What is an offshore platform and how is it different an onshore drilling rig?

An offshore platform is a structure that is installed over as group of wells that was drilled by an offshore drilling rig. The function of the platform is to produce the oil from these wells. A platform can be mounted to the seabed or could be a floating type platform. Offshore drilling rigs are for drilling the wells and are mobile and moved from area to area.

Onshore drilling rigs are mobile units too and are moved from pad to pad for drilling and exploration. After a well is drilled onshore, a wellhead is installed on the well. There is no need for a platform as this only economically viable in offshore applications.

There have been cases where an offshore well was drilled from land into the sea, but operated from land. This can only be possible if the oil formation is not too far offshore.