Summary
The thermal and mechanical loading of oceanic hydrate-bearing sediments
(HBS) can result in hydrate dissociation and a significant pressure increase
with potentially adverse consequences on the integrity and stability of the
wellbore assembly, the HBS, and the bounding formations. The perception of HBS
instability, coupled with insufficient knowledge of their geomechanical
behavior and the absence of predictive capabilities, has resulted in a strategy
of avoidance of HBS when locating offshore production platforms and can impede
the development of hydrate depo-sits as gas resources.
In this study, we investigate coupled (interacting) hydraulic,
thermodynamic, and geomechanical behavior of oceanic HBS in three cases. The
first involves hydrate heating as warm fluids from deeper conventional
reservoirs ascend to the ocean floor through uninsulated pipes intersecting the
HBS. The second case describes system response during gas production from a
hydrate deposit, and the third involves mechanical loading caused by the weight
of structures placed on the ocean floor overlying the HBS.
For the analysis of the geomechanical stability of HBS, we developed and
used a numerical simulator that integrates a commercial geomechanical simulator
and a simulator describing the coupled processes of fluid flow, heat transport
and thermodynamic behavior in the HBS. Our simulation results indicate that the
stability of HBS in the vicinity of warm pipes may be affected significantly.
Gas production from oceanic deposits may also affect the geomechanical
stability of HBS under the conditions that are deemed desirable for production.
Conversely, the increased pressure caused by the weight of structures on the
ocean floor increases the stability of underlying hydrates.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
27 February 2007
- Meeting paper published:
30 April 2007
- Revised manuscript received:
28 July 2008
- Manuscript approved:
30 July 2008
- Published online:
1 June 2009
- Version of record:
1 June 2009
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