Study on the Measurement System of Volume Fraction and Axial Velocity in Upward Vertical Pipe of Oil-water Two-phase Flow

With the six-electrode probe, a two-phase flow measurement system was designed for oil well logging. The whole system consists of the excitation signal generating circuit, the signal conditioning circuit, the data sampling & processing circuit. This apparatus can run into oil production well and interface to a PC on the ground via RS485 bus. Hybrid processor MC56F8323 was the control center of the proposed system. It sampled the up-stream and down-stream fluid flowing signals and cross-correlated in frequency-domain for axial velocity measurement. Simultaneously, MC56F8323 sampled the distributed information of oil-water two-phase flow and estimated the normalized conductivity which is a function of water volume fraction. Especially, the probe was excited by the bidirectional pulse constant-current source, and the traditional complex AC circuit such as demodulation wasn´t required, so the circuit simplified and the measurement accuracy improved. The experiments, which were performed in vertical upward oil-water two-phase flow loop, indicate that the measurement error of water volume fraction is plusmn3% when the flowrate of oil-water mixture exceeds 10 m³/d, and the flow axial velocity can resolve the flowrate difference with 2 m³/d.