The Optimization Design Of The Impedance Sensor

It is a big technological challenge to precisely measure the water-cut (hold-up) of downhole oil-water two-phase flow when oilfield development is at the high water-cut stage. The Impedance sensor has the following advantages: First, measuring water-cut through flowing fluid decreases the effect of heading flow when water is at its continuous phase and achieves real-time monitoring thus more reliable measurement; second, the measurement result has neither temperature nor salinity dependency, very small error imposed by electrode contamination and minor influence from the flow regime. The design of the sensor is mainly determined by large numbers of experiments and the theoretical analysis is inadequate, so as the technique needs further development and optimization design. For example, the optimal number and space between electrodes are still in lack of guidance from simulation techniques. Furthermore, many experimental observations have found that the adsorptive action between the oil and the inner wall of a sensor will build up in case of low temperature and low flux of the fluid, so the sensor will be affected by electrode contaminations. Therefore, further improvements of the Impedance sensor still exist.This paper starts from the overview of hold-up measurement theory using conductance method, and then illustrates the Maxwell water cut measuring model and Begovich&Watson water cut measuring model. The difference between the two models is also explained.In this paper, we present the simulation results of impedance sensor's electric field distribution and the optimization of the sensor structure by simulating with ANSYS and MATLAB software. From static simulations of annular flow and dynamic simulations of bubble flow, we proved that using Impedance sensor to measure hold-up is hardly or less affected by fluid salinity, temperature and flow regime. We also proved that the response of water cut has a linear relationship with the water holdup, which resembles the Begovich & Watson measuring model. The actual measuring model of the impedance water cut meter should be gotten from the dynamic simulation because the static test cannot reveal the slippage effect.Thanks to the optimization design, the Impedance sensor can have more credibility and higher precision. The optimization design can offer the theoretical guidance to the future research and design of the Impedance sensor...