How do you calculate the depth of penetration in a Schlumberger array?

Asked by: Amber Candelaria

How does Schlumberger array work?

The Schlumberger array is an array where four electrodes are placed in line around a common midpoint. The two outer electrodes, A and B, are current electrodes, and the two inner electrodes, M and N, are potential electrodes placed close together.

What is the difference between Schlumberger and Wenner array?

Schlumberger is the best method used for vertical electrical sounding for practical reasons. It is less labor-intensive than the Wenner array (see below) because you only need to move the two transmitting electrodes for each new reading, whereas the Wenner requires moving all four electrodes for each new measurement.

Which electrical resistivity array has maximum depth of penetration?

Both Pole-dipole and Dipole-dipole have the highest penetration depths of 34.9 m, followed by Schlumberger and Wenner-gamma arrays with a depth of 30.9 m.

What is the geometric factor for Schlumberger array?

The geometric factor for the three main electrode configurations are: dipole—dipole, K _g = πn(n + 1)(n + 2)p; Schlumberger, K _g = (πp ²/q)(1 − q ²/4p ²); Wenner, K _g = 2πp, where p and q are defined for each case.

How do you calculate apparent resistivity in Schlumberger?

ρ = Δ V I G . ρ a = Δ V I G . We refer to as the apparent resistivity and it is understood to be the resistivity of a halfspace which produces the observed potential measured by a particular electrode geometry.

Does resistivity increase with depth?

The laboratory and field survey studies of rock electrical properties show that both the dielectric constant and soil resistivity increases with depth and density.

What is Wenner method?

Wenner Method



The Wenner alpha four-pin method is the most commonly used technique for soil resistivity measurements. It is performed by placing four pins at equal distance, injecting a known current on the outermost electrodes and recording the voltage between the interior electrodes.

How do you calculate soil resistivity?

That resistance value R can then be converted into a soil resistivity value with the formula: ρ=2×π×a×R where “ρ” is measured in ohm-cm and “a” is the spacing of the pins in cm.

How do you interpret resistivity data for groundwater?

The groundwater potential zone covered by high to very high resistivity value. Those high resistivity value 200 – 1000 Ωm interpreted as dry top soil at near surface while at deep zone is interpreted as fresh bedrock. Chargeability value of groundwater potential area ranging from 0 up to 8 msec.

What is resistivity Pseudosection?

A resistivity pseudosection is a combination of these two. techniques: A pseudosection determines how resistivity changes with both position down a line and also with. depth. As the separation between the grounding electrodes of the resistivity equipment increases, electrical.

What is 2D resistivity survey?

Unlike VES, a 2D survey allows the user to get a visual image of a slice of the earth, not unlike an X-ray of the human body. This makes 2D resistivity surveys ideal for cave and void detection, environmental spill mapping, mineral exploration, and many other endeavors.

What is resistivity formula?

See all related content → Resistivity, commonly symbolized by the Greek letter rho, ρ, is quantitatively equal to the resistance R of a specimen such as a wire, multiplied by its cross-sectional area A, and divided by its length l; ρ = RA/l. The unit of resistance is the ohm.

What is half Schlumberger?

Half Schlumberger array is a kind of Pole-dipole array, a voltage-measuring pair of grounded potential electrodes separated successively from one current electrode (pole) while traversing a survey line.

What is the apparent resistivity?

Apparent resistivity is defined as the resistivity of an electrically homogeneous and isotropic half-space that would yield the measured relationship between the applied current and the potential difference for a particular arrangement and spacing of electrodes.

What is Schlumberger method?

The Schlumberger method was developed to increase the voltage signal for the earlier, less sensitive instruments, by placing the potential probes closer to the current probes. The soil resistivity measurements will be affected by existing nearby grounded electrodes.

How does vertical electrical sounding work?

Vertical electrical sounding (VES) is a geophysical method for investigation of a geological medium. The method is based on the estimation of the electrical conductivity or resistivity of the medium.

What is Schlumberger configuration?

Schlumberger is a configuration that has a larger electrode current than the potential electrode spacing. The arrangement of the Schlumberger array can be seen in Figure 2.

What is Wenner array?

What is the Wenner array? The Wenner electrode array is the simplest of arrays; in it, the four electrodes—A, M, N, and B—are placed in line and spaced equidistant from each other. The two outer electrodes, A and B, are current electrodes, and the two inner electrodes, M and N, are potential electrodes.

What is half Schlumberger?

Half Schlumberger array is a kind of Pole-dipole array, a voltage-measuring pair of grounded potential electrodes separated successively from one current electrode (pole) while traversing a survey line.

How do you calculate soil resistivity?

That resistance value R can then be converted into a soil resistivity value with the formula: ρ=2×π×a×R where “ρ” is measured in ohm-cm and “a” is the spacing of the pins in cm.