Sonic Log, Density log and Neutron logs are all what type of logs in Well Logging?

• A. Porosity Logs
• B. Lithology Logs
• C. Gamma Ray Logs
• D. Pressure Logs

Answer: (A)

These three logs all serve to estimate how much pore space a rock contains, i.e., porosity. The sonic log sends a sound pulse and records its travel time through the formation; rocks with more porosity slow the wave more, so the measured travel time increases and, with the right rock constants, porosity can be inferred. The density log measures the bulk density of the rock; since porosity is the portion of rock that is fluid-filled, a rock with higher porosity has a lower bulk density (for a given mineral matrix density), allowing porosity to be calculated from the difference between the matrix density and the bulk density. The neutron log responds to hydrogen content, which is abundant in fluids within the pores; higher hydrogen content typically indicates more pore space, providing a porosity estimate as well. Together, these logs give complementary ways to quantify porosity, and they’re distinct from logs that primarily identify lithology or natural gamma radiation.