Over the past twenty years, horizontal drilling, hydraulic fracturing, and, most recently, carbon dioxide sequestration have raised novel and difficult legal issues involving the development and use of oil and gas reservoirs. Much of the difficulty has come in reconciling three key oil and gas doctrines: the rule of capture, correlative rights, and subsurface trespass. This presentation introduces the "fair opportunity doctrine," which synthesizes these rules into a single workable legal test that defines the limits of reservoir property rights. The fair opportunity doctrine addresses cases involving cross-boundary hydraulic fracturing (like Coastal Oil & Gas Corp. v. Garza Energy Trust), horizontal drilling (like Lightning Oil & Gas v. Anadarko Onshore E&P), and underground fluid migration from saltwater disposal, secondary and enhanced recovery, and carbon dioxide sequestration or storage, among others. The presentation is based on Prof. Joe Schremmer's forthcoming article in Volume 46 of the Harvard Environmental Law Review, entitled A Unifying Doctrine of Subsurface Property Rights.