Does it mean you have to let them come and actually dig in your land? Or just tolerate the drilling sound as they bore from outside your territory?
The prior owner may have granted use of the land for mining without further compensation or requiring the surface be usable.
Surface mining in Appalachia for coal is a good example.
A modest survey of the topic:
Mineral Rights in Central Appalachia: A Brief History of the Broad Form Deed in Kentucky and Tennessee Blakely Elizabeth Whilden
http://studentorgs.law.unc.edu/documents/elp/2012/whilden_fi...