DETERMINATION OF LOCAL SEISMICITY DURING OPERATIONS OF PRODUCTION AND GEOTHERMAL FLUID REINJECTION IN THE CESANO AREA
The aim of the contract was to correlate induced seismic activity and brine reinjection in the Cesano area. A complete absence of signals made this correlation impossible. It is, however, possible that the injection rates of 100 - 150 m**3/h in a well that can absorb 400 m**3/h were too low to cause any seismic events. The investigations were shifted to Latera where reinjection in well Latera 1 was monitored. A test was carried out with a flow rate of approximately 100 m**3/h. The pressure variations at wellhead and the time distribution of the microseismicity detected are reported. A total of 148 events were recorded that can be clearly correlated with the operations carried out. The microearthquakes recorded always exhibited close analogies concernig signal frequency, amplitude and polarity of the first arrivals. The foci were located in the immediate vicinity of the well at a depth of 0.7 to 2.7 km. The maximum magnitude that was measured was 0.4. The use of the integrative three-component stations with digital recording made it possible to perform some interesting and advanced analyses on the signals. It was possible to estimate the corner frequency of the spectrum of displacement of the P phase and therefore to determine the main parameters at the source such as seismic moment, source radius, stress drip and strain release. Even more important was the contribution that the integrative stations, placed in the vicinity of the reinjection well, gave in determining the hypocentre and in the solution of the focal mechanisms.
Bibliographic Reference: EUR 8765 EN (1983) MF, 78 P., BFR 120 - EUROFFICE, LUXEMBOURG, POB 1907
Availability: Can be ordered online
Record Number: 1989122001600 / Last updated on: 1987-01-01
Available languages: en