Oil rigs were instalations used to drill for and collect Oil. In the late 20th century, several companies maintained Oil rigs out of the cost of Scotland.
Four of these were destroyed within one month, amongst them the Ben Nevis and Prince Charlie rigs. UNIT with the help of the doctor investigated case and discovered that a Skarasen was responsible. (DW: Terror of the Zygons)
By the 40th century, the Oil Corp had devised large, insectoid mecha oil rig vehicles that could move and drain oil on other planets after Earth's wells had dried up. Rigs were in use on Boukon, since the planet was full of oil. These rigs were armored as pirating practices were common in this era. (DW: The Infinite Quest)