The objective of production logging is normally to determine reservoir inflow, but changing multiphase flow behaviour may mask the reservoir inflow response. In production logging of sub-horizontal wells the tool response may be dominated by changes in multiphase flow behaviour due to varying well inclination. These difficulties may be compounded by oscillations in PLT readings due to slug flow. Furthermore, in low API oil the high viscosity oil/water flow influences PLT measurements. Four field examples are presented illustrating the impact of this multiphase flow behaviour: Changes in slip velocities and holdup due to changing well inclination may be incorrectly interpreted as reservoir inflow. But even when these flow conditions are correctly identified, there is a large uncertainty in the interpreted reservoir inflow profile. And in high gravity oil one may fail to detect water and gas inflow unless the appropriate sensors are selected. The field examples demonstrate the strengths and weaknesses of some frequently used PLT sensors in dealing with these multiphase flow conditions.
Synnøve has been working for Hydro Oil & Energy since 1980. Initially she worked for 7 years as a petrophysicist. Later on she has held various technical and management positions within Operations. Since 2002 she has been working as a production engineer, and has planned and followed up a number of production logging jobs.
Øyvind graduated from the Department of Physics University of Bergen in 1988. He worked 9 years as a Research Scientist at Christian Michelsen Research. Since 1998 he has been working for Hydro Oil & Energy Operations as a Production Technologist. He has planned and followed up several production logging jobs.