Measurement of water holdup in oil-in-water emulsions in wellbores using microwave resonance sensor

In this study, we propose a new method for water holdup measurement of oil-in-water emulsions with a microwave resonance sensor (MRS). The angle and length of the electrode plate are optimized by HFSS simulation software. Using a vector network analyzer (VNA), a static calibration experiment is conducted, and the resonant frequency distribution of oil-in-water emulsions is analyzed within an 80%-100% water holdup range. In addition, we observe and analyze the micron-sized oil bubble structure in the emulsified state with an optical microscope. On this basis, a dynamic experiment of oil-in-water emulsions with high water cut and low velocity in a vertical upward pipe is conducted. S-21 response curves of the MRS are obtained by the VNA under different working conditions in real time. Finally, we analyze the relationship between the resonant frequency and water cut. Experimental results show that the MRS has an average resolution of 0.096% water cut for high water cut oil-in-water emulsions within the frequency range of 2.2-2.8 GHz.