there are three types of header being used for the processing of crude oil
A) group header
B) Test header
C) Emulsion header

my question is this
Why do we need group header and Emulsion header separately?
the function of both are exactly same.
from both the header, fluid goes into separator where oil and gas are separated than gas is sent to gas collection station and oil is sent to
heater -Treater for further processing.