Page 183 - Well Control for Completions and Interventions

Well Control Surface Equipment 175

rotating the ball through a quarter turn using a hexagonal wrench. Most
drilling contractors and operating companies recommend using the upper
kelly when working with a BOP stack that has a rated working pressure
of 5000 psi or more. The upper valve isolates the kelly hose, swivel, and
surface equipment from the high well pressure.
A lower kelly valve is used as a back-up to the upper valve, and is also
often used as a mud saver.

4.10.2 Top drive valves
Rigs equipped with a top drive have two ball valves located on the top
drive equipment, in an arrangement very similar to that used with a kelly.
Indeed, they are sometimes referred to as kelly valves, kelly cocks, or
inside BOPs. In most installations the lower valve is a standard manually
operated ball kelly valve. The upper valve is hydraulic or pneumatically
operated from the driller’s console, and is normally the first valve to be
closed.

4.10.3 Full opening safety valve (FOSV)
When running or pulling of completion tubulars, the pipe in the rotary
table is not connected to the top drive (or kelly). If there is a kick, flow
through the pipe is normally shut-in by stabbing a FOSV into the tubing
in the rotary table, and then closing it. Most valves are uni-directional,
only holding pressure from below, and are closed by rotating a ball
through a quarter turn using a hexagonal wrench. Both valve and wrench
must be kept close to the rotary table for immediate access. The valve
must be left in the open position to enable it to be made up even if the
well has begun to flow. Since FOSVs are manufactured with drill pipe
connections (box up, pin down), a range of cross-overs from the FOSV
thread to each of the thread forms used during a completion must be
available. The relevant cross-over should be kept with the FOSV ready
for immediate use. The reason for having the box up connection on top
of the FOSV is so drill pipe can be made up above the valve, and the tub-
ing stripped back into the well below an inside BOP (Fig. 4.27).
In some circumstances, the response to a kick is to shut-in the annulus
by closing the annular BOP, whilst at the same time making up the
FOSV to the tubing in the rotary table and then shutting the ball. There
are, however, circumstances where additional measures are needed to
properly secure the well. These are fully described in Chapter 7, Well