Quantifying remaining oil in waterflooded reservoirs is critical for successful reservoir management. For wells with narrow producing tubings, the slimhole induction tool is used because of its deep depth of investigation (DOI). Mixed formation water salinity is characterized using bottomhole samples. Ideally, running an induction tool requires non- or low-conductive borehole fluid uniformly distributed in the borehole. This may not always be achievable under production conditions. In this study, the following were investigated:
The slimhole induction tool was first tested in a newly drilled well and its measured data were compared with that of the standard induction log.
The tool was run in a borehole under both flowing and shut-in conditions. In this case, the effect of borehole fluid distribution was evaluated.
The multiple DOI capabilities of the slimhole tool were used to study the phenomenon of borehole fluid reinvasion during both flowing and shut-in conditions.
From this study, the following were concluded:
Slimhole induction measurement agrees well with standard induction measurement.
Mixed formation water salinity can be characterized using bottomhole samples and production logs.
The following borehole characteristics affect shallow DOI measurements, but not deep DOI measurements:
Borehole fluid contact and conductivity.
Borehole fluid re-invasion.
Guidelines for running slimhole induction log and collecting bottomhole samples for quantifying remaining oil in mixed salinity environments are summarized based on experiences learnt from this pilot field test of more than 30 wells.