Estudo experimental e numérico da utilização do método de flushing no deslocamento de fluidos miscíveis em um duto horizontal

Abstract

The increasing reliance on deepwater oil production has intensified operational challenges in Flow Assurance, particularly in hydrate management. Although the flushing method is widely adopted for obstruction mitigation and pipeline commissioning, critical gaps remain regarding its hydrodynamic efficiency and the definition of optimal volumes for industrial applications. This research systematically investigates miscible liquid-liquid flushing in horizontal pipes through an integrated approach, combining physical experimentation and computational modeling. Using water-glycerin mixtures to mimic the behavior of thermodynamic inhibitors, the study characterizes the dynamics of flow front and trailing edge velocities and the evolution of the mixing zone (𝐿𝑚𝑖𝑥) as a function of viscosity and injection velocity. Computational Fluid Dynamics (CFD) modeling, using Ansys CFX® software, was validated with experimental data obtained from a 26 𝑚𝑚 diameter flow loop, with volumetric fraction measurements via resistive sensors. The results identify a critical velocity threshold of 0.3 𝑚/𝑠, below which flushing efficiency undergoes severe degradation due to gravitational dominance (𝐹𝑟 < 2,0). It was observed that at high velocities (≥ 0,5 𝑚/𝑠) the flow approaches a plug flow pattern, while at low velocities (0.2 𝑚/𝑠) interface stretching occurs, expanding the mixing zone to values exceeding 14 𝑚. By incorporating front and trailing edge velocities, the 𝐿𝑚𝑖𝑥-based methodology proved to be more conservative and robust, estimating injection volumes between 22% and 27% higher than conventional methods in low-energy regimes. This work provides fundamental guidelines for the optimization of offshore operations, establishing objective criteria for cost reduction and operational integrity assurance.