Exploitation, Subsidence and Gravity Changes in the Travale-Radicondoli Geothermal Field

Abstract

Thirteen precision leveling surveys, beginning in 1973, in the Travale-radicondoll geothermal area (Tuscany, Italy). Maximum subsidence values of about -26 cm have been observed. Since March 1979 the microgravity changes have been monitored. The pressure variations of the fluids at the top of the main reservoir have been reconstructed from 1973 on (beginning of exploitation of the "new" field). The "old" water dominated field shows initial low pressures, which increased in some cases when the wells were shut in, and small vertical changes in ground movement. Residual gravity changes are usually positive (max 40 ugal) with respect to 1979 data. The "new" vapor or gas (CO2) dominated field has been producing since July 1973. So far the pressures in the exploited reservoir have decreased by about 4 MPa in the central part of the field; ground subsidence of the order of 20-25 cm has been observed, accompanied by generally negative microgravity changes (-20ugal).