Resistivity logging of fractured basalt

• Main Authors: Stefansson, V., Axelsson, G., Sigurdsson, O.
• Language: unknown
• Published: 2006
• Subjects: 15 GEOTHERMAL ENERGY; BASALT; RESISTIVITY LOGGING; FRACTURED RESERVOIRS; BOREHOLES; GEOTHERMAL SYSTEMS; ICELAND; MATHEMATICAL MODELS; POROSITY; CAVITIES; DEVELOPING COUNTRIES; ELECTRIC LOGGING; EUROPE; IGNEOUS ROCKS; ISLANDS; ROCKS; VOLCANIC ROCKS; WELL LOGGING; WESTERN EUROPE; Iceland
• Online Access: http://www.osti.gov/servlets/purl/7369540; https://www.osti.gov/biblio/7369540

A lumped double porosity model was studied in order to estimate the effect of fractures on resistivity - porosity relations. It is found that the relationship between resistivity and porosity for fractured rock is in general not simple and depends both on the amounts of matrix porosity as well as the fracture orientation. However, when fractures dominate over matrix porosity the exponent <m> is close to 1.0. Resistivity-porosity relations have been determined for large amounts of basaltic formations in Iceland. An exponent close to 1.0 is found in all cases investigated. This is interpreted as fractures constitute a considerable part of the porosity of the basalts. In the IRDP-hole in Eastern Iceland it is found that the ratio of fracture porosity to total porosity decreases with depth.