Influence of erosive fluidization on the morphology of fluid flow and escape structures

Abstract

Mechanisms of fluid flow localization and pockmark formation remain an open question. Many conceptual models have been proposed, but very few predictive models exist. We propose a model based on erosive fluidization where seepage induced erosion, fluidization, and transport of granular material leads the formation of fluid escape structures (FES) like pipes, chimneys and pockmarks. The model predicts: 1) formation of conical focused flow conduits with brecciated core and annular gas channels encased within a halo of low permeability sediment, 2) pockmarks of diverse shapes and sizes, including W-, U-, and ring-shapes, and 3) pulsed gas release. Results show that the morphology of FES depends on properties related to sediment-fluid interactions (like erodibility and flow anisotropy), not on intrinsic sediment properties (like permeability). Although the study is theoretical, we show that our predicted FES have many real world analogs, highlighting the broad scope of the predictive capability of our model.