Mineral rights search, and purchase

I’ve recently hired a lady to do the research to find who might own the mineral rights to the land I own. I own two separate plots of land in two different sections. I’m under the impression that it is two different parties that have ownership. I have an idea on one plot that the previous owner retained the rights when it was purchased by my father, and it is rumored that BP owns the rights to my other plot, though that is not confirmed. My question is how hard is it to try to get mineral rights from a former landowner, also what would it take to get them from BP if they are owners.

Depends on what they think of the prospects for the area. If the BP you refer to is a certain oil company, I would expect to pay dearly. If prospects are good I think neither would sell unless you offered ridiculous money, $10,000 or more per unproven mineral acre.

Ok well let me ask this, I found both deeds, the particular deed that I believe the previous owner has the rights on says nothing about him retaining mineral rights. So I did some digging and found the contract that the previous owner and my father signed. It states “loss arising from oil, gas, or other minerals conveyed, retained, assigned or any other activity concerning the sub-surface rights or ownership, including but not limited to the right of egress or ingress for said sub-surface rights.” Does this mean the previous owner retains the sub-surface rights? And if so should the deed not state it?

I am a little confused on another matter, what got me thinking of this was a contract that was signed by my father and Western Land Services for what appears to be a five year lease, this contract was signed less than a year before my father died. The story goes they signed the contract only to have Western Land Services come back a few days later to say we don’t own the mineral rights, while doing a search in the county clerk’s office yesterday I was informed that the deed does still in fact show a lease on the land from Western Land Services. So my question here is should upon realizing we don’t own the rights, the contract have gone void? To my knowledge we were never paid for a lease.