KAUST DepartmentAli I. Al-Naimi Petroleum Engineering Research Center (ANPERC)
Earth Science and Engineering Program
Energy Resources and Petroleum Engineering
Physical Science and Engineering (PSE) Division
Online Publication Date2019-03-15
Print Publication Date2019-03
Permanent link to this recordhttp://hdl.handle.net/10754/631114
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AbstractGas 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.
CitationSun Z, Santamarina JC (2019) Grain-Displacive Gas Migration in Fine-grained Sediments. Journal of Geophysical Research: Solid Earth. Available: http://dx.doi.org/10.1029/2018jb016394.
SponsorsSupport 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.
PublisherAmerican Geophysical Union (AGU)