Page 87 - Well Control for Completions and Interventions

78 Well Control for Completions and Interventions

• On the tubing side, integrity is provided by closure of the Christmas
tree valves. An additional barrier can be provided in the form of a
SC-SSSV.
Installing a packer in the well brings with it additional complications.
• Annulus pressure build-up (APB) caused by fluid expansion must be
anticipated and controlled by regular monitoring and bleed off.
Failure to do so could result in tubing collapse or casing burst.
• The annulus usually becomes an integral part of the well integrity
envelope (the secondary barrier), and therefore annulus integrity must
be monitored and maintained. Loss of integrity will almost certainly
require a well intervention.
• With a packer in place, a circulation path is no longer available.
Circulation, for well kill or any other purpose, can only take place if a
circulation path is created. This must be close to the packer (for maxi-
mum effect). Some completions will include a circulation device, such
as a sliding sleeve or side pocket mandrel. In the absence of circulation
equipment, the only method of creating a circulation path is to perfo-
rate (punch) the production tubing above the packer.
• Workover (re-completion) becomes more complex. If the tubing is
connected (anchored) to the packer it must be released before it can
be recovered. If a dynamic (moving) seal assembly is stabbed into the
packer, then the completion below the packer remains in place unless
the packer is recovered separately. Packer replacement can be prob-
lematic, if permanent packers have to be removed.
• The tubing will be subjected to much higher loads (axial, burst col-
lapse, and tri-axial). Detailed tubing stress analysis will need to be car-
ried out to confirm the design (Fig. 2.10).

2.2.10 Single production tubing string with production
packer (mono-bore configuration)
A mono-bore completion is generally defined as one where the internal
diameter of the production tubing is the same or larger than the internal
diameter of the production liner.
A completion configured in this way has some distinct advantages.
• Water and gas shut-off interventions can be easily accomplished using
full bore (liner ID) mechanical bridge plugs, packers, and straddles.
• There is no need to kill the well and recover the production tubing to
gain access to the reservoir.
• Prior to a workover (re-completion), full size mechanical bridge plugs
can be run through the upper completion and set in the liner, above