In depleted reservoirs producing with high water cuts, it is often difficult to evaluate which intervals are producing oil. Such wells typically use electric submersible pumps (ESPs) to lift the fluids, so logging operations are limited. Even when logging is possible, identifying oil production that amounts to 5% or less from a zone producing water can be a challenge.

This problem can be addressed by installing fiber-optic distributed temperature sensors (DTS) below the ESP of a well producing oil with a high water cut from multiple reservoir intervals. Differentiating between water and oil production with a DTS system is not directly possible at such high water cuts; however, by switching the water injection support from surrounding injectors on and off, the reservoir intervals being supported by each injector can be identified and the injection pattern that maximizes oil production can be found. The information obtained will allow an operator to shut off the water-only producing intervals during a subsequent workover, resulting in increased oil production from the well.

This novel application of DTS monitoring below ESP pumps in depleted, high-water-cut wells and the low-cost monitoring procedure employed has the potential to significantly increase oil production in old oil fields under water flood.