Half of the lease has not been developed. The primary lease has expired. What steps are necessary to push the operator/lessee to officially let go of the undeveloped acreage that is no part of the pooled unit? Is it normally automatic, or must the lessor initiate action?
It won’t happen automaticly.
If your lease includes a provision saying any acreage not pooled will be released at the end of primary term (probably with an additional 90-180 days provided for drilling operations to be initiated on that unpooled acreage) then I suggest sending the lessee/operator’s land department a certified letter, that they will be required to sign for, requesting that they record a release of your un-pooled acreage.
If your lease doesn’t have a Pugh clause or other wording requiring that type of release there may not be a way to make it happen.