IANAL and this is my experience and opinion only - not legal advice.
I’ve been through and am going through this exact issue. what I’ve found is that an oil company may be willing to use an affidavit of heirship to get their well drilled; but they are not going to put a well in pay status for the next generation without clear marketable title. clear title is going to require probate (depending on the state as has been mentioned). in my case, the minerals are owned in a state different than my grandfather passed in. his will was probated in the state of passing; but not in the state the mineral interest are in.
I’ve consulted 3 attorneys and the consistent message is that this will cost thousands of dollars to handle probate. the revenues (in my case) will never pay out the attorney fees. given this, I am currently in the process of trying to do this myself. my feeling is that there is nothing to lose, and possibly large amounts to gain (the “large amounts” is because there are also unleased minerals close to existing production).
another point to make is that depending on the state, you may have been paying taxes on your grandparents minerals for some time now (on their behalf); which is not fun - but at least keeps the minerals from going to a sheriff sale.
there is no easy answer here. in your case, you need to consider the total cost of ownership. if the value in these minerals exceeds the cost of the attorney, then by all means - consider getting the ancillary probate completed. if (as is the situation I have) the value of these minerals will never pay the attorneys’ costs - then you can either go it alone, or stop paying the annual ad valorem taxes; in which case the minerals will eventually be sold by the county.