Pulsed Neutron Spectroscopy Logs Add Value to Steam Flood Management Process by Monitoring Oil Saturation in Kern River Field, California

Abstract

ABSTRACT A PNS logging program was designed to evaluate the economic potential of vertical steam flood expansion and to identify bypassed oil, based on a comparison of oil saturations from a Pulsed Neutron Spectroscopy (PNS) log to conventional core in a Kern River field well. In the comparison, PNS log oil saturations agreed with those from conventional core within ±5.4 saturation units 68% of the time (log accuracy: 1 σ = 5.4). From multiple passes of the PNS log, it was found, for one effective pass at 60 feet/hour that the measurement repeats within ±5.7 saturation units 68% of the time (log precision: 1 σ = 5.7). After the comparison of log to core, a multiwell logging program was designed to determine oil saturations for several reservoir zones above and below existing steam flood zones. The results were used to optimize patterns for future steam flooding. In addition, oil saturations were obtained for zones within the existing steam flood to determine the economic value and risk for producing bypassed oil. For a proposed vertical expansion project, Expected Value Decision Analysis showed a benefit/cost ratio of 39/1 of running three PNS logs in the project area. The fraction of the total uncertainty associated with simulated production was reduced from 72% before to 39% after running the PNS logs. In addition, the PNS logs identified several million barrels oil in place that had not responded to conductive heating.