Subsurface Easement

Thanks. Here is a little more info. I leased minerals in July of 2017 to lessee who is also drilling two wells near me with no surface rights. They will be coming under a county road and into my property where the permitted well is. Drill pad was just completed and now all of a sudden they are asking for a subsurface easement. So I was just interested to know what is the common, as to whether or not they should compensate me.