A new look at I.P. electrode arrays

Abstract

Over the past several years little attention has been paid to the electrode arrays used in induced polarisation (IP) surveys. However, arrays are very important in relation to anomaly detection and interpretation and to survey cost. Currently popular arrays are gradient and dipole?dipole. Other arrays are used for resistivity surveying, but generally suffer more inductive coupling. Some new arrays have been investigated in order to look at: the advantages of current or potential dipoles parallel to strike; the virtues of broadside arrays; minimisation of inductive coupling; and a possible reduction in survey costs. A perpendicular dipole?dipole array can reduce inductive coupling with horizontal layers and give an IP anomaly similar to that from a collinear array, if run across strike with both dipoles oblique to strike. Rather different, crossover type, responses are obtained with an L-array, in which one dipole is parallel to the strike of a target zone. This arrangement may locate the target more clearly. A broadside parallel dipole?dipole array can take advantage of the common strike elongation of a target deposit, and relative to a collinear array run across strike, can provide improved resolution, dip information, and efficiency in reconnaissance. Some of the features and benefits of various arrays are demonstrated by modelling results. With further work, including development of interpretation methods, attempts can be made to optimize array geometry for a specific exploration scenario.