Numerical studies on the geomechanical stability ofhydrate-bearing sediments
The thermal and mechanical loading of oceanicHydrate-Bearing Sediments (HBS) can result in hydrate dissociation and asignificant pressure increase, with potentially adverse consequences onthe integrity and stability of the wellbore assembly, the HBS, and thebounding formations. The perception of HBS instability, coupled withinsufficient knowledge of their geomechanical behavior and the absence ofpredictive capabilities, have resulted in a strategy of avoidance of HBSwhen locating offshore production platforms, and can impede thedevelopment of hydrate deposits as gas resources.In this study weinvestigate in three cases of coupled hydraulic, thermodynamic andgeomechanical behavior of oceanic hydrate-bearing sediments. The firstinvolves hydrate heating as warm fluids from deeper conventionalreservoirs ascend to the ocean floor through uninsulated pipesintersecting the HBS. The second case describes system response duringgas production from a hydrate deposit, and the third involves mechanicalloading caused by the weight of structures placed on the ocean flooroverlying hydrate-bearing sediments.For the analysis of the geomechanicalstability of HBS, we developed and used a numerical model that integratesa commercial geomechanical code and a simulator describing the coupledprocesses of fluid flow, heat transport and thermodynamic behavior in theHBS. Our simulation results indicate that the stability of HBS in thevicinity of warm pipes may be significantly affected, especially if thesediments are unconsolidated and more compressible. Gas production fromoceanic deposits may also affect the geomechanical stability of HBS underthe conditions that are deemed desirablefor production. Conversely, theincreased pressure caused by the weight of structures on the ocean floorincreases the stability of underlying hydrates.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Fossil Energy.Gas
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 928016
- Report Number(s):
- LBNL-62759; R&D Project: G30801; BnR: AB0565000; TRN: US200816%%983
- Resource Relation:
- Conference: 2007 Offshore Technology Conference, Houston,Texas, 29 April-2 May 2007
- Country of Publication:
- United States
- Language:
- English
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