A new pressure-pulse decay method is presented to measure permeabilities of tight rock samples. Existing pressure-pulse methods yield pressure decays which are either slow or difficult to analyse. Often approximations are made which may yield considerable errors in the derived permeability values. The new method is simple and enables very fast and accurate permeability measurements.
The exact solution of the differential equation describing the decay curve resulting from a pressure-pulse measurement was analysed in detail. This showed how the decay curve is influenced by various parameters in the design of the pressure-pulse permeameter. In this way various existing designs could be compared. Furthermore, the analysis showed how a pressure-pulse permeameter should be designed such that the measured decay is fast and simple to analyse. Also an approximate solution was obtained which is accurate to within 0.3% of the exact solution which is much more difficult to handle. Using this solution a new and simple analysis procedure was developed. Combining the new design with the new analysis method results in an elegant method for fast and accurate pressure-pulse measurements.