| Abstract |
Since April 2005, nine geothermal wells (WK243-251) have been completed at Te Mihi, western Wairakei Geothermal Field. Shallow geological formations encountered during drilling are similar to other wells in the area, and comprise Oruanui Formation, Huka Falls Formation (including Rautehuia Breccia), Waiora Formation, Karapiti - 2A and - 2B Rhyolites. Beneath the Karapiti Rhyolites, a previously unknown stratigraphy has been encountered, including plagioclase-quartz-pyroxene phyric, coalesced rhyolite lavas (informally named Poihipi Rhyolite - 1 and - 2), that represent two of several domes underlying the Te Mihi area, welded and non-welded crystal-rich ignimbrite (informal name: Stockyard Ignimbrite), andesite lava and subordinate pyroclastic and volcaniclastic units. Interpretation of the units encountered by WK243-WK251 provides a framework for investigating production drilling targets, stratigraphic and structural controls on deep fluid flow in the western Wairakei Geothermal Field. |