4b. Exploration Drilling

Exploration drilling is what miners use to learn more about an area. They drill one hole every mile to determine if they want to apply for a mining permit in the area. While drilling, a core sample is taken every 5 feet of depth and analyzed. A geological engineer describes the core’s contents and logs the hole.

If exploration drilling shows a sizable coal field, a permit is secured. In the next phase of exploration drilling, geologists drill one overburden hole every 40 acres. Again, samples are taken and analyzed every 5 feet of depth and a profile of the entire coal field is created. 

In many cases, the drilling happens three years before mining starts. For better modeling, geologists might repeat the drilling process again with holes spaced 660 feet apart.