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The formation resistivity is a key parameter for determining the hydrocarbon saturation. Electricity can pass through a conductive formation due to water containing such training.

Conventional electrical records
In the first 25 years of using well logs, the only records available were resistivity soundings conventional electric. Were carried out thousands of them each year throughout the world. Since then, we have developed methods for measuring resistivity more sophisticated in order to measure the resistivity of the area rinsed, Rxo and resistivity area real virgin, Rt
The conventional electric log is to measure the resistivity of the formation, thus providing a very important tool for the geologist, geophysics, petrophysics, petroleum engineering and drilling, as it allows to identify forward-looking and other areas.

In general, the profile contains four power curves:

Short normal (SN) of 16 ", this measures the resistivity of the area rinsed (Rxo), ie the area that was invaded by mud filtrate.

Long Normal (NL) 64, it measured the resistivity in the virgin resistivity (Rt).

Side (18 '- 8 ") is used to measure the true resistivity of the formation when it is not possible to obtain a precise value of the long normal curve.

Spontaneous potential (SP) is a record of the potential difference between the electric potential of an electrode moving in the shaft and the electric potential of electrode fixed on the surface as a function of depth.
Across from shales, the SP curve usually defines a more or less straight line in the registry, which is called baseline shales.
Opposite permeable formations, the line shows deflections with respect to the baseline of shales in the thick layers of these deflections tend to reach an essentially constant deflection, thus defining a line of sand.
This spontaneous potential curve is useful because it allows the detection of permeable layers, matching layers, determine the resistivity of formation water and a rough estimate of the clay content.

Principle of operation of the electrical profiles
Introducing currents into the formation through current electrodes and measuring voltage between the electrodes measured. These voltages provide the resistivity of each device.

Sludge should be used conductive water-based muds or oil emulsion.

In general, the larger the spacing between the electrodes, the greater the research within the formation. Thus, the lateral curve of 18 feet 8 inches, has a greater depth of research and 16 short normal ", the most cursory fashion.