Numerical modeling of gas hydrate emplacements in oceanic sediments
Journal
Marine and Petroleum Geology
Journal Volume
28
Journal Issue
10
Pages
1856-1869
Date Issued
2011
Author(s)
Abstract
We have implemented a 2-dimensional numerical model for simulating gas hydrate and free gas accumulation in marine sediments. The starting equations are those of the conservation of the transport of momentum, energy, and mass, as well as those of the thermodynamics of methane hydrate stability and methane solubility in the pore-fluid. These constitutive equations are then integrated into a finite element in space, finite-difference in time scheme. We are then able to examine the formation and distribution of methane hydrate and free gas in a simple geologic framework, with respect to the geothermal heat flow, fluid flow, the methane in-situ production and basal flux. Three simulations are performed, leading to the build up of hydrate emplacements largely linear through time. Models act primarily as free gas accumulators and are relatively inefficient with respect to hydrate emplacements: 26-33% of formed methane are converted to hydrate. Seepage of methane across the sea-floor is negligible for fluid flow below 2. 10-11 kg/m2/s. At 5.625 10-11 kg/m2/s however, 9.7% of the formed methane seeps out of the model. Moreover, along strike variation arising in the 2-dimensional model are outlined. In the absence of focused flow, the thermodynamics of hydrate accumulation are primarily one-dimensional. However, changes in free methane compressibility (density) and methane solubility (the intrinsic dissolved methane flux) subtlety impact on the formation of a free gas zone and the distribution of the hydrate emplacements in our 2-dimensional simulations. © 2011 Elsevier Ltd.
Subjects
Finite-elements; Gas hydrates; Methane solubility; Simulation
SDGs
Other Subjects
Dissolved methane; Finite difference; Finite Element; Focused-flow; Free gas; Geothermal heat flow; Hydrate accumulations; In-situ production; Marine sediments; Methane hydrates; Methane seep; Methane solubility; Numerical modeling; Numerical models; Oceanic sediments; Sea floor; Simulation; Anoxic sediments; Constitutive equations; Flow of fluids; Gases; Geothermal energy; Geothermal heating; Hydration; Methane; Numerical methods; Sedimentology; Solubility; Submarine geology; Thermodynamics; Transport properties; Gas hydrates; accumulation; compressibility; constitutive equation; emplacement; finite element method; gas hydrate; heat flow; marine sediment; mass transport; methane; momentum transfer; numerical model; seepage; solubility; thermodynamics; Calluna vulgaris
Type
journal article