This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 1 GY 305: Geophysics GY 305: Geophysics Lecture 6: Lecture 6: Electric (Wire Line) Logs 2: Electric (Wire Line) Logs 2: Gamma Ray Logs Gamma Ray Logs UNIVERSITY OF SOUTH ALABAMA Last Time Last Time Electric Logs 1 • Introduction (first electric logs) • Resistivity Logs • SP Logs (Spontaneous Potential) Electric Logs Formation Resistivity Pelchelbronn, France September 5, 1927 Consisted of a line dropped down the bore hole Doveton, J.H., 1994. Geological Log Interpretation. SEPM Short Course Notes 29 ., 169p. Electric Logs •There are numerous types of logs that provide a wide variety of information. •We’ll look at the most important 1) Resistivity 2) SP 3) Gamma Ray 4) Neutron 5) Sonic/Density Resistivity Logs Can be used to resolve lithology, but they are most useful for assessing fluid composition. Shallow versus deep induction Resistivity Logs Ultimately resistivity of a rock (R t ) is controlled by: •Salinity of formation pore water •Volume of pore space •Geometry of pore space (Lab 2) •Temperature of the logged zone •Morphology and types of clays •Phases of pore fluids 2 ht p:/ www.spwla.org/library_info/glos ary/reference/glos s/images/glsp85f1.gif Spontaneous potential is... …most useful as a basic tool to distinguish lithology (sandstone versus shale) SP Logs ht p:/ www.kgs.ku.edu/Dakota/vol1/petro/gifs/fig08.gif SP Logs Sand line versus Shale Line Beware of signal drift SP Logs htp:/www.gomr.mms.gov/images_opt/graphics/re/sp.gif SP logs can also allow you to resolve broad stratigraphic and...
View Full Document
- Fall '10
- Radioactive Decay, Gamma ray, gamma ray logs