on representative core plugs with the given fluid system from the well a commonly used method is to apply a filter cake on the core plug and apply a pressure through the core plug towards the backside of the filtercake and measure the required pressure drop to initiate flow 2 determine the required pressure to initiate flow through the icd screen this depends on the screen design for a nozzle based icd with wire wrapped screen and sufficient drainage area under the wrapping and into the icd housing the pressure required to initiate flow will in most cases be close to zero for other designs this threshold pressure can be significant to determine this pressure a flow test in the actual mud system may be carried out 3 take benefit of the fact that the pressure drop through an icd is small when fluid is not flowing through it and high when fluid is flowing this means that zones or sections not cleaned up will basically be exposed to the differential pressure from the formation into the tubing the tubing pressure will be kept at a lower level due to the added pressure drop through the icds in the flowing zones 4 calculate the icd setting that will provide sufficient pressure drop in the flowing zones or sections to reduce the tubing pressure to a level whereby non cleaned up sections gets exposed to the required differential pressure this icd setting can be calculated.