dear fried
i want to find the optimum diameter(s),correspond to a minimum cost, for a pipeline  transport two phase flow

i suppose that the two phase pipeline system,is along distance large diameter pipeline this line transports the oil and gas mixture (coming from a gathering sytem which
transports the fluid of many wells).At the head of this line thers is a pumping station,in this station the
mixture is pumped into the trunkline and transported to processing facilities.?
                                                                                     

how can i calculate the total cost(cost of pipes +cost of energy)

if any one can provide me with these equations ,i would be very thankfull