Make sure to get the Echo's Bigger Workbenches mod so you can actually work on it :)
It has a height of ~103 meters to the top deck, but the recommended operating depth is around ~60 meters.
I recommend spawning it in with the addon editor and enabling "is static" so it is properly in place.
I will be uploading a finished version to the workshop (that won't be operational it'll just be a cool prop or something)
The oil rig structural tower isn't the most accurate or realistic but I uh... got lazy.