Petrophysics is the study of the physical properties and the rock and fluid interaction in petroleum systems. A petrophysicist in the oil and gas industry helps fill in some of the details after geologists and geophysicists have found a reservoir target. Specifically, they create a clear picture of the reservoir’s rock formation, fluid content, permeability and porosity. Petrophysicists are able to determine this information via data collected by samples from the surface, as well as downhole sensors. These tests usually occur during the earliest stages of drilling and are used to create a reservoir model outlining the capabilities of the well. Once the well is in production, petrophysicists continue to play an important role as they will examine and record surface samples and design the LWD or wireline log program to ensure accurate records are kept.