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Drilling risers auxiliary lines
Despite the term of auxiliary lines used here usually being associated to specific lines attached to the outside of the riser main tube but excluding Kill and choke lines (K&C), the tab Auxiliary lines is used in the GUI to define the characteristics of ALL such line types:
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Kill & choke lines: External lines arranged along the outside of the drilling riser and used for circulation of fluids into and out of the well bore to control well pressure.
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Hydraulic lines: Auxiliary lines from the rig to the BOP stack that supply control system operating fluid to the LMRP and BOP.
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Booster lines: Auxiliary line which provide supplementary fluid from the surface and inject it into the riser at the LMRP to assist in the circulation of drill cuttings up the marine riser when required.
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Buoyancy control lines: Auxiliary lines dedicated to controlling, charging or discharging air can buoyancy chambers.
Auxiliary lines effective tensions are taken into account during the calculations and tension and stresses are then post processed. For each type of line, the following parameters must be defined :
Number: The number of lines of the relevant type (2 Kill&Choke lines means we have 1 Kill and 1 Choke line).
Internal diameter: Inner diameter of the auxiliary line.
Wall thickness: Wall thickness of the auxiliary line.
Hoop compound thickness: This parameter allows the user to take into account Hoop effect, for example in case of hybrid tubes combining steel and compound materials.
Water tightness diameter: Water tightness diameter of the auxiliary line used to compute the effective tension in the line, with respect to the internal and external pressures.
Surface pressure: Pressure in the line at the top.
Fluid specific gravity: Each auxiliary line is filled of fluid whose density divided by 1000 is the fluid specific gravity.
Residual pressure: Residual pressure due to hooping effect, associated to the aforementioned hoop compound thickness.
Note
It is assumed that the auxiliary lines are able to slide along the riser main tube and that their stiffness does not impact the riser behavior. Only the pressure effects in the auxiliary lines are accounted for during calculations:
