Neutron Log Operation Tool

Neutron Log Operation Tool

Muhamad Hibri Hafiz b. Hazli

15366

Principle of Operation •

Neutrons emitted from radioactive source

•

Collide the formation fluid and lose energy

•

producing high energy gamma rays

•

Detect either epithermal neutrons, thermal neutrons, capture gamma rays or combination

•

Thus, measures the formations porosity

Tool Operation There are two main types of neutron tool, which are: •

The Sidewall Neutron Porosity Tool (SNP)

•

The Compensated Neutron Log (CNL)

Comparison between SNP and CNL SNP

CNL

Tool

Pad-type Single detector

Mandrel-type 2 detectors

Detects

Epithermal neutrons

Thermal Neutrons

Depth Investigation

Shallow, 8”

Deeper, 12”

Borehole effect

Sensitive to mudcake and rugosity

Minimized by compensation

Vertical Resolution

16”

10”

Limitation

Open hole only

Open & cased hole

Porosity

Count rate vs Ø

Ratio vs Ø

Advantage

Insensitive to thermal neutron absorbers, e.g., Cl, Boron, Barite

Insensitive to borehole environment