How do gas and mineral rights work when property is combined?

Yes you can sell the property without mineral rights with the property that includes them. The part that doesn't include the mineral rights will include specifications on title to the right to access these rights and the willing buyer must accept these terms to ownership. If they don't the property will not transfer and the sale will not occur.

True the gas underneath does not know property lines but I think you are assuming that the pockets of gas cross the borders of the parcels. This may or may not be the case and if they do, the first person to access them will win. But the ones that are secured will stay in tact.For more info visit uniroyalties.com