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tamu - pemex offshore drilling

2. Lesson 5A - The Drilling Riser. Riser Components Riser Tensioning Fatigue Kill/Choke Lines Inspection

Samuel
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tamu - pemex offshore drilling

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    1. 1 TAMU - Pemex Offshore Drilling Lesson 5A The Drilling Riser

    2. 2 Lesson 5A - The Drilling Riser Riser Components Riser Tensioning Fatigue Kill/Choke Lines Inspection & Maintenance Reentry

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    4. 4 Integral Marine Riser Joints

    5. 5 Integral Marine Riser Connector

    6. 6 Integral Marine Riser Connector

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    13. 13 Combined Effect of Mean Stress and Alternating Stress Consider: Max Stress of 40 ksi Alternating Stress: 10 or 20 ksi Mean Stress: ? Life: ?

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    17. 17 Estimating Pressure Drop in Choke Lines It is important to be able to determine if the pressure drop in the choke line will be a problem (excessive). Most drilling fluids are Non-Newtonian. The Bingham Plastic or Power-Law models may be used. More about this later.

    18. 18 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.

    19. 19 Riser Considerations – cont’d No Field Welding on Riser! Fatigue of riser cannot be measured prior to some indication of failure. Routine inspection required.

    20. 20 Riser Considerations – cont’d 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.

    21. 21 Riser Inspection Visual Inspection of the riser should occur every time the riser is run. Check all the seals Check all the sealing areas

    22. 22 Riser Inspection – cont’d 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.

    23. 23 Riser Inspection – cont’d 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.

    24. 24 Riser Instrumentation Heave Gauge: Pointer attached to guide line moving in front of graduated board. Riser Angle Indicator (at ball joint):

    25. 25 Riser Instrumentation – cont’d Accurate Positioning System: For detecting and monitoring vessel position.

    26. 26 Ball Joint A Ball Joint Angle > 4 degrees is an indication that something is wrong! Vessel has excessive offset Riser tension is inadequate

    27. 27 Ball Joint – cont’d Must decrease ball joint angle before operations are resumed. Remedial Action: Decrease Offset Increase Riser Tension

    28. 28 Vessel to Seafloor Guidance System Guidelines are used for guiding equipment from the vessel to the seafloor (except in deepwater) Selection and care of guidelines is critical

    29. 29 Vessel to Seafloor Guidance System – cont’d Guidelines should not be tensioned beyond 1/3 of breaking capacity But…inadequate tension is the most common cause of failure in guidelines

    30. 30 Vessel to Seafloor Guidance System - cont’d 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.

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