TDS Inc. is proud to use Mainlog software, designed to produce the most accurate mud logs possible with modern computer technology. Rapid drilling (drill rates less than 30 sec per foot) are very common today and loggers require a computer to be able to accurately resolve the drill times and gasses to acquire accurate and meaningful mud log data.

Mainlog has been in production since 1995 and is used in most oil fields in the continental United States. The software is one of the most widely used field mud logging programs, providing a fully automated system for gathering data and computer assisted log drawing. The program was written to conform, as closely as possible, to the SPWLA Recommended Standards for Hydrocarbon Well Logging. Some extensions to the standards have been made to satisfy customer needs not addressed by the original standard or to take advantage of the computer capabilities not anticipated when the standards were published.

The Mainlog program is part of the continuing upgrades for the Windows based SCADA system. Industrial computing does not necessarily follow the popular computing fevers, nor should it as many firms have large investments in software that works. Mainlog is intended for the field geologist, as a convenient data gathering system, printing and viewing program. Convenience, and not complexity, was the aim.

Mainlog is a versatile Windows 98, ME, 2000 NT, Windows XP, Vista, and Windows 7 program for mud log viewing, printing and data import and export. The log can be viewed on the screen or printed at depth scales of 5"/100’, 2"/100’, 2 1/2"/100, or 1"/100’. The scales for drill rates and hydrocarbon gas curves can be changed to several linear or logarithmic ranges. MWD, Wireline log data and offset mud log data may be imported and printed/viewed on the mud log beside the ROP curve. Mainlog also has a LAS (Log ASCII Standard) export feature. The data can be exported in LAS standard format, allowing the data to be used in any log analysis program. This feature makes the mud log an extremely powerful tool for today’s skilled geologist. The digital mud log files can be compressed (zipped) and archived on a hard drive, tape etc. rather than stored as paper files. Reduced storage space and perfect quality over a very long time are just a couple of the benefits.

Thousands of wells have been logged with Mainlog software. Most major oil companies are familiar with Mainlog, and enjoy the high quality log presentation of Mainlog data.

Come and join us as we bring mud logging into the 21st century. Our mission is to make the mud log a more powerful and useful tool for the industry. We recognize that the technology progresses and needs change. If you have an idea please let us know.  

Features and Instructions 


Mainlog office version provides you with an easy and powerful set of tools to use to view and print your mud logs and reports created for you by TDS, Inc. We give you all of the advanced features available in Mainlog at no additional cost to you.

Enhanced Office Features

Allow importing E-LOG data and offset ROP and setting up various schemes to view any selection of available mud log and ELOG data. Water saturation and bulk volume waters are automatically calculated. This data will be displayed as curves for viewing or printing on your mud log.

Receiving Files

  1. Your mud logs and reports are available for downloaded from our web site at page by selecting the correct TDS1XXLog box and using the correct USER NAME and PASSWORD that we supply to you at the beginning of your well. When you download the file and save it to your Desktop or your place of choice. Locate the icon for the file you just downloaded TDS123.exe (should be on your desktop)
  2. Double left-click this icon and follow the instructions, accepting all defaults
  3. Open the My MudLogs In folder and Double left-click the WellName.exe file
  4. Mainlog will start and display the log file


There are many ways to navigate through the file.

Using the scroll bars will move you up or down in the file 20ft if clicking the arrows (2 ft if control key is held down),100’ when clicking above or below the arrows, (500 ft  with the control key down) .

Dragging the thumb button on the scrollbar will display a depth in a small text box, the screen will be redrawn from the depth shown when you let the mouse button up.

Page up, page down will move you up or down 100’,.500’ if the control key  is held down. Left clicking above or below the grid (when possible) will move you up or down 100’ in the file. Right clicking these areas will move you 500’.

1. File Menu

Open: Displays a file open dialog with the default extension set to “mlw”. This is the default extension for a Mainlog 32 bit windows data file.

Save As:

Brings up a windows “Save As” dialog box to save the file to a different drive (ie floppy disk) or to a different name.

Send File:

Will zip all files for the current well into a file Well_Name.exe. This file will be placed in the C:\Mainlog\sendfile\Well_Name.exe directory and can then be e-mailed to a partner or home, or wherever. The file can be opened from your mail program by double clicking the attachment and selecting “Open”. (Provided the Mainlog software has been correctly installed on the computer).

Page Setup:

Displays a printer page setup dialog box to allow setting paper size, and or changing printers etc. Also available directly from the print dialog box.


Displays a print dialog which allows you to select print interval, line styles, formats and scales to use for this print job.  It also provides access to printer setup if needed.


Exits the Mainlog Program.

2. View Menu:



Show Report…


Data as Text..

Each selection will display and in some cases allow editing of the report type selected, provided they exist for the current file.

Dst and Show will allow you to create a new report of each type in all modes.

View data as text will display a dialog box with much of the raw data used to draw the current screen displayed. The data is not editable. The dialog will update as you navigate through the file.

3.  Options Menu:

a.   Gas as percent of total…Displays an additional grid over the description area of the log, which displays C1 through C5 as a percent of the total chromatograph gases.

b.  Save reports as text…Saves each report type as an Ascii text file which can then be opened with any text editor.

c.   Create LAS…Will prompt for interval to create a LOG ASCII STANDARD file from the current log file. Will be saved in the home directory as filename.las where filename is the name of the file currently opened…..

d.   Other Options… 

Append File Depth…Allows you to make the file deeper than actual logged depth. Zero’s out data through the new interval. Can not be used to truncate file in office mode.

Adjust File Depth…Adjust the whole file by the number of feet you specify.  For instance, to sync the file to e-log depth. Adjustments can be positive (deeper) or negative(shallower).

e.  Adding Notes

To enter notes, click on Add Note… and a dialog box and a red number line (at the bottom of your screen) should appear asking you for a depth.  Enter the depth (on an even foot) and then enter your text and the position of your note.  The red number line at the bottom determines where you would like your note to be on the log.  You can have up to two notes per line. Notes only two(2) ft apart in the same location will overlap. Once you are finished, click the <Save> button with your mouse.   To exit, click the <Done> button.


Lines and Scales:  Allows you to change the default line styles and scales used by the loggers in the field, scale changes can be made permanent by checking the save as default check box and entering the appropriate interval when prompted. Also allows setting a ROP (rate of penetration) value below which the rates will be highlighted.

Allows turning on or off the tops lines if any. (all or none).

To edit any lines or scales, select Setup on the toolbar and choose Lines and Scales.  A menu will then appear, showing you different rates, rate styles, scales, and other options you can use. 

Rates:  You can use this to modify the screen rates.  You can choose between one, two, ten, and five foot rates.  This is handy for correlation to different size logs.  To select a rate, click next to one of the rates in the check box.

Rate & Gas Line Style:  This option allows you to view your rates and gas in either blocked or point to point format.  Choose one by clicking in the check box next to your desired choice.   

Changing Rate or Gas Scales: To change either rate or gas scales, click on the pull down menu under rates scales or gas scales.  This will give you a number of different scales to choose from.  Select a scale by clicking on the option of your choice.  Next, (and this is important) click on the box next to Save scale as default or Save gas scale as default.  This will then bring up another dialog box asking for a depth to change the scale.  Enter the depth and click <OK>.

Other Options: 

Highlighting rates:  This option allows you to set an ROP,below which the rates will be highlighted (color filled).

Draw tops: If you have any tops labeled, this will allow you to turn this feature on and off simply by clicking on the box.  (Tops on if box is checked)

Alternate Format: Turns on or off an option that will put the descriptions on the right of the gas grid instead of the left. Not available from all logging companies.

SW… If e-log curve feature is enabled, this dialog allows editing of the values used to calculate water saturation. Different values can be saved through different intervals of the log, allowing accurate SW and BVW curves to be plotted


Edit … Edit existing or add a new top. Enter the depth for the top. If you want the top added to the tops menu, enter a name for the top in the appropriate text box  (i.e. Morrow). Enter any text you want displayed with the top line (max 40 char including sub sea depth). If you check the Append sub sea check and there is a KB entered in the header, the sub sea depth will be appended to the text. Enter a location for the text if desired, and the default location is the left border of the rate grid. A red line will be drawn at the depth selected across the whole log excepting the description section. You can drag this line up and down to make corrections, the sub sea depth (if any) will automatically be updated.

You can turn the top lines off in the setup dialog. This turns off printing of the tops as well, otherwise the tops lines and text will be printed on all log formats, in red if color is selected in the print setup.

If you added the top to the menu, by entering a menu name, selecting that top from the menu will scroll the log to start ten ft above the top depth (if the top is not already on screen)

You can create as may tops as you like, with or without text. A maximum of 15 can be added to the tops menu for fast access to those points in the file.

If you have 2 or more wells close by, you can import an existing tops file by clicking the import button. This will bring up a file open dialog. Select the tops file you want to import, and the tops from that file will be saved to “filename”.tops, where filename is the first part of the file name now open. Once imported, you can simply drag the tops line up or down to correct for this well file.

Advanced Features:


The import function allows you to import e-log data from any certified LAS (log ascii standard) file generally provided by most, if not all wire line companies. If the LAS file is in “wrap” mode this function will not work (an “unwrapped” file should be available from the wire line company). The depths have to be sequentially shallow to deep in the file. You will first be prompted for the file name of the source file. This file should have an “LAS” extension, and should reside in the same directory as Mainlog. Once the file name is selected, assuming it is a certified LAS file, a dialog box will be displayed showing the file names and depths, and on the right side of the dialog a list box which contains the names of the various “curves” found in the LAS file.

(“curves” will always refer to e-log data in this manual).

Mainlog will allow you to import the following “curves”

Gamma Ray

Density, neutron, cross plot, and sonic porosity

Up to five resistivity curves


If no cross plot is available, AND you are importing both a neutron and a density curve

The cross plot will be calculated as an average of the neutron and density.

Select from the “curves” list box the curve you want to import, and then match it to the curve “type” from the list box on the left., Click on the ADD button and that curve and type will be displayed in the selected list box. Repeat this for each appropriate curve, and when all curves are selected, click Import. Before  importing, be sure the KB displayed is correct, if not, correct it in the edit box. You can import additional curves into the same file provided the total depth of the file is equal to or greater than the las file you are importing. Additionally, if the required information is available in the file, the water saturation and bulk volume water will be calculated and added to the “curve file”.

The file will have an “mlc” (mainlog curve) extension. It is in binary format and can not be edited.

Once imported, the scheme feature can be used to display any or all the curves. 

It is not unusual to have more than one source file for the same well. If this is the case, import the deepest file first, and then any other files can be added. This will change at some point to allow any order.

Water Satuation: (Archie Method)

When you import any e-log data, the water saturation’s(Sw) will be calculated and added to the file if the values are present for density porosity and deep restivity(Rd). Bulk volume water(BVW) will also be calculated. The calculation is made using default values for resistivity of the formation water (Rw), ‘a’ and ‘m’. Once the values are imported, you can change these default values through any interval of the file. To do this, select Sw from the Setup menu. This will display a dialog box allowing you to set the various values and entering a start depth and end depth for the settings you select. You may set as many different intervals as you like. When the curves are displayed or printed, the values you select will be used to calculate the curve positions.

When you have the density porosity displayed on screen, right clicking in the gas column at the depth of interest will bring up a dialog showing the values for that depth. You may enter different values and click recalculate, the Sw & BVW will be recalculated using the values you entered. This will not change anything in the file.


Schemes allow you to turn on or off any data type contained in the log file, or the Elog curve file. Checking the data type in the schemes dialog will turn it on if that data type is available. Once set, you can name the “data set” and these lines will be displayed when the named scheme is selected from the scheme menu. This feature is only useful if there is elog data available to display. The same “scheme” will print as displayed on screen.

Additionally you can check the ‘plot density on rate grid’ checkbox, which will cause the density porosity curve to draw on the rate grid instead of the normal porosity grid (gas grid). This can be useful for correlating. You can elect to draw total gas only by checking the Total gas only check. Wrap applies only to the e-log curves, and can be turned on or off for each scheme. Once created and saved, the name you selected will be added to the menu, (max 6 schemes), and will apply to any file that contains the appropriate data.

When displaying resistivity curves, a logarithmic grid is used. The various scales for each curve displayed is drawn at the bottom of the grid, lines are identified in the legend above the gas grid. There is no ability at this time to change the line style or color.


.log …16 bit data file

.mlw … 32 bit data file (Windows only)

.hdr … contains header information, one for each data file

.rpt … contains all the daily mud log reports, if any

.sho … file containing all the show  reports, if any

.dst … contains all dst information if any

.top… contains information about any Tops associated with this file

.cfg …contains setup information and closing info so display will be restored to the same state it was in when Mainlog last closed, one for each data file

.ini …contains file name of last open file, and in some cases other information

.sch…contains settings for schemes if any

.mlc…if advanced features are enable, contains imported elog data

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