Continuous pressure and temperature can be recorded versus depth while tripping in the well to obtain a baseline temperature gradient and verify underbalance pressure. A gamma ray (GR) tool with a casing collar locator (CCL) is switched on to correlate and position the perforating gun. The PWP tool is activated just after perforating to record bottomhole pressure and wellbore temperature changes versus time.

The PWP log data is recorded in real time for immediate confirmation of perforation penetration and fluid movement. The information is digitally recorded to allow post job processing and calculation of parameters such as initial reservoir pressure, skin factor, and permeability.