What is compensated neutron log?
Compensated neutron log is a type of well log that is used to determine the porosity of each formation in a cased or open well and is adjusted for irregularities in the wellbore.
What is neutron density log?
The density–neutron log is a combination log that simultaneously records neutron and density porosity. The matrix density used by the logging program to calculate porosity is different from the actual formation matrix density. Gas is present in the formation pore space. Shale/clay is present in the formation.
Which logging tool has largest depth of investigation?
Downhole logging tools had largest depth of investigation .
What are neutron logs?
The neutron log is sensitive mainly to the amount of hydrogen atoms in a formation. Its main use is in the determination of the porosity of a formation. The tool operates by bombarding the formation with high energy neutrons. The count rate of slow neutrons or capture gamma rays in the tool is therefore higher.
What is porosity log?
The “Porosity” logs. There are three types of logging tools that are used to estimate the amount of pore space in a rock: the neutron, density, and acoustic velocity (or sonic) tool. So, the log is mainly a measure of hydrogen concentration (mostly contained by the pore fluids of the formation).
What is a neutrons mass?
neutron, neutral subatomic particle that is a constituent of every atomic nucleus except ordinary hydrogen. It has no electric charge and a rest mass equal to 1.67493 × 10−27 kg—marginally greater than that of the proton but nearly 1,839 times greater than that of the electron.
What is the radius of a neutron?
The neutron has a mean square radius of about 0.8×10−15 m, or 0.8 fm, and it is a spin-½ fermion.
What kind of tools are used for neutron logging?
These are represented by the sidewall neutron log (SNP) tools. The third type uses detectors sensitive to thermal neutrons. These have dual detectors that allow for some borehole compensation, represented by compensated neutron logging tools (CNL).
Why are neutron porosity logs so difficult to read?
The size of the fluid-filled borehole is obviously an important environmental effect that must be taken into account. As a result, even “raw” CNL porosities are reported with a borehole-size correction already applied. By far, the most difficult nuclear logs to interpret are those that exploit neutron scattering to estimate porosity.
Can a neutron log be replaced by an equal sign?
In the case of a purely epithermal neutron log, the approximately equal sign can be replaced by an equal sign. Because most logs encountered are thermal neutron logs, the rest of the discussion will center on thermal neutron interpretation.
How are neutrons detected in the sidewall neutron log?
In the sidewall neutron log, fast neutrons are emitted and epithermal neutrons are detected, and related to porosity by an algorithm built into the surface recording equipment.