Detection of Free Water in Multi-Phase Pipelines With AC Impedance

Free water that wets steel pipes accelerates corrosion via a number of different mechanisms. We report a novel sensor based on ac impedance that has successfully detected free water under laboratory and flow loop conditions with minimal effects from oil fouling. The sensor has also successfully differentiated between free water and water emulsified in oil. This free water sensor is one means for the earlier detection of pipeline corrosion. Smart-pig inspections are expensive and require a significant slowdown in production. The free water sensor is designed to be small and flow with the fluid current. Since the sensor is significantly smaller than the internal diameter of the pipelines, the fluid flow would be minimally impacted. It is also designed to be used more frequently than smart-pig inspection. The sensor is capable of detecting water despite fouled electrodes, determining the difference between free and emulsified water (emulsified water does not, generally, cause a corrosion issue), can potentially be used to determine the amount of free water, and has been demonstrated to work in a system with multi-phase fluid flow.