1. Petroleum Engineering 406 Floating Drilling
Lesson 10
The Drilling Riser

2. Lesson 10A - The Drilling Riser
Riser Components
Riser Tensioning
Fatigue
Kill/Choke Lines
Inspection & Maintenance
Reentry

3. Riser system for a floating drilling rig
RISER TENSION
SLIP JOINT INNER BARREL
SLIP JOINT OUTER BARREL
UPPER BALL JOINT
KILL AND CHOICE LINES
RISER JOINTS
LOWER BALL JOINT
BOP
Mudline
Riser system for a floating drilling rig
Marine riser = drilling riser, get returns to surface, well control, communications link

4. Integral Marine Riser Joints
Choke and kill lines are integral with the marine riser , flanged connections; clamp, etc

5. Integral Marine Riser Connector
Flanged connection - 6 bolts
NOTE: Choke and Kill Lines
O-ring type seals
- inspect when running

6. Integral Marine Riser Connector

7. Marine Riser Flexible Joint
Flexible joint, binding from high tensile forces, inject lubricant, up to 1,500,000 lbf!

8. Upper Section Marine Riser System.
MARINE RISER DIVERTER ASSEMBLY
FLEXIBLE JOINT
RISER TENSIONING LINES
TELESCOPIC JOINT
KILL AND CHOKE LINES
Upper Section Marine Riser System.

9. A diverter system. Mud returns L.P. Annular Control valve Vent line
Re-directs flow from rig floor to blooey line (10”+), downwind, do not shut in, erosion -10E8

10. Figure 6-6. Vertical steel loops used for kill / choke line transition around the ball joint.

11. Schematic diagram of riser with imposed forces
The Drilling Riser
MEAN WATER LEVEL
RISER ELEMENT
Schematic diagram of riser with imposed forces
Optimum riser tension to minimize damage to riser and wear-and-tear on tensioners, sag

12. Applied tension in riser, kips
Maximum stress
Mean tension
Stress in riser, kips
Minimum stress
Applied tension in riser, kips
Tension in riser must be not too low and not too high. Set at 118 kips - will fluctuate kips ~ 15%

13. Riser Considerations:
Riser Metallurgy is very important.
Correct heat treatment is essential.
80,000 psi min. yield strength and good toughness is preferred.
Preheating, welding & normalizing after welding is critical for riser integrity & long life.

14. Riser Considerations:
No Field Welding on Riser!
Fatigue of riser cannot be measured prior to some indication of failure.
Routine inspection required.

15. Riser Considerations:
Fatigue is an embrittlement of the metal. It often starts in the vicinity of welds or other places of high stress concentration.
Fatigue is caused by cyclic loading.

16. Riser Inspection:
Visual Inspection of the riser should occur every time the riser is run.
Check all the seals
Check all the sealing areas

17. Riser Inspection: A complete inspection should be made annually.
Dyes: Will detect cracks. To use dyes, paint must be removed.
Magnetic Particle Inspection: Sand blast areas around welds prior to magnetic particle inspection.

18. Riser Inspection:
Ultra-Sonic Inspection: May detect cracks below the surface. This test is run inside pipe. Paint removal is not necessary.
X-Ray Inspection: Is for cracks inside the metal. It may miss surface cracks.
*No one technique will find all the cracks.

19. Riser Instrumentation:
Heavy Gauge: Pointer attached to guide line moving in front of graduated board.
Riser Angle Indicator (at ball joint):

20. Riser Instrumentation:
Accurate Positioning System:
For detecting and monitoring vessel position.

21. Ball Joint: Vessel is offset Riser tension is inadequate
A Ball Joint Angle > 4 degrees is an indication that something is wrong!
Vessel is offset
Riser tension is inadequate

22. Ball Joint:
Must decrease ball joint angle before operations are resumed.
Remedial Action:
Decrease Offset
Increase Riser Tension

23. Vessel to Seafloor Guidance System
Guidelines are used for guiding equipment from the vessel to the seafloor.
Selection and care of guidelines is critical.

24. Vessel to Seafloor Guidance System
Guidelines should not be tensioned beyond 1/3 of breaking capacity
But…inadequate tension is the most common cause of failure in guidelines

25. Vessel to Seafloor Guidance System
Tension should be maximum when landing the BOP stack, or when landing the riser onto the stack.
When the guidelines are not being used to run equipment, tension may be slacked off to ~ twice the weight of the line in seawater.

26. Table 6-1. Recommendations for Conventionally Used Guidelines
As water depth increases, larger diameter guidelines must be used.
Higher tensioning is required.
Don’t forget to limit tension to < 1/3 of breaking strength.