Determination of phase wetting in oil-water pipe flows

Oil-water two-phase flow is often a problem in transportation since the corrosion rate is closely related to which phase wets the pipe. The problem has been investigated on a large scale, in a 60 meter-long flow loop with Saudi Arabian crude oils. In this paper extensive experimental studies of flow pattern as well as phase wetting determination have been carried out for different crude oils and different pipe inclinations. Four experimental techniques have been applied to determine which phase, either water or oil, wets the pipe inner wall at different flowing conditions: wall conductance probes, wall sampling, flow visualization, and corrosion monitoring by electric resistance probes. Based on the overlapping information from these techniques, comprehensive phase wetting maps as a function of water cut and flow velocities were obtained. Three flow patterns were observed: stratified flow, stratified flow with mixed layer, and dispersed flows. The comparison of flow pattern and wetting regimes gives good understanding of the water wetting mechanism. Moreover, the phase wetting maps produced are a precious tool which can be used as a useful reference for corrosion engineers and pipeline operators to manipulate oil-water two-phase flow systems under corrosion free conditions