10,323
edits
Changes
Jump to navigation
Jump to search
mLine 6:
Line 6: − + − + Line 14:
Line 14: − + − During the drilling process, filtrate water from the drilling fluid invades the formation. Its resistivity (R<sub>mf</sub>) is either greater than, less than, or equal to R<sub>t</sub> and can distort deep resistivities. Distortions to resistivities due to invasion must be corrected to get a valid R<sub>t</sub> value. The diagram below shows resistivity profiles of formations with fresh and saltwater mud filtrate invasion. − + + + − + − + − ! Then… − + − − + − − + − + + Line 51:
Line 50: +
True resistivity determination (view source)
Revision as of 16:16, 5 April 2022
, 16:16, 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 = 9-48
| topg = 9-156
| topg = 9-48
| 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
}}
}}
The true resistivity (R<sub>t</sub>) of a formation is its resistivity when not contaminated by [[drilling fluid]]s. It may contain formation water only (S<sub>w</sub> = 100%) or formation water and hydrocarbons (S<sub>w</sub> t is fundamental when analyzing well logs for the presence of hydrocarbons. For a discussion of resistivity concepts see Asquith, 1982.
The true resistivity (R<sub>t</sub>) of a formation is its resistivity when not contaminated by [[drilling fluid]]s. It may contain formation water only ([[water saturation]] [S<sub>w</sub>] = 100%) or [[formation water]] and hydrocarbons (S<sub>w</sub> < 100%). Using a valid R<sub>t</sub> is fundamental when analyzing well logs for the presence of hydrocarbons. For a discussion of resistivity concepts see Asquith, 1982.
==How invasion affects r<sub>t</sub> measurement==
==How invasion affects r<sub>t</sub> measurement==
[[file:predicting-reservoir-system-quality-and-performance_fig9-29.png|thumb|{{figure number|9-29}}See text for explanation.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-29.png|500px|thumb|{{figure number|1}}Resistivity profiles of formations with fresh and saltwater mud filtrate invasion.]]
During the drilling process, filtrate water from the drilling fluid invades the formation. Its [[Resistivity of mud filtrate|resistivity (R<sub>mf</sub>)]] is either greater than, less than, or equal to R<sub>t</sub> and can distort deep resistivities. Distortions to resistivities due to invasion must be corrected to get a valid R<sub>t</sub> value. The diagram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-29.png|Figure 1]] shows resistivity profiles of formations with fresh and saltwater mud filtrate invasion.
==Obtaining a valid r<sub>t</sub> value==
==Obtaining a valid r<sub>t</sub> value==
To obtain an uninvaded zone resistivity (R<sub>t</sub>)
To obtain an uninvaded zone resistivity (R<sub>t</sub>)
# Read the resistivity of the log with deepest investigation (ILD, LLD, etc.).
# Read the [[Basic_open_hole_tools#Resistivity|resistivity]] of the log with deepest investigation (deep induction log [ILD], deep laterolog [LLD], etc.).
#Use the table below to determine how to make corrections.
#Use the table below to determine how to make corrections.
{| class="wikitable"
{| class="wikitable"
|-
|-
! If…
! If… || Then…
|-
|-
| Bed is <20 ft thick for an induction log or <4 ft thick for a laterolog
| Bed is < 20 ft thick for an [[Basic open hole tools#Induction|induction log]] or < 4 ft thick for a [[Basic open hole tools#Laterologs|laterolog]] || Correct for this bed using appropriate service company chart
| Correct for this bed using appropriate service company chart
|-
|-
| Bed is shallow, medium, and deep investigating tools measure, different resistivities (i.e., log has step profile)
| Shallow, medium, and deep investigating tools measure different resistivities (i.e., log has step profile) || Correct for invasion using appropriate service company tornado chart
| Correct for invasion using appropriate service company tornado chart
|}
|}
==See also==
==See also==
* [[Determining water saturation]]
* [[Determining water saturation]]
* [[Calculating Sw from the Archie equation]]
* [[Archie equation]]
* [[Calculating Rw from SP logs]]
* [[Calculating Rw from SP logs]]
* [[Constructing a Pickett plot]]
* [[Pickett plot construction]]
* [[Basic open hole tools]]
==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]]