Oil-in-Water Measurement for Separator/Desalter Optimization

Problem

An oil production facility needed to monitor the performance of a large separation vessel.  Operations personnel suspected that excess crude oil was being drawn into the water leg of the separator, complicating additional separation further downstream.  There was no oil-in-water meter on the water leg, and installation of an in-line or slipstream instrument would be very expensive and require shutdown.

Solution

A Process Composition Monitor (PCM) was strapped to the outside of the water-leg pipe, below the separator (Figure 1). Due to the non-intrusive design of the monitor, installation was easy and did not interfere with operations. As shown in Figure 2, the on-line measurements confirmed that excessive oil was being drawn into the water leg at repetitive intervals. The large swings in water quality were due to improper control of the water dump valve. The PCM gave the operators the information needed to better control the valve and improve water quality.