Page 264 - Hydrocarbon

Well Dynamic Behaviour 251

flapper open flapper closed
Figure 10.23 Downhole safety valve (DHSV).

Below the packer, there is usually a section (the tailpipe) with a nipple profile for
the setting of plugs, temporary gauges or downhole chokes. Nipple profiles are also
often found inside the tubing hanger, immediately above a safety valve and sometimes
(in older completions) above the packer. The nipple profile (Figure 10.24)is a
permanent part of the completion, but the lock is installed and removed by slickline.
The lock can have a variety of components screwed to it, including a blank plug,
check valve or a gauge.
In this example, the screen is connected (and sealed to) the casing via a further
packer. Without this seal, sand could flow into the tubing. Below this gravel pack
packer is another valve (formation isolation valve) that crops up in many modern
completions (often with a confusing array of proprietary names!) for a variety of
purposes. In this case it is used to safely isolate the reservoir whilst the upper
completion is run. In other applications it can, for example, be used as a downhole
barrier to run long perforating guns. They are usually mechanically closed (e.g. by
the pipe used to run the screens) and then opened by a series of pressure cycles.
A further type of completion is the well with remote downhole flow control.
These are often called smart wells or intelligent wells, although as there is rarely any