Evaluation of C-14 as a natural tracer for injected fluids at theAidlin sector of The Geysers geothermal system through modeling ofmineral-water-gas Reactions
A reactive-transport model for 14C was developed to test itsapplicability to the Aidlin geothermal system. Using TOUGHREACT, wedeveloped a 1-D grid to evaluate the effects of water injection andsubsequent water-rock-gas interaction on the compositions of the producedfluids. A dual-permeability model of the fracture-matrix system was usedto describe reaction-transport processes in which the permeability of thefractures is many orders of magnitude higher than that of the rockmatrix. The geochemical system included the principal minerals(K-feldspar, plagioclase, calcite, silica polymorphs) of themetagraywackes that comprise the geothermal reservoir rocks. Initialsimulation results predict that the gas-phase CO2 in the reservoir willbecome more enriched in 14C as air-equilibrated injectate water (with amodern carbon signature) is incorporated into the system, and that thesechanges will precede accompanying decreases in reservoir temperature. Theeffects of injection on 14C in the rock matrix will be lessened somewhatbecause of the dissolution of matrix calcite with "dead"carbon.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Energy Efficiency andRenewable Energy. Solar Energy Technology Program
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 890689
- Report Number(s):
- LBNL--60321; BnR: EB4005020
- Country of Publication:
- United States
- Language:
- English
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