HR: 1340h
AN: OS43A-0611    [Abstracts]
TI: Importance of Overpressure in 2D Gas Hydrate Modeling
AU: * Hauschildt, J
EM: j.hauschildt@iu-bremen.de
AF: International University Bremen, Campus Ring 1, Bremen, 28759 Germany
AU: Unnithan, V
EM: v.unnithan@iu-bremen.de
AF: International University Bremen, Campus Ring 1, Bremen, 28759 Germany
AB: Numerical models for sub-seafloor gas hydrate formation [1],[2],[3] which describe the driving fluid transport processes only in the vertical direction, restrict the computationally expensive problem to one dimension. This assumption is only valid in regions where permeable sediments induce no overpressure and where there is little lateral variation of physical properties and boundary conditions. Local accumulations of gas hydrates or authigenic carbonates can significantly reduce the porosity and permeability. In combination with topographic and structural features, subtle but important deviations from the 1D model are considered to occur. This poster shows results obtained from a 2D finite difference model developed for describing the evolution of the gas hydrate zone in structurally complex areas. The discretisation of the terms governing the thermodynamic and transport processes is implemented explicitely in time for the advection and diffusion processes, but implicitely for phase transitions. Although the time scales for transport and phase transitions can differ by several orders of magnitude, this scheme allows for an efficient computation for model runs both over the system's equilibration period in the order of 10⁷ yr or to resolve the effects of sea-level changes within 10³ yr. A sensitivity analysis confines the parameter space relevant for hydrate formation influenced by lateral fluid flow, and results for the predicted deviations from a multi-1D model for high gas hydrate fractions and fluid flow rates are presented. References [1] M.K. Davie and B.A. Buffett. Sources of methane for marine gas hydrate: inferences from a comparison of observations and numerical models. Earth and Planetary Science Letters, 206:51-63, 2003. [2] W. Xu and C. Ruppell. Predicting the occurrence, distribution, and evolution of methane hydrate in porous marine sediments. Journal of Geohphysical Research, (B3):5081-5095, 1999. [3] J.B. Klauda and S.I. Sandler. Predictions of gas hydrate phase equilibria and amounts in natural sediment porous media. Marine and Petr. Geol.,20:459-470, 2003.
DE: 3004 Gas and hydrate systems
DE: 3653 Fluid flow
DE: 4255 Numerical modeling (0545, 0560)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005