The Bonga FPSO was designed to process 280 MBLPD gross liquid, constrained by the three-phase low pressure (LP) separator capacity. The projected production forecast indicated that additional future volumes of produced fluids from the Bonga field could exceed the design capacity of the installation. FMC's Inline PhaseSplitter was identified as a solution for debottlenecking the three-phase LP separator liquid handling capacity. The PhaseSplitter is a compact pipe-based cyclonic separator that splits the feed flow into a gas stream with limited liquid carry-over and a liquid stream with limited gas carry-under. The performance objective for the PhaseSplitter is 70 % or more gas removal while keeping liquid carry-over in the gas outlet below 1 % volume fraction. In this paper, we report results of a technical qualification program (TQP) for the PhaseSplitter as a debottlenecking tool for the three-phase LP separator. We used a down-scaled 3 inch pipe of the PhaseSplitter as compared to a 24 inch full-scale field unit. A model fluid whose physical properties resemble the Bonga fluids was used, thereby giving credence to the test results. A test matrix covering a range of representative feed conditions was probed: gas volume fraction (GVF) 75 - 90%, water cuts 20 - 80% and inlet momentums 4500 - 11000 Pa. We measured the percentage of gas removed from the feed and the amount of liquid carry-over into the removed gas as function of the flow split to the gas outlet. The results show that for almost all test conditions, acceptance criteria that were set for the PhaseSplitter were met, i.e. 75 - 80% gas removal and liquid carry-over with the gas less than 1%. Gas-liquid separation performance gradually decreases with decreasing momentum and GVF in the feed. We observed no dependence of separation performance on the feed water cut. We plotted the results as function of the normalized flow split showing universal trends. These trends provide a means to control the separation performance by monitoring the pressure drop over both outlets. We conclude that the PhaseSplitter delivers a robust performance under steady-state conditions over a wide range of operating conditions.

CFD analyses to determine the performance of the thermal insulation system during cool-down of an Enhanced Vertical Deepwater Tree (EVDT) and a manifold for a subsea tie-in to an existing Floating Production Storage and Offloading (FPSO) are described in this paper. The produced fluid was assumed to be a multiphase mixture of gas and liquid with a gas volume fraction (GVF) of 14.05% for the EVDT and 73.46% for the manifold. The external environment was modeled as seawater at 4 °C, and a seawater current of 0.2 m/s was assumed. An Eulerian-Eulerian approach was used to solve the multiphase behavior of the produced fluid, in which one set of conservation equations is used for each phase at each mesh cell. Seawater flow patterns were solved with a single-phase, constant density solver with Boussinesq approximation. In general, it was found that cool-down times might be significantly different at some locations when the produced fluid is a multiphase fluid mixture as compared to the case where it is a single phase. Interestingly, Computation Fluid Dynamics (CFD) models predict a more rapid cool-down within the first 30 minutes of shutting down production as compared with traditional methods of determining cool-down times by modeling only heat diffusion with finite element techniques. Results from these analyses are a useful tool to determine the cool-down time that the produced fluid might remain above hydrate formation temperature prior to intervention. This has a direct implication on methanol system design and consumption. In addition, these results are an aid to determine which components of the equipment should have more insulation, as well as the impact of cold spots on cool-down times. Introduction One of the top priorities for oil and gas companies is flow assurance in the field. The main challenge of flow assurance is to overcome flow problems, which are generally associated with blockage of the flow path due to the formation of solid deposits or hydrates. These hydrates are crystals that form in flows where water and gas are present under a combination of temperature and pressure conditions. In general, it can be said that gas hydrate formation will occur at high-pressure and low-temperature conditions. Thus, there is a potential risk of gas hydrate formation as drilling and production operations expand into deepwater environments. Several works can be found in the literature that describe flow assurance challenges involving the prevention of solids formation [see, for example, Javora et al. (2005); Alboudwarej et al. (2006); Wang et al. (2006a, 2006b); Kopps et al. (2007); Harun and Watt (2009)]. Preventing the formation of solids may be accomplished by keeping the system in a thermodynamic state out of the regions in which the solids form. For example, hydrates do not usually form during normal operation in which the temperature of the fluids is above the formation temperature of solids. However, stagnant production fluids during shut-in operations will eventually reach seawater ambient temperature, thus potentially increasing the risk of hydrate formation. Therefore, special emphasis is placed on the effective control of heat losses in subsea equipment during shut-in and startup operations, because the ambient temperatures in deepwater are typically 40°F (approximately 4°C).