Equivalent Dielectric Permittivity Model of Low Water Cut Oil-Water Two-Phase Flow

The capacitance method is widely used to measure the water content of oil-water two-phase flow, whether it is the surface oil-water measurement or the stratification test of the production profile in the well. To measure the water holdup (water phase volume fraction), it is necessary to establish the relationship between the water holdup and the sensor capacitance, so it is necessary to establish the theoretical or empirical model of the miscible equivalent dielectric constant and the water holdup. Since the formation water produced from wells and tap water used in surface laboratory calibration have good electrical conductivity at low and medium frequencies, considering only the dielectric property without considering the electrical conductivity will have a significant impact on the accuracy of water retention measurement. Based on the effective electric field theory of dielectric polarization, the equivalent dielectric constant model of oil-water two-phase flow is established, considering water as a good conductor under the condition of low water content and fine bubble flow. According to this model, the equivalent permittivity of oil-water two-phase flow is determined only by the water holdup and the permittivity of oil phase, and has nothing to do with the permittivity of water phase and the conductivity of water phase. The correctness of the model is verified by preliminary experiments. The research is of great significance for the design and field application of the water content sensor for oil-water two-phase flow when the oil is continuous phase.