Abstract
Gas migration mechanisms control the release of gas from seafloor sediments. We study underlying phenomena using transparent sediments subjected to controlled effective stress; this experimental approach allows high-resolution real-time monitoring of gas migration through cohesionless granular materials under 3D-boundary conditions. Observed migration patterns depend on the effective stress at the time of injection and the stress history. Gas migration transitions from pore-invasive to grain-displacive when the capillary pressure for air entry ΔPAE is greater than the effective stress σ'. This study focuses on grain-displacive gas migration. The morphology of grain-displacive gas bodies changes with depth as the sediment stiffness G increases and the effect of surface tension γ vanishes: spheroidal gas bubbles form in the near-surface, faceted cavities further down, and eventually open-mode fractures develop at depth. The gas injection pressure is proportional to the effective stress in grain-displacive migration. Pre-loading and overconsolidation cause the rotation of principal stresses and gas-driven openings align with the new minimum principal stress direction. Cyclic loading promotes the upwards migration of gas-filled openings, and there is mechanical memory of previous gas pathways in sediments.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2274-2285 |
| Number of pages | 12 |
| Journal | Journal of Geophysical Research: Solid Earth |
| Volume | 124 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 15 2019 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledgements: Support for this research was provided by the KAUST endowment. G. E. Abelskamp edited the manuscript. Data sets presented as part of this study are available from the KAUST Repository: http://hdl.handle.net/10754/630965.