The highly viscous heavy oil in horizontal wells in ChevronTexaco's Captain field in the North Sea presents difficult conditions for most horizontal production-logging instruments because of plugging and coating of the sensors. Recently, production profiles in three of the Captain field screened horizontal wells were determined by use of an advanced horizontal production-logging system. The system combines 2D parallel-plate capacitance-array measurements of three-phase holdup and velocity profiles, pulsed-neutron measurements of three-phase holdup and water velocity, and conventional production-logging measurements to determine the production profile.