Cook, Ann Elizabeth et al. (2006): Cohesive strength of gas-hydrate-bearing marine sediments

Leg/Site/Hole:
ODP 164
ODP 204
Identifier:
2008-126197
georefid

Creator:
Cook, Ann Elizabeth
Columbia University, Palisades, NY, United States
author

Goldberg, David
Schlumberger Doll Research, United States
author

Kleinberg, R. L.
author

Identification:
Cohesive strength of gas-hydrate-bearing marine sediments
2006
In: Anonymous, AAPG 2006 annual convention; abstracts volume
American Association of Petroleum Geologists and Society for Sedimentary Geology, Tulsa, OK, United States
15
21
We examine the relationship between gas hydrate saturation and the cohesive strength of marine sediments in a variety of continental margin settings. The cohesive strength (cohesion) is a fundamental physical property controlling sediment resistance to compressive failure. The cohesion (C (sub o) ) can be related to the dynamic Young's modulus (E (sub D) ), where: C (sub o) = 1.5*10 (super -3) E (sub D) . The dynamic Young's modulus is computed using in situ Vp, Vs, and bulk density borehole logs. The C (sub o) profiles are compared to estimates of the in situ hydrate saturation, S (sub h) , calculated using electrical resistivity logs and the modified Archie formula: S (sub h) = 1 - (aR (sub w) /Rp (super m) ) (super 1/n) . We will present results of these comparisons from data collected during: Ocean Drilling Program Legs 204 (at Cascadia margin) and 164 (at Blake Ridge); the JIP gas hydrate drilling project in the Gulf of Mexico; and Mallik permafrost wells. In general, C (sub o) steadily increases downhole as sediments compact due to overburden. In the marine sediment environments, cohesion ranges from 500-2000kPa above the BSR, with a baseline gradient between 5 and 10 kPa/m. Preliminary results at Cascadia margin show that in sediments with S (sub h) > 15%, C (sub o) increases dramatically, at least 200kPa greater than the general trend of the downhole gradient. This suggests that C (sub o) is affected directly by S (sub h) , and may be related to the rate of change in S (sub h) (e.g. gradual or sharp) as a function of depth. Further study on the relationship between C (sub o) and S (sub h) may provide information on the growth habit of gas hydrates in sediment pore spaces.
English
Coverage:Geographic coordinates:
North:43.3000
West:-130.0000East: -130.0000
South:43.3000

Economic geology, geology of energy sources; Atlantic Ocean; Blake-Bahama Outer Ridge; Cascadia Channel; cohesive materials; continental margin; depth; East Pacific; elastic constants; gas hydrates; Leg 164; Leg 204; marine environment; marine sediments; natural gas; North Atlantic; North Pacific; Northeast Pacific; Ocean Drilling Program; Pacific Ocean; petroleum; porosity; saturation; sediments; Young's modulus;

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