Articles | Volume 9, issue 3
Research article
30 May 2018
Research article |  | 30 May 2018

Squirt flow due to interfacial water films in hydrate bearing sediments

Kathleen Sell, Beatriz Quintal, Michael Kersten, and Erik H. Saenger

Abstract. Sediments containing gas hydrate dispersed in the pore space are known to show a characteristic seismic anomaly which is a high attenuation along with increasing seismic velocities. Currently, this observation cannot be fully explained albeit squirt-flow type mechanisms on the microscale have been speculated to be the cause. Recent major findings from in situ experiments, using the gas in excess and water in excess formation method, and coupled with high-resolution synchrotron-based X-ray micro-tomography, have revealed the systematic presence of thin water films between the quartz grains and the encrusting hydrate. The data obtained from these experiments underwent an image processing procedure to quantify the thicknesses and geometries of the aforementioned interfacial water films. Overall, the water films vary from sub-micrometer to a few micrometers in thickness. In addition, some of the water films interconnect through water bridges. This geometrical analysis is used to propose a new conceptual squirt flow model for hydrate bearing sediments. A series of numerical simulations is performed considering variations of the proposed model to study seismic attenuation caused by such thin water films. Our results support previous speculation that squirt flow can explain high attenuation at seismic frequencies in hydrate bearing sediments, but based on a conceptual squirt flow model which is geometrically different than those previously considered.

Short summary
Sediments containing hydrates dispersed in the pore space show a characteristic seismic anomaly: a high attenuation along with increasing seismic velocities. Recent major findings from synchrotron experiments revealed the systematic presence of thin water films between quartz and gas hydrate. Our numerical studies support earlier speculation that squirt flow causes high attenuation at seismic frequencies but are based on a conceptual model different to those previously considered.