Gas hydrates are ice-like structures that usually form at low-temperature and high-pressure conditions where a small hydrocarbon molecule is trapped inside a cage of hydrogen-bonded water molecules. Their formation can be very harmful for the transport and production of hydrocarbons, because they can form obstructions that decrease the flow rates or even completely block the pipeline. The common practice in the industry has been to design the system to operate fully outside the hydrate stable region, what may imply in increased costs.
CAPEX savings will be a constant requirement in the coming years, due to uncertainties in oil prices and margins, as well as producing assets moving to harsher environments. In such scenarios hydrate management strategies can be an alternative to traditional hydrate avoidance methods.
One potential strategy for hydrate management involves allowing hydrates to form, while minimizing the risks of creating large deposits that agglomerate and adhere to the pipeline walls, which may severely restrict flow. In order to employ such a strategy, it is fundamental to understand the right conditions that allow hydrate particles to be transported safely within a multiphase slurry flow. These may involve various inter-related aspects of the fluids composition and chemical additives/inhibitors, the thermal and hydrodynamic aspects of the flow (including emulsion behavior) and, of course, the optimal operational conditions.
The present Project aims at building an offline transient model adviser to understand the relevant hydrate mechanisms for a given system, and assist the design and optimization of field operations inside the hydrate envelope. Some of the important knowledge elements are related to the following aspects:
1) Thermodynamic and kinetic behavior (hydrate equilibrium, thermodynamic inhibition, nucleation limitation, induction time increase, role of anti-agglomerants, etc)
2) Emulsion, free water and interfacial behavior: how is the water distributed in the system? What is the water-cut threshold above which free water is present? How does surface chemistry play a role?
3) Slurry transport: even in non-plugging systems, high hydrate particle concentrations may create a very viscous (eventually non-Newtonian) slurry with low transportability
In future developments, an online/look ahead model with continuous improvement/optimization using field data will also be built.
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