Check out this website and paper. Oklahoma O&G Title Law. Is the life tenant's lease still in effect after that life estate terminates? I'm not 100% sure in Oklahoma. According to this, the life tenant is entitled to the bonus, delay rentals and interest from the royalty. And it says the life tenant can't execute an effective lease with the joinder of the remainderman. Here's what it says exactly:
The life tenant of a life estate has the right to possession of the property with the remainderman obtaining possession upon the death of the life tenant. Neither the life tenant nor the remainderman can execute an effective oil and gas lease without the joinder of the other. Nutter v. Stockton, 626 P.Zd 861, 69 O&GR 497 (Okla. 1981).
and
Oklahoma Statutes Title 60 $$71 and 72 provide the procedure for appointing a trustee to execute an oil and gas lease on behalf of contingent remaindermen.