Influence of aqueous foam on gas–liquid flow development of hilly-terrain wet gas pipeline with surfactant injection

Abstract

This study presents surfactant injection as a replacement technology for mechanical pigging to reduce liquid accumulation for wet gas transmission. The hilly terrain gas/liquid flow development characteristics under surfactant injection were explored in pipelines, and a comprehensive experiment was performed through flow observation and the measurement and analysis of the flow characteristic parameters. The 250 ppm sodium dodecyl sulfate (SDS) surfactant was employed according to the variation characteristics of the flow pattern and pressure drop at different concentrations. Flow observations and liquid holdup characteristics indicate that owing to the formation of aqueous foam, the gas/liquid interface and phase characteristics change significantly, and the liquid holdup decreases by several or even more than ten times and maintains a low value (0.004–0.070), except for the initial gas–liquid flow at low gas flow and high liquid flow rates. The aqueous foam effectively suppresses the slug and pseudo slug initiation, the gas/liquid convection of the slug body, and the large wave rolling of the pseudo-slug body, which induces the dissipation of intermittent flow. The pressure drop under the influence of aqueous foam decreases drastically (60% ∼ 85%) at certain gas and liquid velocities and fluctuates smoothly near zero over a wide experimental range. The surfactant suppression on partially blocked pseudo-slug body induces a significant decrease of pseudo-slug frequency from 0.17 ∼ 0.42 Hz to 0 ∼ 0.06 Hz and transitional velocity from 1.21 ∼ 1.90 m/s to 0 ∼ 1.11 m/s. This research is highly significant for surfactant injection schemes and efficient and sustainable production.