An Advanced Discrete Fracture Methodology for Fast, Robust, and Accurate
Simulation of Energy Production from Complex Fracture Networks
Abstract
Fracture networks are abundant in subsurface applications (e.g.,
geothermal energy production, CO2 sequestration). Fractured reservoirs
often have a very complex structure, making modeling flow and transport
in such networks slow and unstable. Consequently, this limits our
ability to perform uncertainty quantification and increases development
costs and environmental risks. This study provides an advanced
methodology for simulation based on Discrete Fracture Model (DFM)
approach. The preprocessing framework results in a fully conformal,
uniformly distributed grid for realistic 2D fracture networks at a
required level of precision. The simplified geometry and topology of the
resulting network are compared with input (i.e., unchanged) data to
evaluate the preprocessing influence. The resulting mesh-related
parameters, such as volume distributions and orthogonality of control
volume connections, are analyzed. Furthermore, changes in fluid-flow
response related to preprocessing are evaluated using a high-enthalpy
two-phase flow geothermal simulator. The simplified topology directly
improves meshing results and, consequently, the accuracy and efficiency
of numerical simulation. The main novelty of this work is the
introduction of an automatic preprocessing framework allowing us to
simplify the fracture network down to required level of complexity and
addition of a fracture aperture correction capable of handling
heterogeneous aperture distributions, low connectivity fracture
networks, and sealing fractures. The graph-based framework is fully
open-source and explicitly resolves small-angle intersections within the
fracture network. A rigorous analysis of changes in the static and
dynamic impact of the preprocessing algorithm demonstrates that explicit
fracture representation can be computationally efficient, enabling their
use in large-scale uncertainty quantification studies.