Designing Subsea Production Systems for Efficient Startup to Mitigate Costly Topside Downtime

Abstract

Starting up a subsea production system for large offshore developments is a time-consuming task that can take multiple hours or days. The startup is particularly inefficient during an unplanned shutdown, where the operator may have a threshold time (e.g., 4–6 hours) to fix the problem and startup the production system, before having to preserve the field. The workflow discussed in this paper aims to determine and reduce the startup time of a subsea production system (SPS). At the center of the workflow, a dynamic integrated model is used to accurately assess and effectively adjust scheduled startup time of the SPS. The integrated model evaluates the dynamic simulation response of a large field startup by integrating a reservoir and gathering network model. The overall workflow incorporates subsurface simulation model, equipment design, field layout design, control systems, and system constraints to create a complete field architecture capable of handling quick, efficient field startups throughout the field life. The integrated workflow presented in this paper captures a full dynamic response, from the reservoir to the topside. Among other things, a full reservoir model has been integrated with a full dynamic network model that allows for startup evaluation and adjustment to be performed at different points throughout the field life.

Development of Downtime Cost Calculator for Offloading Operations Influenced by Parametric Rolling

“…The authors have discussed operational downtime of a floating platform in extreme cold regions and further determined the causes responsible for it. An integrated work flow was proposed to counter act the downtime problem due to unplanned shutdown of a subsea production system [23]. The hydrodynamic interaction between vessels and the effect of motion responses on offloading operations were studied in [24].…”