Well logging, an activity in drilling operation, uses for recording formation properties related to the depth. Well logging tool is inserted to the well then starts to record the formation condition. Although the well logging operation can be done by both lowering and pulling the tool in the well, well logging is often done during pulling the tool.
There are several types of well logging that familiar in drilling. Each of them records different properties of the well such as hole diameter, resistivity, radioactive component, porosity, etc.
Some of general types of well logging:
1. Gamma Ray, to estimate the formation rock type (shale, sandstone, or limestone) by recording natural radioactive radiation in the formation. Shale has a large amount of radioactivity on the other hand sandstone and limestone have a small amount of radioactivity. We can estimated the permeable zone(sandstone/limestone) by using Gamma Ray logging.
2. Spontaneous Potential, to estimate shale component in formation by recording voltage different between electrodes in the tools. SP log only available in conductive drilling fluid (water base mud).
3. Induction logging, to estimate the water saturation in formation by recording the resistivity of the formation.
4. Sonic Logging, to estimate material characteristic behind the casing by recording the deflected sonic wave. Sonic log usually known as Cement Bond Log (CBL) and Variable Density Log (VDL).
5. Neutron log, to estimate the porosity by recording deflected neutron. Neutron log tool radiates neutron to formation. Neutron will be deflected if collide with the particle that has same size and weight. Hydrogen is relatively has same size with neutron, so neutron will be deflected every collide the hydrogen. Actually, the recorded deflected neutron expresses the amount of hydrogen particle in the formation.
A little opinion from my little brain..
OK, those are some of logging type i know, do you know another type? or do you have some correction? Please leave a comment!
