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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

significant factors, such as with deep-water drilling and under adverse weather

conditions. The ideal riser tension has been defined as "the tension that will

minimize the probability of damaging the riser or drilling equipment, yet cause

minimal wear to the tensioners" in any given situation. In some cases, it is

desirable to use buoyancy modules along the length of the riser. Frequently, the
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