skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present

Abstract

The Ngatamariki geothermal field, located 7 km south of Orakeikorako, discharges dilute chloride-bicarbonate waters of almost neutral pH from springs mostly on the margins of the field. Rhyolite tuffs in the northwestern part of the field are weakly silicified, probably due to their having reacted with heated groundwaters. Sinter deposits are common at Ngatamariki but are mostly relict from former activity. In 1994, the natural heat loss from the field was 30 {+-} 5 MW{sub thermal}. There has been a shift of thermal activity southward over the past 60 years; the changes were recognized by comparing air photographs taken in 1941 and 1991. In 1948, a hydrothermal eruption deposited breccia around its crater, which is now occupied by a pool at 52.5 C. Another pool at 88 C, first noticed in 1993, deposits a mixture of silica and calcite.

Authors:
; ;
Publication Date:
Research Org.:
Geothermal Institute and Geology Department, University of Auckland, NZ
Sponsoring Org.:
USDOE
OSTI Identifier:
895919
Report Number(s):
GEO-PROC-95-02
TRN: US200703%%744
Resource Type:
Conference
Resource Relation:
Conference: Proceedings of The 17th New Zealand Geothermal Workshop 1995
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; CALCITE; GEOTHERMAL FIELDS; IMAGES; MIXTURES; RHYOLITES; SILICA; Geothermal Legacy

Citation Formats

Brotheridge, J.M.A., Browne, P.R.L., and Hochstein, M.P.. The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present. United States: N. p., 1995. Web.
Brotheridge, J.M.A., Browne, P.R.L., & Hochstein, M.P.. The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present. United States.
Brotheridge, J.M.A., Browne, P.R.L., and Hochstein, M.P.. Sun . "The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present". United States. doi:. https://www.osti.gov/servlets/purl/895919.
@article{osti_895919,
title = {The Ngatamariki Geothermal Field, NZ: Surface Manifestations - Past and Present},
author = {Brotheridge, J.M.A. and Browne, P.R.L. and Hochstein, M.P.},
abstractNote = {The Ngatamariki geothermal field, located 7 km south of Orakeikorako, discharges dilute chloride-bicarbonate waters of almost neutral pH from springs mostly on the margins of the field. Rhyolite tuffs in the northwestern part of the field are weakly silicified, probably due to their having reacted with heated groundwaters. Sinter deposits are common at Ngatamariki but are mostly relict from former activity. In 1994, the natural heat loss from the field was 30 {+-} 5 MW{sub thermal}. There has been a shift of thermal activity southward over the past 60 years; the changes were recognized by comparing air photographs taken in 1941 and 1991. In 1948, a hydrothermal eruption deposited breccia around its crater, which is now occupied by a pool at 52.5 C. Another pool at 88 C, first noticed in 1993, deposits a mixture of silica and calcite.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 1995},
month = {Sun Jan 01 00:00:00 EST 1995}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • The governing equations for a two phase geothermal reservoir are presented for the case when a substantial amount of carbon dioxide is present. Sample results for a model reservoir based on the Broadlands geothermal field are given.
  • Four wells drilled into the Poihipi Sector on the Western margin of the Wairakei geothermal field have found a similar lithostratigraphy to that encountered in wells previously drilled in the general area. Young pumice breccias overly the Huka Falls Formation, with the latter containing intercalations of the Rautehuia Breccia. This in turn overlies ignimbrites and tuffaceous sediments of the Waiora Formation, which contains flows of Haparangi Rhyolite. This sequence is cut by steeply dipping normal faults which strike to the northeast and for the most part dip towards the northwest. Hydrothermal alteration is virtually limited to the Waiora and Haparangimore » units where a sequence of interlayered illite-smectite and illite clays are found along with chlorite, quartz, pyrite and calcite. There is a minor occurrence of zeolites. Despite large changes in the area's hydrology in response to exploitation, changes in alteration are limited to a comparatively deep occurrence of kaolinite and minor overprinting of epidote by illitic clay.« less
  • I'm pleased to be here as your keynote speaker from the utility industry. Today is fitting to discuss the role of an alternative/renewable energy resource such as geothermal. Three years ago today, the Exxon Valdez oil tanker spilled 11 million gallons of oil into Prince William Sound, Alaska. This ecological catastrophe was another of those periodic jolts that underscores the importance of lessening our nation's dependence on oil and increasing the use of cost-effective, environmentally benign alternative/renewable energy sources. Alternative/renewables have come a long way since the first oil crisis in 1973. Today, they provide 9 percent of electric powermore » used in the United States. That's nearly double the figure of just two years ago. And since 1985, one-third of a new capacity has come from geothermal, solar, wind and biomass facilities. Nevertheless, geothermal supplies only about three-tenths of a percent of the country's electric power, or roughly 2,800 megawatts (MW). And most of that is in California. In fact, geothermal is California's second-largest source of renewable energy, supplying more than 5 percent of the power generated in the state. Today, I'd like to discuss the outlook for the geothermal industry, framing it within Southern California Edison's experience with geothermal and other alternative/renewable energy sources.« less
  • The near-surface pressure distribution in the Wairakei Geothermal Field prior to exploitation is estimated from early bore hole measurements and drilling logs. Pressure distributions in a bore were rarely measured but can be calculated from the recorded temperature profiles. For a number of bores, a depth and corresponding pressure was estimated, to associate with the undisturbed field conditions, by examining drilling logs for major circulation losses in uncased sections and temperature patterns for internal flows between feeding fissures. In the shallower boiling zone of the field, some points of rapid temperature rise were found in cased sections of bores. Thesemore » were interpreted as being heated by flow of boiling fluid in fissures outside the casing, and pressures were obtained for these depths from the highest temperatures recorded at them, assuming the fluid to be pressurized water at its boiling point.« less