A Modeling Study of Geomechanical Performance of Sloping Oceanic Hydrate Deposits Subjected Production Activities

摘要

Oceanic Hydrate-Bearing Sediments (HBS) subjected to production activities can induced strongly coupled fluid flow and geomechanical changes that may have adverse consequences on wellbore integrity, the HBS, and the bounding formations. For a sloping hydrate bearing system, the geomechanical changes could potentially be catastrophic if triggering large slides of the seafloor. In this study we investigate two cases of coupled hydraulic, thermodynamic and geomechanical behavior of sloping oceanic HBS: 1) hydrate heating as warm fluids from deeper conventional reservoirs ascend to the ocean floor through uninsulated pipes intersecting an HBS adjacent to the seafloor, 2) system response during gas production from a hydrate deposit located 400 m below the seafloor. In the first case we consider a situation when a hydraulically confined hydrate layer near the ocean floor is dissociated by heating from the well with associated gas release and forced pressure increase, which could undermine the stability of the slope. In the second case, depressurization leads to hydrate dissociation over a large lateral distance that may provide a weakening potential slip surface along the sloping hydrate system. The results of our analysis indicate that although these production activities induces strongly coupled geomechanical responses that may adversely impact the production itself, they are unlikely to trigger large scale slides of the seafloor.