# Difference between revisions of "Dictionary:Static self-potential (SSP)"

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The maximum SP that would be recorded when the borehole logging sonde passes from within a very thick, porous, permeable, clean sand to a point that is well within a thick shale. The <b>electrochemical SSP</b> (the electrokinetic SP is often neglected) is approximately given by: | The maximum SP that would be recorded when the borehole logging sonde passes from within a very thick, porous, permeable, clean sand to a point that is well within a thick shale. The <b>electrochemical SSP</b> (the electrokinetic SP is often neglected) is approximately given by: | ||

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<center><math>SSP=-K log_{10} \frac{a_w}{a_{mf}}</math>,</center> | <center><math>SSP=-K log_{10} \frac{a_w}{a_{mf}}</math>,</center> | ||

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where ''a''<sub>''w''</sub> is the activity of the formation water and ''a''<sub>''mf''</sub> that of the mud filtrate. Because of the inverse relationship between activity and equivalent resistivity, this equation can be written: | where ''a''<sub>''w''</sub> is the activity of the formation water and ''a''<sub>''mf''</sub> that of the mud filtrate. Because of the inverse relationship between activity and equivalent resistivity, this equation can be written: | ||

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<center><math>SSP=-K log_{10} \frac{a_{mfe}}{a_{we}}</math>.</center> | <center><math>SSP=-K log_{10} \frac{a_{mfe}}{a_{we}}</math>.</center> | ||

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where ''R''<sub>''mfe''</sub>=equivalent mud filtrate resistivity, ''R''<sub>''we''</sub>= equivalent water resistivity. For NaCl muds that are not too saline, ''R''<sub>''mfe''</sub>=''R''<sub>''mf''</sub>; for other muds an activity correction should be made. In these equations <math display="inline">K=60+0.133 T</math> where ''T''=Fahrenheit temperature. See also [[Special:MyLanguage/Dictionary:SP|''SP'']] and [[Special:MyLanguage/Dictionary:pseudostatic_SP_(PSP)|''pseudostatic SP'']]. | where ''R''<sub>''mfe''</sub>=equivalent mud filtrate resistivity, ''R''<sub>''we''</sub>= equivalent water resistivity. For NaCl muds that are not too saline, ''R''<sub>''mfe''</sub>=''R''<sub>''mf''</sub>; for other muds an activity correction should be made. In these equations <math display="inline">K=60+0.133 T</math> where ''T''=Fahrenheit temperature. See also [[Special:MyLanguage/Dictionary:SP|''SP'']] and [[Special:MyLanguage/Dictionary:pseudostatic_SP_(PSP)|''pseudostatic SP'']]. | ||

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## Latest revision as of 03:12, 27 November 2017

The maximum SP that would be recorded when the borehole logging sonde passes from within a very thick, porous, permeable, clean sand to a point that is well within a thick shale. The **electrochemical SSP** (the electrokinetic SP is often neglected) is approximately given by:

where *a*_{w} is the activity of the formation water and *a*_{mf} that of the mud filtrate. Because of the inverse relationship between activity and equivalent resistivity, this equation can be written:

where *R*_{mfe}=equivalent mud filtrate resistivity, *R*_{we}= equivalent water resistivity. For NaCl muds that are not too saline, *R*_{mfe}=*R*_{mf}; for other muds an activity correction should be made. In these equations where *T*=Fahrenheit temperature. See also *SP* and *pseudostatic SP*.