NOVELTY - A hydrocarbon conversion system comprises a pre-reformer (12), a synthesis gas generator (14) fluidly coupled to the pre-reformer, and a synthesis unit (16) fluidly coupled to the synthesis gas generator. The pre-reformer is operable to receive steam, natural gas having greater than 3% hydrocarbon components with at least 2 carbons, and hydrogen; and converts the hydrocarbons to methane and carbon dioxide.    USE - For converting light hydrocarbons to heavier hydrocarbons.    ADVANTAGE - The system allows for an efficient production of synthesis gas to be used in producing heavier hydrocarbons.    DETAILED DESCRIPTION - A system (10) for converting light hydrocarbons to heavier hydrocarbons (having at least 5C) comprises a pre-reformer (12), a synthesis gas generator (14) fluidly coupled to the pre-reformer, and a synthesis unit (16) fluidly coupled to the synthesis gas generator. The pre-reformer is operable to receive steam, natural gas having greater than 3% at least 2C hydrocarbon components (C2+), and hydrogen. It is adapted to convert the C2+ to methane and carbon dioxide (CO2), to prepare a synthesis gas feedstock. The synthesis gas generator receives the synthesis gas feedstock. It is operable to produce a synthesis gas having 2:1 hydrogen gas (H2)-to-carbon monoxide (CO) ratio, without forming soot or carbon. The synthesis unit receives the synthesis gas from the generator and converts it to heavier hydrocarbons.    An INDEPENDENT CLAIM is also included for a method of converting light hydrocarbons to heavier hydrocarbons using the above system and employing Fischer-Tropsch (FT) reaction. Steam, natural gas having greater than 3% C2+ components, and hydrogen are provided to a pre-reformer. The pre-reformer is then allowed to convert more than 50% of the C2+ components to methane and CO2, to produce a synthesis gas feedstock. This feedstock is delivered to a synthesis gas generator to produce a synthesis gas having a 2:1 H2:CO ratio. The synthesis gas produced is then delivered to the Fischer-Tropsch synthesis unit to convert it to heavier hydrocarbons.    DESCRIPTION OF DRAWING(S) - The figure shows the hydrocarbon conversion system.    System (10)    Pre-reformer (12)    Synthesis gas generator (14)    Synthesis unit (16)