About Jack(et) and Topsides

Jacket act as 2 function. The first one provide the leg to the topside and keeping it stable above the pounding of waves. Secondly, they support laterally and protect the 26-30in well conductors and the pipeline rise.
If you look at the jacket, you can see the different shoes that they used. The first one, the piling it done through the jacket leg, and the hammer pounding is done above the water level. One the other hand, the piling around the skirt which surround the jacket's legs. So in this case, the hammer is pound under the water. Well, how deep we need to put the piling then? Depend on the sea and the soil, could be as deep as 120m.
Well, topsides would be human body if oil platform is human being. Think about the size of human baby is limited by the opening of pelvis, and the limiting capacity of crane vessels and the load out capacity at the yards that limit the sizes of topsides. You will probably stumble upon this words MSF (Module Support Frame).