Drillhole validation issues and how to resolve them


Discover's new drillhole project Validation Tool (in version 2011) is a powerful and comprehensive error-checking facility, essential for problem-free section/plan generation and annotation.

This tool will consecutively check the project's collar, survey and downhole data tables as assigned during Project Setup. For each of these drillhole data types, the Validation tool will present both Compulsory (ticked and greyed out) and Optional (can be enabled by user) error checks. See Discover's interactive Help system for detailed use of this functionality.

Below are the Errors that may be listed by this tool, and their common causes and resolutions. The content of this article is also available as a PDF attachment for offline reference.

NOTES:

1. If using a database or shared dataset (e.g. read-only files on a server), it is strongly recommended to resolve all issues in the source dataset, not just on the user's local native MI Pro table copies.

2. All data changes should be first checked and verified against field logs/records.

3. Failure to resolve compulsory errors may cause project corruption or erroneous/misleading section displays.


Collar Validation report

Mismatched Collar Object (compulsory)

Cause  - The spatial position of a collar (in the map window) does not match the values in the assigned collar easting/northing fields. The collar object may have been either:

  • Physically moved/edited, or
  • Generated from a different set of coordinate fields. For instance, the collar point may have been made mappable (using Create Points) via a pair of AGD66 easting/northing fields, but a different set of GDA94 easting/northing fields were assigned during Project Setup).

Fix  – A number of options are available:

  • Ensure the correct collar coordinate fields (as used to make the collars mappable) have been assigned in the Project Setup routine
  • Remap the collar objects (Create Points) using the assigned easting/northing fields
  • 'Autofix' can be used to automatically move the collar object to the coordinates in the collar table.


Duplicate Collar (compulsory)

Cause - More than one drillhole record with the same HoleID exists in the collar file

Fix - Manually check the duplicate instances with the same HoleID's in the collar file, and resolve (e.g. rename or delete the duplicate HoleID)


Duplicate Collar Location (optional)

Cause – Multiple drillholes share the same collar coordinates. The following are valid examples of coincident collar locations: daughter/wedge/splay holes, diamond tails on RC collars, or re-entries of old collars.

Fix - Manually check holes with the same collar location coordinates in the collar file.


Survey Validation Report

EOH Longer than Collar (compulsory)

Cause - One or more survey measurements have depths greater than the hole's Total Depth in the collar file. This may result from a hole extension/tail where the collar total depth has not been updated, or it could be due to a data entry error.

Fix - Use the 'Show' button to visualise the hole's deepest survey record. Query the same hole in the collar table, and compare their depths. Resolve as necessary.

NOTE: Incorrectly changing the end-of-hole (EOH) value in the collar file may then cause errors with the downhole tables.


Field outside range (optional)

Cause – Dip values must be between -90 and 90 degrees (with 0 degrees for horizontal drillholes).

Fix – Manually check and resolve.

 

Collar missing (optional)

Cause – No survey records exist for the highlighted drillholes. This may be correct: these holes may be 'straight' drillholes with solely collar survey information (e.g. RAB, aircore or vacuum).

Fix – Manually check the hole types and field data.

 

Duplicate depth value

Cause – Multiple survey measurments at the same depth may be due to either:

  • Data entry error or
  • Follow up survey's (e.g. post drilling with for instance more accurate survey devices)

Fix - Manually check survey data and remove erroneous or less accurate duplicates

 

Dip Sign Mismatch (optional)

Cause - Identifies any dip values outside the Down Dip direction (as set in the Project Setup wizard). These may be correct; underground drilling in a project set with 'Down Dip is negative' may have some positive dips (such as upwards and horizontal drilling).

Fix - The autofix option will convert these to the 'dip sign' as set for the project. However it is recommended to check these manually.

For instance, if Down Dip is set to 'Negative' and positive dip values are encountered (e.g. 64 & 45), these will be changed with the Autofix option to negative dips (i.e. -64 and -45)


Large Dip Change (optional)

Cause – Difficult and/or highly variable ground conditions may lead to large dip fluctuations between survey measurements

Fix – Manually check survey data (e.g. against field logs and previous drilling)

 

Large Azimuth Change (optional)

Cause  – Difficult and/or highly variable ground conditions may lead to large azimuth fluctuations between survey measurements

Fix - Manually check survey data (e.g. against field logs and previous drilling)



Downhole Validation Report

EOH Longer than Collar (compulsory)

Cause  - One or more downhole intervals have depths in excess of the hole's Total Depth in the collar file. This may result from a hole extension/tail where the collar total depth has not been updated, or it could be due to a data entry error.

Fix  - Use the 'Show' button to visualise the hole's deepest downhole record. Query the same hole in the collar table, and compare their depths. Resolve as necessary.

NOTE: Incorrectly changing the end-of-hole (EOH) value in the collar file may then cause errors with the survey and other downhole tables.


Values of '0'? and tiny overlaps (small decimal values such as 0.0007613)?

Cause
- Data imported from Access databases commonly display this problem

  • Resize/widen the "Amount" cell and check that there are not significant figures after the decimal point (e.g. 0.000341).
  • Examine the browser records; if no overlap is apparent, click in each cell successivley to check no siginificant figures are hidden

Fix – Use the Autofix option with an appropriate 'Gap Check Precision' to auto-resolve as necessary.



An example of a 'hidden' overlap:

1/. Both cells (in the Assay and Collar tables) look to have the same value of 786.1m






2/. But clicking in the Assay table cell reveals extra significant figures after the decimal place:





3/. Applying an Autofix 'Gap Check Precision' of 0.1m corrects the problem:





Overlapping Sample (compulsory)

NOTE: No sample overlaps should exist within any one downhole data table. Generally different sample types (e.g. assays, geophysics and lithology) should be stored in different tables (unless logged with exactly the same intervals over every hole in the entire drillhole project). Composited assay tables should also be stored in a table separate to the source assay table.

Values of '0' and tiny overlaps (small decimal values such as 0.0007613)?

Cause - Data imported from Access databases commonly display this problem

  • Resize/widen the "Amount" cell and check that there are not significant figures after the decimal point (e.g. 0.000341).
  • Examine the browser records; if no overlap is apparent, click in each cell successivley to check no siginificant figures are hidden

Fix  - Manually check downhole data (e.g. against field logs and previous drilling) and resolve



Overlaps greater than 1m

Cause
  - This is typically a data entry error

Fix  - Visualise, check and fix manually.


Collar Missing (compulsory)

Cause  - No matching HoleID's exist in the collar file for the highlighted downhole data records. Collar entry may have been inadvertently deleted, no included in the output Access database query, etc.

Fix  - Check and resolve manually.


Collar Added (optional)

Cause - A HoleID in the collar file exists for which there are no samples/intervals in the highlighted downhole data table. This may be correct as:

  • Sample data is yet to be incorporated into the database (e.g. awaiting laboratory results)
  • No samples were logged/recorded for that data type (e.g. a RAB or aircore hole failed to penetrate alluvial sediments/cover, therefore no assay samples collected)

Fix  – Sections and plans can still be created with missing data.


Sample Gap (optional)

Cause

  • Samples may intentionally have been not taken  for the entire hole due to overburden/alluvial sediments/etc, or only selective sampling of lithologies of interest was conducted
  • Samples may have been lost during transport or at the laboratory

Fix  –  Check if appropriate and resolve manually.


Duplicate sample number

Cause  –

Fix  -

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Last Updated on: 15th of December, 2011