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

Title: Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ

Abstract

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 Haparangi 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.

Authors:
; ;
Publication Date:
Research Org.:
Kingston Morrison Ltd, Auckland, NZ
Sponsoring Org.:
USDOE
OSTI Identifier:
895916
Report Number(s):
GEO-PROC-95-02
TRN: US200703%%794
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; CLAYS; DRILLING; EPIDOTES; HYDROLOGY; HYDROTHERMAL ALTERATION; ILLITE; KAOLINITE; PYRITE; QUARTZ; SEDIMENTS; WAIRAKEI GEOTHERMAL FIELD; ZEOLITES; Geothermal Legacy

Citation Formats

Bogie, I., Lawless, J.V., and MacKenzie, K.M. Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ. United States: N. p., 1995. Web.
Bogie, I., Lawless, J.V., & MacKenzie, K.M. Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ. United States.
Bogie, I., Lawless, J.V., and MacKenzie, K.M. Sun . "Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ". United States. doi:. https://www.osti.gov/servlets/purl/895916.
@article{osti_895916,
title = {Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ},
author = {Bogie, I. and Lawless, J.V. and MacKenzie, K.M.},
abstractNote = {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 Haparangi 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.},
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 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
  • This report reviews the results from two shallow drilling programs recently completed as part of the United States Department of Energy Continental Scientific Drilling Program. The purpose is to provide a broad overview of the objectives and results of the projects, and to analyze these results in the context of the promise and potential of research drilling in crustal thermal regimes. The Inyo Domes drilling project has involved drilling 4 shallow research holes into the 600-year-old Inyo Domes chain, the youngest rhyolitic event in the coterminous United States and the youngest volcanic event in Long Valley Caldera, California. The purposemore » of the drilling at Inyo was to understand the thermal, chemical and mechanical behavior of silicic magma as it intrudes the upper crust. This behavior, which involves the response of magma to decompression and cooling, is closely related to both eruptive phenomena and the establishment of hydrothermal circulation. The Salton Sea shallow research drilling project involved drilling 19 shallow research holes into the Salton Sea geothermal field, California. The purpose of this drilling was to bound the thermal anomaly, constrain hydrothermal flow pathways, and assess the thermal budget of the field. Constraints on the thermal budget links the local hydrothermal system to the general processes of crustal rifting in the Salton Trough.« less
  • 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.
  • 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 inmore » 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.« less
  • Tracer tests performed in geothermal reservoirs have indicated inter-well flows at speeds up to 100m/hr. Such rapid movement of injected water underground indicates a clear danger of premature thermal breakthrough during reinjection. Early thermal drawdown has in fact been observed in several fields. The very rapid returns suggest that fractures are the principal conduits for tracer transport and thus a new method of tracer profile interpretation has been formulated. This method is based on flow through individual fractures rather than through porous medium as has been the case in standard methods. Applications of the method to tracer tests performed atmore » the Wairakei geothermal field show excellent matching of the observed tracer profiles based on a model of only two fractures joining the injection and production wells.« less