Changes

===Procedure===

===Procedure===

The procedure for determining ''R''_w from the resistivity ratio method is outlined as follows. The data that are required include ''R''_t from ILd or LLd, ''R''_xo from SFL or another shallow-reading resistivity device, ''R''_mf, and ''T''_f.

The procedure for determining ''R''_w from the resistivity ratio method is outlined as follows. The data that are required include ''R''_t from ILd or LLd, ''R''_xo from SFL or another shallow-reading resistivity device, ''R''_mf, and ''T''_f.

* Correct ''R''_mf to the appropriate formation temperature (''T''_f) value.

* Correct ''R''_mf to the appropriate formation temperature (''T''_f) value.

* Calculate ''R''_w from Equation 8.

* Calculate ''R''_w from Equation 8.

Note that an equivalent “quick look” solution can be obtained by an overlay technique using logarithmically scaled ''R''_t and ''R''_xo logs. If one log is placed over the other and shifted so that the two curves coincide in clean, water-bearing zones, the 1 ohm-m line on the ''R''_xo log grid will lie on the ''R''_t grid at a value equal to ''R''_w/''R''_mf. Since ''R''_mf is known, ''R''_w can then be easily calculated. [[:file:determination-of-water-resistivity_fig4.png|Figure 4]] shows an example of original and shifted logs indicating a ''R''_t/''R''_mf ratio of 0.45.

Note that an equivalent “quick look” solution can be obtained by an overlay technique using logarithmically scaled ''R''_t and ''R''_xo logs. If one log is placed over the other and shifted so that the two curves coincide in clean, water-bearing zones, the 1 ohm-m line on the ''R''_xo log grid will lie on the ''R''_t grid at a value equal to ''R''_w/''R''_mf. Since ''R''_mf is known, ''R''_w can then be easily calculated. [[:file:determination-of-water-resistivity_fig4.png|Figure 4]] shows an example of original and shifted logs indicating a ''R''_t/''R''_mf ratio of 0.45.