Geothermal Exploration

ÍSOR provides a range of geochemical and geophysical exploration services for the geothermal energy sector.

Geochemical geochemical and geoophysical exploration plays a very important role in geothermal exploration. Chemical composition of geothermal steam and water from natural manifestations provides initial constraints on reservoir temperature and production properties of the geothermal fluid. As part of geophysical exploration, various physical parameters are measured, such as resistivity, density, sound velocity and magnetism of the subsurface rocks.

Geochemical exploration

Geochemical exploration surveys, as carried out by Iceland GeoSurvey, yield important information about the temperature of the geothermal reservoir. Temperature sensitive equilibria between the geothermal waters and secondary minerals in the reservoir control the composition of the geothermal steam and water accessible in geothermal manifestations on the surface.

Chemical composition of geothermal steam and water also provides initial information about production properties with respect to scaling and corrosion problems as well as potential environmental concerns related to utilization of the reservoir fluids. Conservative components in geothermal steam and water and stable isotopes provide valuable information about the origin of the geothermal solutions.

Soil gas studies may provide important information about fluid pathways to the surface and can be used to identify feasible drilling targets.

A joint interpretation of all geoscientific data (geochemical, geological, and geophysical) is a crucial last stage in geothermal exploration.

Iceland GeoSurvey offers the following geochemical services for geothermal exploration:

• Specialized collection of samples of geothermal steam and water – Many components in geothermal steam and water are sensitive and need special preservation treatments upon sampling.
• Analytical services – Iceland GeoSurvey has a fully equipped geochemical laboratory for analysis of all relevant major and trace components of geothermal solutions as well as stable isotopes of hydrogen and oxygen in water and steam. Some sensitive components are analyzed in situ during sampling.
• Diffuse soil degassing surveys – Iceland GeoSurvey has extensive experience in measurements of diffuse soil degassing in geothermal fields for exploration and environmental monitoring purposes.
• Hydrogeological studies and chemical surveys of natural surface waters in geothermal fields – Provide important information about recharge of the geothermal system as well as valuable data for defining environmental baseline for geothermal projects.

Geophysical exploration

Resistivity surveys, as carried out by Iceland GeoSurvey, yield important information on physical properties of geothermal systems. Temperature-dependent assemblies of secondary minerals are formed by water-rock interaction (alteration) in the geothermal systems resulting in a very distinctive resistivity structure that can be used to map the size and shape of the reservoirs.

Monitoring and locating micro earthquakes gives information on fault movements and permeability as well as heat mining from heat sources and tomography inversion give information on sound veloc- ity anomalies. Gravity surveys can give information on density variations such as dense intrusions. Magnetic measurements can be used to locate dikes and give information on demagnetization due to alteration.

A joint interpretation of complementary data (geophysical, geological and geochemical) is the crucial last stage in geothermal exploration.

Iceland GeoSurvey offers the following geophysical services for geothermal exploration and other applications:

• Resistivity surveying – Transient ElectroMagnetic (TEM) and MagnetoTelluric (MT) soundings. State of the art processing and interpretation of data including joint 1D inversion of TEM and MT for static shift correction of MT, 2D and 3D inversion. DC resistivity (Schlumberger soundings and head-on profiling).
• Micro seismicity – Setting up and operating local seismic networks, both permanent and temporal. Analyses of passive seismic data for determining hypocentres, magnitudes, focal mechanisms and tomography inversion.
• Gravity and geodetic surveying – Gravity surveys both for rock density studies (Bouguer) and high precision micro gravity surveys for reservoir monitoring. High precision differential GPS and GNS surveying along with gravity surveying and for monitoring crustal movements. State of the art data processing and interpretation.
• Magnetic surveying – Total magnetic field surveys on surface.
• Active seismic methods in engineering geology – Both seismic refraction and seismic reflection surveys for structural and engineering purposes with explosive or airgun energy sources. State of the art 2D data processing and interpretation.