Snug,
Thanks For all the interesting cartoons. Here you go.
In exploration. When they case the hole its normal now to take a GPS location and shoot a dip angle (inclination) and azimuth (direction) on the collar of the hole. They drill the hole, have a geologist look at the end of hole core to make sure the company wants it shut down and then close it down. If yes, they pull the drill rod, pull the casing and stick a post in the collar location (not very sophisticated) to mark it.
Once they hit something the rules change as the location issue start to matter for resource calculations. The grids that people talk about are never accurate so drill collar locations are surveyed in and accurate inclinations and azimuths are shot. Collar locations are given as UTM coordinates. Given that hole NEVER stay straight they are surveyed down hole as well for dip and direction. There are instruments (basically a compass and dip meter) that do single shots at a time (http://www.pajari.com/Tropari/tropari.htm) to gyro system that provide continuous measurements even in magnetic environments such as around nickel deposits (http://www.downhole.com.au/products_flexit_gyro.asp). Bottom line is that you need to know where your holes are going as holes can easily deviate 15+ degree in the vertical and horizontal direction over 300 meters OR you wont know where your intersection actually hit.
Cementing is a necessary evil of infill drilling. Once you suspect you have something you need to start planning for mining it. The drillers mix the cement and pump it through the water pump to the bottom of the hole. It’s more about building a plug then about structural strength so cold and setting times don't mater. Needless to say there is lots of clean up of drill rods and the pump and water trough after it is done.
Some companies leave the casing in the holes while others mark the collar location of the hole in some other way. We used to pull the casing and stick ABS (plumbing) pipe in its place. Everyone does something different. With a hundred holes in a small area it doesn't take long before they get run over by equipment etc so the survey locations are important.
... Been There
