Lattice Boltzmann Simulation of Fluid Flow In Synthetic Fractures
Fractures play
an important role in geothermal reservoir engineering as they dominate the
fluid flow in the reservoir. Because of this reason
determination of fracture permeability is very important to predict the
performance of a geothermal reservoir. A fracture is usually
assumed as a set of smooth parallel plates separated by a constant
width. The absolute permeability of a smooth-walled fracture is
related to the fracture aperture using the cubic law. However, the
flow characteristics of an actual fracture surface would be quite different,
affected by tortuosity and surface roughness.
Though several researchers have discussed the effect of friction on flow, a
unified methodology for studying flow on a rough fracture surface has not
emerged. As experimental methods are expensive and time consuming most of
the time numerical methods are used. In this work, we present results of
the numerical computations for single phase flow
simulations through 2D synthetically created fracture apertures. These
synthetic rock fractures are created using different
fractal dimensions, anisotropy factors, and mismatch lengths that are obtained
from the producing geothermal reservoirs in South Western Turkey. Lattice
Boltzmann Method, which is a new computational approach suitable to simulate
fluid flow especially in complex geometries, was then used to determine the
permeability for different fractures. Regions of high velocity and low
velocity flow were identifies. The resulting permeability values were
less than the ones obtained with the cubic law estimates. It has been found that as the fractal dimension and mean
aperture - fractal dimension ratio increased permeability increased. Moreover as the anisotropy factor increased permeability
decreased with a second order polynomial relationship.
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