Publication History: This article was prepared especially for "Crain's Petrophysical Handbook" by E. R. (Ross) Crain, P.Eng. in 2018. This webpage version is the copyrighted intellectual property of the author.

Do not copy or distribute in any form without explicit permission.

DELTH PLOT BASICS
Log data depth plots are described by the depth scale, number of presentation tracks, and the curve names and scales for each that appear in each track. Logs recorded in the field usually have 3 tracks, one on the left of the depth values and two on the right, the latter may be combined into a single wide track. Depth plots that contain computed results, with or without rae data, can have any number of tracks.

The tables below give details of the common depth scales and curve complement for a few of the more common log suites. The curve name table shows the so-called "correlation track" first; it would appear as the left hand track of almost every depth plot.

A composite plot can merge several log displays into a single plot with any number of tracks, and may also have tracks with computed petrophysical results.

Customized depth plots are common, but to make life easier for those who have to use the data, it pays to make the plots as uniform as possible. This means the curve scale direction,  scale values, line colours, line codes, and overall layout are consistent over time and location.


PRACTICAL CONSIDERATIONS
Traditional depth plots of well log data are 8.25 inches wide so they can be printed on standard 8.5 inch paper at full size. If you create a wider plot, printer defaults will shrink both width and length so it will no longer be at the depth scale you specified. You can still see it full sixe on the computer screen but not on a simple printer. Professional software and wide bed printers overcome this limitation.

For the well log descriptions listed in the tables below, the standard API well log layout is recommended. It consists of 3 tracks, each 2.5 inches wide, with a 0.75 inch wide depth track between Tracks 1 and 2. See examples in the next Section. Each track is divided vertically into 10 equal divisions for lineat scales, or into 3 or 4 logarithmic cycles for logarithmic scales.

A log header with log name and well location (and other useful information) is placed at the top of the log, followed by the curve names and scale information, centered over the appropriate track. Most log headers generated by comercial software omits critical information. The header should include the analyst's name, contact information, and time/date stamp. There is nothing more frustrating than trying to sort these items out two years after the plot was made.

For composite plots of raw data or computed results, a 4 track presentation that fit standard printers is a de facto standard. It consists of a 0.5 inch depth track on the left, followed by 4 tracks of width 1.875 inches. More width and more tracks are often seen, but usually at reduced scale when printed, except for those with expensive wide bed printer/plotters.


DEFAULT  PLOT  LAYOUTS
 

STANDARD DEPTH SCALES and GRID LINES

Scale

Depth # Every

Grid Lines

Ratio Units Description   4 pt 2 pt 1 pt
1:1200 English 1 inch = 100 feet 100 feet 200 feet 100 feet 20 feet
1:1200 Metric 1 inch = 100 feet 50 meters 100 meters 50 meters 10 meters
1:600 English 2 inches = 100 feet 100 feet 100 feet 50 feet 10 feet
1:600 Metric 2 inches = 100 feet 50 meters 100 meters 50 meters 10 meters
1:480 English 2.5 inches = 100 feet 100 feet 100 feet 50 feet 10 feet
1:480 Metric 2.5 inches = 100 feet 50 meters 100 meters 50 meters 10 meters
1:240 English 5 inches = 100 feet 50 feet 50 feet 10 feet 2 feet
1:240 Metric 5 inches = 100 feet 25 meters 25 meters 10 meters 1 meter
1:1000 English 1 cm = 100 meters 100 feet 200 feet 100 feet 20 feet
1:1000 Metric 1 cm = 100 meters 50 meters 100 meters 50 meters 10 meters
1:500 English 1 cm = 100 meters 100 feet 200 feet 100 feet 20 feet
1:500 Metric 1 cm = 100 meters 50 meters 50 meters 25 meters 5 meters
1:200 English 1 cm = 100 meters 50 feet 50 feet 10 feet 2 feet
1:200 Metric 1 cm = 100 meters 25 meters 25 meters 10 meters 1 meter

 

 

RECOMEMDED  DEPTH PLOT LAYOUTS

Curve Name Left Right M or E Lpg / Linear Colour Width Line Code
Correlation Track -- All Logs -- Track 1            
GR Gamma Ray 0 150 api Linear Red 2 Solid
SP Spontaneous Potential -80 +20 mv Linear Blue 2 Solid
Metric                
CAL Calipeer 150 375 mm Linear Black 2 Long Dash
BITZ Bit Sizw 150 375 mm Linear Black 1 Short Dash
English                
CAL Calipeer 6 16 in Linear Black 2 Long Dash
BITZ Bit Sizw 6 16 in Linear Black 1 Short Dash
                 
Resistivity Logs - All Types -- Tracks 2 + 3            
RESD Deep Resistivity 0.2 2000 ohm-m Log Red 2 Long Dash
RESM Medium Resistivity 0.2 2000 ohm-m Log Blue 2 Short Dash
RESS Shallow Resistivity 0.2 2000 ohm-m Log Black 2 Solid
** RESxxx Optional eg Array RES 0.2 2000 ohm-m Log Blue 1 Dot Dash
                 
Sonic Logs -- All Types -- Tracks 2 + 3            
DTC Compressional Travel Time 500 100 ms/m Linear Blue 2 Solid
DTS Shear Travel Time 500 100 ms/m Linear Green 2 Solid
DTC Compressional Travel Time 140 40 ms/ft Linear Blue 2 Solid
DTS Shear Travel Time 140 40 ms/ft Linear Green 2 Solid
** DTxxx Optional eg dipole x-y DT -- -- -- Linear --- 2 Lomg Dash
                 
Alternate for Low Porosity Rocks              
Metric                
DTC Compressional Travel Time 300 100 ms/m Linear Blue 2 Solid
DTS Shear Travel Time 300 100 ms/m Linear Green 2 Solid
English                
DTC Compressional Travel Time 100 40 ms/ft Linear Blue 2 Solid
DTS Shear Travel Time 100 40 ms/ft Linear Green 2 Solid
** DTxxx Optional eg dipole x-y DT -- -- -- Linear --- 2 Lomg Dash
                 
Density Neutron Logs -- All Types --Tracks 2 + 3            
CDN Sand                
PHIN_SS Neutron Porosity 0.60 0.00 fraction Linear Black 2 Long Dash
PHID_SS Density Porosity 0.60 0.00 fraction Linear Red 2 Solid
PEF Photoelectric Effect -15 +5 cu Linear Purple 2 Dot Long Dash
DCOR Density Correction 750 -250 kg/m3 Linear Black 2 Short Dashd
                 
CDN Carb                
PHIM_LS Neutron Porosity 0.45 -0.15 fraction Linear Black 2 Long Dash
PHID_LS Density Porosity 0.45 -0.15 fraction Linear Red 2 Solid
PEF Photoelectric Effect 0 20 cu Linear Purple 2 Dot Long Dash
DCOR Density Correction 250 -750 kg/m3 Linear Black 2 Short Dashd
                 
USA Sand                
PHIN_SS Neutron Porosity 0.60 0.00 fraction Linear Black 2 Long Dash
DENS Density 1.65 2.65 g/cc Linear Red 2 Solid
PEF Photoelectric Effect -15 +5 cu Linear Purple 2 Dot Long Dash
DCOR Density Correction 0.75 -0.25 g/cc Linear Black 2 Short Dashd
                 
USA Carb                
PHIN_LS Neutron Porosity 0.45 -0.15 fraction Linear Black 2 Long Dash
DENS Density 1.95 2.95 g/cc Linear Red 2 Solid
PEF Photoelectric Effect 0 20 cu Linear Purple 2 Dot Long Dash
DCOR Density Correction 0.25 -0.75 g/cc Linear Black 2 Short Dashd
                 
Composite Log -- Basic Raw Data -- 4 Track Grid            
Correlation Track 1              
Resistivity Track 2              
Sonic Track 3              
Density Neutron Track 4              
   Log curves as defined in each individual log descriptiom              
                 
                 
                 


DEFAULT  PLOT  LAYOUT  EXAMPLES


Typical resistivity log (left) and sonic log (right) displayed on traditional log tracks. Correlation curves in Track 1 to the left of the depth track and specific log curves in Tracks 2 +3.  Shading on sonic log indicates bad data caused by fractures.


Density neutron PE log on Limesyome scale (left) and same log displayed on Dolomite scale (right). Red shading indicates density meutron crossover which could indicate light hydrocarbons OR limestone. PE curve indicates pure dolomite so crossover shows gas or very light oil.


Composite plot in this example combines correlation and resistivity tracks, with porosity,
 saturation, permeability, and lithology results tracks.

 

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