Thermal Drawdown Induced Flow Channeling in Fractured Geothermal Reservoirs: Rock Mechanics and Rock Engineering

Abstract
We investigate the flow-channeling phenomenon caused by thermal drawdown in fractured geothermal reservoirs. A discrete fracture network-based, fully coupled thermal "hydrological" mechanical simulator is used to study the interactions between fluid flow, temperature change, and the associated rock deformation. The responses of a number of randomly generated 2D fracture networks that represent a variety of reservoir characteristics are simulated with various injection-production well distances. We find that flow channeling, namely flow concentration in cooled zones, is the inevitable fate of all the scenarios evaluated. We also identify a secondary geomechanical mechanism caused by the anisotropy in thermal stress that counteracts the primary mechanism of flow channeling. This new mechanism tends, to some extent, to result in a more diffuse flow distribution, although it is generally not strong enough to completely reverse flow channeling. We find that fracture intensity substantially affects the overall hydraulic impedance of the reservoir but increasing fracture intensity generally does not improve heat production performance. Increasing the injection-production well separation appears to be an effective means to prolong the production life of a reservoir.

DOI: 10.1007/s00603-015-0776-0.
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Additional Info

DOE Project Name: Validation of EGS Feasibility and Explosive Fracturing Techniques
DOE Project Number: FY15 AOP 1.3.2.4
DOE Project Lead: Elisabet Metcalfe
Last Updated: over a year ago
Nov
2015
Data from November, 2015
Submitted Nov 25, 2015

Lawrence Livermore National Laboratory

Contact

925.422.3941

Authors

Pengcheng Fu
Lawrence Livermore National Laboratory
Charles R. Carrigan
Lawrence Livermore National Laboratory
Stuart D. C. Walsh
Lawrence Livermore National Laboratory
Yue Hao
Lawrence Livermore National Laboratory

Keywords

geothermal, thermal drawdown, flow channeling, thermomechanical coupling, reservoir simulation, stimulation, egs, enhanced geothermal reservoirs, explosive fracturing

Status

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