API UNIT MEASURE – LOGS

API unit: 1. A counting unit for gamma-ray logs. The difference between the high and low radioactivity sections in the API calibration pit at the University of Houston is defined as 200 API units. 2. A counting unit for neutron logs. The reading in the Indiana limestone portion of the API neutron log calibration pit (which has 19 percent porosity and is saturated with fresh water) is defined as 1000 API units.