Engineering Tip: Run Multiple Drawdown/Buildups On A Pressure Transient Test
Pressure transient tests are a common well testing technique and they are the primary way to identify average permeability and skin factor for a well. In theory, only a single drawdown/buildup is necessary to analyze permeability and skin, as these parameters will not change across different flowrates. However, there is a great benefit to be gained by running multiple drawdown/buildups (at different flowrates) during a single well test. First, you can identify (and quantify) skin due to turbulence, which is the only component of skin that is flowrate-dependent. Additionally, by running multiple drawdown/buildups, you can use the same data to calculate deliverability parameters (C and n), which will yield more accurate AOF and IPR curves.
I prefer to run 3 drawdown/buildups during a single well test. This allows me to get more meaningful data out of my well test, which means I get more bang for my buck!