Method of injecting lift gas and gas lift flow control device

Abstract

A method is disclosed for injecting lift gas or other fluid into a production conduit of an oil well via one or more wear resistant downhole gas lift flow control devices which each comprise: a tubular valve housing () comprising a flow passage () having an upstream end () which is connected to a lift gas supply conduit and a downstream end () which is connected to the interior of the production conduit; a flapper type valve body () which is pivotally connected to the valve housing () and is arranged in the flow passage () such that if the valve body is pivoted in the open position the valve body is oriented substantially parallel to the flow passage and that if the valve body is pivoted in the closed position the valve body is oriented substantially perpendicular to the flow passage and is pressed against a ring shaped valve seat (), thereby blocking passage of lift gas through the flow passage (); a valve protection sleeve () which is slidably arranged in the flow passage () between a first position (shown in FIG.) wherein the sleeve () extends through the ring-shaped valve seat, whilst the valve body () is pivoted in the open position thereof, thereby protecting the valve body and seat against wear by the flux of lift gas or other fluid and a second position (shown in FIG.) wherein the sleeve () extends through the section of the flow passage () upstream of the valve seat (), whilst the valve body () is pivoted in the closed position thereof; and a flow restrictor () forming part of the valve protection sleeve (), which is dimensioned such that the flux of lift gas flowing through the flow restrictor () creates a pressure difference which induces the sleeve () to move towards the first position.