Supri Soengkono

• PhD
• Senior Geothermal Geophysicist at GNS Science, New Zealand, Wairakei

The total force magnetic anomaly (termed in this chapter as ∆F) is defined by algebraic (scalar) subtraction of |Bo| (the strength “undisturbed” earth’s magnetic field) from |Bobs|, that is: ∆F = |Bobs|-|Bo|. As |Bo| cannot (are not) directly measured, the value |Bo| it is usually taken from computation of the IGRF (see Section 2). The ∆F computed...

Gravity, ground magnetics, DC resistivity traversing, and time domain electromagnetic soundings (fixed-loop and in-loop) were conducted to investigate the Okauia Low Temperature Geothermal System near the eastern boundary of the Hauraki Depression in North Island of New Zealand. The gravity study revealed a hidden extension of the Tertiary-age Wait...

Shallow warm water resources associated with low enthalpy geothermal systems are often difficult to explore using geophysical techniques, mainly because the warm water creates an insufficient physical change from the host rocks to be easily detectable. In addition, often the system also has a limited or narrow size. However, appropriate use of geop...

Contact Energy Ltd (Contact) undertook a magnetotelluric (MT) survey at the Wairakei-Tauhara geothermal system during early 2010. This study presents MT interpretations for the Wairakei system. Both one-dimensional (1D) and three-dimensional (3D) MT models were developed to maximize confidence in MT data interpretations. While the 3D model is usefu...

Geophysical studies of the Wairakei sector of the Wairakei–Tauhara geothermal system started shortly after exploration drilling began in the early 1950s. These investigations have made a major contribution in defining the boundary of geothermal systems and understanding the changes that have occurred in the reservoir as a result of fluid production...

In New Zealand, the search for hot water resources at shallow depths for the purposes of direct heating applications has a long history. Geophysical methods, particularly resistivity, are frequently called upon to provide a robust exploration target for drill hole siting (often in conjunction with less scientifically robust methods such as water di...

Distinct magnetic total force anomalies are associated with many, but not all, liquid-dominated geothermal reservoirs in the Taupo Volcanic Zone, which stand in thick, young (<0.7 Ma) volcanic host rocks. The anomalies are caused by demagnetised rocks (a result of hydrothermal alteration) in the upper 0.5–1 km section of the reservoirs; the phenome...

The central Taupo Volcanic Zone (TVZ) is a region of intense Quaternary rhyolitic volcanism and geothermal activity in the North Island of New Zealand from which about 14,000 km3 of pyroclastics and lavas have been erupted during the last 1.6 Ma. Analysis of aeromagnetic surveys over the TVZ showed the presence of long-wavelength (10 to 25 km) magn...

The extent of thermally altered rocks in high temperature geothermal reservoirs hosted by young volcanic rocks can be assessed from magnetic surveys. Magnetic anomalies associated with many geothermal field in New Zealand and Indonesia can be interpreted in terms of thick (up to 1 km) demagnetized reservoir rocks. Demagnetization of these rocks has...

The Orakeikorako geothermal field was covered by two aeromagneticsurveys which were conducted at different altitudes (760 m and 60 m above the ground). Interpretation of the residual magnetic anomalies from both surveys has shown that hydrothermally demagnetised rocks inside the Orakeikorako reservoir to about 0.6 below sea level. The residual anom...

An open access copy of this article is available from the publishers website. Negative residual anomalies are widespread. Paleomagnetic study of eight rhyolitic ignimbrite units and two lava flows which are exposed in this area, together with new K-Ar dates of four of the ignimbritic units, indicate that the two lava units and seven of the ignimbri...

The Taupo Volcanic Zone (TVZ, New Zealand) is a NE-SW fault controlled volcano-tectonic depression, about 350 km long and 60 km wide, infilled by Quaternary volcano-sedimentary rocks with underlying faulted Mesozoic greywacke basement. The depth of the basement is constrained by drillholes in several geothermal fields, including at Ohaaki, Kawerau,...

-The Reporoa geothermal field is located in an area of the Taupo Volcanic Zone (TVZ) which exhibits a complex magnetic source pattern since hydrothermally demagnetised rocks occur together with younger normally magnetised and older reversely magnetised volcanic rocks. No distinct negative residual magnetic anomalies could be observed over the centr...