1 Headache or Energy Source of the Future? Murray Gray Department of Chemical and Materials Engineering University of Alberta

2 Outline Chemistry and phase behavior of hydrates Natural occurrence Methane recovery from hydrates Hydrates in natural gas and oil production Control of hydrate formation

3 Gas Hydrates

4 Hydrogen Sulfide-Water Binary

5 Hydrogen sulfide + Water at 5 MPa

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8 Occurrence of Methane Hydrates

9 Offshore Hydrates Potential for production of methane Safety issues for offshore oil and gas drilling –Hydrates stabilize soft sediments –Melting of hydrates can destabilize drilling rigs and offshore pipelines

10 Arctic Hydrates

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12 Mackenzie Delta Hydrates Gas trapped under permafrost Hydrates from m depth Potential volume m 3 of methane Mallick Well - Mackenzie Delta

13 Production from Hydrates Need to reduce the stability of hydrates to recover the methane –Heat the reservoir - very energy intensive –Reduce the pressure - need permeable formations for flow of produced gas –Chemical addition - very high cost Significant technical challenges

14 Hydrates for Lunch? Ice worm, Gulf of Mexico Depth = 550 m

15 Typical Hydrate Diagram- Dry Gas

16 Typical Hydrate Diagram Wet Gas or Crude Oil

17 GPSA Fig Hydrate Formation

P=pressure, v=molar volume, T=temperature a and b are calculated from critical properties, T c, P c and  Peng-Robinson Equation

DBR HYDRATE V5.0

20 Inhibition of Hydrates Chemical inhibitors suppress the stability of hydrates Any antifreeze compound also inhibits hydrates –Salt –Methane –Ethylene glycol

21 Inhibition of Hydrates H 2 S plus methanol

22 Well Head Inhibitor Injection Natural gas well Underground pipeline to processing plant Ground T < 15 o C Water Gas Inhibitor Injection

23 Dehydration + NGL Recovery

24 Kinetic Inhibitors Methanol, ethylene glycol are effective indefinitely In production applications, need only to slow formation of hydrates Recent reports on inhibition by proprietary polymers that slow rate of crystal formation

25 Outline Chemistry and phase behavior of hydrates Natural occurrence Methane recovery from hydrates Hydrates in natural gas and oil production Control of hydrate formation