Real Time Online Hydrate Monitoring and Prevention in Offshore Fields

Abstract

Hydrate blockage had caused impeded flow in offshore pipelines and resulted production stoppage and significant economic loss. Hydrate blockages can occur very rapidly especially during winter conditions. The amount of inhibitor used need to be frequently revisited to ensure sufficient inhibition due to temperature change and other affecting parameters. The objective of this study is to provide an online monitoring of hydrate formation for four offshore pipelines to ensure sufficient mono-ethylene glycol (MEG) inhibition. It also provides an integrated operations monitoring that can be accessed anywhere and anytime. The system can provide early warning of hydrate formation to avoid blockage and production disruption. There are three parts in this study:-Part 1-Hydrate Prediction Model, Part 2-Integration with PETRONAS Integrated Operations platform and Part 3-Hydrate Monitoring and MEG Tracking. In Part 1, fluid composition for each pipeline was used to develop the hydrate curve. The minimum inhibition concentration model was built using mathematical curve fitting at maximum operating pressure under varying temperature. Another computational model was built to determine the MEG injection rates based on various parameters such as water cut, lean MEG concentration and safety margin. The model was then integrated with both real-time and sporadic data and run on predetermined schedule on the Integrated Operations (IO) platform. Part 2 ensures the critical parameters are linked to the hydrate prediction model and provide results such as hydrate operating condition, minimum inhibitor concentration requirement and MEG injection rates. In Part 3, real-time hydrate monitoring has to be readily accessible to everyone via a mobile compatible web interface. Actual MEG concentration vs minimum MEG concentration is analyzed to represent adequacy of current MEG injection rates. Further analysis can be done to predict the MEG recovery plan by tracking MEG inventory. The online hydrate monitoring is frequently used by offshore operations in their daily meetings. The system assists in advising the amount of MEG injection rates and ensure sufficient inhibition for all of the pipelines. From available trending, operator can optimize the MEG rates based on current operating temperature, pressure, watercut and relevant parameters. This online monitoring is useful to avoid re-occurrence of hydrate blockage in the pipelines and to optimize MEG usage. There are many hydrate inhibition technologies in existence, but this is the first in the world of its kind which is simple, innovative and inexpensive method to monitor the pipeline from entering hydrate region in real-time, which can be conveniently accessed anytime and anywhere. Not only the system had prevented production loss in millions of dollars, it also saved operating cost of MEG which may cost operations several million dollars.