This document discusses gas hydrates, which are crystalline structures formed when gas molecules are trapped within cages of water molecules. It covers the natural occurrence of gas hydrates, particularly methane hydrates found offshore and in arctic regions. The document outlines challenges for recovering methane from gas hydrates, such as the need to reduce hydrate stability through heating, depressurization, or chemical addition. It also discusses controlling hydrate formation in oil and gas production through chemical inhibition or kinetic inhibitors that slow hydrate crystal formation.

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

2. 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. 3
Gas Hydrates

4. 4
Hydrogen Sulfide-Water Binary

5. 5
Hydrogen sulfide + Water at 5 MPa

6. 6

7. 7

8. 8
Occurrence of Methane Hydrates

9. 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. 10
Arctic Hydrates

11. 11

12. 12
Mackenzie Delta Hydrates
• Gas trapped under permafrost
• Hydrates from 200-1200 m depth
• Potential volume - 1013 m3 of methane
Mallick Well - Mackenzie Delta

13. 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. 14
Hydrates for Lunch?
Ice worm, Gulf of Mexico
Depth = 550 m

15. 15
Typical Hydrate
Diagram-
Dry Gas

16. 16
Typical Hydrate
Diagram
Wet Gas or Crude Oil

17. 17
GPSA Fig 20-27
Hydrate Formation

18. • P=pressure, v=molar volume,
T=temperature
• a and b are calculated from critical
properties, Tc, Pc and w
P
RT
v b
a T
v v b b v b



  
( )
( ) ( )
Peng-Robinson Equation

19. DBR HYDRATE
V5.0

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

21. 21
Inhibition of Hydrates
H2S plus methanol

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

23. 23
Dehydration + NGL Recovery

24. 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. 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