Sometimes using surface pressure data is the only practical testing method available. This example illustrates a #welltest where downhole gauges were set below an open sliding sleeve that was above the perforations. Valid pressure transient data were totally obliterated by liquid interference. Quiet-side (annulus) surface pressure data may very well have provided valid pressure transient data in this case. An acoustic well sounder (#AWS) survey is recommended at rig-off to confirm any fluid level.