The purpose of this paper is to study planar sensor geometries for the measurement of film thickness in a viscous oil-water flow. The study is relevant due to there are only a few measurement techniques for oil-water flow and these techniques involve oil with low viscosity (close to the water viscosity). Specifically, some techniques have been used in the studies of annular flow (gas-liquid and liquid-liquid flows), but applications in other flow patterns were not encountered. Different sensor geometries were numerically simulated to compare their characteristics and choose the best to measure the water film thickness in the oil-water flow through an impedance-based technique. Finite element method was used for resolving the tridimensional electric field over each sensor. The compared characteristics were the penetration depth, the sensitivity, the minimum spatial resolution (high spatial resolution) and the quasi-linear curve. The best geometry tested has a spatial resolution of 2 x 2 mm, a penetration depth of 700 mu m and a quasi-linear response in the measuring range. This geometry was tested by means of conductance and capacitance static experiments. From these experiments, it could be determined that conductance and the capacitance systems are promising for measuring water film thickness in an oil-water flow. Several measurement techniques such as micro-PIV, planar laser-induced fluorescence and planar conductive or capacitive sensors that are supposed to be adaptable to the liquid-liquid flow have been proposed recently. Micro-PIV and planar-induced fluorescence need transparent pipes and fluids. On the other hand, conductive or capacitive methods have been only applied to low viscosity fluids. In that context, this paper proposes to study a new technique for non-intrusive measurement of the liquid-liquid flow. The main goal is the validation of the new planar sensor as a reference tool for the development of instrumentation for oilfield application Ver menos