Complex gas hydrate from the Cascadia margin


Natural gas hydrates are a potential source of energy1 and may play a role in climate change2 and geological hazards3. Most natural gas hydrate appears to be in the form of ‘structure I’, with methane as the trapped guest molecule4, although ‘structure II’ hydrate has also been identified, with guest molecules such as isobutane and propane, as well as lighter hydrocarbons5,6. A third hydrate structure, ‘structure H’, which is capable of trapping larger guest molecules, has been produced in the laboratory7, but it has not been confirmed that it occurs in the natural environment. Here we characterize the structure, gas content and composition, and distribution of guest molecules in a complex natural hydrate sample recovered from Barkley canyon, on the northern Cascadia margin8. We show that the sample contains structure H hydrate, and thus provides direct evidence for the natural occurrence of this hydrate structure. The structure H hydrate is intimately associated with structure II hydrate, and the two structures contain more than 13 different hydrocarbon guest molecules. We also demonstrate that the stability field of the complex gas hydrate lies between those of structure II and structure H hydrates, indicating that this form of hydrate is more stable than structure I and may thus potentially be found in a wider pressure–temperature regime than can methane hydrate deposits.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The powder X-ray diffraction pattern of the gas hydrate studied, from Barkley canyon, offshore Vancouver island.
Figure 2: Solid state 13 C NMR spectra of the gas hydrate from Barkley Canyon.
Figure 3


  1. 1

    Kleinberg, R. & Brewer, P. Probing gas hydrate deposits — Exploiting this immense unconventional energy resource presents great challenges. Am. Sci. 89, 244–251 (2001)

    ADS  Article  Google Scholar 

  2. 2

    Xu, W., Lowell, R. P. & Peltzer, E. T. Effect of seafloor temperature and pressure variations on methane flux from a gas hydrate layer: Comparison between current and late Paleocene climate conditions. J. Geophys. Res. 106, 26413–26424 (2001)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Dillon, W. P. et al. in Natural Gas Hydrates: Occurrence, Distribution, and Dynamics (eds Paull, C. K. & Dillon, W.P.) 211–233 (AGU Monogr. 124, American Geophysical Union, Washington DC, 2001)

    Google Scholar 

  4. 4

    Ginsburg, G. D. & Soloviev, V. A. Submarine Gas Hydrates (Norma Publishers, St Petersburg, Russia, 1998)

    Google Scholar 

  5. 5

    Davidson, D. W. et al. Laboratory analysis of a naturally occurring gas hydrate. Geochim. Cosmochim. Acta 50, 619–623 (1986)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Sassen, S. & McDonald, I. R. Evidence of structure H hydrate, Gulf of Mexico continental slope. Org. Geochem. 22, 1029–1032 (1994)

    CAS  Article  Google Scholar 

  7. 7

    Ripmeester, J. A., Tse, J. S., Ratcliffe, C. I. & Powell, B. M. A new clathrate hydrate structure. Nature 325, 135–136 (1987)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Chapman, N. R., Pohlman, J., Coffin, R., Chanton, J. & Lapham, L. Thermogenic gas hydrates in the Northern Cascadia Margin. Eos 85, 361–368 (2004)

    ADS  Article  Google Scholar 

  9. 9

    Ripmeester, J. A. et al. Structure and composition of gas hydrate in sediment recovered from the JAPEX/JNOC/GSC et al. Mallik 5L–38 gas hydrate production research well, determined by X-ray diffraction and Raman and solid-state nuclear magnetic resonance spectroscopy. Geol. Surv. Can. Bull. 585, 106 (2005)

    Google Scholar 

  10. 10

    Lu, H. et al. The occurrence and structural characteristics of the gas hydrates associated with a cold vent field, Offshore Vancouver Island. J. Geophys. Res. 110 B10204 doi: 10.1029/2005JB003900 (2005)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Spence, G. D., Chapman, N. R., Hyndman, R. D. & Cleary, C. Fishing trawler nets massive “catch” of methane hydrates. Eos 82, 621–627 (2001)

    Article  Google Scholar 

  12. 12

    Ripmeester, J. A. & Ratcliffe, C. I. 129Xe NMR studies of clathrate hydrates: new guests for structure II and structure H hydrates. J. Phys. Chem. 94, 8773–8776 (1990)

    CAS  Article  Google Scholar 

  13. 13

    Lee, J., Lu, H., Moudrakovski, I. L., Ratcliffe, C. I. & Ripmeester, J. A. n-pentane and n-hexane as coguests in a structure H hydrate in mixtures of 2,2-dimethylbutane and methane. Angew. Chem. Int. Edn Engl. 45 doi: 10.1002/anie.200504366 (2006)

  14. 14

    Pohlman, J. W. et al. The origin of the thermogenic gas hydrates on the northern Cascadia Margin as inferred from isotopic (13C/12C and D/H) and molecular composition of hydrate and vent gas. Org. Geochem. 36, 703–716 (2005)

    CAS  Article  Google Scholar 

  15. 15

    Bernard, B. B., Brooks, J. M. & Sackett, W. M. Natural gas seepage in the Gulf of Mexico. Earth Planet. Sci. Lett. 31, 48–58 (1976)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Sassen, R. et al. Free hydrocarbon gas, gas hydrate, and authigenic minerals in chemosynthetic communities of the northern Gulf of Mexico continental slope: relation to microbial processes. Chem. Geol. 205, 195–217 (2004)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Diaconescu, C. C., Kieckhefer, R. M. & Knapp, J. H. Geophysical evidence for gas hydrates in the deep water of the South Caspian Basin, Azerbaijan. Mar. Petrol. Geol. 18, 209–221 (2001)

    CAS  Article  Google Scholar 

  18. 18

    Woodside, J. M., Modin, D. I. & Ivanov, M. K. An enigmatic reflector on subbottom profiler record from the Black Sea — the top of the shallow gas hydrate deposits. Geo-Mar. Lett. 23, 269–277 (2003)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Mazzini, A. et al. Methane-related authigenic carbonates from the Black Sea: geochemical characterization and relation to seeping fluid. Mar. Geol. 212, 153–181 (2004)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Matsumoto, R. et al. Gas hydrate layer and prominent flares of gas plumes in Naoetsu Basin, Eastern margin of Japan Sea. Eos Trans. 86(AGU Fall meet. suppl.), abstr. OS41C-04. (2005)

  21. 21

    Kvenvolden, K. A. & Bernard, L. A. Gas hydrates of the Blake Outer Ridge, Site 533, Deep Sea Drilling Project Leg 76. Init. Rep. DSDP 76, 353–365 (1983)

    CAS  Google Scholar 

  22. 22

    Milkov, A. V. et al. Ethane enrichment and propane depletion in subsurface gases indicate gas hydrate occurrence in marine sediments at southern Hydrate Ridge offshore Oregon. Org. Geochem. 35, 1067–1080 (2004)

    CAS  Article  Google Scholar 

  23. 23

    Milkov, A. V., Claypool, G. E., Lee, Y.-J. & Sassen, R. Gas hydrate systems at Hydrate Ridge offshore Oregon inferred from molecular and isotopic properties of hydrate-bound and void gases. Geochim. Cosmochim. Acta 69, 1007–1026 (2005)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Lambeck, K., Esat, T. M. & Potter, E.-K. Links between climate and sea levels for the past three million years. Nature 419, 199–206 (2002)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Tulk, C. A., Ratcliffe, C. I. & Ripmeester, J. A. Chemical and physical analysis of natural gas hydrate from the JAPEX/JNOC/GSC Mallik 2L–38 gas hydrate research well. Geol. Surv. Can. Bull. 544, 263–267 (1999)

    Google Scholar 

  26. 26

    Lu, H., Dutrisac, R., Ripmeester, J. A., Wright, F. & Uchida, T. Measurement of gas hydrate saturation in sediment cores recovered from the JAPEX/JNOC/GSC et al. Mallik 5L–38 gas hydrate production research well. Geol. Surv. Can. Bull. 585, 89 (2005)

    Google Scholar 

Download references

Author information



Corresponding author

Correspondence to John A. Ripmeester.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Figures 1 -2 and Supplementary Tables 1-2.

Supplementary Figure 1 shows gas chromatographic data of the gas sample recovered from the dissociated gas hydrates from Barkley Canyon, offshore Vancouver Island. Supplementary Figure 2 shows the stability zones of methane hydrate and naturally occurred sII-sH complex gas hydrates from Barkley Canyon, offshore Vancouver Island. * The influence of pore water chemical compositions on sII and sH complex hydrates has been roughly adjusted according to the empirical equation of Lu and Matsumoto (2005). Supplementary Table 1 shows the X-ray Powder Data for sII and sH gas hydrates recovered from Barkley Canyon, offshore Vancouver Island Supplementary Table 2 shows the chemical shifts of hydrocarbons in their pure gas (or liquid) and hydrate phases. (PDF 183 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lu, H., Seo, Y., Lee, J. et al. Complex gas hydrate from the Cascadia margin. Nature 445, 303–306 (2007).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.