Dynamic Simulation of the Europa and Mars expansion projects : A new approach to coupled subsea and topsides modeling

Accurate computational modeling of time-dependent flow in petroleum production systems - Dynamic Simulation -remains a crucial ongoing effort within Shell to identify and implement significant improvements in facility design and operation, particularly for Deepwater applications. To date, dynamic simulations of topsides processing facilities have been decoupled from flow transients in wellbores and subsea flowlines. An innovative approach to full-system dynamic modeling has been developed for the Mars Tension Leg Platform to accommodate production from the Europa Subsea Project that will utilize an existing topsides model and interface to an expanded topsides facility and subsea system flow model. The resulting simulation is unprecedented in scope and size, providing full thermal-hydraulic data from the sand face to the export pipelines. Despite the impressive scope of the model, its cost is reasonably low in relation to the total engineering effort. The dynamic interface consists of (i) OLGA simulation of transient multiphase flow in four subsea wells (with individual reservoir characteristics) and dual pipe-in-pipe insulated flowlines (20 mile offset), coupled to (ii) OTISS simulation of Mars topsides production equipment, including parallel compressor trains, multi-stage separators, oil export pumps, and numerous control valves, in addition to chemical injection umbilicals and well annulus vent facilities. The principal goals of this integrated modeling approach were to identify, understand, and control unique transient operating conditions, including implications of varying field characteristics. Hence, this dynamic model is a powerful tool for (i) validating facility design, (ii) training of operations personnel (including elimination of surface/sub-surface communication barriers), and (iii) for optimization in surveillance planning. In fact, preliminary model results have revealed the necessity for some important modifications of facilities and operating procedures. Using the model in this fashion allows the engineer to reduce uncertainty factors in the design, which then lead to lower capital costs and/or operating expenses. A survey of the model's functionality is presented and discussed, including, but not limited to, well start-up and flowline blowdown.