Exploration Technique: Neutron Log
|Exploration Technique Information|
|Exploration Group:||Downhole Techniques|
|Exploration Sub Group:||Well Log Techniques|
|Parent Exploration Technique:||Well Log Techniques|
|Information Provided by Technique|
|Lithology:||if used in conjunction with other logs, this technique can provide information on the rock type and the porosity|
|Stratigraphic/Structural:||Corelation of rock units|
|Hydrological:||Estimate of formation porosity|
When the hydrogen concentration of the zone surrounding the well bore is large because there is a large amount of fluid in that zone, most of the neutrons are slowed down and captured close to the well bore. This results in a low count rate and is interpreted as an indication of high porosity meaning that a large portion of the volume is filled with fluid. If the zone surrounding the well bore has a small concentration of hydrogen because of low amounts of fluid, the neutrons must travel farther from the source before being captured. This in turn results in a high measured count rate and is interpreted as an indication of low porosity. Hard, dense dolomites and limestones with low porosities usually have high count rates, while porous zones such as sandstones usually have lower count rates.
Calibration curves developed for the oil and gas industry from porosoties calculated from core analysis have set a standard based on limestone porosity. It has been observed that limestone porosity calibration used in the logs when compaired to igneous rocks varies by about 3%.
- Alum Geothermal Area
- Coso Geothermal Area
- Fort Bliss Area
- Silver Peak Area
- Valles Caldera - Redondo Geothermal Area