working interest.Oil & gas. The rights to the mineral interest granted by an oil-and-gas lease, so called because the lessee acquires the right to work on the leased property to search, develop, and produce oil and gas, as well as the obligation to pay all costs. See ROYALTY(2). — Also termed leasehold interest; operating interest. [Cases: Mines and Minerals  73.1(2). C.J.S. Mines and Minerals §§ 241, 243, 265.]
[Blacks Law 8th]