Dear Mr. Monroe,
It may be much about nothing, if the rights were granted years ago in a perpetual disposal agreement. If the rights were granted in a perpetual agreement, then it is very likely that the SWD is a commercial SWD well and injects wastewater from a number of wells.
The other type of SWD well is on a lease basis only. The permitting requirements are much less, the surface owner has almost no negotiating power on the more typical lease forms.
Are you looking to break the agreement that your grandfather entered into many years ago?
As to whether the rate is right is entirely dependent on how many barrels of salt water are being disposed.
In Jasper County (Texas), typical commercial wells pay to the landowner about $0.50 per barrel in today’s market.