Analysis of the bipole--dipole resistivity method for geothermal exploration

Technical Report · Wed Jun 01 04:00:00 EDT 1977

DOI:https://doi.org/10.2172/7280170· OSTI ID:7280170

Dey, A

Bipole-dipole (B-D) resistivity mapping has been widely used as a reconnaissance method in geothermal exploration. In this technique, apparent resistivities are plotted at roving dipole receiver locations and the current source (bipole) is left fixed. Interpretation to date has been in terms of simple layered, dike, vertical contact, or sphere models. In the case of more complicated two-dimensional models the interpretation is much more ambiguous and the detection of buried conductors depends very much on the choice of transmitter location. Since apparent resistivities taken on a line collinear with the bipole are roughly equivalent to the apparent resistivities for one sounding in a dipole-dipole (D-D) pseudo-section, the two methods have been compared for several two-dimensional models. A buried quarter space and a buried horizontal block of rectangular cross section, with or without an overburden layer, have been used in the comparison. Unless the target is very shallow or close to the bipole or dipole, the resolution of the horizontal position or depth extent for the B-D method is very poor. A further experiment of calculating a residual map by subtracting the half-space or layered half-space response from the response of the buried models was also unsuccessful in improving the interpretability of the B-D method. Finally, a model representative of a typical Basin-and-Range valley with and without a hypothesized geothermal reservoir shows that in more complex models the B-D map would not, in a practical survey, reveal the reservoir. From these model studies it is clear that, except for some simple geologic situations, the B-D method is not effective for subsurface mapping. Selected D-D lines would be far more useful and more cost effective.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7280170
• Report Number(s): LBL-6332
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys
CONFIGURATION
COST
EFFICIENCY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRICAL SURVEYS
EXPLORATION
GEOPHYSICAL SURVEYS
GEOTHERMAL EXPLORATION
Geothermal Legacy
MAPS
MATHEMATICAL MODELS
MEASURING METHODS
PHYSICAL PROPERTIES
RESOLUTION
SHAPE