IFP to test hydrate transport

May 1, 2006
Preventing hydrate blockage in pipelines becomes more trying as production heads to ultra-deep waters.

Preventing hydrate blockage in pipelines becomes more trying as production heads to ultra-deep waters. The Institut Francais du Petrole suggests that conventional deepwater techniques based on insulation and methanol injection may already be close to their technical limits.

As an alternative approach, IFP is proposing to transport hydrate as a slurry dispersed in multiphase flow, under a project named Thyssi. Theoretically, hydrates could be conveyed either in a natural state, by cooling the flow, or via controlled formation, achieved through injecting anti-agglomerant additives to limit particle size.

In partnership with Norwegian R&D institute Sintef, IFP aims to study the behavior of hydrate slurries in flowing conditions, with and without the stimulus of these additives. Previous experimental research has revealed a critical alteration in pressure drop when hydrates are formed.

The proposed new program, due to start early in 2007 with sponsorship from several oil companies, will analyze the following phenomena:

  • setting/stratification of hydrate particles
  • effects on pressure drop and rheology
  • slippage between gas and hydrate slurry flowing simultaneously
  • plug formation during stop and restart, especially with low and high points in the pipeline.

Experimental work will be conducted using both the Lyre loop at IFP’s research center in Solaize, and Sintef’s cold flow loop in Trondheim. Acquired data will be used to develop sub-models for transportation equations and to estimate the risk of plugging during shutdown and restart.

The Lyre loop in Solaize

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IFP is currently assembling sponsors for a separate project to study hydrate plug dissociation, known as Hydis. This work would be split into six phases.

Hydrate plugs comprise a water/gas phase mixture, but when they occur in real pipelines, a third phase, liquid hydrocarbon, is also normally present. IFP aims firstly to recreate this third phase, either through adding condensate or a heavier crude. The team will then study various influences such as water cut, gas velocity, and composition of the phases (i.e. with salts or additives in the water).

Under the proposed third stage of the program, they will attempt to characterize the hydrate plug and its permeability, possibly through the use of advanced techniques such as tomography.

The fourth stage will involve implementation of three hydrate plug dissociation methods, namely depressurization, heating samples to different dissociation temperatures, and injecting various inhibitors at different injection rates.

The final two stages will involve experimental evaluation of existing dissociation models, including one devised by the Deepstar consortium, and analyzing plugging risks by adapting the experimental set-up.