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Modeling methane gas hydrate precipitation in porous media using numerical reservoir simulation and digital rock physics
Rathmaier, Daniel
Rathmaier, Daniel
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2024
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2026-04-04
Abstract
In-situ solids precipitation within petroleum reservoirs alters key rock properties like porosity and permeability by clogging pore spaces, impacting fluid flow. Numerous commercial reservoirs are subject to the risk of solids precipitation, including asphaltenes, paraffin, salt, and gas hydrate formation during water flooding operations. This thesis investigates the impact of solids precipitation on reservoir rock flow properties using numerical simulation and pore-scale modeling. The study evaluates the permeability effect of methane hydrate formation from dissolved gas in an undersaturated oil reservoir, improving previous continuum-scale fluid flow simulations. It presents a novel Digital Rock Physics (DRP) workflow to model the influence of different hydrate deposition morphologies on permeability, previously assumed using idealistic mathematical and empirical descriptions. The numerical models achieve a maximum hydrate saturation of 16.47% before complete methane consumption. Field-scale upscaling suggests up to a 40% permeability reduction in the near-wellbore zone due to hydrate formation within three years of simulation. These improved reservoir fluid flow simulations more closely match laboratory observations from a previous study that formed hydrates during coreflooding experiments under temperature control. However, the maximum hydrate saturation could not create a quantitatively similar resistance to fluid flow as observed by pressure differential measurements in the laboratory due to simplified flow assumptions, necessitating a pore-scale modeling approach. The new DRP workflow applies mathematical morphology to map hydrate deposition morphologies, i.e., pore filling and grain/pore coating, combined with intrinsic hydrate formation kinetics for temporal analysis. This approach establishes unique relationships for permeability reduction with hydrate saturation for each morphology based on virtual single-phase flow experiments using the Lattice Boltzmann Method on real rock structures, rather than relying on idealistic or empirical models. Thereby, the DRP workflow enables testing hypotheses from experimental observations. Additionally, the thesis presents two-phase flow simulations resulting in relative permeability curves of oil and water, and capillary pressure curves of the system. This research advances the understanding of methane hydrate formation and its impact on reservoir rock permeability, providing valuable insights for petroleum productivity and injectivity in carbon sequestration or gas storage projects.
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