This problem cannot be solved properly without use of a full-fledged chemical process simulator, such as Hysys, PRO II, Aspen Plus, Chemcad, or PD Plus. Do you need to demethanize the gas? If so, there are innumerable tradeoffs between capital expenditure v/s operating cost for the compressor-turbine assembly, demethanizer operation, downstream fractionation to recover the natural gas liquid components, etc.
Seek out the best process simulation experts to help you navigate this area, as the thermodynamic and simulation issues are highly non-trivial, in my opinion.