AP Downhole Throttle Valve
Annulus-operated downhole choke that prevents hydrate formation in gas-condensate wells
Description
The AP downhole throttle valve is a downhole choke used in the exploration of gas-condensate wells. It is run to the planned depth with the production string, so that throttling, depressurization, expansion and heat absorption take place in the wellbore. This prevents natural gas hydrates from forming in surface gathering lines and at the wellhead, where they could plug the production line and disrupt production.
Features
- Used singly, two pressure applications give the sequence: initial full bore → throttling → permanent full bore
- With several valves in series, it can switch between different nozzles and full bore
- Shear pin structure keeps full bore while running in
- Lock block structure holds the throttling or full-bore state during production
Operation
The valve switches from full bore to throttling by applying annulus pressure, bursting a rupture disc and moving the operating mandrel. A single valve has two rupture discs; two valves in series have three, and so on. Each rupture disc should have a 1,000–1,500 psi interval.
