Numerical Simulation of Injectivity Effects of Mineral Scaling and Clay Swelling in a Fractured Geothermal Reservoir
A major concern in the development of hot dry rock (HDR) and hot fractured rock (HFR) reservoirs is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths such as those caused by thermally-induced stress cracking. Past analyses of HDR and HFR reservoirs have tended to focus primarily on the coupling between hydrology (flow), heat transfer, and rock mechanics. Recent studies suggest that rock-fluid interactions and associated mineral dissolution and precipitation effects could have a major impact on the long-term performance of HFR reservoirs. The present paper uses recent European studies as a starting point to explore chemically-induced effects of fluid circulation in HFR systems. We examine ways in which the chemical composition of reinjected waters can be modified to improve reservoir performance by maintaining or even enhancing injectivity. Chemical manipulations considered here include pH modification and dilution with fresh water. We performed coupled thermo-hydrologic-chemical simulations in which the fractured medium was represented by a one-dimensional MINC model (multiple interacting continua), using the non-isothermal multi-phase reactive geochemical transport code TOUGHREACT. Results indicate that modifying the injection water chemistry can enhance mineral dissolution and reduce clay swelling. Chemical interactions between rocks and fluids will change a HFR reservoir over time, with some changes favorable and others not. A detailed, quantitative understanding of processes and mechanisms can suggest chemical methods for reservoir management, which may be employed to improve the performance of the geothermal system.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Energy Efficiency and Renewable Energy. Office of the Geothermal Technology Program (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 834641
- Report Number(s):
- LBNL-55113; R&D Project: G31902; TRN: US200433%%263
- Resource Relation:
- Conference: Geothermal Resources Council 2004 Annual Meeting, Palm Springs, CA (US), 08/29/2004--09/01/2004; Other Information: PBD: 10 May 2004
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
CHEMICAL COMPOSITION
CLAYS
DILUTION
DISSOLUTION
FRESH WATER
GEOTHERMAL RESOURCES
GEOTHERMAL SYSTEMS
HEAT TRANSFER
HYDROLOGY
MODIFICATIONS
PRECIPITATION
ROCK MECHANICS
ROCK-FLUID INTERACTIONS
SWELLING
WATER CHEMISTRY
Geothermal Legacy
RHFR HDR EGS MINERAL SCALING CLAY SWELLING INJECTIVITY ENHANCING INJECTATE MITIGATION REACTIVE TRANSPORT MODELING