Proceedings of the 6th New Zealand Geothermal Workshop 1985. Production and reinjection strategies at Ohaaki-Broadlands geothermal field. New Zealand Geothermal Workshop [7-9 Nov. 1984, New Zealand].

Grindley, G.W.

[1984]

171
CIENA

0-86869-056-2

On the West Bank of Ohaaki, the Ohaaki Rhyolite consist of eastward-thinning flows and coulées from an unknown source outside the field to the west. Similarly, the older Broadlands Rhyolite (B) is a northeast-trending flow lobe from a nearby source outside the southwest margin of the field. Both rhyolites have permeable margins ideally suited for reinjection sinks. Testing has shown that reinjection fluids will disperse within these rhyolites and not affect the Ohaaki production wells provided reinjection well are sited more than 1 km away and not adjacent to faults. On the East Bank, Broadlands Rhyolite (A) is a small buried dome, strongly fractured and mineralised, on the crest of a basament horst. The overlying Broadlands Dacite consists of westward-thinning flows and coulees from a source near the southeast field margin. Primary permeability on the East Bank is low because the thin Waiora and Rautawiri aquifers are partly self-sealed below the Ohaaki Rhyolite, Huka Falls formation and Broadlands Dacite. Production is reliant on secondary permeability in steep northwest-dipping normal faults onthe northwest flank of the basement horst and on associated hydraulic fractures below the capping formations. Temmperature/pressure data support a single source in southeast, possibly the cooling rhyodacite magma chamber that fed the broadlands Dacite and Rhyolite A. High temperatures (310°C) exist in the mainly impermeable basement rocks.

Incluye solo abstract.

NUEVA ZELANDIA; ENERGIA GEOTERMICA; POZOS GEOTERMICOS; REINYECCION; PRODUCCION;