Abstract:

For the extremely complex working conditions in VOCs transportation in subsea pipelines of a project, such as gas-liquid multiphase flow, acid corrosion (H?S 1400 ppmv), and large fluctuations in flow rate (10.35 to 111.32 t/h), this study proposes a coupled optimization approach that integrates flow assurance simulation with comprehensive economic study. Based on the multiphase flow simulation using a professional simulation software, a collaborative analysis on the flow assurance performance and economic feasibility of VOCs transportation in multiphase flow subsea pipelines is carried out incorporating third-order flow velocity constraint criteria (gas-phase flow velocity ≤ 18.3 m/s, inner wall shear stress ≤ 120 Pa, and erosional velocity ratio EVR < 1.0) and the minimum pressure requirements for pigging (≥ 1.0 MPaG). The results indicate that the combined scheme with a compressor outlet pressure of 1.0 MPaG and a DN500 pipeline offers the most cost-effective solution while satisfying the process and pigging requirements under acidic service conditions. This study provides theoretical support and engineering insights for the systematic optimization of subsea pipelines for VOCs with condensation phase change.

Key words: VOCs transportation')">

VOCs transportation, multiphase subsea pipeline, flow assurance, pipeline diameter optimization, life cycle cost