Testing a thermo‐chemo‐hydro‐geomechanical model for gas hydrate‐bearing sediments using triaxial compression laboratory experiments. (13th September 2017)

• Record Type: Journal Article
• Authors: Gupta, S.; Deusner, C.; Haeckel, M.; Helmig, R.; Wohlmuth, B.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 18:Number 9(2017)
• Page Start: 3419
• Page End: 3437
• Publication Date: 2017-09-13
• Subjects: gas hydrates -- hydro‐geomechanical reservoir model -- numerical methods -- triaxial testing -- model validation; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2017GC006901
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Natural gas hydrates are considered a potential resource for gas production on industrial scales. Gas hydrates contribute to the strength and stiffness of the hydrate‐bearing sediments. During gas production, the geomechanical stability of the sediment is compromised. Due to the potential geotechnical risks and process management issues, the mechanical behavior of the gas hydrate‐bearing sediments needs to be carefully considered. In this study, we describe a coupling concept that simplifies the mathematical description of the complex interactions occurring during gas production by isolating the effects of sediment deformation and hydrate phase changes. Central to this coupling concept is the assumption that the soil grains form the load‐bearing solid skeleton, while the gas hydrate enhances the mechanical properties of this skeleton. We focus on testing this coupling concept in capturing the overall impact of geomechanics on gas production behavior though numerical simulation of a high‐pressure isotropic compression experiment combined with methane hydrate formation and dissociation. We consider a linear‐elastic stress‐strain relationship because it is uniquely defined and easy to calibrate. Since, in reality, the geomechanical response of the hydrate‐bearing sediment is typically inelastic and is characterized by a significant shear‐volumetric coupling, we control the experiment very carefully in order to keep the sample deformations small and well within the assumptions of poroelasticity. The closely coordinated experimental and numerical procedures enable us to validate the proposed simplified geomechanics‐to‐flow coupling, and set an important precursor toward enhancing our coupled hydro‐geomechanical hydrate reservoir simulator with more suitable elastoplastic constitutive models. Key Points: A simplified coupling concept is proposed for modeling geomechanical feedback on gas production behavior of hydrate reservoirs Coupling concept is validated by numerical simulation of gas hydrate formation and dissociation in a controlled triaxial compression test Coupling concept applies to pore‐filling hydrates as well as for hydrates in the transition zone between pore‐filling and load‐bearing habits