JMEE Home · Issue Contents · Forthcoming Papers
Stability of Hydrate Bearing Sediments During CH4-CO2 Replacement: A Geomechanical Perspective
Reddi Srinivasa Rao, K.P. Lijith and Devendra Narain Singh
Exploitation of methane gas from hydrate bearing sediments (HBS) can be achieved by altering thermodynamic stability conditions in the hydrate stability zone (HSZ) by resorting to various dissociation techniques. This process, which alters geomechanical properties (viz., shear strength, stiffness, and permeability) of the HBS might also trigger instability of submarine slopes, reservoir subsidence, sand migration, wellbore instability, etc. To alleviate such a situation, replacing CH4 from HBS, by injecting CO2, a process designated as CH4-CO2 replacement, and which is in line with SDGs 7 (Affordable & Clean Energy) & 13 (Climate Action), seems to be a panacea. However, to achieve this, it is imperative to understand the thermodynamic feasibility, pore-scale mechanisms, and variations in geomechanical properties of HBS during and after the replacement. With this in view, data available in the literature that focus on the thermodynamic conditions, pore-scale mechanisms and geomechanical stability of the HBS, were critically synthesized. It has been noticed an insignificant difference in the normalized peak shear strength for CH4 HBS and CO2 HBS with hydrate saturation (SH). Furthermore, the shear strength parameters (viz., cohesion and angle of internal friction) of both CH4 HBS and CO2 HBS, which predominantly influence geomechanical stability of HBS during CH4-CO2 replacement, are directly dependent on SH. In addition to this, the pore-scale mechanisms that would provide an insight into CH4-CO2 replacement have been conceived to demonstrate how replacement facilitates geomechanical stability of HBS. Based on the analysis of the data, empirical relationships between the cohesion and SH for both CH4 HBS and CO2 HBS have also been proposed. It is our hunch that such an exercise would provide a preliminary insight for field scale implementation of CH4-CO2 replacement successfully by maintaining the stability of HBS.
Keywords: Hydrate Bearing Sediments, Dissociation, CH4-CO2 Replacement, Geomechanical Stability, Pore-Scale Mechanisms, Empirical Relationships
DOI: 10.32908/JMEE.v12.CZ-2025032001a