Well, it's been a while since I've done a post on Oil and Gas Law, but that's changing now.
When last we spoke on the subject, we discussed Gas Storage. Today, we're going to address a related subject, Pressure Maintenance.
One of the ways of storing gas is through injecting gas into a producing reservoir. Essentially, what you're doing is increasing the efficiency and lengthening the life of an oil reservoir spurred by solution gas expansion or from a "gas-cap drive." (the authors of the Book link to Tex. Nat. Res. Code Ann Sec. 91.176). They do this by removing gas that has been produced with the oil and then they will re-inject it at various places in the oil reservoir. to help keep up the pressure that produces the oil.
Inasmuch as gas and oil migrate, there is no way to ensure that the gas that is re-injected will not end up moving to other parts of the oil reservoir and then be produced by other companies who might hold a lease on a different spot. The question that would arise when it's re-produced would be, "who owns it?" As of the time of printing of Texas Law of Oil and Gas (second edition), there has not been a Texas case on point - the authors note that this is native gas withdrawn and replaced, citing the correlations to the wild animal theory. Additionally, gas withdrawn for reinjection is done so expressly not for future withdrawal, but to make the efficient production of oil last longer.
The authors cite a couple cases related to the subject that differentiate between a true pressure maintenance situation where multiple parties own leases in a reservoir and where only one does, as well as reinjection into a depleted gas reservoir for storage, but the crux of the matter is, while not decided as a matter of law, ownership of native gas that has been reinjected for the purpose of prolonging production of an oil well would belong to the subsequent producer of said gas.