Market value determination of lease use gas clause

How is the royalty consideration determined for lease use gas in an area where only casinghead gas is produced in quantities that will never justify building gas gathering pipelines? Or, to say it another way, how would the market value of gas at the point of use be determined when it is used by the Lessee but the gas is not being sold to determine a price and there is no gas being sold in the area to determine a price?

Check the General Land Office lease from the State of Texas. If there’s a good way to handle it, my experience is that Texas has thought of it.