<p>In accordance with an illustrative embodiment of the present invention, a valve placed in a subsea blowout preventer stack during a production test of a well producing gas comprises a valve body containing two valve elements in series and a releasable control unit. A fluid to inhibit the formation of natural-gas hydrates can be injected into the valve body by means of a pump on the surface and through a high-pressure hose. A lateral connector fixed to the control unit is fitted in a sealed manner into a receptacle on the valve body to allow reconnection of the inhibiting fluid injection system.</p>