GB2479000A - A surface controlled annular safety device - Google Patents

Abstract

A down-hole failsafe valve comprising a hydraulic control line attached to a hydraulic chamber acting on a trigger element, an inflatable packer element, a spring assisted pressurised air chamber and a pusher plate. The trigger element acts to hold the pusher plate in place when the hydraulic pressure is high enough. When the hydraulic pressure in the control line is reduced, by control from the surface or due to damage to the line, the hydraulic pressure will drop and allow the spring assisted pressurized air chamber to act on the pusher plate and inflate the packer element to block the well-bore annulus.

Description

Description

Surface Controlled Annular Safety Valve A typical oil! gas well schematic is shown, this can be land or offshore Concentic strings of casing are run as the well is drilled and cemented in place, the object of these are to provide a barrier against high pressure gas,oil or water from unwanted formations and to provide a stable solid stucture that supports the production string,which is the flow path for the desired oil I gas from the target formation.

In some instance gas is injected down the space between the the production tubing 5 OD and the last casing pipe that is run 9 5/8" OD, this is called the A annulus, The injected gas enters the production tbg at a pre -determind point through a previously installed check valve, this gas then makes it's way back to surface and in so doing helps the oil to also reach surface. This is normally called Gas Lift.

In the event of an emergency the well path can be closed of by means of a down hole hole safety valve, in a catastrophy this valve which is fail safe can be closed by bleeding down or severing a pressurised 1/4', control line that keeps the valve open.When the pressure is lost the valve slams shut. (a catastrophy would be an act of terroism or a tanker colliding with the oil platform and shearing the well heads.) This action stops the flow of highly combustable hydrocarbons flowing up the production pipe,but it does not address the highly immflamable injection gas in the A annulus.

What the Surface Controlled Annular Safety Valve does is allow a fully opened annulus that can be fail safe closed in the same fashion as the Down Hole Safety valve, only packoff elements would seal the A annulus See Drawing A Surface Controlled Annular Safety Valve A typical oil! gas well schematic is shown, this can be land or offshore Concentic strings of casing are run as the well is drilled and cemented in place, the object of these are to provide a barrier against high pressure gas,oil or water from unwanted formations and to provide a stable solid stucture that supports the production string,which is the flow path for the desired oil I gas from the target formation.

In some instance gas is injected down the space between the the production tubing 5 "OD and the last casing pipe that is run 9 5/8" OD, this is called the A annulus, The injected gas enters the production tbg at a pre -determind point through a previously installed check valve, this gas then makes it's way back to surface and in so doing helps the oil to also reach surface. This is normally called Gas Lift.

In the event of an emergency the well path can be closed of by means of a down hole hole safety valve, in a catastrophy this valve which is fail safe can be closed by bleeding down or severing a pressurised 1/4" control line that keeps the valve open.When the pressure is lost the valve slams shut. (a catastrophy would be an act of terroisrn or a tanker colliding with the oil platform and shearing the well heads.) This action stops the flow of highly combustable hydrocarbons flowing up the production pipe,but it does not address the highly immflamable injection gas in the A annulus.

What the Surface Controlled Annular Safety Valve does is allow a fully opened annulus that can be fail safe closed in the same fashion as the Down Hole Safety valve, only packoff elements would seal the A annulus Operation Construction.

The N2 chamber is charged on surface, the trigger assy keeps the pusher plate above the N2 chamber in place.

Hydraulic pressure acts on the trigger and keeps the trigger in place, which in turn locks the sealed pusher plate.

There is a spring behind the trigger acting against the hydraulic pressure.

Operation to set tool * Hydraulic pressurized at surface.

* Bleed of pressure * Trigger releases * N2 acts on the pusher plate * Packer sets by being pushed by plate Operation to release * Pressure up on the control line this compress the sping and relaxes the packer element.

This is a fail safe tool, no valves are required in the tool for gas injection because in normal operating mode the packer is relaxed and gas injection can be between the element and the casing ID.

See drawing B Claim that Operation differs from any other because Construction.

The N2 chamber is charged on surface, the trigger assy keeps the pusher plate above the N2 chamber in place.

Hydraulic pressure acts on the trigger and keeps the trigger in place, which in turn locks the sealed pusher plate.

There is a spring behind the trigger acting against the hydraulic pressure.

Operation to set tool * Hydraulic pressurized at surface.

* Bleed of pressure * Trigger releases * N2 acts on the pusher plate * Packer sets by being pushed by plate Operation to release * Pressure up on the control line this compress the sping and relaxes the packer element.

This is a fail safe tool, no valves are required in the tool for gas injection because in normal operating mode the packer is relaxed and gas injection can be between the element and the casing ID.