A working interest is a percentage of ownership in an oil and gas lease that grants its owner the right to explore, drill and produce oil and gas from a tract of property. Working interest owners are obligated to pay a corresponding percentage of the cost of leasing, drilling, producing and operating a well or unit. After royalties are paid, the working interest also entitles its owner to share in  revenues with other working interest owners, based on the percentage of working interest that is owned.