"I am use to all drilling rights being part of the lease(s), but I have no lease experience in La. It seems odd (to me) that you could have a lease, but limited to depth.
Can you expand on what is typical in La?"
Probably the great majority of older leases were all depths and provided for a 1/8 royalty. Over the years, as these leases were assigned, the assignor (the guy doing the assigning) would retain something for himself when he conveyed to the assignee (the guy who is on the receiving end). He could retain certain depths and/or some override, or not assign all of the lands covered. Imagine this happening over and over for 80 years and you can see how complicated running title could be.
New vintage leases have base royalty from between 3/16ths (18.75%) up to 22%, or higher, maybe 25%. A farm in may only have a 70% NRI but that's about the economic limit.
Production is necessary to hold the lease beyond its initial or "primary" term.
In the past 30 years Pugh Clauses have become normal when granting a new lease.
Example: Vertical Pugh Clause. "At the expiration of the primary term this lease will automatically expire as to all depths 100' deeper than the depth being then produced."
Horizontal Pugh Clause: "At the expiration of the primary term this lease will automatically expire as to all lands not then included in a govermentally approved producing unit."
To make it even more fun there is this thing called "Prescription" in Louisiana. If I sell you my land but retain the mineral rights, and there is no drilling to "interrupt" the running of prescription, then the minerals will automatically, (without the necessity of filing any paperwork) will revert to the owner of the surface AT THAT TIME. If on the last day of the 10th year somebody spuds a well in a good faith effort to obtain production of oil or gas in paying quantities then prescription is interrupted and the ten years starts all over again.
Production continuously interrupts the running of the 10 year prescriptive period so you could sell you land, reserving the minerals thereunder, and the minerals wouldn't pass to the surface owner until ten years after the date of last production.