Oriented Core Drilling versus Downhole Imaging 1

[moe333]

Hi all,

I have a project where I am evaluating the stability of a proposed quarry rock cut in probably igneous rock in which the stability will likely be controlled by the discontinuities. I have previously worked with oriented core drilling to assist in this type of evaluation but we are considering using a high end downhole imaging/geophysical method that provides pictures of the discontinuities and resolves their orientation. Was wondering if anyone has experience with this method, and if so, thier opinion in comparison to oriented core drilling method.

I do like the oriented core method since you get a good feel for the joint surfaces. Although I suppose you can match the photo's to the core to help with this, but I'm thinking it may be very time consuming.

Any comments appreciated.

 

[epongra2]

Why not do both? Seems like you would want the core for shear strength testing along the discontinuities and all the usual visual classifications. I reviewed a project where they cored and then subsequently lowered a down-hole camera into the borehole.

Might want to talk with a company called Crux Subsurface, Inc. out of Spokane, WA.

 

[moe333]

We will be coring and performing tests on the core to evaluate shear strength. My question is what method to use to evaluate the orientation of the joints. The oriented core method is time consuming and we would not be able to do both the oriented core and the downhole with budget constrainrts.

 

[epongra2]

moe333,

My bad, I thought perhaps you might have been thinking of drilling via a method (air rotary, ODEX, etc.) other than coring and subsequently doing the camera work.

I don't know which method takes less time. The video method provides output which is nice to include in a report and, it would seem, allows you to discard portions or nearly all of the core boxes after testing is completed.

 

[rsully75]

I completed a job on a dam for the ACOE a few years ago using both methods to analyze the fractures in the concrete from AAR. In the end the only data that was used was the camera images and subsequent rose diagrams. It was also easier to place the camera in the hole one time to get the required information (which can be stored on you computer) than placing the cores in a gronometer to get your fracture sets.