Do you normally receive royalty interest on injection wells? State of New Mexico, Lea County.
There is usually a contract for injection that stipulates a price per unit injected although I am sure it will vary depending on the materials injected. Are you looking at salt water injection (saltwater disposal) or gas storage?
I also believe that since salt water disposal/injection is to non-producing formations, the contract would be with the surface owner as part of the surface disturbance.
I hope this helps.