Wireline retrievable injection valve assembly with a variable orifice
A wireline retrievable injection valve for an oil or gas well has an internal valve that is initially moved to open a flapper safety valve and also opens to allow fluid flow through the valve. The internal valve includes a sleeve that opens the flapper safety valve and shields the flapper safety valve from fluid. In this manner the flapper valve is protected from being caused to “flutter” or “chatter” due to pressure variations in the fluid flow, thereby damaging the seat.
1. A wireline retrievable injection valve comprising:
a valve body having an inlet and outlet;
a flapper valve element pivotably mounted in a lower portion of the valve body; and
an axially movable valve assembly positioned within the valve body including a second valve and a sleeve, the sleeve adapted to move the flapper valve element to an open position when the valve assembly moves in a downwardly direction in response to fluid flow through the valve, said second valve being biased to a fully closed position in the absence of fluid flow, wherein movement of the sleeve is resisted by a spring and movement of the second valve is resisted by a second spring, the strengths of the springs being such that upon initial flow the sleeve will move to open the flapper valve element while the second valve remain closed.
2. An injection valve according to claim 1 wherein the valve assembly includes a stationary central body and an axially movable nozzle surrounding the central body which together form a variable annular fluid passageway.
3. An injection valve according to claim 2 wherein the nozzle is moved by a pressure differential.
4. An injection valve according to claim 3 wherein the nozzle includes a converging inlet, a throat portion and a diverging outlet.
5. An injection valve according to claim 2 wherein the stationary body is secured within a flow passage formed within the valve body between the inlet and the outlet.
6. An injection valve as claimed in claim 1 wherein the second valve is adapted to open in response to increased flow with respect to the initial flow of fluid through the injection valve.
7. An injection valve as claimed in claim 1 wherein the flapper valve and the valve assembly both prevent fluid flow in an uphole direction when they are in a closed position.