Yes I agree you need legal assistance and I am not an attorney. First Kaufman County, TX which is a thousand miles from any Bakken Shale. To me the document is confusing in the respect it seems to convey a royalty vs mineral interest and it only conveyed a 1/16 and a 50% interest. What happened to the balance of her royalty? Secondly, the document commentary references her lease meaning there was, a one time, mineral ownership. Did the royalty balance plus the mineral rights remain in the name of the estate?
That said, if this was a producing entity, there were most likely mineral taxes so was the balance part of a Sheriff`s tax sale?
You will need title run to answer any of these questions and answer your initial question.