Fluid and heat flow in enhanced geothermal systems considering fracture geometrical and topological complexities: An extended embedded discrete fracture model

Accurate and efficient simulation of fluid and heat flow in fractures has long been a topic of interest for fractured reservoirs, e.g., enhanced geothermal systems (EGS) and unconventional oil/gas formations. In this paper, we propose a flexible and effective modeling approach, the extended embedded discrete fracture model (XEDFM), to simulate fluid and heat flow in fractured reservoirs with 3-D non-planar fracture networks. Compared with the conventional embedded discrete fracture model (EDFM), the XEDFM possesses two major merits: (1) separation of fracture discretization and matrix gridding provides maximum flexibility in handling fractures with complex geometry/topology, regardless of the resolution of the matrix grid; and (2) the combination of connection-list strategy and the concept of non neighboring connection facilitates the construction of fluid-heat flux between the fracture and the matrix/fracture. With systematically validated XEDFM, the impacts of fracture roughness and heat extraction strategy on hydrothermal behaviors and heat mining efficiency are investigated. Another example introduces a workflow for design and modeling of 3-D non-planar fracture networks, with which the performance of horizontal and vertical wells in tapping heat energy from EGS are explored. This work presents a flexible and effective approach for modeling fluid/heat transfer accurately in 3-D non-planar fractures, and provides a set of framework and efficient algorithms for non-planar fractures design, discretization and simulation, establishing the foundation to build and simulate models with complicated fractures. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

The paper proposes an extended embedded discrete fracture model (XEDFM) for simulating fluid and heat flow in fractured reservoirs with 3-D non-planar fracture networks, which offers more flexibility and advantages compared to conventional models. By systematically validating XEDFM, the study investigates the impacts of fracture roughness and heat extraction strategy on hydrothermal behaviors and heat mining efficiency.