The question as to which source of porosity data is more reliable cannot be answered without reference to a specific interpretation problem.These techniques will yield correct porosity values under favourable conditions.the core analysis porosity determination has the adventage that no assumptions need to be made as to mineral composition,borehole effects,etc. However,since the volume of the core is less than the rock volume which is investigated by a logging device,porosity values derived from logs are frequently more accurate in heterogeneous reservoirs.