(petro is Latin for "rock" and physics is the study of nature) is the study of the physical and chemical properties that describe the occurrence and behavior of rocks, soils and fluids [1]. Petrophysics mainly studies reservoirs of resources, including ore deposits and oil or natural gas reservoirs. Petrophysicists in the oil and gas industry typically are employed in helping the engineers and other geoscientists understand the rock properties of the reservoir. Petrophysicists evaluate the reservoir rock properties by employing well log measurements, in which a string of measurement tools are inserted in the borehole, core measurements, in which rock samples are retrieved from subsurface, and sometimes seismic measurements too, and combining them with geology and geophysics.

Petrophysical studies are utilized by Petroleum engineering, Geology, Mineralogy, Exploration geophysics and other related studies.

Some of the key properties studied in petrophysics are lithology, porosity, water saturation, permeability, density, solid mechanics, Magnetization, electrical conductivity, thermal conductivity and radioactivity.

Source: Wikipedia