First off, welcome to this site.
I do not know what the agreement states, but the general premise seems to be eerily to one that I signed years ago. ie, changing royalties, gaining units, etc.
In my case, I signed away 3/4 of my percentage without realizing it. I was told that they needed to do a ‘water flood’ procedure and if it worked it would be beneficial to all involved. Well, it did not work and my percentages on 5 wells did not go back to the original percentages. I lost big time.
My checks went from $400-700 dollars a month to about $100-150 a month. My last check was $16 (sixteen) dollars.
Be careful. Get a qualified lawyer. Pray you did the right thing for you.
Good luck. 
