1 Gas Hydrate basics

2 Gas Hydrates Ice-like, crystalline solid May exist at temperatures up to 25 ° C at high pressure ‘Practical discovery’ by Hammerschmidt, 1934: Hydrates, not ice, were blocking North American gas pipelines = Sm 3 gas 1 m 3 hydrate 0.8 m 3 water

3 Ice-like, crystalline solid May exist at temperatures up to 25 ° C at high pressure Requirements: - light hydrocarbons (C1-C4) - free water - “low” temperature (offshore: 20 bar) Gas Hydrates

4 Hydrates in comets Makogon (1987) claimed that Halley’s comet consists of sand, rocks, and large amounts of CO 2 -hydrates, based on observed gas blowouts when the comet approached the sun. Photo: MWO Museum Exhibit

5 Hydrates in our solar system Saturn - Average temp: -220°C - Outer ring: hydrate lumps up to 10 m in diameter? Pluto - Average temp: -230 °C - Methane and water in large amounts Picture by NASA Pluto Charon Pictures by NASA

6 Saturn’s largest moon: Titan -180°C, liquid methane and ethane January 2005 Huygens landing Methane hydrate plain?

7 Hydrates in the earth Hydrates exist in enormous amounts in permafrost regions and in deep ocean floors. These in-situ hydrates might: prove to be enormous energy resources be a factor in possible global climate change lead to sea floor instabilities

8 Storegga landslide ( years ago)

9 Seafloor hydrate occurrences ref: Naval Research Laboratory

10 Hydrates in petroleum production A hydrate plug might form about anywhere the conditions are favorable: wells, X-mas trees, manifolds, jumpers, production pipelines, export pipelines, production risers, export risers, separators, valves, flanges, orifices, dead-legs, instrumentation lines, pipe bends etc.

11 Microscopic structure Structure II hydrate: unit cell 16 8 Water lattice/cavities in hydrates

12 Appearance Ca. 1 cm Gas system Oil system Hydrate crystal

13 Hydrate equilibrium Hydrates Safe area Temperature Pressure Hydrate existence limit

14 Effect of water composition on the hydrate curve

Multiphase Transport TEMPERATURE PRESSURE 0 m Depth 7000 m 1: onshore well 1 WAX HYDRATES ? 2: deep offshore 2 Original slide courtesy of Emile Leporcher, Total

16 Hydrate kinetics Induction time: hours/days in stability region without hydrates Growth rates: - heat and mass transfer controlled - influenced by flow PRESSURE TEMPERATURE

17 Hydrate kinetics time Hydrate amount Induction time How long ??? Formation rate How big ??? Formation period How long ???

18 Demonstration...