1. A system for managing production from a plurality of subsea wells, the system comprising: a collection manifold having a plurality of headers, each header adapted to collect well fluid from a fluid output of each of a plurality of subsea wells and convey the well fluid to a vessel positioned at a surface of a sea; a plurality of flow control valves positioned between each of the plurality of subsea wells and the collection manifold to control the flow of well fluid entering each of the plurality of headers; at least one sensor positioned adjacent a well fluid inlet of the collection manifold for sensing a plurality of properties of the well fluid entering the collection manifold; a computer in communication with the at least one sensor, the computer having a memory and defining a server, calculator software stored in the memory in communication with the at least one sensor to calculate well fluid properties of the well fluid entering the collection manifold from each of the plurality of subsea wells and well fluid properties of the well fluid conveyed from the collection manifold to a vessel positioned at a surface of a sea to thereby selectively open or to selectively close a subset of the plurality of flow control valves defining a desired arrangement of the plurality of flow control valves to control the well fluid flow into each header responsive to predetermined criteria, the calculator software comprising: a well fluid inlet property calculator responsive to the sensed plurality of properties to calculate a specific heat capacity, and a density for a selected fluid of the well fluid from each of the plurality of subsea wells, a mixture calculator responsive to well fluid inlet property calculator to calculate a mixing temperature and a water content of a mixture of the well fluid, the mixture being defined by the mixing of well fluid from each of the plurality of subsea wells in each of the plurality of headers, and a flow rate determiner responsive to the mixing temperature and the water content from the mixture calculator and a desired temperature and a desired water content of the mixture of well fluid exiting the collection manifold to determine a selected flow rate of well fluid entering each of the plurality of headers from each of the plurality of subsea wells to thereby attempt to achieve the desired temperature and desired water content, the flow rate determiner determining a plurality of well fluid inlet flow rates entering each of the plurality of headers to define a desired arrangement of the flow control valves; and a controller responsive to the calculator software that is adapted to control each of the plurality of flow control valves.