An embedded 3D fracture modeling approach for simulating fracture-dominated fluid flow and heat transfer in geothermal reservoirs

Journal Article · Sat Feb 29 00:00:00 EST 2020 · Geothermics

DOI:https://doi.org/10.1016/j.geothermics.2020.101831· OSTI ID:1603924

Wang, Cong ^[1]; Winterfeld, Philip ^[2]; Johnston, Henry ^[3]; Wu, Yu-Shu ^[2]

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1. Saudi Aramco, Dharhan (Saudi Arabia); Colorado School of Mines, Golden, CO (United States)
2. Colorado School of Mines, Golden, CO (United States)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States)

In this paper, we describe an efficient modeling approach, named embedded discrete fracture method (EDFM), for incorporating arbitrary 3D, discrete fractures, such as hydraulic fractures or faults, into modeling fracture-dominated fluid flow and heat transfer in fractured geothermal reservoirs. This technique allows 3D discrete fractures to be discretized independently from surrounding rock volume and inserted explicitly into a primary fracture/matrix grid, generated without including 3D discrete fractures in prior. An effective computational algorithm is developed to discretize these 3D discrete fractures and construct local connections between 3D fractures and fracture/matrix grid blocks representing the surrounding rock volume. The constructed gridding information on 3D fractures is then added to the primary grid. This embedded fracture modeling approach can be directly implemented into a developed geothermal reservoir simulator via the integral finite difference (IFD) method or with TOUGH2 technology. This embedded fracture modeling approach is very promising and computationally efficient to handle realistic 3D discrete fractures with complicated geometries, connections, and spatial distributions. Compared with other fracture modeling approaches, it avoids cumbersome 3D unstructured, local refining procedures, and increases computational efficiency by simplifying Jacobian matrix size and sparsity, while maintaining enough accuracy. Several numeral simulations are presented to demonstrate the utility and robustness of the proposed technique. Our numerical experiments show that this approach captures all the key patterns about fluid flow and heat transfer dominated by fractures in these cases. Thus, this approach is readily available to the simulation of fractured geothermal reservoirs with both artificial and natural fractures.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1603924
• Alternate ID(s): OSTI ID: 1702753
• Report Number(s): NREL/JA--5500-75463
• Journal Information: Geothermics, Journal Name: Geothermics Journal Issue: C Vol. 86; ISSN 0375-6505
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
EDFM
fracture simulation
geothermal
geothermal reservoir
reservoir simulation