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Drill hole validation - Wedge Holes

Andrew Barker 1 month ago in General updated by Keith Whitehouse 1 month ago 5

I am working on a project where we are drilling wedge holes (parent with multiple daughters holes).

When I try to create my drillhole database I am getting a validation error (coincident collars) which I cannot resolve.

Is there a way to ignore or turn-off the coincident collar error?

How do other people doing wedge drilling manage this?

Hi Andrew,

We have a number of wedges from parent holes. All our wedges are named ParentName_W1, _W2...etc, WGDD001 would be the parent hole, WGDD001_W1 for daughter 1, WGDD001_W2 for daughter two. All wedges carry the parent holes collar details and survey details to the wedge point where they then become "independent". Can't say I have ever had these coincident collar type of warnings in Micromine (yes I do other software programs such as Leapfrog),  you get other warnings such as missing interval for the top portion of the wedge, although I usually carry a code in the database fields to indicate it is missing because it is a wedge such as WEDGE in the lithology or WEDGE_WGDD001W1_NS0m_125m in the assay table sample ID field so that it is not left empty.

If you want to remove them fully you could filter them - but then you can't validate them!

Andrew, the error is a non critical error and you can turn it off by unchecking the Check Collar Locations in the Drillhole | Validation | Drillhole Database form.

I have looked at various ways of dealing with wedge holes in MM and think that the correct approach is to have multiple holes with the same collar location, the wedges having all the characteristics (downhole survey points) of the parent hole to the wedge point.


The alternative is to desurvey the parent hole and calculate the coordinate of each wedge point and to use those as the collar coordinates for the wedges.  It works but is very open to error.

But Keith - how sure are you that where the deservey says the collar of the wedge is - is really there? A couple of degrees of error in azimuth and 800m down the hole could actually be 10's+m away from where you think it is. Calculating a wedge collar somewhere down the drill string of the parent seems to me to be calculating the exactly wrong location in preference to an approximately right one... adding additional error on top of more errors. Even Gyro's are not infallible - we had a gyro survey that kicked 10 degees downhole in a 1800m drill hole (operator error but was not picked up for 6 months!), it placed the actual intersection 100+m further north than originally interpreted (using the erroneous hole). 

Thanks Richard, Keith,

I think I have resolved that issue by unchecking the check collar location option.

I agree the correct approach is to have the same collar details and survey data down to the point the daughter commences

Andrew

Ronald,  exactly !!! that's why you should be using the collar location of the parent hole.  Its also much easier to store in an external drill hole DB like Geobank or similar with co located collars.