Transient Simulation and Dynamic-Compositional Analysis in Natural Gas Pipelines Using Integrated Hydraulic–Thermodynamic Models

Resumen

Long-distance natural gas pipelines constitute critical infrastructure for ensuring energy supply continuity and therefore require predictive tools capable of anticipating how gas properties evolve under changing operating conditions, particularly when batches with increased water, H2S, CO2, or heavy-hydrocarbon content are introduced. However, traditional approaches do not adequately integrate compositional dynamics with transient hydraulic effects, limiting early identification of risks such as localized condensation and critical pressure variations, which may lead to flow instability, capacity reduction, and operational constraints. This study develops a hydraulic–predictive model coupled with compositional thermodynamic analysis to evaluate batch evolution in a real natural gas transportation system under different flow-rate scenarios. Monophase transient modeling was implemented in Pipeline Studio, while phase stability and compositional analysis were performed in HYSYS. When phase-envelope crossing indicated potential condensate formation, the flow regime was represented using OLGA, enabling simulation of liquid accumulation and transport under transient conditions. Results, evaluated through a real case study, show that the batch front preserves a well-defined structure; however, its propagation speed and deformation depend on flow rate, composition, and local thermal conditions. Zones prone to liquid formation were identified in pipeline segments characterized by lower pressure and temperature, and OLGA simulations revealed that condensates may remain trapped for up to 12 hours if appropriate drainage or pigging operations are not executed. The proposed integrated approach constitutes a robust tool for anticipating critical events, optimizing batch management, and strengthening the reliability of natural gas transportation systems.