Theresa, the sale price is usually alot less that the long term value of the producing acres. The buyer usually assumes that the decline will be more than the usual to be on the safe side and also that the price of oil may fall as much as 30% or more. The buyer may expect more wells to be drilled but since he has no way of guranteeing that they will be drilled, it's a windfall if the are drilled but they are not directly involved in the buy offer on a dollar for dollar basis, probably just a small premium considering the wells already there.
I don't know if your wells have declined to their more stable flatter decline rate, if your wells are only a year old, the buyer probably wouldn't want to offer you 5 years royalty at the current rate because in 5 years your wells might not be producing even half as much oil with a price 30% less per barrel at which point the buyers tidy 5 year investment starts looking like a 15 year slog just to get his money back.
If you are leased, you already probably conveyed away 80% of the value of your mineral acres for the lease bonus, and a royalty on what is sold, and you are probably subject to deductions from your royalty so if you bargained for 20% royalty, your net effective royalty after deductions and taxes is probably closer to 17.5% or less. If you perform another transaction, selling your remaining interest in the mineral acres, your royalty, you are probably just going to lose even more money, anywhere in the rage from 30% to 80% over the long haul and 15% capital gains tax this year for selling.
Theresa, if you must have the money from the sale, do what you have to do. I just wanted you to know what the most likely outcome is.
If you will give the legal description of your acres, I would be glad to take a look at them and tell you what I can deduce from the information I gather. Possibly all your wells are Bakken and you could have Three Forks potential equal to or greater than your Bakken production. I know, I have acres in Dunn county also, one spacing with Bakken and Three forks production and one with just Bakken. If you are in the good part of Dunn county, you could eventually have 12-16 wells per spacing. How many wells do you have now and how many would you be giving up if you sell? The buyer is wanting to buy your acres with a fraction of your own money, if you wait, you should get all of the purchase price and more from the royalty and avoid the 15% capital gains tax. Let me know if you want my analysys of your acres.