Editing Well logging (section)

===Miscellaneous logs===

====Caliper====
{{See also|Caliper log}}
A tool that measures the diameter of the borehole mechanically, using either 2 or 4 arms,<ref name="darling" /> or through high-frequency acoustic signals.<ref>{{cite web |title=ultrasonic caliper |url=https://glossary.slb.com/en/terms/u/ultrasonic_caliper |website=Schlumberger Energy Glossary |publisher=Schlumberger}}</ref> Because most logs are dependent on borehole regularity to record accurately, the caliper log can indicate where logs are potentially compromised due to the borehole being either over-gauged (due to washout) or under-gauged (like mudcake buildup).

====Nuclear magnetic resonance====
{{See also|Nuclear magnetic resonance logging}}
Nuclear magnetic resonance (NMR) logging uses the [[nuclear magnetic resonance|NMR response]] of a [[Formation (stratigraphy)|formation]] to directly determine its [[porosity]] and [[Permeability (earth sciences)|permeability]], providing a continuous record along the length of the [[borehole]].<ref>Gluyas, J. & Swarbrick, R. (2004) Petroleum Geoscience. Publ. Blackwell Publishing</ref><ref name="Kleinberg">Nuclear Magnetic Resonance Imaging – Technology of the 21st century.  Kenyon, Kleinberg, Straley, Gubelin, and Morris. Oilfield Review. http://eps.mcgill.ca/~courses/c550/Literature/NMR-21st-century.pdf{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
The chief application of the NMR tool is to determine moveable fluid volume (BVM) of a rock. This is the pore space excluding clay bound water (CBW) and irreducible water (BVI). Neither of these are moveable in the NMR sense, so these volumes are not easily observed on older logs. On modern tools, both CBW and BVI can often be seen in the signal response after transforming the relaxation curve to the porosity domain. Note that some of the moveable fluids (BVM) in the NMR sense are not actually moveable in the oilfield sense of the word. Residual oil and gas, heavy oil, and bitumen may appear moveable to the NMR precession measurement, but these will not necessarily flow into a well bore.<ref>{{Cite web|url=https://www.spec2000.net/07-nmrlog.htm|title = Crain's Petrophysical Handbook &#124; Login Page}}</ref>

====Spectral acoustic logging====
Spectral acoustic logging is an acoustic measurement technique used in [[oil well|oil]] and [[gas well]]s for well integrity analysis, identification of production and injection intervals and hydrodynamic characterisation of the reservoir. Spectral acoustic logging records acoustic energy generated by fluid or gas flow through the reservoir or leaks in downhole well components.

Acoustic logging tools have been used in the [[petroleum industry]] for several decades. As far back as 1955, an acoustic detector was proposed for use in well integrity analysis to identify casing holes.<ref>Enright, R.J. 1955. Sleuth for Down-Hole Leaks, Oil & Gas J.:78-79</ref>
Over many years, downhole acoustic logging tools proved effective in inflow and injectivity profiling of operating wells,<ref>Britt E.L. 1976. Theory and applications of the borehole audio tracer survey, the SPWLA Seventeenth Annual Logging Symposium, Denver, Colorado</ref><ref>[http://www.onepetro.org/mslib/servlet/onepetropreview?id=SPE-162081-MS Spectral Noise Logging Data Processing Technology]</ref> leak detection,<ref>[http://www.onepetro.org/mslib/servlet/onepetropreview?id=SPE-161983-MS Leak Detection by Temperature and Noise Logging]</ref><ref>[http://www.onepetro.org/mslib/servlet/onepetropreview?id=SPE-161712-MS Innovative Logging Tool Using Noise Log and High Precision Temperature Help to Diagnoses Complex Problems]</ref> location of cross-flows behind casing,<ref>McKinley, R.M. 1994. Temperature, Radioactive Tracer, and Noise Logging for Well Integrity: 112-156</ref> and even in determining reservoir [[fluid]] compositions.<ref>Wang J, Alex van der Spek et al. 1999. Characterizing Sound Generated by Multiphase Flow, SPE Annual Technical Conference and Exhibition held in Houston, Texas</ref> Robinson (1974) described how noise logging can be used to determine effective reservoir thickness.<ref>Robinson W.S. 1974. Field Results From the Noise-Logging Technique, 49th Annual Fall Meeting of the SPE of AIME in Houston, Texas</ref>

====Corrosion well logging====
Throughout the life of the wells, integrity controles of the steel and cemented column (casing and tubing) are performed using calipers and thickness gauges. These advanced technical methods use non destructive technologies as ultrasonic, electromagnetic and magnetic transducers.<ref>Stéphane Sainson, ''Les diagraphies de corrosion''. Ed. Lavoisier, 548 p., 2010</ref>