Electromagnetic sounding of geothermal zones

Spichak, Viacheslav V.; Manzella, Adele

doi:10.1016/j.jappgeo.2008.05.007

Cited by 130 publications

(61 citation statements)

References 64 publications

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“…3. development of conductive minerals. All of these can be indicative of modern or past geothermal fluid circulation (Newman et al, 2008;Spichak and Manzella, 2009;Wannamaker et al, 2007Wannamaker et al, , 2006. Magnetotelluric methods in particular are commonly used at the geothermal field-scale in order to identify conductive zones and locate and characterize geothermal fluid flow conduits and conductive clay caps (e.g., Bertrand et al, 2012;Cumming and Mackie, 2007;Uchida and Sasaki, 2006;Wannamaker et al, 2013aWannamaker et al, , 2011Wannamaker et al, , 2008Wannamaker et al, , 2007Wannamaker et al, , 2006.…”

Section: Crustal Conductivity Datamentioning

confidence: 99%

Regional crustal-scale structures as conduits for deep geothermal upflow

Siler

Kennedy

2016

Geothermics

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a b s t r a c tGeothermal fluids produced from two of the largest production geothermal fields in the Great Basin have helium isotope ratios that are anomalously high relative to basin-wide trends. These data indicate that the geothermal systems, Dixie Valley, Nevada and McGinness Hills, Nevada have an anomalously high fraction of mantle derived fluid. These connections to deeply derived fluid and heat may supplement crustal heat production and be responsible, in part, for the anomalously high production capacity, relative to other Great Basin geothermal fields, that Dixie Valley and McGinness Hills support. Deep-seated crustal structures across the Great Basin and around the world are known to be associated with structural reactivation, can have relatively high permeability, and can act as fluid flow conduits. These deep seated structures across the Great Basin control upflow of deeply derived heat and fluids into the shallow geothermal systems at Dixie Valley and McGinness Hills, contributing to their productivity.

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Section: Crustal Conductivity Datamentioning

confidence: 99%

Regional crustal-scale structures as conduits for deep geothermal upflow

Siler

Kennedy

2016

Geothermics

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“…2 (Spichak andManzella 2009, Zhang, et al 1994). However, these petrological properties are not always directly related as conductivity and permeability of a formation increase or decrease differently with temperature, pressure and depth (Spichak and Manzella 2009).…”

Section: Methodsmentioning

confidence: 99%

Magnetotelluric monitoring of hydraulic fracture stimulation at the Habanero Enhanced Geothermal System, Cooper Basin, South Australia

Didana

Thiel²,

Heinson

et al. 2016

ASEG Extended Abstracts

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SUMMARYMagnetotelluric (MT) data were collected across the Habanero Enhanced Geothermal System project in the Cooper Basin, South Australia. A baseline regional MT survey consisting of two profiles was collected to delineate the pre-injection resistivity structure. Two dimensional inversions of the MT data reveal three main resistivity structures to a depth of 5 km. The low resistivity surface layer (about 1.5 km thick) is interpreted as poorly consolidated sediments of Lake Eyre and Eromanga Basins. Below the conductive layer, a zone with relatively high resistivity with thickness of 2 km can be correlated to consolidated Cooper Basin sediments. A high resistivity zone below depths of 3.5 km is interpreted as the hot intrusive granodiorite (granite) of the Big Lake Suite with low porosity and permeability. This deep structure is also related to the Habanero EGS reservoir. The second MT survey was conducted during stimulation of Habanero-4 well by Geodynamics Ltd, where 36.5 ML of water with a resistivity of 13 Ωm (at 25°C) was injected at a relatively continuous rate of between 27-53 L/s over 14 days at a depth of almost 4 km. Analysis of pre-and post-injection residual phase tensors for periods greater than 10 s indicate conductive fractures oriented in a N/NNE direction. Apparent resistivity maps also revealed that injected fluids possibly propagated towards N/NNE direction. This result is in agreement with the micro-seismic events with an area of 4 km 2 observed during fluid injection, as well as orientation of pre-existing N-S striking sub-horizontal fractures susceptible to slip due to stimulation. The MT responses close to injection show on average 5% decrease in apparent resistivity at periods greater than 10 s. The main reasons for observing subtle changes in resistivity at Habanero EGS is the screening effect of the conductive thick sedimentary cover (about 3.6 km thick) and the presence of preexisting saline fluids with resistivity of 0.1 Ωm (equivalent to salinity of 16.1 g/L at 240°C) in the natural fractures. Overall, the MT monitoring at Habanero EGS highlights the need for favourable geological settings to measure significant changes in resistivity in EGS reservoirs.

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“…Many references in the literature are concerned with the relationship between resistivity and rock temperature [7,28,30,32,33]. To map a temperature distribution based on MT and AMT results is problematic because too many factors can influence the electrical properties of rocks [30].…”

Section: The Geothermal Reservoirmentioning

confidence: 99%

Mapping the Geothermal System Using AMT and MT in the Mapamyum (QP) Field, Lake Manasarovar, Southwestern Tibet

Chen

Dorji

et al. 2016

Energies

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Southwestern Tibet plays a crucial role in the protection of the ecological environment and biodiversity of Southern Asia but lacks energy in terms of both power and fuel. The widely distributed geothermal resources in this region could be considered as potential alternative sources of power and heat. However, most of the known geothermal fields in Southwestern Tibet are poorly prospected and currently almost no geothermal energy is exploited. Here we present a case study mapping the Mapamyum (QP) geothermal field of Southwestern Tibet using audio magnetotellurics (AMT) and magnetotellurics (MT) methods. AMT in the frequency range 11.5-11,500 Hz was used to map the upper part of this geothermal reservoir to a depth of 1000 m, and MT in the frequency range 0.001-320 Hz was used to map the heat source, thermal fluid path, and lower part of the geothermal reservoir to a depth greater than 1000 m. Data from 1300 MT and 680 AMT stations were acquired around the geothermal field. Bostick conversion with electromagnetic array profiling (EMAP) filtering and nonlinear conjugate gradient inversion (NLCGI) was used for data inversion. The AMT and MT results presented here elucidate the geoelectric structure of the QP geothermal field, and provide a background for understanding the reservoir, the thermal fluid path, and the heat source of the geothermal system. We identified a low resistivity anomaly characterized by resistivity in the range of 1-8 Ω·m at a depth greater than 7 km. This feature was interpreted as a potential reflection of the partially melted magma in the upper crust, which might correlate to mantle upwelling along the Karakorum fault. It is likely that the magma is the heat source of the QP geothermal system, and potentially provides new geophysical evidence to understand the occurrence of the partially melted magmas in the upper crust in Southwestern Tibet.

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Electromagnetic sounding of geothermal zones

Cited by 130 publications

References 64 publications

Regional crustal-scale structures as conduits for deep geothermal upflow

Regional crustal-scale structures as conduits for deep geothermal upflow

Magnetotelluric monitoring of hydraulic fracture stimulation at the Habanero Enhanced Geothermal System, Cooper Basin, South Australia

Mapping the Geothermal System Using AMT and MT in the Mapamyum (QP) Field, Lake Manasarovar, Southwestern Tibet

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