Total field resistivity mapping and sounding over horizontally layered media

Conference · Thu Jun 01 04:00:00 EDT 1978 · Geophysics; (United States)

OSTI ID:5839342

Zohdy, A A.R.

The bipole-dipole resistivity mapping method has been used extensively in reconnaissance surveys of geothermal areas. Although the method has been used primarily for delineating lateral changes in resistivity, it is shown that significant anomalies can be produced by horizontal layers. Formulas are derived for the calculation of five types of bipole-dipole apparent resistivities, and a distinction is made between what is defined as primary field, simple total field, and total field apparent resistivities. It is shown that, if the Schlumberger sounding curve for a given horizontally layered medium is known, then the magnitude and direction of the bipole electric field, as well as all types of bipole-dipole apparent resistivity maps, can be calculated by use of simple algebraic equations (without having to solve the boundary-value problem). Conversely, it is also shown that for each total electric field measurement, two Schlumberger apparent resistivities can be calculated easily, except along the polar axis of the current bipole. In addition, a useful formula is given for extending a symmetric Schlumberger sounding curve by use of measurements that are made with an asymmetric array. This method isillustrated by field examples. Theoretical examples of perpendicular, parallel, primary field, total field, and simple total field apparent resistivity maps (as well as Schlumberger AB profiles and rectangle of resistivity maps) are calculated for a four-layer earth model to illustrate the type of anomalies that can be obtained over layered media. The characteristic peanut shape of simple total field apparent resistivity maps, over horizontally layered media, is illustrated by four field examples from three different geothermal areas. The calculation of residual or percent-lateral-effect maps or profiles is recommended for the interpretation of all types of bipole-dipole apparent resistivity data, and is also illustrated by a field example. 18 figures.

• Research Organization: Geological Survey, Denver, CO
• OSTI ID: 5839342
• Conference Information: Journal Name: Geophysics; (United States) Journal Volume: 43:4
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys
58 GEOSCIENCES
580203 -- Geophysics-- Geophysical Survey Methods-- (1980-1989)
DATA ANALYSIS
EARTH CRUST
ELECTRIC CONDUCTIVITY
ELECTRIC FIELDS
ELECTRICAL PROPERTIES
ELECTRICAL SURVEYS
GEOPHYSICAL SURVEYS
GEOTHERMAL FIELDS
LAYERS
MAPS
PHYSICAL PROPERTIES
PROSPECTING