Geophysical methods in geothermal prospecting in New Zealand

Hatherton, T.; Macdonald, W. J. P.; Thompson, G. E.

doi:10.1007/bf02597171

Cited by 35 publications

(13 citation statements)

References 2 publications

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“…Schlumberger and Wenner methods were used for most of the early resistivity surveys, especially in New Zealand (Banwell and Macdonald, t965;Hatherton et al, 1966;Macdonald and Muffler, 1972), but have also been used in some recent surveys (e.g. Meidav and Furgerson, 1972;Zohdy et al, 1973;Stanley ez" at., 1976;Trippet al, 1978;Razo et at., 1980).…”

Section: The Electrical Methodsmentioning

confidence: 99%

Electromagnetic studies in geothermal regions

Berktold¹

1983

Geophysical Surveys

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Abstract. During the past 25 yr, nearly all available electromagnetic and geoelectric techniques have been tested for their usefulness in geothermal exploration and exploitation. Dipole-dipole profiling, audiomagnetotellurics and controlled source electromagnetic methods are examples of those which have proven to be rather efficient for geothermal exploration. From the hundreds of field surveys which have been performed in many geothermal regions of the world, a large variety of geothermal regions and local geothermal systems, with different geological, hydrological and heat transfer characteristics, has been found to exist. Depending on the combination of these different characteristics each geothermal region or system presents a new problem which may need a different field technique or group of field techniques for optimal exploration. Despite these problems, new geothermal regions have been detected and structures and processes in geothermal systems are now much better understood. For example, advances have been made in the study of (a) the characteristics of porous/permeable hot water/vapor reservoirs and of fractioned zones for hot water/vapor circulation and production (b) the distribution and movement of cold meteoric and of hot water (c) the thermal insulation of reservoirs by cap-rocks (d) convective and/or conductive heat transfer and (e) the thermal influence of magma intrusions to high crustal levels.New exploration techniques, data analysis procedures and model calculations have been developed in the course of research in geothermal areas. They include the controlled source electromagnetic methods, the remote reference field technique and the development of better and faster algorithms for direct and inverse model calculations. Problems for the future are (a) the development and improvement of equipment and field techniques for more precise delineation and resolution of the conductivity distribution in geothermal areas especially those with productive zones of high porosity/permeability and fracturing, (b) the improvement of computerised data analysis in the field to optimise progress during the field measurements and (c) the development of more efficient interpretation procedures for the rather inhomogeneous conductivity distribution which exists in most geothermal areas.

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Section: The Electrical Methodsmentioning

confidence: 99%

Electromagnetic studies in geothermal regions

Berktold¹

1983

Geophysical Surveys

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“…Shallow-penetration electrical resistivity mapping has been used extensively in the TVZ for locating and delineating the high-temperature geothermal fields (e.g., Hatherton et al 1966;Risk 1983), which are characterised by distinctive low-resistivity signatures. during the early geothermal investigations, direct current resistivity measurements were made at more than 12 000 sites covering most of the TVZ.…”

Section: Electrical Resistivity Surveysmentioning

confidence: 99%

Resistivity structure of western Taupo Volcanic Zone, New Zealand

Bibby

Risk

Caldwell

et al. 2008

New Zealand Journal of Geology and Geophysics

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data from two deep-penetration electrical resistivity surveys crossing the western margin of the Taupo Volcanic Zone (TVZ) near Tihoi, northwest of lake Taupo, North island, New Zealand, have been used to identify the elements of the margin. in this vicinity the volcanologically defined boundary of the TVZ includes the andesitic cones of Pureora and Titiraupenga. The faulted margin of the TVZ lies east of these cones and is marked in the resistivity data by a dipping interface (faulted margin) between the resistive greywacke rocks to the west and the relatively conductive volcanic rocks that fill the upper few kilometres of the TVZ. The resistivity and gravity signatures of the margin are coincident in this vicinity. To the immediate east of the margin is a low-resistivity zone c. 10 km wide and 2.5 km deep. The low-resistivity material within this region is identified as old (>1 Ma) volcaniclastics that contain clays produced by low-temperature alteration and devitrification. This material is reversely magnetised. we suggest that this zone was formed following the onset of active extension of the TVZ and has since remained relatively undisturbed while the focus of volcanism and deformation has moved to the east. The eastern boundary of this low-resistivity zone coincides with the western edge of the whakamaru caldera (the boundary of the "young TVZ"). although the resistivity data can be matched using an interface with a dip to either the east or west, an eastward dip would be consistent with the boundary having been formed during the collapse associated with the formation of the whakamaru caldera. The resistivity signature within the whakamaru caldera is consistent with >2 km thickness of younger, more resistive volcanic sequences, suggesting the low-resistivity layers found to the west have been disrupted and downfaulted to be replaced with young, resistive caldera infill.

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“…Different techniques are available for detecting faults at depth in geothermal fields, including geological, gravity, magnetic, electromagnetic, and seismic surveys (Hatherton et al, 1966). Seismic methods are excellent tools for detecting faults because it could effectively map the locations and extension of buried faults both laterally and vertically.…”

Section: Introductionmentioning

confidence: 99%

Directly imaging steeply-dipping fault zones in geothermal fields with multicomponent seismic data

Chen

Huang

2015

Geothermics

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For characterizing geothermal systems, it is important to have clear images of steeply-dipping fault zones because they may confine the boundaries of geothermal reservoirs and influence hydrothermal flow. Elastic reverse-time migration (ERTM) is the most promising tool for subsurface imaging with multicomponent seismic data. However, conventional ERTM usually generates significant artifacts caused by the cross correlation of undesired wavefields and the polarity reversal of shear waves. In addition, it is difficult for conventional ERTM to directly image steeply-dipping fault zones. We develop a new ERTM imaging method in this paper to reduce these artifacts and directly image steeply-dipping fault zones. In our new ERTM method, forward-propagated source wavefields and backwardpropagated receiver wavefields are decomposed into compressional (P) and shear (S) components. Each component of these wavefields is separated into left-and right-going, or downgoing and upgoing waves. The cross correlation imaging

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Geophysical methods in geothermal prospecting in New Zealand

Cited by 35 publications

References 2 publications

Electromagnetic studies in geothermal regions

Electromagnetic studies in geothermal regions

Resistivity structure of western Taupo Volcanic Zone, New Zealand

Directly imaging steeply-dipping fault zones in geothermal fields with multicomponent seismic data

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