Electrode arrays are different arrangements of electrodes used to perform geophysical resistivity measurements. Electrode arrays were developed in order to make field measurements more efficient and data interpretation easier.

This is the second article in our series exploring 11 electrode arrays and methods. We’ve also covered the Wenner array. Today, we’re discussing the Schlumberger array.

Electrode arrays are different arrangements of electrodes used to perform geophysical resistivity measurements. Electrode arrays were developed in order to make field measurements more efficient and data interpretation easier. In this series, we’ll explore 11 electrode arrays. The first array we’ll discuss is the Wenner array.

Streaming-potential (SP) is an electrical surveying method used when fluids or electrolytes—typically water—move through porous areas in the ground. This creates a change in voltage that can be read using a voltmeter and two electrodes.

Before we dive into details, let’s start with a primer on three different terms that are abbreviated “SP.” In this article, we’ll be discussing self-potential, which is synonymous with spontaneous-potential. The self-potential method in geophysics refers to an electrical surveying method used for looking at electrical anomalies in the ground. It is primarily used in mineral exploration. Streaming-potential, on the other hand, is caused by a fluid —typically water with dissolved minerals (an electrolyte)—moving in the ground, which causes a change in voltage.

One-dimensional (1D) resistivity surveys are not ideal because they assume that the geological layers are horizontal and homogeneous—which is rarely the case. Two-dimensional (2D) resistivity surveys are an improvement but still an approximation, as they assume the geology continues infinitely in both directions perpendicular to the survey line.