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An integral marine riser system is the modern approach to
running the BOP stack and is the method most commonly used
today. With this system, the individual choke-and-kill lines and, in
some cases, hydraulic fluid supply lines are attached integrally to
each riser joint. Running the BOP stack, riser, and choke-and-kill
lines all in one operation represents a significant economical
advantage because it takes less time. Also, the choke-and-kill lines
can be pressure tested against the closed choke-and-kill line valves
on the stack as they are run (fig. 2.15).
The physical integrity of the riser joints is preserved by
eliminating all welding except circumferential welds of the
connectors to the pipe ends. The main support flanges for the
choke-and-kill lines are fabricated as part of the connector, with
clamps for additional support for the lines positioned as necessary
on the pipe body.
Ribs to guide the riser through the rotary table are
fabricated as part of the support flange, making welding
unnecessary—again protecting against areas of stress
concentration. To accommodate high tensile and bending loads
further, a gradual thickening of the pipe wall is incorporated where
it connects to the marine riser connector. Usually, marine riser
joints are made from seamless X-52 line pipe material and come in
50-ft lengths. Deep-water marine riser can be furnished in 65-ft
lengths. A set of pup joints to space out the riser for any water
depth usually consists of four joints: 5 ft, 10 ft, 20 ft, and 25 ft.
The telescopic joint consists of an inner barrel that slides
into an outer barrel, compensating for the heave of the drilling
vessel. The inner barrel, connected to the vessel by a ball joint or
gimbal, allows the vessel to pitch and roll without twisting the
riser. The mud flow line and the diverter system are located
between the inner barrel and the rig floor. The diverter is a low-
pressure annular preventer that seals off the well bore. The diverter
redirects the flow during a kick, keeping mud and cuttings from
blowing onto the rig floor. The outer barrel of the telescopic joint
supports the riser. Riser tension is maintained by the tensioning
system, attached by wire rope to the tensioning ring at the top of
the outer barrel. Marine-riser tensioning systems provide constant
tension to support the riser while compensating for wave-induced
motion of the floating drilling rig. These systems are best suited to
situations where excessive string weight or vessel heave are

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