Please can you offer a definition of the terms 'Stock Tank' (as in Stock Tank Conditions) and 'shrinkage'. Is Stock tank condition the same as standard condition (1 atm, 60°F)?
Stock tank barrels are at 60F. My copy of the GPSA Engineering data book says it is at equilibrium vapor pressure but I would say 1 atm would be consistent with that.
Shrinkage "the reduction in volume of a gas stream by removal of some of its constituents such as for recovered products, fuel or losses"