A blockage detection model for subsea natural gas condensate pipelines considering fluid components and valve characteristics

Traditional pressure wave detection models for subsea natural gas condensate pipelines often overlook the dynamic flow and multiphase interactions under high-pressure and low-temperature conditions, and the pressure wave excitation methods are not suitable for subsea pipelines. To address these issues, this study proposes a multiphysics-coupled blockage detection method. By integrating the equation of state with multiphase flow regime discrimination criteria, a wave velocity calculation model with dynamic thermo-pressure corrections was developed, resolving prediction deviations in temperature-pressure gradient coupled fields. Pressure wave excitation is achieved through pressure relief operations of branch valves on offshore platforms. A coupled algorithm for pressure wave propagation and blockage feature inversion was developed by combining the method of characteristics with valve dynamic characteristic parameters. This algorithm quantifies the influence of valve operation time on excitation amplitude. Experimental validation demonstrated that the proposed model effectively integrates temperature-pressure coupled computations, pressure wave propagation analysis, and blockage detection, with wave velocity calculation errors below 2 %. The method successfully detects blockages with a minimum severity of 25 %, kilometer-scale blockage lengths, and multipoint blockage scenarios. This study provides a high-precision detection method for safe flow assurance of subsea pipelines.