Modular topsides system and method having dual installation capabilities for offshore structures

The present disclosure provides an improved method and system for loading a topsides onto an offshore structure by functional modules. A module support frame forms a supporting structure to which production modules can be assembled. The production modules are adapted to extract or process hydrocarbons from a hydrocarbon well in an offshore location. One production module is a well bay production module to which other production modules can be coupled, including a drilling support production module, separation production module, export module, and utility module. The module support frame can be loaded onto floating barges and other modules assembled thereto to allow the barges to provide incremental and controlled support during the loading process and for the floatover installation. The barges can be floated out to the offshore structure and loaded onto the offshore structure by methods including a floatover method or with a heavy-lift crane vessel.