Search for a command to run...
Gas hydrate plugs are among the major concerns in flow assurance. Since remediating a hydrate plug is costly and challenging, a proper risk evaluation is required to avoid it. Understanding hydrate formation and the strategies to address their formation, therefore, becomes essential to proper risk management. To that end, accurate and reliable models are needed. In this paper, we present an analysis of a reported hydrate plugging event in an oil field. The event happened over a window of 50 h, and the situation remained for about 13 days total. The analyses were conducted using hydrate models coupled with an OLGA one-dimensional transient multiphase flow simulator, identifying the main parameters to be adjusted for a good representation of the event. A communication test was attempted by increasing the pressure from the topside, but the wellhead pressure did not respond, indicating a potential hydrate blockage. The simulation without hydrate formation allowed for pressure communication, which did not agree with field data and indicated that hydrates must have formed during shutdown. OLGA predicted a lack of pressure communication from hydrate suspension in oil at the time of the communication test. The gas consumed to form hydrates was estimated from the drop in the wellhead pressure over time in the closed pipeline system. From that, the scaling factor controlling the rate of hydrate formation was indirectly determined. Further increasing the pressure at the topside in the simulation showed that the wellhead pressure would have responded, indicating that hydrate formation had not necessarily created a plug. Simulation results indicate that hydrate deposition (and not suspension) at the time of the communication test would have allowed for communication, indicating that increased viscosity was the mechanism preventing communication. Considering the same rate of formation over the course of 13 days would have produced a soft plug if the hydrates had remained suspended. Our hypothesis is that hydrates deposited over time, allowing for the field interventions that took place.