Mr. Motley,
I believe there is some good advice here as well as some horribly ignorant advice.
As far as some of the general advice you have received is concerned to "Never sell your minerals" that's just plain stupid. Mr. Cunningham is right on. That's like saying never sell your stock in XYZ Corp. - It could go up in value or start paying dividends. I purchase minerals for a living and I'm about to sell a large amount of minerals at the end of this month, because the math works out and I believe it to be a fair deal. There's no blanket statement that applies to buying or selling anything (minerals included).
You just have to do the math and see what makes sense. As I believe you are aware of, we are missing some key information here in the size of the property that your Aunt owns the interest to. Mr. Tooke estimated the tract or lot to be 30' x 70', or 2100 sq ft, or roughly 0.05 acre rounded. We can use that number as a good estimate. If she owned a .00005% interest in that lot, that would be insanely small and I would suggest you sell immediately no matter what kind of well was hit. However, likely she would own the entire lot and would have a .00005% interest in some unit of some kind? That's the only place I could see that .00005% number coming from.
So, if your Aunt had a .00005% interest her decimal interest would be .0000005. J. Michal mentioned the Eagle Ford Shale. Good Eagle Ford Wells are thought to have an EUR (Estimated Ultimate Recovery) of 300,000-500,000 BOE (Barrels of Oil Equivalent). That would make your Aunt's ultimate pay out from a great Eagle Ford well at : .0000005 x 500,000 BOE = .25 x $100/BBL Oil = $25. If the operator happened to drill 5 wells on whatever unit this was pooled into, that would mean $125 over the next 20-30 years. By that math, selling is the no brainer option, but I think we might be missing some information here or the .00005% number that was given to you was not correct. At these numbers, I'm not sure why anyone would be interested in buying these minerals/royalties at this price.
Some other things to consider:
Should a well be drilled, properly keeping up with royalties can be a time consuming task. When your royalties are $20,000 or $200,000/month, this is well worth your time. When your royalties are $5 per year, it's a total waste of time.
If this interest is an unleased mineral interest, her decimal interest quoted earlier of .00005% would be further diluted by the lease royalty. if she signed a lease with a 1/4th royalty, her .00005% would be diluted down to .0000125%.
Should/when your Aunt passes away, you will need to file her probate in Ward County. If she doesn't have a probated Will, you will need to draft Affidavits of Heirship or other documentation showing how the minerals passed intestate (this might take an Attorney's help). This all costs money. Refiling a probate will likely cost you $10-$15 for the first page of each document within the probate and $4-$10 for each additional page. Therefore, filing a 30 page probate consisting of 5 different "documents" would cost 5 x $15 + 25 x $5 = $200. This is more that what Clear Fork is offering you for the whole property!
I'm just trying to help you make a good financial decision and sometimes that decision involves selling the rights. At this point, however, it appears you need more information about the property itself before making an informed decision, so I think you're on the right track with researching the property and it's ownership.
Best of luck!