The designer must ensure that there is critical flow through the choke in order to eliminate the effects of downstream pressure variations on the formation. This is achieved when the FTHP is approximately 1.7 times the downstream flowline pressure. There are additional factors to be considered in choke selection.
1 Actuated chokes
By its very nature the choke is subjected to very high pressure drops, which can lead to mechanical problems.
1.1 Start up and shut down
With zero pressure in the flowline and maximum CITHP the choke is subjected to . . .