10. Regional/Global Structural Applications
Numerical Simulation to Estimate the Influence of Structural Deformation on Fluid Flow in a Modeled Accretionary Wedge
Ayumu Miyakawa, Takayuki Miyoshi, Yasuhiro Yamada and Toshifumi Matsuoka
Dept. Civil and Earth Resources Eng., Kyoto Univ., Japan.
Abstract
In this research, we estimate the porosity and permeability in a modeled accretionary prism by combining two simulation techniques to examine the influence of the structural deformation on fluid flow. The deformation geometry of the prism was constructed by the Distinct-Element Method (DEM), which approximates the prism as an assembly of particles and that was also used to calculate the porosity distribution. The permeability and the velocity of fluid flow were calculated by the Lattice Boltzmann Method (LBM).ˇˇAs a first step by using DEM, a particles assembly of rectangular slopes was constructed, then the side wall was pushed inward to cause accretionary prism type of deformation. The distribution of the particles was then extracted for the simulations result and the inter-particle porosity the prism model was calculated. We found that the region of low porosity exists in the hanging wall, whereas that of high porosity extends from the footwall to the surface. The porosity at the prism base is much decreased from the initial value, suggesting that the deformation produced tectonic compaction in the prism.ˇˇThe prism model was then divided into unit cubes to calculate the permeability distribution with LBM. Virtual fluid was injected into each cube in constant pressure, and the permeability was calculated from the amount of the water that came out. The results showed that the low permeability-region exists in the hanging wall, whereas that of high permeability extends from the footwall to the surface. The permeability difference between the hanging wall and the footwall, coincides with porosity distribution that is affected by the tectonic deformation.ˇˇFinally, we simulated the virtual fluid injection into the prism model from the bottom to estimate the fluid flow structure in the model prism. This injection simulation corresponds to the fluid supply from the base d¨¦collemant. The result showed that the flow velocity is also affected by the fault and the tectonic compaction that corresponds well with the permeability distribution.ˇˇThis research shows that tectonic compaction and faulting due to accretionary process have significant impact the porosity and permeability structures of the prism.
Last modified: Thu May 25 16:10:19 2006