Design of downhole double-throttling choke for gas wells

The biggest disadvantage of installing a choke is that great pressure difference exists between before and after the choke,which tends to cause choke seal failure.That is why the downhole choke is often used only in shallow wells at present.but its application in medium or deep wells is restricted to some degree.To solve this problem,this paper introduced a kind of double-throttling choke,and also built up its designing model.The investigation results show this model can reflect the actual double-choked wellbore flow behavior,and the double-throttling choke can reduce the pressure difference across each choke so as to reduce the possibility of choke damage.This paper also suggests that the double-throttling choke should be located in such a way that no hydrates will be produced after throttling,and the shallower choke should be set at such a depth where the tern perature drop effects of the deeper one have been diminished.