Noble gases in a section across the vapor dominated geothermal field of Larderello,Italy |
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| Authors: | Emanuel Mazor |
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| Institution: | (1) Geo-Isotope Group, Weizmann Institute of Science, Rehovot, Israel |
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| Abstract: | Noble gases were studied in six wells, located on a 4.5 km south to north section across the Larderello field. Depth of wells, flow and gas/steam ratios are known to increase from south to north. Exploitation progressed in the same direction. The following noble gas patterns are observable: (a) Atmospheric Ar, Kr and Xe reflect productions of gas-depleted water at Colombaia 2 and progressively more gas-enriched steam towards the Gabbro wells. (b) Radiogenic4He and40Ar are observed in increasing concentrations from south to north. (c) The radiogenic and atmospheric gases reveal a positive correlation, indicating that the recharging water enters deep into the system, and gets well mixed with the radiogenic gases prior to the steam separation. (d) Gas contents and relative abundances of radiogenic argon decrease with production, thus supplying markers for the degree of exploitation in a well and a guide for optimum well spacing. (e) Excess neon over argon is observed and discussed in terms of  crustal origin versus possible fractionation of atmospheric noble gases due to pertial steam separation. |
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| Keywords: | Atmospheric Ar Xe Kr Radiogenic4He 40Ar Gas content of steam Partition coefficients of noble gases Recharging water Production well spacing |
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