text: how does an oil rig stand in the water where is it anchored to?   im sorry i've not got the sources for this but i've had experience on several rigs. for a start there are two main kinds of rigs.    for drilling a mobile rig is usually used (cos theres no garuntee of oil!). this is usually a large floating structure which is held in place with anchors. barges carefully transport the massive anchors about 3-4km away then they're dropped and winched in until the line is taught. were talking 20-30 ton anchors and 4 inch thick cable. the anchors have to be in a close to perfect triangle/square as possible.  this rig will drill down, hopefully strike oil and cap the well.    then a production rig will be moved into that place.  the most common technique these days is to have a huge hollow metal cylinder, capped at each end (i cant remember the design name, help me!) about 100-150m long 20-50m wide. this is dragged out to sea then pumped with water until it stands slightly above the surface. its amazingly stable and can deflect strong currents.(some dynamics principals i can't remember). all the production lines are protected very well inside the cylinder. sometimes anchorage is used but its rarely neccessary.    the production unit/platform is then neatly plonked ontop of the cylinder.   in the olden days most offshore oil was close enough to the surface you could built a structure from the sea bed up. this almost never happens anymore.  sorry i can't be more precise!