Page 263 - Hydrocarbon

250 Completion Technology and Intelligent Wells

wing valve (W)
swab valve
(SV)
Flowline
lower & upper
master valves christmas tree
(LMV,UMV)
tubing hanger
wellhead
control line for
safety valve casing
downhole safety valve (DHSV)
gauge cable
chemical
tubing
injection line
side pocket mandrel (SPM)
with gas lift valve (GLV)
permanent downhole gauge (PDHG)
chemical injection valve
polished bore receptacle (PBR)
production packer with seals (optional)
wireline entry guide (WEG)
gravel pack packer
formation isolation casing shoe
valve
sand control screens

Figure 10.22 Completion schematic.

(and other completion equipment) is often made out of corrosion resistant alloys
(CRAs) such as stainless steel – especially for critical, high-rate wells. The tubing,
like casing, comes in joints typically 40 ft long and is screwed together on the rig.
Most offshore and some onshore completions employ a downhole safety valve
(DHSV), as indicated in Figure 10.23. This valve is held open by pressure down a
control line. If the pressure is bled off either deliberately or because the control line is
damaged, a spring in the valve releases a flapper valve into the flow stream and the
well is closed. For example, if there was a major incident on a platform and the tree
was badly damaged, the control line would break and the well would automatically
shut-in. The safety valve will also be tied into the facility shut-down control system.
Below the safety valve, comes a range of optional equipment. Shown in Figure 10.22
are three types of mandrel. One for the injection of gas, one for a pressure gauge and
the other for chemical injection. The types of chemicals injected could include scale
inhibitors, methanol for hydrate inhibition and corrosion inhibitors. Another
optional piece of equipment (not shown) is a sliding side door (SSD) for the
circulation of fluids into and out of the tubing.
In the example shown, the tubing is anchored and sealed to the casing with a
production packer. Sometimes above the packer, an expansion device (such as the
polished bore receptacle (PBR) shown) is used to allow for thermal expansion or
contraction of the tubing.