Electrical conductivity and P-wave velocity in rock samples from high-temperature Icelandic geothermal fields

Kristinsdottir, Liney Halla; Flóvenz, Ólafur G.; Árnason, Knútur; Bruhn, David; Milsch, Harald; Spangenberg, Erik; Kulenkampff, Johannes

doi:10.1016/j.geothermics.2009.12.001

Cited by 59 publications

(40 citation statements)

References 17 publications

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“…Emerging from the SW edge of the hypocenter swarm, there is a low V p anomaly also extending SW to the coast in the direction of HWP. V P has been shown to decrease by roughly 10% when rock samples from high-temperature geothermal fields are heated from 50 C to 250 C [Kristinsdóttir et al, 2010]. When viewed in relation to the MT and EQ results, the V p anomaly in the SW is consistent with a hightemperature geothermal reservoir.…”

Section: Discussionmentioning

confidence: 79%

“…[20] The temperature-dependent V p measurements of Kristinsdóttir et al [2010] should be applicable to Montserrat since these rocks contain hydrothermally altered minerals, such as smectite, chlorite, and epidote, which we would expect to be present in the Montserrat system. However, V p variations may also be due to variation in porosity as well as degree of alteration [Han et al, 1986;Johnston and Christensen, 1997].…”

Section: Discussionmentioning

confidence: 99%

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Montserrat geothermal system: A 3D conceptual model

Ryan

Peacock

Shalev

et al. 2013

Geophysical Research Letters

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[1] We constructed a three-dimensional conceptual model of a geothermal system on the Caribbean island of Montserrat. The model was generated using magnetotelluric resistivity data, earthquake hypocenter data, and a three-dimensional P wave velocity model, all plotted using a shared geographical reference. The results of the study suggest a high-temperature fracture-controlled geothermal system at the intersection of two faults in the SW of the island. We also present a "prospectivity index" map that represents a proxy of the spatial variation in harvestable heat flux at 1500 m depth. The index is the product of relative permeability around modeled faults and a proxy for the subsurface temperature calculated using P wave velocity anomalies. Citation: Ryan, G. A., J. R. Peacock, E. Shalev, and J. Rugis (2013), Montserrat geothermal system: A 3D conceptual model, Geophys.

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Section: Discussionmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Montserrat geothermal system: A 3D conceptual model

Ryan

Peacock

Shalev

et al. 2013

Geophysical Research Letters

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“…Hydrothermal alteration can drastically change the elastic wave velocities and permeabilities of rock in both the natural and laboratory environment (Jaya et al 2010;Kristinsdóttir et al 2010;Pola et al 2014). However, coupled studies of physical properties such as porosity, permeability, and strength on geothermal reservoir rocks have not been extensively presented.…”

Section: Previous Studies Of Relevancementioning

confidence: 99%

Physical property relationships of the Rotokawa Andesite, a significant geothermal reservoir rock in the Taupo Volcanic Zone, New Zealand

et al. 2014

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Background: Geothermal systems are commonly hosted in highly altered and fractured rock. As a result, the relationships between physical properties such as strength and permeability can be complex. Understanding such properties can assist in the optimal utilization of geothermal reservoirs. To resolve this issue, detailed laboratory studies on core samples from active geothermal reservoirs are required. This study details the results of the physical property investigations on Rotokawa Andesite which hosts a significant geothermal reservoir. Methods:We have characterized the microstructure (microfracture density), porosity, density, permeability, elastic wave velocities, and strength of core from the high-enthalpy Rotokawa Andesite geothermal reservoir under controlled laboratory conditions. We have built empirical relationships from our observations and also used a classical micromechanical model for brittle failure. Further, we compare our results to a Kozeny-Carman permeability model to better constrain the fluid flow behavior of the rocks. Results: We show that the strength, porosity, elastic moduli, and permeability are greatly influenced by pre-existing fracture occurrence within the andesite. Increasing porosity (or microfracture density) correlates well to a decreasing uniaxial compressive strength, increasing permeability, and a decreasing compressional wave velocity. Conclusions:Our results indicate that properties readily measurable by borehole geophysical logging (such as porosity and acoustic velocities) can be used to constrain more complex and pertinent properties such as strength and permeability. The relationships that we have provided can then be applied to further understand processes in the Rotokawa reservoir and other reservoirs worldwide.Keywords: Geothermal; Uniaxial compressive strength; Permeability; Physical properties; Elastic modulus; Microstructure BackgroundFractures on multiple scales are the dominant control on fluid flow in most geothermal systems worldwide. Geothermal environments are prone to variable heat fluxes, dynamic fluid flow regimes, and active tectonics which impact the physical and mechanical properties of the reservoir rocks in which they are hosted. The influence of such a dynamic environment can render the host rocks highly altered, fractured, and microstructurally complex. As a result, the empirical correlation of physical properties to

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“…In addition to rock physics models to relate resistivity or seismic velocity to parameters like porosity or temperature, this approach also requires empirical support for these relationships (e.g. Kristinsdóttir et al, 2010;Jaya et al, 2010). The second approach is to use suitable data to empirically fit a direct relationship between rock properties, such as between seismic velocity and electrical resistivity using the Faust equation for consolidated sandstones (Faust, 1953).…”

Section: Integration Of Velocity and Resistivity Modelsmentioning

confidence: 99%

“…Ussher et al, 2000) and complement seismic methods. Árnason et al (2010), Kristinsdóttir et al (2010) and have shown that, at temperature below 350°C, resistivity (and P-wave velocity) in Icelandic fields have dependencies comparable to the rest of the world's geothermal fields (e.g. Newman et al, 2008).…”

Section: Introductionmentioning

confidence: 99%