Nonlinear dynamical analysis of large diameter vertical upward oil–gas–water three-phase flow pattern characteristics

Abstract

Based on two kinds of signals measured from mini-conductance probe array and vertical multi-electrode array (VMEA) conductance sensor, we study oil–gas–water three-phase flow in a vertical upward 125 mm ID pipe. Using the ratio of oil flowrate to total liquid flowrate ( f o ) and the superficial gas velocity ( U sg ), we draw the six different flow pattern maps under four total mixture liquid flowrates. In addition, we indicate that: (a) the increase of f o makes oil in water type slug flow occur at lower U sg ; (b) for large diameter pipe and low flow velocity, the phase inversion of liquids occurs at about f o =0.9 and the increase of U sg makes the phase inversion of liquids move to low f o . Furthermore, we investigate the nonlinear dynamical characteristics of five water continuous phase flow patterns in terms of chaotic attractor morphological description and complexity measures (Lempel–Ziv complexity and approximate entropy), and find that: (a) the chaotic attractor morphological characteristics can identify three-phase flow patterns; (b) the combination of Lempel–Ziv complexity and approximate entropy can serve as a unique classification criterion of three-phase flow patterns. In this regard, the nonlinear analysis of conductance fluctuating signals can give an effective indicator to understand and identify the oil–gas–water three-phase flow pattern characteristics.