Emergency Disconnect Procedures: Industry Approaches to DP Drift-Off - PowerPoint PPT Presentation

Emergency Disconnect Procedures: Industry Approaches to DP Drift-Off Analysis James N. Brekke, P.E. Account Manager, Offshore Energy Project Development American Bureau of Shipping BSEE Standards Workshop – May 8, 2015

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Preview  Background on DP Drillship Operations  DP Watch Circles – Emergency Disconnect  Drift-off Analysis Techniques  Operations  Conclusions 2

Drillship Operations Derrick Rig Floor Heave Compensator Riser Tensioners Drilling Riser DP Thrusters Blow Out Casing Preventer 3

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Drilling Riser Management  Objective:  Protect the vessel, riser and well  Establish limits on operations  Scope:  Riser deployment  Riser tensioning  Emergency disconnect  Riser recoil  Storm hang-off 4

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Emergency Disconnect  What is emergency disconnect?  How often does it happen?  Allowable limits:  Conductor pipe – bending stress  Wellhead – bending moment  Riser bottom flex joint – limiting angle  Riser top flex joint – limiting angle, moonpool contact  Riser slip joint – stroke limits  Riser tensioners – stroke limits  How are these managed? Watch Circles and Drift-Off Analysis. 5

~ ~ Watch Circles: Concept , ..... Drift off analysis results \. ,J n EDS 90 sec , Time " " r r ..... > > Yellow Red Alert POD Alert I I Offset Offset "- "- .,J \. I ~1 ~1 Tpod = t (sec) T RED= t- EDS Time (sec) T YELLOW = t- EDS Time (sec) - 90 sec 6

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Watch Circles  Thresholds that are color-coded yellow and red  Established using drift-off analysis  Based on scenarios of drift-off under total loss of power, drive-off, degraded thrusters, or other events  Offset definitions:  Point of disconnect (POD) – offset at which any allowable limit is first exceeded  Red – offset at which the emergency disconnect sequence (EDS) must be activated. Drillpipe would be sheared during EDS.  Yellow – offset at which preparations begin prior to EDS 7

Watch Circles: Compass View 320 300 310 8

~ ~ Drift-Off Analysis Results Drift Off Analysis - Vessel Excursion From Well Centre - Vessel Excursion - 10 ppg Mud Weight & 1455 k/p Top Tension 6 00 500 POINT OF DISCONNECT 469 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - § 400 ' ui ... :::::l (.) X w a> 300 RED ALERT OFFSET 281 - - - - - - - - - - - - - - - - - - - - - - - - - 2 C 2 200 ·;:: 0 I 70sec I 1• 100 I 187 257 0 L--~==- -+-----+---+----+--+----+-- 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Time (sec) 9

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Drift-Off Analysis Techniques  Fully coupled analysis (state-of-the-art)  Riser analysis fully coupled with vessel analysis  Includes riser restoring force, riser dynamics – Ref: O’Sullivan, Soles, Dib, “Fully Coupled EDS/Drift-off Analysis for a Harsh Environment Deepwater Site” OMAE 2004 – 51631  Uncoupled techniques  Vessel drift-off analysis without riser, static riser analysis  Vessel drift-off analysis without riser, dynamic riser analysis  Fixed offset  Constant watch circle sizes, typically based on % water depth 10

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Operations  Dynamic Watch Circles (updates on the rig every 6 hours)  Prevailing or forecast weather  Changes in riser top tension or drilling mud weight  Can use coupled or uncoupled drift-off analysis 11

~ Fixed vs. Dynamic (Fully Coupled) _,. w I\.) 0 0 0 0 0 0 0 0 0 I I I I I 1430 3/27 1230 3/28 1200 3/29 2200 3/30 2200 3/30 2100 4/1 4/2 2100 4/3 2200 2130 4/4 Courtesy of Wood Group Kenny 0300 4/6 4/7 0300 4/8 0900 1500 4/9 1500 4/10 0900 4/12 0900 4/13 I ~ I I "&' ,, ,, ::0 C C CD Q. 0 '< '< r :;E () () ,, 3 r 0 0 C C r-t- ,, 3 "O "O r-t- CD CD >< Q. Q. CD Q. >< ::0 CD "&' CD Q. Q. 0 r :;E 3 r r-t 3 ;::;: 12

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Conclusions  Use of fully-coupled drift-off analysis makes a difference; providing a more realistic solution  Regular updates of watch circles also make a difference, accounting for:  Prevailing weather  “What-if” forecast weather  Changes in top tension and mud weight  Fully-coupled drift-off analysis is referenced as part of marine drilling riser assessments in ISO 13624-1 and ISO 13624-2. 13

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