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Line 25: − [[file:predicting-reservoir-system-quality-and-performance_fig9-32.png|thumb|{{figure number|1}} Copyright: Schlumberger.]]+ − If the log header gives R<sub>m</sub> only, then R<sub>m</sub> must be converted to R<sub>mf</sub> using this procedure:+ + − + − |- − ! Step − ! Action − |- − | 1 − | Enter R<sub>m</sub> and move across ([[:file:predicting-reservoir-system-quality-and-performance_fig9-32.png|Figure 1]]) to the appropriate mud weight. − |- − | 2 − | Project to the bottom of the chart to estimate R<sub>mf</sub> − |} − There are five steps for calculating R<sub>w</sub> from the SP log. The table below summarizes these steps, which are detailed in the rest of this section. − + − |-+ − ! Step+ − ! Action+ − |-+ − | 1+ − | Estimate formation temperature.+ − |-+ − | 2+ − | Convert R<sub>mf</sub> to formation temperature. − |- − | 3 − | Convert R<sub>mf</sub> to R<sub>mf</sub><sub>eq</sub> . − |- − | 4 − | Read SP response and estimate R<sub>we</sub> . − |- − | 5 − | Convert R<sub>we</sub> to R<sub>w</sub> and NaCl at formation temperature. − |} Line 79:
Line 58: − + − {| class = "wikitable"+ − |-+ − ! Step+ − ! Action − |- − | 1 − | Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-33.png|Figure 2]] along the resistivity of solution axis and the temperature axis using the measured values for R<sub>mf</sub> and surface temperature found on the log header. − |- − | 2 − | Follow the appropriate salinity line intercepted at step 1 to the appropriate formation temperature and mark on the chart. − |- − | 3 − | Project down the chart from this mark to the resistivity scale and read R<sub>mf</sub> at formation temperature. Record the value of R<sub>mf</sub> at a specific temperature. − |} − + − {| class = "wikitable"+ − |-+ − ! Step+ − ! Action − |- − | 1 − | Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-34.png|Figure 3]] with R<sub>mf</sub> at formation temperature on the vertical axis. − |- − | 2 − | Move across the chart to the appropriate formation temperature contour, and mark this point on the figure. − |- − | 3 − | Read down to R<sub>mf</sub><sub>eq</sub> . This value is used in the equation R<sub>we</sub> = R<sub>mf</sub><sub>eq</sub> (R<sub>mf</sub><sub>eq</sub> /R<sub>we</sub> value). − |} − + − {| class = "wikitable"+ − |-+ − ! Step+ − ! Action+ − |- − | 1 − | On the log, establish the shale base line for the SP curve. − |- − | 2 − | Read the maximum SP response in a zone at least [[length::20 ft]] thick. − |- − | 3 − | Enter the base of [[:file:predicting-reservoir-system-quality-and-performance_fig9-35.png|Figure 4]] with SP (SP is negative if it deflects to the left of the shale base line). Follow the SP grid line up the chart to the appropriate formation temperature. At this point, move across the chart and read the R<sub>mf eq</sub> /R<sub>we</sub> Value. − |- − | 4 − | Solve for R<sub>we</sub> using the equation R<sub>we</sub> = R<sub>mf</sub><sub>eq</sub> /(R<sub>mf</sub><sub>eq</sub> /R<sub>we</sub> value). − |} − {| class = "wikitable"+ − |-+ − ! Step − ! Action − |- − | 1 − | Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-34.png|Figure 3]] again with R<sub>we</sub> (along the base). Move up the chart until R<sub>we</sub> intersects the temperature slope. − |- − | 2 − | Directly across from the intersection point, read R<sub>w</sub> from the vertical axis. − |} Line 162:
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Spontaneous potential logs in water resistivity calculation (view source)
Revision as of 16:40, 5 April 2022
, 16:40, 5 April 2022added Category:Treatise Handbook 3 using HotCat
| part = Predicting the occurrence of oil and gas traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Predicting reservoir system quality and performance
| chapter = Predicting reservoir system quality and performance
| frompg = 9-1
| frompg = 9-54
| topg = 9-156
| topg = 9-59
| author = Dan J. Hartmann, Edward A. Beaumont
| author = Dan J. Hartmann, Edward A. Beaumont
| link = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm
| link = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm
| isbn = 0-89181-602-X
| isbn = 0-89181-602-X
}}
}}
Water resistivity or R<sub>w</sub>, is a critical component of log analysis in calculating [[water saturation]] using the Archie equation. R<sub>w</sub> can be measured from a sample of formation water taken from the zone of interest at the well site or a nearby well, or it can be calculated using spontaneous potential (SP) log data.
Water resistivity or R<sub>w</sub>, is a critical component of log analysis in calculating [[water saturation]] using the [[Archie equation]]. R<sub>w</sub> can be measured from a sample of formation water taken from the zone of interest at the well site or a nearby well, or it can be calculated using spontaneous potential (SP) log data.
==Data required==
==Data required==
==Converting r<sub>m</sub> to r<sub>mf</sub>==
==Converting r<sub>m</sub> to r<sub>mf</sub>==
If the log header gives R<sub>m</sub> only, then R<sub>m</sub> must be converted to R<sub>mf</sub> using this procedure:
# Enter R<sub>m</sub> and move across ([[:file:predicting-reservoir-system-quality-and-performance_fig9-32.png|Figure 1]]) to the appropriate mud weight.
# Project to the bottom of the chart to estimate R<sub>mf</sub>
{| class = "wikitable"
{{clear}}
==Steps for calculating r<sub>w</sub>==
==Steps for calculating r<sub>w</sub>==
{| class = "wikitable"
[[file:predicting-reservoir-system-quality-and-performance_fig9-32.png|thumb|450px|{{figure number|1}}SP log data. Copyright: Schlumberger.]]
There are five steps for calculating R<sub>w</sub> from the SP log. The list below summarizes these steps, which are detailed in the rest of this section.
# Estimate formation temperature.
# Convert R<sub>mf</sub> to formation temperature.
# Convert R<sub>mf</sub> to R<sub>mf</sub><sub>eq</sub> .
# Read SP response and estimate R<sub>we</sub> .
# Convert R<sub>we</sub> to R<sub>w</sub> and NaCl at formation temperature.
==Step 1: Estimate formation temperature==
==Step 1: Estimate formation temperature==
==Step 2: convert r<sub>mf</sub> to r<sub>mf</sub> at formation temperature==
==Step 2: convert r<sub>mf</sub> to r<sub>mf</sub> at formation temperature==
[[file:predicting-reservoir-system-quality-and-performance_fig9-33.png|thumb|{{figure number|2}} Copyright: Schlumberger.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-33.png|300px|thumb|{{figure number|2}}SP log data. Copyright: Schlumberger.]]
Follow this procedure to convert R<sub>mf</sub> (measured at surface temperature) to R<sub>mf</sub> at formation temperature.
Follow this procedure to convert R<sub>mf</sub> (measured at surface temperature) to R<sub>mf</sub> at formation temperature.
# Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-33.png|Figure 2]] along the resistivity of solution axis and the temperature axis using the measured values for R<sub>mf</sub> and surface temperature found on the log header.
# Follow the appropriate salinity line intercepted at step 1 to the appropriate formation temperature and mark on the chart.
# Project down the chart from this mark to the resistivity scale and read R<sub>mf</sub> at formation temperature. Record the value of R<sub>mf</sub> at a specific temperature.
==Step 3: convert r<sub>mf</sub> to r<sub>mf eq</sub>==
==Step 3: convert r<sub>mf</sub> to r<sub>mf eq</sub>==
[[file:predicting-reservoir-system-quality-and-performance_fig9-34.png|thumb|{{figure number|3}} Copyright: Schlumberger.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-34.png|300px|thumb|{{figure number|3}}SP log data. Copyright: Schlumberger.]]
Use the R<sub>mf</sub> at formation temperature obtained above and follow the procedure below to convert R<sub>mf</sub> to equivalent mud filtrate resistivity (R<sub>mf</sub> <sub>eq</sub>).
Use the R<sub>mf</sub> at formation temperature obtained above and follow the procedure below to convert R<sub>mf</sub> to equivalent mud filtrate resistivity (R<sub>mf</sub> <sub>eq</sub>).
# Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-34.png|Figure 3]] with R<sub>mf</sub> at formation temperature on the vertical axis.
# Move across the chart to the appropriate formation temperature [[contour]], and mark this point on the figure.
# Read down to R<sub>mf</sub><sub>eq</sub> . This value is used in the equation R<sub>we</sub> = R<sub>mf</sub><sub>eq</sub> (R<sub>mf</sub><sub>eq</sub> /R<sub>we</sub> value).
==Step 4: convert SP to r<sub>we</sub>==
==Step 4: convert SP to r<sub>we</sub>==
[[file:predicting-reservoir-system-quality-and-performance_fig9-35.png|thumb|{{figure number|4}} Copyright: Schlumberger.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-35.png|300px|thumb|{{figure number|4}}SP log data. Copyright: Schlumberger.]]
Follow the procedure below to convert SP from the zone of interest to equivalent formation water resistivity (R<sub>we</sub>).
Follow the procedure below to convert SP from the zone of interest to equivalent formation water resistivity (R<sub>we</sub>).
# On the log, establish the shale base line for the SP curve.
# Read the maximum SP response in a zone at least [[length::20 ft]] thick.
# Enter the base of [[:file:predicting-reservoir-system-quality-and-performance_fig9-35.png|Figure 4]] with SP (SP is negative if it deflects to the left of the shale base line). Follow the SP grid line up the chart to the appropriate formation temperature. At this point, move across the chart and read the R<sub>mf eq</sub> /R<sub>we</sub> Value.
# Solve for R<sub>we</sub> using the equation R<sub>we</sub> = R<sub>mf</sub><sub>eq</sub> /(R<sub>mf</sub><sub>eq</sub> /R<sub>we</sub> value).
==Step 5: convert r<sub>we</sub> to r<sub>w</sub>==
==Step 5: convert r<sub>we</sub> to r<sub>w</sub>==
Follow the procedure below to convert R<sub>we</sub> to R<sub>w</sub>.
Follow the procedure below to convert R<sub>we</sub> to R<sub>w</sub>.
# Enter [[:file:predicting-reservoir-system-quality-and-performance_fig9-34.png|Figure 3]] again with R<sub>we</sub> (along the base). Move up the chart until R<sub>we</sub> intersects the temperature slope.
# Directly across from the intersection point, read R<sub>w</sub> from the vertical axis.
==See also==
==See also==
* [[Archie equation]]
* [[Archie equation]]
* [[Determining Rt]]
* [[Determining Rt]]
* [[Constructing a Pickett plot]]
* [[Pickett plot construction]]
==External links==
==External links==
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting reservoir system quality and performance]]
[[Category:Predicting reservoir system quality and performance]]
[[Category:Treatise Handbook 3]]