Proceedings of the 6th New Zealand Geothermal Workshop 1985. Modelling the gravity changes at Wairakei geothermal field. New Zealand Geothermal Workshop [7-9 Nov. 1984, New Zealand].

Allis, R.G. Hint, T.M.

[1984]

CIENA
171

0-86869-056-2

The principal cause of gravity change at Wairakei has been the drawdown of liquid and the formation of a steam zone in the upper part of the reservoir. Small but significant gravity changes have also been caused by subsequent saturation changes in the steam zone, groundwater level decline and changing pore water density due to temperature changes. Pore compaction, pore water, decompression and mineral precipitation are unlikely to have caused significant gravity changes <30 µgal. An example of modelling the gravity changes in the eastern production borefield indicates a residual saturation in the steam zone, immediately after liquid drawdown, of 0.6. Dry out of the steam zone during the 1960's caused the saturation to decrease to less than 0.5. During the 1970's there appears to have been negligible change. Continuing pressure and temperature declines in the steam zone are apparently now caused mainly by groundwater invasion..

Presenta gráfs.

NUEVA ZELANDIA; ENERGIA GEOTERMICA; GRAVIMETRIA; ESTUDIOS GEOFISICOS; AGUAS SUBTERRANEAS; CAMPOS GEOTERMICOS; FLUIDOS GEOTERMICOS;