pulsed neutron holdup log

A record of the fractions, or holdups, of gas, oil and water present at different depths in a producing well using a combination of nuclear measurements recorded by a pulsed-neutron spectroscopy device. The technique is used mainly in deviated and horizontal wells, where the complex flow regimes cause conventional holdup measurements to be inaccurate. The pulsed-neutron spectroscopy measurement is processed to obtain the volume of oil in the borehole rather than the oil in the formation as in a conventional carbon-oxygen measurement. The gas holdup is determined from the ratio of counts received by the near and far detectors in either the inelastic or capture mode, a technique similar to the compensated-neutron log. The water holdup is the remaining fraction. Alternatively, the capture cross section of the borehole can be determined from the pulsed-neutron capture measurement. If the water is saline, and its salinity is known, the water holdup can be determined directly.