An oil platform, offshore platform, or (colloquially) oil rig is a large structure with facilities to drill wells, to extract and process oil and natural gas, or to temporarily store product until it can be brought to shore for refining and marketing.n oil platform, offshore platform, or (colloquially) oil rig is a large structure with facilities to drill wells, to extract and process oil and natural gas, or to temporarily store product until it can be brought to shore for refining and marketing.