A subsea field in the deepwater of the Gulf of Mexico will be installed and commissioned in phases. The uniqueness of the subsea construction activities presented several flowline displacement operational challenges with oil circulation and seawater circulation procedures that will be conducted from the host platform. In order to validate and optimize the operational procedures for these displacement operations, transient simulations have been performed.
Of particular concern is the effectiveness of the dead oil sweep of live fluid. Preliminary simulations using the standard version of a three-phase transient simulator indicate that available dead oil circulation rates are insufficient to sweep remnant gas from downwardly inclined sections of the flowline, thereby generating an ongoing hydrate formation hazard. In order to evaluate the effectiveness of solution of this remnant gas in the highly undersaturated dead oil, the Compositional Tracking version of the simulator was employed. Compositional Tracking simulations indicated that the remnant gas is promptly removed by solution in the dead oil. The comparison between the standard and Compositional Tracking simulations illustrates another class of operations in which accounting for the transient variation in fluid chemical composition is important.
