What is a laterolog

Laterolog resistivity tool injects electric currents into geological formations and records the potential drop across a specific length along the open hole well. Laterolog measurements are related to the electrical resistivity of the formation. Laterolog tools are reliable in boreholes drilled with water-based muds.

What is Guard log?

1. n. [Formation Evaluation] A measurement made by a type of electrode device in which the current flow and hence the measurement is focused in a disk that is concentric with and perpendicular to the sonde. The term usually refers to a Laterolog-3 device.

How does a resistivity tool work?

Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. … In these logs, resistivity is measured using four electrical probes to eliminate the resistance of the contact leads.

What is Laterlog?

(lat, ∂r ō’ log) A resistivity log generally used in salt muds, made with a sonde that is focused by use of guard or bucking electrodes which forced the ”surveying current” to flow nearly at right angles to the logging sonde. Also called guard log or focused log.

What is Dual Laterolog?

The Dual Laterolog (DLL) provides two resistivity measurements with different depths of investigation: deep (LLD) and shallow (LLS). … For the deep measurement, both measure and focusing currents return to a remote electrode on the surface at large distance.

What is an induction log?

PetroWiki. Induction logging was originally developed to measure formation resistivities in boreholes containing oil-based muds and in air-drilled boreholes because electrode devices could not work in these nonconductive boreholes.

What does Laterolog measure?

Laterolog resistivity tool injects electric currents into geological formations and records the potential drop across a specific length along the open hole well. Laterolog measurements are related to the electrical resistivity of the formation. Laterolog tools are reliable in boreholes drilled with water-based muds.

What is resistivity in drilling?

1. n. [Formation Evaluation] The ability of a material to resist electrical conduction. It is the inverse of conductivity and is measured in ohm-m.

Why is resistivity important?

The resistivity of materials is important as it enables the right materials to be used in the right places in electrical and electronic components. Materials used as conductors, for example in electrical and general connecting wire need to be able to have a low level of resistivity.

What are the types of resistivity logs?

Resistivity Logging. There are three main categories of well Logging: Electrical, Nuclear and Acoustic/Sonic.

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What do you mean by micro resistivity devices?

Microresistivity devices measure the resistivity of the flushed zone and delineate permeable beds by detecting the presence of mudcake.

What is flushed zone in well logging?

The volume close to the borehole wall in which all of the moveable fluids have been displaced by mud filtrate. The flushed zone contains filtrate and the remaining hydrocarbons, the percentage of the former being the flushed-zone water saturation, Sxo.

What does sonic log record?

The sonic or acoustic log measures the travel time of an elastic wave through the formation. This information can also be used to derive the velocity of elastic waves through the formation. Its main use is to provide information to support and calibrate seismic data and to derive the porosity of a formation.

What is the induction tool is used to measure?

The induction log actually measures conductivity, and hence is sometimes called the conductivity log. The modern tool for measuring resistivity in high salinity (low resistivity) muds is the laterolog, which focuses its current into a thin sheet to improve vertical resolution and penetration depth.

What is induction resistivity?

1. adj. [Formation Evaluation] Related to a wireline log of formation resistivity based on the principle of inducing alternating current loops in the formation and measuring the resultant signal in a receiver.

What is electric logging?

Electric logging consists of lowering a device used to measure the electric resistance of the rock layers in the downhole portion of the well. This is achieved by running an electric current through the rock formation and measuring the electrical resistance that the current encounters along its way.

What causes resistivity?

The resistivity of a material is dependent upon the material’s electronic structure and its temperature. For most (but not all) materials, resistivity increases with increasing temperature.

How do you change resistivity?

The resistivity ρ of a material depends on the molecular and atomic structure, and is temperature-dependent. For most conductors, resistivity increases with increasing temperature.

What is difference between resistance and resistivity?

Resistance is the physical property of a substance because of which it opposes the flow of current i.e. electrons. Resistivity is the physical property of a particular substance which is having particular dimensions.

What does high resistivity mean?

Electrical resistivity is a measure of a material’s property to oppose the flow of electric current. This is expressed in Ohm-meters (Ω⋅m). … A high resistivity means that a material does not conduct electric charge well.

What is mud resistivity?

The resistivity (Wm) of a drilling mud is influenced by the dissolved salts (ppm) or (gpg, grain per gallon) in the water portion and the insoluble solid material contained in the water portion. The greater the concentration of dissolved salts, the lower resistivity of the solution.

What is water resistivity?

Type of WaterApproximate resistivity in Ohms (Ω)Distilled Water500,000Rain Water20,000Tap Water1,000 – 5,000 Ω

What is borehole environment?

The borehole environment begins with the fluid within the borehole which is usually drilling mud but can be air or water. The resistivity of the borehole fluid is referred to as Rm.

Which logging tool has largest depth of investigation?

Downhole logging tools had largest depth of investigation .

Why Does Clay have low resistivity?

Clay minerals have a substantial negative surface charge that causes log resistivity val- ues to plummet. 2 This negative surface charge—the result of substitution in the clay lattice of atoms with lower positive valence —attracts cations such as Na+ and K+ when the clay is dry.

What is depth of investigation in logging?

1. n. [Formation Evaluation] A distance that characterizes how far a logging tool measures into the formation from the face of the tool or the borehole wall. The depth of investigation summarizes the radial response of the measurement in one or more directions.

What is the difference between flushed zone and invaded zone?

The volume close to the borehole wall in which some or all of the moveable fluids have been displaced by mud filtrate. It consists of the flushed zone and the transition zone or annulus. In simple models, the invaded zone and the flushed zone are considered synonymous.

What is mud filtrate?

1. n. [Formation Evaluation, Drilling Fluids] The liquid that passes through a filter cake from a slurry held against the filter medium, driven by differential pressure. Dynamic or static filtration can produce a filtrate.

What is open hole logging?

Open-hole logging refers to logging operations that are performed on a well before the wellbore has been cased and cemented. In other words, the logging is done through the bare rock sides of the formation.

How does a sonic log work?

Sonic logging tools emit a sound pulse every second. … Essentially the basic principle of these sonic logging tools is to measure the travel time of sound through rock. Newer generation logging tools can use a cross correlation of waveforms to determine this travel time.

What is compressional slowness?

A technique for recording the formation compressional slowness based on the transit time between transmitter and receiver. … The time between emission and reception is measured for each receiver, and subtracted to give the traveltime in the interval between the two receivers.