Mineral division of royalties

In North Dakota I have two separate parcels of land with royalties. One where the total percentage equals the leased amount. The second it does not even come close. Eg. 80 mineral acres with 18.75 lease is only paying out at 1% (no others have share in the 80). The last is a horizontal well but stays within the 80 acre sections. ?? It was my mothers and only recently given to me. I feel she was not given her full share. I asked the Oil Co. to send me the documents from which they calculated her percentage. (I have the original lease 80ac/18.75%), but they said I need to find them at the court house. The court house does not have division orders or deeds recorded that I could find.

There could be some non-participating royalties (NPRIs) at play that come out of the mineral estate and effectively reduce the royalty percentage. If you’re comfortable posting the legal description, some title can be run on it; all the oil producing counties have online records that require a subscription. Also, don’t confuse the net royalty interest (NRI) with ownership % i.e. 80 acres in a 1280 acre unit is 80 / 1280 * .1875 = 0.011719 NRI.