completely dominate the pressure buildup and the afterfl ow analysis is the only method of formation permeability and skin factor. Assuming that the afterfl ow rate can be approximated by an exponential function we developed a direct method of computing the Duhamel integral (see Chapter 9). In the previous Chapter we utilized the fl ow rate-time and pressure-time data to present a data processing technique for estimation formation permeability and skin factor.