If you have production, you can ask the Operator what their title opinion says for the net acreage that they are carrying for you.
You can find a copy of your lease (maybe) at www.okcountyrecords.com. It will have your royalty on it. It will probably have the gross acres on the lease, not your net acres. But judging from any pooling in that section, you may be able to get a ballpark and work backwards. ALWAYS keep a copy of your original lease and any documentations or correspondence or payments in your files. Quite often the check stub that came with your payment will have the amount of net acres on it.