# RESISTIVITY LOGS

Logs are induced. The resistivity is the ability of rocks to oppose the passage of electric current induced and is the inverse of conductivity.

The resistivity depends on the salt dissolved in the fluids in the pores of the rocks. Provides evidence of fluid content in rocks. If the pores of a formation containing salt water present high conductivity and thus the resistivity will be low, but if oil or gas filled with low conductivity and therefore the resistivity is high. Compact slightly porous rocks such as massive limestones have high resistivities.

There are two main types of resistivity profiles: Side Profile (Laterolog) and the Profile of Induction (Induction Log). The side profile is used in conductive mud (mud salty) and the profile of induction is used in resistive sludge (fresh or oil-based mud).

Within Induction Resistivity Profiles are:

a) SFL = Spherical Induction Log. For shallow depths (0.5 – 1.5 ‘). The resistivity log measures the resistivity of the washing area (Rxo).
b) MIL = LIM = Medium Induction Log. For medium distances (1.5 – 3.0 ‘)
c) DIL = ILD = Deep Induction Log. For depths greater than 3.0. » The resistivity log measures the formation resistivity (Rt).

Within the Lateral Resistivity logs are:

a) MSFL = Microspheric Laterolog. For nearby (1.0 and 6.0»). Read the resistivity of the washing area (Rxo).
b) MLL = LLM = Micro Laterolog. For nearby (1.0 and 6.0»)
c) SLL = LLS = Someric Laterolog. For shallow depths (0.5 and 1.5 ‘)
d) DLL = LLD = Deep Laterolog. For depths greater than 3.0. » Measure formation resistivity (Rt).

Read from left to right, on a logarithmic scale. The unit of measurement for profiles of resistivity is the ohm-m with a range of values ranging from 0.2 to 2000 ohm-m.

Resistivity logs are used to estimate oil-water contacts, to calculate the formation water resistivity (Rw) and training erdadera resistivity (Rt). Read from left to right.