An Integrated Online Transient Simulation Solution for Subsea Pipeline Operations

Abstract

Abstract An integrated online solution for a complex gas gathering network consisting of offshore and onshore pipelines is presented. The system combines single phase and multiphase flow models with a rigorous corrosion calculation tool in an online environment to provide a comprehensive picture of the system state for assistance with operations management, planning, and forecasting. While the pipeline network is operated in the dense phase region, the use of both single phase and multiphase simulation technology makes it possible to have a robust system that is valid during any operational state of the field. The system is designed for use by operators and engineers to assist in daily operations, coordination, and planning. The integrated online solution monitors the pipelines for abnormal operating conditions, such as hydrates, dew point, and leak detection, that are occurring in real time and uses forecasting technology to determine if any abnormal conditions may occur in the near future. As part of the online condition monitoring a rigorous corrosion calculation that includes the effects of sour gas, acid gas, water chemistry, and multiphase flow effects is incorporated into the system. The online models provide the data on gas composition and pipeline operating conditions required by the corrosion tool so that in situ corrosion rates can be calculated as profiles along the entire length of the pipeline. Detailed, on demand corrosion analysis can be performed at user specified points if further analysis is required. The integrated online solution architecture is designed for high uptime and redundancy. The design includes consideration for databases, communications, virtual machines, simulation results handling, network redundancy, and maintainability. The architecture takes advantage of virtual machine technology and network redundancy to provide a high level of system performance while ensuring robustness to hardware failures. The system was deployed in late 2016 and has operational ever since. Value has been realized through use of the tool to: evaluate pig tracking using the multiphase model to provide operations with an estimated pig arrival time; predict real time dew point to assist with managing rich gas and lean gas mixtures within the network; perform pack and draft modeling to allow pipeline operators to predict the run-down time of gas delivery; assess the risk of hydrates, dew point, or off spec gas and take preventive actions. Cost saving have been realized by the ability to optimize multimillion dollar inline inspection frequencies using the corrosion monitoring module and the overall operating conditions of the pipelines.