Old HBP leases and identification of lands leased, retained and/or held by production from older wells has become more of a title curative nightmare as the plays have unfolded. seeing as how some recent players that have moved into the area have been "burned" upon finding out that an older lessee/operator has alleged HBP claims that have subsequently proven out to be true, many companies have become risk-averse to acquiring a lease on lands that may be held by older leases or older production. Where many of these new players have come from areas in which they have been used to fairly consistent reporting, the lack of consistent well history, production reporting (mandatory or voluntary) and other title vagaries has helped to create a climate where new players are just not willing to take a risk in paying significant bonus money for a lease on lands on which title may fail due to existing leases, wells, and/or production.
As several others have mentioned here, if the operator / purported leaseowner is willing to grant a release as to the purported "held" acreage, this seems like the most straightforward fix. I would communicate this to Shell's personnel, lease broker or landman, and verify that if that release is forthcoming whether you would still have a deal. Most large-scale operators seem amenable to that at present; some will even provide you with a form that will contain language sufficient to cure whatever potential problem that they have identified for execution by the purported working interest owners and/or lessees and/or sublessees. If there are other title issues, have them brief you on those - some you may be able to fix, others you may need to retain legal counsel to see through - but you won't know unless you ask.
I would normally tell you in the areas in which I usually work the landowner or mineral owner does not have to be so proactive, but where the creation of a drilling unit and recovery of drilling costs and revenues is so incumbent upon the inclusion of established viable leases, and where the maintenance of leases (particularly older leases) can get so fuzzy, it would behoove you to work on your own behalf - many operators are much more willing to put off "potential problem tracts" at this time in favor of working on drilling their wells on tracts with clean title.
First, do not sign any document or cash any checks received. By cashing checks you could be agreeing to extend the purported lease. Second, you need to demand an accounting. This will demonstrate the lack of payment in producing quantities. Third, you should hire an attorney to resolve your situation, but I doubt you will need to spend anything close to $4000 to get your answers. They can always change units, but if the lease is invalid it cannot be placed in a unit. I haven't read the entire thread, so if I missed something I apologize.
Also, if it wasn't producing and it was orphaned, the operator can face fines for failing to plug it. Don't let CHK or Longt trick you into believing anything until you get documentation and have it reviewed by someone qualified. What county are you in?
Better get a good attorney to search your property deed title and all at the courthouse.. there's too much at stake to lose the game.
You could call the Attorney General's Office in your state. They might have some ideas.
I'm having trouble understanding. You say you have done a title search and have all the documents. But you say in the original post that your father acquired the property in the 1950's but maybe actually it was your grandfather that took possession. This is a key question--exactly when and how did your father acquire it? And did your grandfather own it when the lease was signed in 1973?
Second problem--you say Vista is willing to write a release. So why not just do this? Wouldn't this solve everything? Seems like you could pay whatever Vista asks to get this, and be way ahead.